Edited by Jarle I. Holten - NINA naturforskningEffects of climate change on terrestrial ecosystems...

00 4 Effects of climate change onterrestrial ecosystems

Report from a seminar inTrondheim 16.01.1990

Edited byJarle I. Holten

NINA NORSK INSTITUIT FOR NATURFORSKNING

Effects of climate change onterrestrial ecosystems

Report from a seminar inTrondheim 16.01.1990

Edited byjarle I. Holten

NORSK NSTITUIT FOR NATLJRFORSK:MNG

Holten, J.I. red. 1990Effects of climate change on terrestrial ecosystemsReport from a seminar in Trondheim 16.01.1990NINA Notat 4: 1-82

Trondheim, oktober 1990

ISSN 0802-3115ISBN 82-426-0046-5

Klassifisering av publikasjonenNorsk: Forurensning og miljøovervåking i terrestriskmiljøEnglish: Pollution and monitoring of terrestrialecosystems

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Abstract

Holten, J.I., ed. 1990. Effects of climate change onterrestrial ecosystems. Report from a seminar inTrondheim 16.01.1990. - NINA Notat 4: 1-82.

A new Norwegian climate scenario predicts atemperature increase of about 2 °C for the summermonths and 3-4 °C for the winter months, underdoubled atmospheric CO, . The new climate willinfluence several physiological processes in plants,like photosynthesis and respiration. Higher agricul-tural production is predicted. However, limitedpossibilities for genetic adaptation for forest treesand slow migration will lead to a retreat of NorwaySpruce northeastwards in northern and CentralEurope. The frost-sensitive Beech and Oak willexpand their areas northwards and northeastwardsin Europe. Rapid climatic change will disturb thephenological cycle of many plants. The southernregions of Scandinavia may experience an increasein plant diversity, whereas there will be a decreasein plant diversity in the mountains. The existence ofmany high mountain plants is threatened. Frostsen-sitive, thermophilous and weedy species will expand.A large number of retarding factors will probablyresult in only small changes in the flora and vegeta-tion during the next 50 years. The changes willmainly be quantitative in most districts of NorthEurope. In Central Norway a new temperate zoneand a more thermic oceanic section will allowinvasion of strictly Central European and southwestEuropean species. Extreme climatic events mayenhance certain developments, for instance cata-strophic death of forests caused by drought or frost.

Key words: Climatic change, primary production,genetic adaptation, plant diversity, vegetation zones,migration barriers.

Jarle I. Holten, Norwegian Institute for NatureResearch, Tungasletta 2, N-7004 Trondheim.

3

Referat

Holten, J.I., red. 1990. Virkninger av klimaforan-dringer på terrestriske økosystemer. Rapport fraseminar i Trondheim 16.1.1990. NINA Notat 4:1-82.

Et nytt norsk klima-scenario forutsier en tempera-turøkning på ca 2 °C for sommermånedene og 3-4°C for vinter-månedene, ved fordoblet CO, innholdi atmosfæren. Det nye klimaet vil påvirke mangefysiologiske prosesser i planter, slik sorn fotosynteseog respirasjon. Det forutsies høyere jordbrukspro-duksjon. Begrensede muligheter til genetisk tilpasing(lang levetid) for skogstrær, og lav spredningshastig-het vil føre til en retrett nordøstover i Nord- ogSentral-Europa for bartrær som gran og furu.Frostømfintlige arter, f.eks. bøk, vil ekspanderenordover og østover i Europa. Raske klimaendringervil forstyrre den fenologiske syklusen hos mangeplanter. Sørlige deler av Skandinavia vil få øktplantediversitet, mens fjellområdene vil få lavereplantediversitet. Eksistensen til en del fjellplanter ertruet. Et stort antall forsinkende faktorer vil sann-synligvis føre til bare små forandringer i flora ogvegetasjon de neste 50 årene. Forandringene vil ihovedsak være kvantitative i de fleste deler avNord-Europa. I Midt-Norge vil en ny temperertvegetasjonssone og en mer termisk oseanisk seks jontillate invas jon av sterkt varmek jære og frostømfint-lige arter fra Mellom- og Sydvest-Europa. Ekstremeklima-episoder vil forsterke visse utviklingstenden-ser, f.eks. katastrofe-død av skogstrær forårsaket avtørke eller frost.

Emneord: Klimaendringer, primærproduksjon,genetisk tilpasning, plante-diversitet, vegetas jons-soner, vandringsbarrierer.

Jarle I. Holten, Norsk institutt for naturforskning,Tungasletta 2, 7004 Trondheim.

Preface

Trondheim Oktober 1990Jarle Inge Holten

©Norwegian institute for nature research (NINA) 2010 http://www.nina.noPlease contact NINA, NO-7485 TRONDHEIM, NORWAY for reproduction of tables, figures and other illustrations in this report.

A seminar including 7 invited lecturers from Nor-way, Sweden and the Netherlands, was held 16January 1990 at the Museum of Science and Ar-chaeology, University of Trondheim. The seminartopic was "ecological effects of climatic change". Theseminar was arranged by the Norwegian Institute forNature Research, Trondheim, and funded by theNorwegian Ministry of the Environment. In additionto the last lecture, chapters 4 and 5 have beenwritten by the editor.


ContentsPage

A bstract 3Referat 3Preface 4

1 Climate scenarios 6

Arne Grammeltvedt. Climate change in Norway due to in-creased greenhouse effect 6

2 Ecosystem processes and primary production

Eilif Dahl. Probable effects of climatic change due to the green-house effect on plant productivity and survival in North Europe 7Oddvar Skre. Consequences of possible climatic temperaturechanges for plant production and growth in alpine and subalpineareas in Fennoscandia 18Atle Håbjørg. Adaptation and adaptability in Scandinavian plants 38

3 Species diversity, plant distribution and vegetation zonation . 43

Lars-Erik Liljelund. Effects of climate change on speciesdiversity and zonation in Sweden 43Pieter Ketner. Impact of climate change on flora and vegeta-tion in Western Europe with special emphasis on the Netherlands 47Jarle I. Holten. Predicted floristic change and shift of vegeta-tion zones in a coast - inland transect in Central Norway . . 61

4 Summary 77

5 Sammendrag 79

6 Appendix (participants) 81

5

1 Climate scenarios


Climate change in Norway due toincreased greenhouse effect

Arne GrammeltvedtThe Norwegian Meteorological InstituteNiels Henrik Abelsv. 40N-Oslo 3

A group of scientists (Eliassen et al. 1989) hasevaluated available results from global climatemodels (GCM) with the aim of preparing variousscenarios for future climate changes in Norway. Dueto uncertainties in the results of GCMs, in particularon the regional level, only one scenario has beenspecified. In this scenario an increase in greenhousegases corresponding to a doubling of CO2 in theatmosphere is assumed. Based on present trends ofgreenhouse gases, this is likely to occur around theyear 2030.

New results are expected to become available inautumn 1990 through the WMO/UNEP Intergovern-mental Panel on Climate Change. The scenario deve-loped for Norway will be re-evaluated in the lightof these new results.

Quantitative results obtained by GCMs are atpresent uncertain. The treatment of feedbackmechanisms, in particular changes in cloud cover,and the coupling between the atmosphere and theocean, are the main sources of uncertainty.

Most of the GCMs predict a global increase inaverage surface temperature by between 2 and 4 °C.The models with the most realistic description ofheat exchange between air and sea, and of heattransport by ocean currents predict a global tempe-rature increase of 2 °C. Only a few of the GCMshave a spatial resolution which allows analysis ofpredicted climate changes in Norway. Importantlocal effects are not included in the models.

The currently rnost likely climate changes to resultfrom a change in the greenhouse effect on theatmosphere corresponding to a doubling of the CO2concentration are as given below. Statements marked)CC are considered to be "almost certain", thosemarked x are "more uncertain".

6

Temperature - globallyThe temperature of the lower stratosphere willdecrease.

XXThe temperature of the lower troposphere and atground level will increase. The annual averageglobal mean temperature is expected to rise byabout 2 °C.

•

The increase of the annual average surfacetemperature will be largest at high latitudes andsmallest in the tropics.

•

At high latitudes, the temperature increase willbe most pronounced during autumn and winter.

Temperature - Norway

•

The average winter (December, January, Febru-ary) temperature will increase by 3-4 °C. Thenorth-south gradient of this increase is expectedto be small. The increase will be smaller incoastal areas compared to inland areas.

X The average summer (June, July, August)temperature will increase by about 2 °C.

Precipitation/Hydrology - globallyxx The water cycle will be intensified.

X At high latitudes, precipitation amounts willincrease during all seasons. Soil moisture will in-crease during winter.

Precipitation/Hydrology - Norwayx Precipitation will increase in all seasons, but

most pronouncedly during spring.

X Showers will bring a larger fraction of theprecipitation.

•

Soil moisture will increase during winter, de-crease during summer.

Variability - NorwayThe present cyclone (low pressure) activity is notexpected to change significantly.

Sea level. The sea level rise will be 15-20 cm. Thiswill be caused by thermal expansion of the ocean.Melting of inland ice is not expected to contributesignificantly.

Literature


Eliassen, A., Grammeltvedt, A., Mork, M., Peder-sen, K., Weber, J.E., Braathen, G. & Dovland,H. 1989. Climate change in Norway due toincreased greenhouse effect. Report to theMinistry of the Environment. - UnpubL

7

2 Ecosystem processes and primaryproduction

Probable effects of dimatic changedue to the greenhouse effect on plantproductivity and survival in NorthEurope

Eilif DahlDepartment of Biology and ConservationAgricultural University of NorwayN-1432 As-NLH

Introduction. A scenario has been constructed by thegeophysicists on the probable climate of NorthEurope with a carbon dioxide content of the at-mosphere double the present level of 330 ppm. Dueto the greenhouse effect summer temperatures areexpected to be about 2 degrees C higher than now,while winter temperatures are expected to be 4degrees C higher than at present. Incidentally, thisis not very different from the climatic conditions inScandinavia during the thermal maximum after thelast ice age. At that time, trees grew up to about 300m higher in relation to present topography thantoday, corresponding to a temperature difference insummer of about 2 degrees C. Heat-demandingplants like the misteltoe (Viscum album) had a widerdistribution than today, suggesting a similar change(Skre 1979). Pollen of holly (Ilex aqui folium), whichis a frost-sensitive plant, has been found in bogsnear Hamar, whereas today it is found not muchnearer than Arendal on the south coast or aroundGothenburg. This suggests a difference in wintertemperatures of more than 4 degrees C, perhaps 6degrees.

In this contribution I shall try to estimate expectedchanges in plant productivity potential and dis-tribution of crops and wild plants due to the heatingof the atmosphere. This is based on results ofresearch on the ecological geography of plantsduring the last decades in Norway.

Greenhouse effect on agricultural production inNorway. The basis of plant production is photosyn-thesis whereby energy from the sun is trapped bythe plants and transformed to chemical energy whichis used in production of organic matter. The amountof organic matter produced is termed the gross

©Norwegian institute for nature research (NINA) 2010 http://www.nina.noPlease contact NINA, NO-7485 TRONDHEIM, NORWAY for reproduction of tables, figures and other illustrations in this report

primary production. However, plants like otherliving beings must respire to live, and this consumessome of the material produced. What is left istermed the net primary production which is thecontribution of the vegetation to the ecosystem. Allanimals, including man, depend on this production.

For photosynthesis, solar energy and carbon dioxideare necessary. The carbon dioxide is taken upthrough the stomata. However, the cells under thestomata are wet. Hence, as carbon dioxide diffusesinwards through the stomata, a loss of water bytranspiration is unavoidable. Water is taken up bythe plant roots and used in transpiration. If thewater uptake is less than transpiration the plantlooses water. If this reaches a certain point theplants close their stomata and the water loss isthereby reduced. But at the same time the uptake ofcarbon dioxide also stops and thus also photosynthe-sis. Hence, a supply of water is necessary for photo-synthesis.

But even if water and solar energy are available,there will be little or no production under coldconditions, something we see in winter. Temperaturemust be sufficiently high to permit necessaryphysiological processes to go on with sufficientspeed. Hence, plant temperature can also be a factorlimiting production.

These are the basic climatic factors limiting plantproduction and all will be affected by the green-house effect. I shall try to assess the changes, theirmagnitude and direction.

Besides the climatic effects of the increased CO,content of the atmosphere there may be a directeffect on plant productivity (Eamus & Jarvis 1989).Numerous laboratory experiments show increasedassimilation as a response to increased concentrationof CO, in the atmosphere. This is used commer-cially in greenhouse cultures by increasing thecontent of CO, in the air to increase productivity.However, such experience cannot uncritically beapplied to what might happen in natural ecosystems.Positive effects might not appear if other factorslimit production, such as available light, availablewater or sufficiently high temperatures. Plants adaptin various ways to increased carbon dioxide con-centration in the environment, and this must beexamined in long-lasting experiments.

Light limitation for photosynthesis. Light absorbedin the chlorophyll provides by photosynthesis the

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energy needed to reduce carbon dioxide to carbohy-drates or equivalent organic compounds. The carbondioxide is attached to an acceptor, in C-3 plantsribulosebiphosphate (RuBP), in C-4 plants phosp-ho-enol-pyruvate (PEP). The energy of 8 lightquanta absorbed in the chlorophyll is needed toreduce a molecule of carbon dioxide. But in theprocess the acceptor is used up and must be rege-nerated. This also requires an additional 4-5 quantaof light energy so that the total becomes 12-13quanta for each molecule of CO, fixed (Farquhar& v. Caemmerer 1982, Raven 1983). In this respectthere is little difference between C-3 and C-4plants. The average energy of 12 moles of quantaabsorbed in chlorophyll (photosynthetically activeradiation, PAR) compared with the combustionvalue of 1/6 of a mole of glucose gives an energyefficiency of the PAR of 19 %.

Only part of the solar radiation is photosyntheticallyactive, about 45 %. Thus, the maximum efficiencyof the total solar radiation becomes 8.5 %

But even this cannot be attained. This is energyabsorbed in the chlorophyll. But some radiation isabsorbed in other organs than leaves, some isreflected and some is attenuated to a level where theplants can no longer use it for production. In cropswell provided with water and fully developedfoliage this loss is assessed to 20 %. Thus the maxi-mum efficiency is now 6.8 %.

This is maximum gross primary production. Butplants must, like all living organisms, respire toprovide energy for the growth processes. From whatwill be explained later this respiratory loss is hardlylower than 20 %. Thus, maximum net primaryproduction limited by light is 5.5 %.

Even this is too high because some respiration isneeded for maintenance and transport. Comparingthis with available data on primary production, peakproductions of 4-5 % have been attained both in C-3 and C-4 crops (Loomis & Gerlakis 1975) whichis not much below the maximum possible. Anefficiency of 2-3 % is obtainable and 1 % is com-mon for plant production during the growth seasonin agriculture. Other factors than light also limitagricultural production, e.g. availability of CO, .

Figure 1 gives the average incoming radiation at Asnear Oslo for each month, based on the period 1966-1975. I have also added a curve for net primaryproduction based on an efficiency of 4 %. It will be

Fig-ure 1 Incoming solar ener-gy /month,triangles)and maximum plant produc-tion (t/ha, squares) in 1966-1975 at A.s, SE Norway, assu-ming that 4 % of the solarenergy is converted to drymatter.

©Norwegian institute for nature research (NINA) 2010 http://www.nin.a.noPlease contact NINA, NO-7485 TRONDHEIM, NORWAY for reproduction of tables, figures and other illustrations in this report.

seen that light is so low in the winter months that ahigher temperature in winter will contribute little toan increased plant production, and might havenegative effects due to increased respiration.

Water as a limiting factor for agricultural produc-tion. For photosynthesis, carbon dioxide must betransported from the atmosphere to the chloroplaststhrough the stomata. As CO, diffuses inwardsthrough the stomata a loss of water by diffusion inthe opposite direction, i.e. transpiration, is unavoi-dable. If the supply of water is lower than thetranspiration, the stomata close; but then uptake ofCO, is prevented.

When CO, is transported from the atmosphere tothe chloroplasts there are a series of resistances.There is a resistance from free atmosphere to thevicinity of the leaves, a boundary layer resistancefrom the surrounding air to the openings of thestomata, a stomatal resistance by the transportthrough the stomata and finally a complex resistan-ce from the air under the stomata to the chloroplastswhich is called mesophyll resistance. We shall try toestimate the minimum number of water moleculeslost per CO, molecule fixed under different clima-tic conditions.

If the concentration of CO, in the atmosphere is caand the concentration of CO, in the air inside thestomata is ci then the flux is

(1) Fc = (ca - ci)/rs'

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

9

(2) Fv (ei - ea)/rs

where rs' is the diffusion resistance for the transportof CO, from the atmosphere to the air inside thestomata.

If the concentration of water vapour in the at-mosphere is ea and the concentration in the air spaceinside the stomata is ei then the transport of waterthrough the stomata to the free air is

where rs is the diffusion resistance for the transportof water vapour from the substomatal cavity to freeair.

The ea can be calculated from meteorologicalmeasurements. It is assumed that the air in thesubstomatal cavity is saturated with water. If thetemperature of the leaf is known ei can be cal-culated. Leaf temperatures depend mainly on theradiation balance and transpiration. In agriculturalcrops with fully developed foliage and well suppliedwith water, leaf temperatures are usually close to airtemperatures. If rs is known the rate of transpirationcan be calculated, or inversely, if transpiration isknown rs can be calculated.

There is a known relationship between rs and rs'.The CO, molecule is larger than the H, 0 moleculeand therefore moves more slowly by diffusion. Thediffusion rate depends on the molecular weight.Hence,

(3) rs' = 1.56 rs


By dividing equation I by 2 and using 3 we get

(4) F = Fc/Fv = 0.64 (ca - ci)/(ei - ea)

where F is the water use efficiency, i.e. the numberof molecules CO, taken up for photosynthesis inrelation to the number of molecules of water lost.The only unknown factor is the ci, the carbondioxide concentration in the substomatal cavity.

The ci depends among other things on the mesophyllresistance to CO, transport. This has been assessedin the following way.

We place a leaf saturated with light in a ventilatedcuvette and measure carbon dioxide uptake as wellas transpiration. The carbon dioxide uptake is usedto estimate the sum of stomatal and mesophyllresistance. The transpiration rate is used to estimatethe stomatal resistance to water vapour transport.Using eq. 3 the stomatal resistance to carbon dioxidetransport is calculated. Then the mesophyll resistan-ce to carbon dioxide uptake can be calculated.

The available measurements have been reviewed byKörner et al. (1979) who found that on average forC-3 plants the mesophyll resistance was 4.7 timesthe stomatal resistance, with extremes 2.9 and 6.3.For C-4 plants an average factor of 1.3 was obtain-ed, testifying that C-4 plants are better adapted tohot and dry environments.

If a factor of 4 and a gradient from free air of 345ppm to a fixation concentration on the acceptor onthe chloroplasts of 30 ppm is assumed, one cancalculate the concentration of CO, under thestomata to 282 ppm or a concentration difference of63 ppm between open air and the substomatal cavity.

There is, however, another method for calculatingthe desired resistances by using carbon isotopes(Farquhar et al. 1982). When carbon dioxide is fixedon the acceptor C 12 is preferred to C 13, i.e. thereis a discrimination against the heavy isotope C 13.Hence the ratio C 12/C 13 is different in thephotosynthate than in the atmosphere. There is alsoa discrimination against C 13 in the diffusion ofCO, from the atmosphere to the substomatal cavitysince C 13 is heavier than C 12, but this is a veryweak discrimination. If the photosynthesis is mainlylimited by the mesophyll resistance there will be astrong discrimination, if the photosynthesis is mainly

10

limited by diffusion the overall discrimination isweak. Hence the C 12/C 13 ratio can be used forthese purposes, i.e. to estimate to what extent CO2concentration in the atmosphere limits plant pro-duction. In this way, Körner et al. (1988, Table 5 p.630) have calculated a difference of close to 90 ppmin the CO, concentration between the substomatalcavity and free air at an altitude of 500 m in Au-stria. This is higher than the 63 estimated above.The question is, which of these is realistic?

It must be emphasized that in the gro-wth cuvettesall other external resistances than the stomatal areminimized. But in the field there is an additionalresistance from the free atmosphere to the airaround the leaves and a boundary layer resistancefrom the surrounding air to the opening of thestomata. During the day the air surrounding theleaves is depleted in CO, . All these factors alsocontribute. And since the C 12/C 13 method mea-sures actual performance in the field, the maximumCO, gradient of 90 ppm is preferred.

If the carbon dioxide concentration in the atmos-phere is doubled, the difference in the concentrationbetween the air and the substomatal cavity isincreased, and this increases Fc. This means that thewater use efficiency is increased. This is also borneout by experimental evidence (Eamus & Jarvis1989). Hence the plants produce more with the sameamount of available water. Since summer drought isan important limiting factor in continental tracts thisis expected to result in higher agricultural produc-tivity. Since a higher precipitation in Norway is alsoenvisaged in the climatic scenario, the importanceof drought as a limiting factor for plant productionin Norway is diminished.

Temperature as a limiting factor for plant produc-tion. It does not help if water and light are availablebut the temperature is low. This is obvious intemperate, boreal and arctic regions in winter; whenthe water freezes the production stops. And even attemperatures above zero the plants grow slowly inthe autumn or early spring. Plant production de-pends on chemical processes and all such processesare slow at low temperatures. But we need a moreprecise model to estimate the limitations of lowtemperatures on plant production.

A producing plant can be thought of (Figure 2) asa factory. It has a raw materials department whichutilizes solar energy, carbon dioxide, etc., and pro-duces raw materials in the form of carbohydrates,


MAINTENANCEand TRANSPORT

FINISHED PRODUCTS(new tissue growth)

fats, amino acids, etc. But the raw materials must betransformed to new tissue, e.g. cellulose, proteins,etc., during the growth process, especially in themeristems. However, the chemical processes fromraw materials to finished products require additionalenergy in the form of ATP. The ATP is producedby dark respiration in the mitochondria. We now seethe dark respiration as an energy department whichprovides energy needed for the growth processes.Energy and raw materials are both necessary forgrowth. Dark respiration is strongly influenced bytemperature. Our hypothesis is that at low tempera-tures the energy supply by respiration becomes therate-limiting factor for growth.

We can support this by results obtained by Penningde Vries (1974, 1975, de Vries et al. 1989). Let usfirst take a simple physiological process in plants,the synthesis of cellulose from glucose. For the

ATP

11

Figure 2 The plant produc-tion system (Dahl 1986). Fur-ther explanation in the text.

incorporation of an additional carbohydrate in thecellulose, two ATP are needed. Thus

n C 6 H 12 0 6 + 2n ATP = (C6 H10 0 5)n + n H20 +2n ADP + 2n P

The ATP is produced from glucose during the darkrespiration and this requires more glucose than isincorporated in the cellulose. This involves anadditional use of glucose of 7 %. In addition, oneATP is used up by the transport of glucose from thechloroplasts to the meristems where growth takespIace.

Similar calculations can be made for differentproducts. Proteins require much energy, about 66 %,fat 20 % and lignin 26 %. To produce an averagemaize plant involves a respiration loss of 20 %(Penning de Vries op. cit.). That is the figure used


previously as the difference between gross and netprimary productivity. In general, crops producingcarbohydrates have higher yields than those pro-ducing proteins.

In a meristem of maize is supplied with carbo-hydrates but producing the ATP in its meristem,one new g of maize tissue cannot be producedbefore an equivalent of 0.2 g glucose is respired.The time it takes to respire the correspondingamount of glucose is necessarily dependent on thetemperature, and the time it takes is inverse of therespiration rate. Thus the efficiency of temperaturefor growth is in proportion to the respiration rate atlow temperatures.

Confirmation of this idea has been obtained bystudying the growth of the apical shoot of spruce ina subalpine forest in Norway. Here, moisture isabundant and daily solar radiation high, but tem-perature is low. The daily growth of the shoot in-creases with increasing temperature. Temperatureswere measured by means of a thermograph, and acurve of respiration as a function of temperaturewas obtained by the Warburg technique. Takingweights from the respiration curve the sum of therespiration values equivalent to the temperaturesfrom the thermograph records (Re sum) was obtai-ned and compared with growth. A very good linearcorrelation was obtained (Figure 3). The regressioncurve crosses the zero axis at a certain value; this isthe amount needed for transport and maintenance(basal respiration). Only respiration in excess of thatneeded for transport and maintenance results ingrowth.

When calculating the limitations of low temperatureson plant production, temperatures must be givenweights according to their effect on respiration.Fortunately, the respiration curves for differenttemperate plants are not very different. At lowtemperatures the respiration follows the Arrheniuscurve with Q 10 (10 to 20 degrees C) between 2.0and 2.8. For spruce the value is 2.7. Methods areavailable for calculation of Re sums for any desiredcombination of Q 10 and basal respiration from datapublished in standard meteorological records (Skre1972). Such Re-sums correlate well with the dis-tribution limits of plants that require high summertemperatures (Skre 1979) and with the altitude ofthe climatic timberline (Dahl 1986).

There is evidence that crop production, at least intemperate areas, is positively correlated with tem-

12

• 1935o 1937

6 • 1940

20 40 60

Respiration equivalent, Re

Figure 3 The relation between the daily apical growth of Norwayspruce (Picea abies) in a subalpine forest in Norway and the sumof temperatures weighted according to their effect on respiration (Resums) (Dahl Mork 1959).

perature. The Japanese International Biological Pro-gram analysed the results of production measure-ments in numerous experimental plots by means ofpartial regression analysis and found a positivecorrelation between yield and temperature down tosubtropical areas. It is also well known that thegrowth of forests in Scandinavia, under similarconditions regarding soil fertility and availability ofwater, is strongly positively correlated to summertemperatures and duration of the growth season.

The greenhouse effect is expected to give us war-mer summers, and especially a longer productionseason. Both are expected to result in higher agri-cultural production. Also new crops can be introdu-ced. Today, Norway is just at the edge of maizeproduction. If the future turns out as suggested bythe scenario, probably the entire boreo-nemoralregion could become an area for maize production.

Also the rather extensive areas in Norway below andabove the timberline today could become importantareas for the production of fodder and root crops.

But these improvements will depend upon theintroduction and development of new cultivars inagriculture. The high productivity in Norwegianagriculture is to a considerable degree the result ofthe development of new and more productive cropcultivars; the small-grain cultivars used todayproduce about 30 % more grain per unit area andyear than those in use 20 years ago. Different typeshave been developed for the different growthconditions in different parts of Norway, and diff e-rent cultivars of grains are used when spring is latethan in years when spring is early. Hence newcultivars of agricultural plants must be developed inresponse to the changed climatic conditions, butwith the help of modern plant breeding methodsthese difficulties can be overcome. The situation isdifferent for wild plants, including our forest trees.


13

The greenhouse effect and the distribution of wildplants. While agriculture has good possibilities foradapting to the new climatic conditions by develop-ing new cultivars, the situation is different forforest trees and for many wild plants. The reason isthat adaptation takes place by evolution; the geneticmake-up of the populations changes as climatechanges. This is a slow process taking many gene-rations. Within a time-span of 100 years we mayexperience a climatic change of about the samemagnitude as the change between the coldest periodof the last ice age 18 000 years ago and-the warmestperiod after the last ice age 6000 years ago. Thepostglacial climatic change took 12 000 years, per-mitting plants to adapt to the new conditions byevolving new biotypes. Now a climatic change ofsimilar magnitude may take place in perhaps twogenerations of forest trees, leaving limited possibili-ties for genetic adaptation.

Figure 4 Distribution of beech(Fagus sylvatica) in relation tothe —3 degrees C isotherm forthe coldest month and its po—tential area if the distribution islimited by the —7 degrees Cisotherm — see figure p. 14.


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We have reasons to believe that the distribution ofseveral forest trees is limited by climatic factorswhich are changing due to the greenhouse effect. Anexample is the distribution of beech (see Figure 4a)which is a frost-sensitive species. Its distributionlimit in Europe is correlated with the -3 degrees Cisotherm of the coldest month as measured atmeteorological stations. Apparently it is unable towithstand frosts with temperatures under -40degrees C, and the probability for occurrence ofsuch severe frosts is correlated with the mean wintertemperatures. Under the new climatic scenario thedistribution of beech is therefore expected tocorrelate with the present-day -7 degrees C isotherm(Figure 4b). Thus an invasion of beech into newareas is expected. Many frost-sensitive plants witha southern and western distribution in Europe areexpected to expand their distribution in response towarmer winters.

The prospect for Norway spruce (Picea abies),our most important forest tree, is the opposite. The

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spruce has a very distinct limit to the southwest inEurope (see Figure 5). In the south it is restricted torelatively high altitudes growing in the Alps mainlyabove 500 m, while it is found at lower levelsfarther north. Its southwestern distribution limitcorrelates well with the -2 degrees C isotherm. Theunderlying physiological mechanism is still obscure;in plantations it grows quite well outside its naturaldistribution limit. But apparently it does not repro-duce well by natural means and when felled, theplanted spruce stands must be replaced by newplanting. Under the conditions of the climaticscenario with doubled CO, its natural distributionlimit is expected to correlate with the -6 degrees Cpresent-day isotherm (see Figure 6), i.e. the sprucemay disappear from large lowland tracts of NorthernEurope. It is also expected that the distribution ofpine will be affected, although it tolerates somewhatmilder winters than spruce. These trees will bereplaced by deciduous trees such as beech and oak.In Norway, spruce is expected to become a montanespecies found at some altitude in the eastern valleys.

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There is a considerable number of other specieswhich do not grow well in areas with mild winters.For the lack of a better term they have been calledsouthwest coast avoiders. The physiological mechan-isms involved are still unclear, but when suchspecies are planted in a garden in Stavanger oneoften sees that they start growth during mild periodsin winter and are subsequently damaged by laterfrost.

Quite a number of wild plants, including importantforest species like oak, ash, and other deciduoustrees, are limited by low summer temperatures. Suchspecies are expected to expand in response towarmer summers. This question will be more fullyexplored by Mr. Skre. On the other hand, manyspecies are restricted to areas of low summer tem-peratures, among them many alpine and arcticspecies. The distribution limits of such species arestrongly correlated with maximum summer tempera-tures (Dahl 1951, Conolly & Dahl 1970) and some ofthem may be killed by overheating on hot days

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15

Figure 5 Distribution of Nor—way spruce (Picea abies) inrelation to the —2 degrees Cisotherm for the coldest monthcalculated for the highest pointsin the landscape.

(Gauslaa 1984). A number of them, such as Campa-nula uniflora (Figure 7), are restricted to highaltitudes on calcareous soils and may have noecological niche left with an increase in maximumsummer temperatures of 2 degrees C.

The greenhouse effect and ecotype differentiation.For a plant to survive in our North Europeanclimates it is important that its phenological cycle iscoordinated with the annual climatic cycle so that itstarts growing at the right time of the year, flowersand sets seeds which become ripe before winter, andthat the winter buds are hardened before wintersets in. This coordination is carried out by reactionsof the plants to day-length and temperature fluc-tuations. A very common mechanism in our flora isthat short days in autumn lead to the formation ofwinter buds, and a period with short days and lowtemperatures in autumn and winter is needed for theinitiation of next years' flowers. But the flowers willnot develop before a period of long days in spring.The critical length of the days, the number of cycles


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needed for the reaction and the level of tempera-tures for the cold treatment varies between speciesand also between different strains in one and thesame species. These parameters are clearly relatedto the growth conditions in the natural environment.Thus a spruce population from Central Norwaystopped growth in autumn when the daylengthbecame shorter than 21 hours, while a populationfom Austria first stopped growth when the photo-period became shorter than 15 hours (Heide 1974).A common experience is that when a northern oralpine biotype is transplanted to more southern orlowland areas it starts growth earlier in spring, butalso stops growth earlier in autumn than localbiotypes. Transplanted populations from south tonorth or from lowlands to higher levels start growthlater in spring, but continue growth later in theautumn. These properties are genetically fixed. Thisresults in a differentiation of widespread species ina number of local ecotypes, in forestry they arecalled provenances, adapted to local conditions. Ifclimate changes, the populations have to adapt by

16

00°

oo\

Figure 6 Potential naturaldistribution of Norway spruce(Picea abies) as limited by the-6 degrees C isotherm for thecoldest month calculated for thehighest points in the landscape.

evolving new biotypes. This is a slow process takingmany generations, and if climate changes abruptlywith a short time for evolution it is more likely thatthe local population will die out. While temperaturewould change, the photoperiod would remain thesame and thus cause a dissociation of the tempera-ture and photoperiod synchronization that wouldhave a similar effect as a corresponding cross-latitudinal transfer of plants.

These features are important in forest plantationswhere provenances are often transplanted; if this isnot done with care there are usually unfortunateresults. Experience shows that transplantation ofspruce provenances within one and the same districtover more than 300 m in altitude is not to berecommended; for pine the altitudinal limit is 200m (Anonymous 1961). If summer temperatureschange 2 degrees C and winter temperatures 4degrees C, this corresponds to an altitudinal diffe-rence of more than the 300 m, corresponding to thelimit recommended by the Norwegian forest aut-


. •

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Figure 7 Distribution of Campanula umflora in Fennoscandia inrelation to the 22 degrees C isotherm for maxiraum summertemperature (Dahl 1951).

horities for planting of spruce, and more than thelimit recommended for pine. One may expectpreviously unknown forest damage in to appearextreme years.

The situation for very many rare and threatenedplants may be still more critical. Plants are usuallyrare because they have specialized habitat require-ments. If habitat conditions change abruptly, with

17

no time for adaptation by evolution, the chances arehigh that the plants will become extinct.

From the point of view of conservation, the abruptchange of climate due to the greenhouse effect mustbe expected to result in the disappearance of a largenumber of plant and animal species, and hence a lossof genetic capital. The plants and animals having thebest chances of survival may be short-lived specieswith a large number of offspring, as we find themin pests and weeds. The more long-lived climaxspecies will have smaller chances of survival.

References

Anonymous 1961. Forskrifter om frø- og plantefor-syningen i skogbruket. Utgitt av skogdirektøren1957 (revidert 1961). - Osio.

Conolly, A.P & Dahl, E. 1970. Maximum summertemperatures in relation to modern and Quater-nary distribution of certain species in the BritishIsles. In Walker, D. & West, R., eds. Studies inthe vegetation history of the British Isles. Cam-bridge Univ.Press. pp. 159-223.

Dahl, E. 1951. On the relation between summertemperatures and the distribution of alpinevascular plants in Fennoscandia. - Oikos 3: 22-52.

Dahl, E. 1986. Zonation in arctic and alpine tundraand fellfield ecobiomes. - In Polunin, N. ed.Ecosystem Theory and Application. Environ-mental Monographs and Symposia. Wiley & Sons.pp. 35-62.

Dahl, E. & Mork, E. 1959. On the relationshipsbetween temperature, respiration and growth inNorway Spruce. - Medd. fra Det norske Skogfor-søksvesen 53: 83-93.

Eamus, D. & Jarvis, P.G. 1989. The direct effectsof increase in global atmospheric CO, concentra-tion on natural and commercial temperate treesand forests. - Advances in Ecological Research19: 1-55.

Farquhar, G.D. & v. Caemmerer, S. 1982. Modellingof photosynthetic responses to environmentalconditions. - In Physiological plant ecology. II.Water relations and carbon assimilation. En-cyclopedia of plant physiology. 12 B. SpringerVerlag. Berlin. pp. 615-676.

Farquhar, G.D., O'Leary, M.H. & Berry, J.A. 1982.On the relationship between carbon isotopediscrimination and the intercellular carbondioxide concentration in leaves. - Austr. J. Plant.Physiol. 9: 121-137.


Gauslaa, Y. 1984. Heat resistance and energy budgetin different Scandinavian plants. - HolarcticEcology 7: 1-78.

Heide, O.M. 1974. Growth and dormancy in NorwaySpruce ecotypes (Picea abies). I. Interaction ofphotoperiod and temperature. - Physiol. Plant. 30:1-12.

Körner, C., Scheel, J.A. & Bauer, H. 1979. Maxi-mum leaf dif fusive resistances in vascular plants.- Photosynthetica 13: 45-82.

Körner, C., Farquhar, G.D. & Roksandic, Z. 1988.A global survey of carbon isotope discriminationin plants from high altitude. - Oecologia 74: 623-632.

Loomis, R.S. & Gerlakis, P.A. 1975. Productivity ofagricultural ecosystems. - In Cooper, J.P., Photo-synthesis and Productivity in Different Environ-ments. Cambridge Univ. Press. pp. 145-172.

Raven, LA. 1983. Evolution of plant life forms. -In Givnish, T.J., ed. On the economy of plantform and function. Cambridge Univ. Press. pp.421-493.

Skre, 0. 1972. High temperature demands forgrowth and development in Norway spruce (Piceaabies (L.)Karst.) in Scandinavia. - Meldinger fraNorges Landbrukshøgskole. 51,7: 1-29.

Skre, 0. 1979. The regional distribution of vascularplants in Scandinavia with requirements for highsummer temperatures. - Norw. Jour. Bot. 26:295-318.

de Vries, Penning, F.W.T. 1974. Substrate utilizationand respiration in relation to growth and mainte-nance in higher plants. - Neth. J. Agr. Sci. 22:40-44.

de Vries, Penning, F.W.T. 1975. Use of assimilatesin higher plants. - In Cooper, J.P., ed. Photosyn-thesis and productivity in different environments.International Biological Programme 5. Cambridge.Univ. Press. pp. 459-480

de Vries, Penning, F.W.T., Jansen, D.M., ten Berge,H.F.M. & Bakema, A. 1989. Simulation of eco-physiological processes of growth in severalannual crops. - Simulation Monographs 29.PUDOC, Wageningen. 271 pp.

18

Consequences of possible climatictemperature changes for plant pro-duction and growth in alpine andsubalpine areas in Fennoscandia

Oddvar SkreNorwegian Forest Research Institute - BergenFanagaten 4N-5047 Fana

-Tree line formation. In alpine and arctic areas whereclimate is constantly changing between a cold anda warm season, most plants will have evolveddifferent methods to survive the unfavourableseason, and the selection pressure will be determinedby abiotic factors rather than by competition (Kallio1984). Plants whose winter buds, bark and needleshave developed a high tolerance against freezing anddrying stress will therefore have an advantage.During the year plants are sub jected to many kindsof damage. To repair this and protect the livingtissue against new damage, and for reproduction,growth and active uptake in roots, more energy isneeded and is obtained by the production of ATPthrough photosynthesis and respiration (see Figure1). Plants growing close to their distribution limitswill therefore usually be restricted by demands forhigh temperatures to complete their life cycle andto produce viable seeds and/or winter buds (e.g.Heikinheimo 1932, Langlet 1960).

One of the most important distribution limits inFennoscandia is the arctic and alpine tree line. Themost important tree-line forming species are moun-tain birch (Betula pubescens), Norway spruce (Piceaabies) and Scots pine (Pinus sylvestris). Accordingto the above-mentioned relationships, the develop-ment of flower buds (Hagem 1917) and vegetativebuds (Romell 1925, Hustich 1944, Junttila & Heide1981) in spruce and pine is mainly determined bythe climate of the preceding summer. After flow-ering, the immature seeds start to develop embryoand storage tissue. Hagem (1917) and Heikinheimo(1921) found that the temperature during seedmaturation was an important restricting factor andthat embryos in the seed from tree line areas wereoften weak and incompletely developed. Accordingto these authors the alpine tree lines of spruce andpine in Scandinavia are mainly seed maturationlimits. In good seed-bearing years, however, viableseed may be dispersed more than 100 m above the


position of their mother trees, giving rise to sterileindividuals. The same relationship is also found inmountain birch (Betula pubescens). Mork (1944),however, found that in birch the limiting factor wasnot seed maturation but rather the low soil tempera-ture that did not allow seeds to germinate, except inclear-felled areas or where the soil surface isexposed to radiation. When the seedlings are esta-blished, however, they often develop a polycormic,shrub-like, life form that is able to reproducevegetatively (Kallio et al. 1983). According toElkington (1968) and Vaaramo & Valanne (1973) thepolycormic life form in birch may be partly a resultof inbreeding by dwarf birch (Betula nana) in thepopulation. Also the spruce (Picea abies) has a highpotential for vegetative reproduction by layerings,so-called "krummholz" (Ti-anquillini 1979). The pine(Pinus sylvestris) does not have this ability, butcompensates by a high seed production. Hagem(1917) found that near the tree line in southeastNorway the pine trees were often of the same age,stemming from one or a few good seed-bearingyears. The mean time between these years was foundto be 45 years in the Femunden area. If this timelapse happens to be too long, the old trees wouldeventually die out without any new seedling establi-shment. The same relationship should also apply tothe vegetative clones of spruce and polycormic birchabove the tree line. Like birch, the pine will easilyreproduce from seeds in burned areas, because of itshigh seed production and the favourable microcli-mate in such areas (Kujala 1927).

Respiration as a restricting factor for growth. Aplant will undergo different stages when growth isconcentrated to certain organs. As a rule stemelongation takes place first, then leaf growth and thesecondary radial growth in the stem. The rootgrowth usually starts in spring but is interruptedduring the period of shoot growth, and thencontinues into the autumn as long as the soil tempe-rature is high enough (Hagem 1947, Rutter 1957).The growth of an organ may be divided into threestages or phases. In a leaf the dry weight increase isexpressed by the growth rate (r) and time (t). As thephotosynthetic and respiratory tissues are develo-ping, growth will increase according to the followinglaw, stated by Blackman (1919):

( I ) W = Woert

where W is the dry weight at time t and W. theinitial weight. This law may be applied to the firstphase, which lasts until the metabolic tissue is fully

19

developed (West, Briggs & Kidd 1920). Then aconstant growth phase will occur, followed by thethird phase during which leaf growth continuouslydecreases and f inally stops (Figure 2). This schememay also be applied to other organs such as stems,roots, etc., and to the total leaf and shoot growth.During the second phase, growth is constant, i.e.independent of time, and its relation to externalfactors may be studied. In spruce shoots this phaselasts from the stage when about 20 % of the finalshoot length is completed until 80 % is attained(Romell 1925, Mork 1941).

To account for the observed requirements for hightemperature, various empirical parameters have beenintroduced (cf. Skre 1972). The most common is theheat sum W = (t-t.), i.e. the accumulated tempera-ture above a certain threshold value. In the cal-culation of heat sums, growth is assumed to be alinear function of temperature.

The triterm or tetraterm, i.e. the mean temperatureduring the three og four warmest months of theyear, has been widely used in forestry to expressthe high temperature demands for seed ripening intree species (e.g. Hagem 1917, Kujala 1927, Mork1933, Heikinheimo 1932, Opsahl 1952, Aas 1964).However, from the exponential shape of growthcurves as a function of temperature (Went 1957) oneshould expect better correlation when high tempera-tures are given relatively more weight than lowtemperatures. To correct for this error Mork (1941)introduced the concept of growth units, based on themean temperature during the six warmest hours aday. When using growth units instead of meantemperatures, Mork (1960) found significantly bettercorrelation with daily apical growth in spruce, aslong as water was not a limiting factor.

However, by using different combinations ofvariables, isolines may be constructed in a strictlyempirical way following almost any limit on themap. For a satisfactory explanation of a distributionlimit a good correlation as well as a physiologicalmechanism explaining the correlation, is needed. Forthe correlation between the distribution limit ofcoastal species like Ilex aqui folium and the Januarymean temperature the limiting factor is presumedto be frost hardiness. For the lower limits of alpinespecies like Koenigia islandica their sensitivity toextreme high temperatures has been suggested (Dahl1951). However, no specified physiological processhas yet been suggested to explain the distributionsof plants restricted to areas with warm summers.

80

40

LIGHT

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ICC

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-1


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10 20

— NET PHOTOSYNTHESISDAR-K RESPIRATION

DAYS

Figure 2 Growth in leaf biomass of elm (Llimus glabra) in mglleaf.

One possible mechanism for the temperature effecton plant distribution has been suggested by Dahl &

20

ALTER NATI V ERESPIRATI ON

ENERGYAT P

Figure 1 Diazram showing theflow of assimilates and energyin plants (top) and net photosyn—thesis and dark respiration ratesin a subarctic moss, Sphagnumsubsecundum,based on Skre St.Oechel (1979), as a function oftemperature.

Mork (1959) and Skre (1972) based on data fromNorway spruce (Picea abies). Through photosynthe-sis solar energy is transformed to chemical energyand stored in different organic compounds. Differ-entiation and growth involve the synthesis of newplant tissue. This is an energy-consuming processdepending on the supply of organic matter fromphotosynthesis as well as chemical energy releasedthrough the dark respiration process (Figure 1). Theenergy is released in small steps through the produc-tion of adenosine triphosphate (ATP) and otherenergy-rich compounds, which are translocated tosites where growth takes place. This part of therespiration process, which is called growth respira-tion (Penning de Vries 1972, Douce & Day 1985), islocated in the mitochondria and is related to ATPproduction, while the light-dependent photore-spiration (Zelitch 1966) and the alternative orcyanide-resistant respiration (e.g. Lambers 1980) donot involve such a formation.


Several authors have examined net photosynthesis(i.e. the difference between gross photosynthesisand photorespiration) and dark respiration in termsof gas exchange and dry-matter increase as a func-tion of temperature, e.g. Mooney et al. (1964) on anumber of alpine plants, Aalvik (1939) and Hagem(1947) on Norway spruce, Vowinckel et al. (1975) onblack spruce (Picea mariana) and Sveinbjörnsson(1983) on mountain birch. They found that net pho-tosynthesis increased with increasing temperaturesup to a certain optimum value and then decreased(Figure 1). If plants are grown for a long time at atemperature close to their compensation temperaturetk, growth may be limited by the supply of organicmatter. 1n the field this situation may occur duringmild winters when net photosynthesis and tk arelowered due to light limitation (cf. Printz r933,Hagem 1947). Due to respiration loss and winterdamage on evergreen needles, buds and stem tissue,plants experience a net loss of organic matter duringthe winter, and before new leaf tissue is formed inspring there is a further net loss of energy toproduce new growth (Kozlowski & Gentile 1958).For this reason the net photosynthesis has beencommonly looked upon as the limiting process forgrowth in a cold environment (e.g. Billings 1974,Chapin 1979, Tranquillini 1979). However, theperiod when net photosynthesis is negative usuallylasts for only one or two months of the growingseason (Rutter 1957) after which the new leaves takeover as the carbon source and produce new growththat will compensate for the loss of organic matterwithin a short time, due to favourable light condi-tions. Figure 1 shows that as temperature dropsbelow t there is an exponential decrease in darkrespiration while net photosynthesis is still high. Atlow and medium temperatures above freezing point,dark respiration or growth respiration may thereforebe the limiting process for growth. In this case alinear relationship between accumulated respirationand growth would be expected. Such a relationshipwas found by Dahl & Mork (1959) by interpretingmeasurements on shoot elongation in spruce from asubalpine area in southeastern Norway (Mork 1941).They found that the daily apical growth during theconstant growth phase was closely correlated (rxy =0.978) with the daily accumulated respiration, orrespiration equivalent (Re). The dark respiration asa function of temperature was found in separateexperiments using the Warburg manometric tech-nique. In general there is an approximately ex-ponential increase in dark respiration as a functionof temperature at low and medium temperatures

21.

(Figure 3) in accordance with Arrhenius' law (Moore1962) for thermochemical reactions (2):

(2) Re ce-u/R.T, ln Re = -u/RT ln C

4

ø

•

3

2

ULMUS GLABRA

PICEA ABIES (010.2.7)

O 6 12 18 24 7 oc

..!

Figure 3 Dark respiration rates in growing shoots of spruce (D ahl& Mork 1959) and leaf dises of eirn, measured in relative units,where the respiration at 10 °C is taken as unity. The elm leaveswere grown at 15 °C eonstant temperature. The mean tempera-ture t and standard deviation St for an arbitary month isindicated to show the effect of Qio on the monthly accumulatedrespiration.

In reactions following Arrhenius' law a straight lineis obtained when the logarithm of the reactionvelocity is plotted against the inverse of the tempe-rature measured in Kelvin degrees (°C+273). Theslope of the line is equal to u/R where R is theideal gas constant and u the activation energy. Whenrespiration curves are plotted this way they usuallyfollow the Arrhenius' law, except at high tempera-tures where other factors may interact, like heatdamage on the respiratory system or starving ef-fects. Instead of u the ratio Q10 between the re-spiration at a given temperature and the corre-sponding respiration at 10 °C lower temperature, isused. In many plant species with normal growthrespiration Q10 varies around 2.5, i.e. the respirationat 20 °C is about 2.5 times the corresponding valuesat 10 °C (Kramer & Kozlowski 1960, Skre 1975).The corresponding activation energy is approxima-tely 15 000 cal/mol (Skre 1975). In growing spruceshoots an activation energy of 16 700 cal/mol was

found, corresponding to Qto 2.65 (Skre 1972).Because of the linear relationship between respira-tion and growth found by Dahl & Mork (1959) oneshould also expect an exponential relationshipbetween temperature and growth at low tempera-tures. From the correlation diagram, however, itwas found that a certain basic respiration wasneeded for maintenance (cf. Penning de Vries 1972),corresponding to a constant temperature of 2.6 °C,and that no growth occurred below this thresholdvalue (Skre 1972).

Additional support for dark respiration as the mainlimiting factor for growth was presented by Penningde Vries et al. (1974) who found good correlationbetween the growth of maize embryos on glucose indarkness, and the respiration loss, measured inglucose units above a certain maintenance respira-tion. The most energy-consuming maintenanceprocesses were found to be resynthesis of proteins("tool maintenance"), active uptake, phloem loadingand osmo-regulation in leaves (Penning de Vries1972). The conclusion was supported by McCree(1970) and Thornley & Hesketh (1972) who foundthat the growth respiration was proportional withthe rate of substrate consumption ds/dt (growth +respiration loss) and the maintenance respirationwith plant biomass W:

(3) Rd = (1-YG) ds/dt + mYGW

MG

30

20

10


BETULA PUBESCENS

3 6 9 12 15 18

22

where YG is the growth yield and m the mainte-nance coefficient.

The existence of an alternative, cyanide-resistantrespiration in tundra plants (Lambers 1980) and ofincreasing sink strength with decreasing tempera-tures in a number of plants is further evidence fordark respiration as a growth-limiting process at lowtemperatures. On an annual basis, however, photo-synthesis may be limiting growth for a short periodin spring, when the plants are exhausted fromrespiration loss during the winter (Aalvik 1939,Rutter 1957).

In Figure 4 the daily growth in leaf biomass (mg/-plant) during the linear growth phase in mountainbirch seedlings is shown as a function of tempera-ture. The plants were grown at 24 hours day-length.It may be noted that at low temperatures there wasan approximately exponential increase up to about15-20 °C, in accordance with the respiration curve(see Figure 3) while at higher temperatures growthfollowed a typical optimum function of temperature,similar to the photosynthesis rates. The figureindicates that dark respiration may be limitinggrowth at low temperatures and the photosynthesisrates at high temperatures.

Respiration and tree lines. Methods are available forcalculating long-term respiration equivalents based

21 24°C

Figure 4 Growth in leaf bio-mass per plant (mg/day) dur-ing the linear growth phaseof mountain birch seedlingsfrom A.s, South Norway (95 maltitude) as afunction of tem-perature at 24 hours photo-perio41 apd 10 000 lux (300 siErn"'s-i) light intensity.


on data published in meteorological summaries (Skre1971, 1972). There is generally a linear decrease intemperatures with increasing altitudes (Werner-Johannessen 1960) varying from 0.4 °C per 100 min winter to 0.7 °C in summer. As respiration is anexponential function of temperature, according to(3), there must be an approximately exponentialdecrease in the annual accumulated respirationequivalent with increasing altitude, according to (4):

(4) ln Re/Reo = kh

where Reo is the respiration equivalent above themaintenance respiration at sea level and Re thecorresponding value at h metres altitude. Thek-value may be found empirically by comparingmeteorological stations at different altitudes, or byusing a linear temperature decrease of e.g. 0.6 °C or0.7 °C per 100 m altitude as a base for calculation.In this way maps of Re0 may be constructed tocompare with isolines of timberline altitude, so-cal-led isohypses (see Skre 1972).

Hult (1971) has published distribution maps forall native and naturalized vascular plant species inNorthern Europe. Aas (1965) and Lindquist (1949)have published distribution maps for the three maintree- line species in Scandinavia. If the supply ofATP by respiration is a limiting process, a bettercorrelation may be expected than between dis-tribution limits and isolines of other climatic para-meters, like triterms or temperatures of the warmestmonth (July). It is therefore tempting to compare thehorizontal distribution limits of the high temperaturedemanding element in the flora with isolines forrespiration equivalents in spruce (Figure 9).

Coastal areas have a lower annual temperatureamplitude and a longer growth period than inlandareas. Plants adapted to a coastal climate wouldtherefore be expected to have a lower Q10 andthreshold temperature for growth than plantsadapted to a continental climate. Measurements ofdark respiration rates in leaf discs of elm (Ulmusglabra) showed a significantly lower temperaturecoefficient (Q10 = 2.0) than for spruce respirationand corresponaing respiration rates in birch leavesof southern origin (Skre, unpubL). Based on theseexperiments the respiration function of elm leaveswas plotted on the diagram (Figure 3) and isolinesconstructed for constant annual elm respirationvalues at low-lying localities throughout Fennoscan-dia (Figure 9).

23

Figure 5b shows the annual spruce respirationrelative to the respiration at 10 °C as a function ofaltitude in six different mountain areas in Scandina-via, shown in Figure 5a. Because of differentk-values the slopes are slightly different. On aseparate figure the corresponding diagram for elmin area A 1 is shown (Figure 5c). The tree lines ofspruce and mountain birch are indicated togetherwith the limits between the low and central alpineregions and between the central and high alpineregions. The calculations are based on temperaturedata from low-lying and sheltered localities withinthe six mountain areas.

Distribution limits and the greenhouse effect. Manyplants are more or less restricted by their frostsensitivity as well as their high temperature require-ment, as shown by Iversen (1944) on Hedera helixand Ilex aquifolium and Fxgri (1960) on a numberof oceanic plants. To simplify the problem Iversen(1944) introduced a new method where plant dis-tributions were shown on a diagram where the meanJuly temperatures (t7) were plotted against the meanJanuary temperatures (ti) of localities where thespecies were present or absent. The author claimedthat frost itself as well as a too short growth seasonmay induce frost damage on the trees. The methodof Iversen (1944) has proved particularly useful instudies of temperature responses in Scandinavianplants.

When the meteorological stations were plotted onsuch diagrams and the direction of the axis wasreversed, the alpine and arctic distribution limits ofa number of species appeared as straight lines withfalling slopes. The reason for the falling slope is thatplants need a higher summer temperature to com-plete their growth in a continental climate with coldwinters and a short growing season than in anoceanic climate with mild winters and a long grow-ing season. It may be shown (Skre 1979) that actualdistribution limits of spruce and elm plotted on suchthermosphere diagrams coincide with isolinesrespresenting certain constant annual respirationequivalents above the maintenance respiration in thetwo mentioned species (Figure 6). Because of itslower temperature coefficient for respiration, elmseems to be a species that is more adapted to acoastal climate than spruce and the good correlationbetween respiration values and actual distributionlimits supports the main hypothesis about darkrespiration as a limiting factor.


100

24

II.

Figure Sa Mountain areas in Scandinavia where observations on altitudinal limits are available for a large number of species.

Re

7

3

2

5


ALDER LIMIT

-d

- c-b

--a

0 1000 2000METER

Figure 5b Annual growth respiration in spruce as a funetion ofaltitude for each of the six mountain areas shown in Figure 6a.The solid line indicates the mean common height limit in Re unitsfor 61 alpine species where observationa are available from all sixareas. The dashed lines show the limits between the high andcentral alpine region (a), the central and low alpine region (b),the bireh lirnit (c) and the spruce limit (d).

In Figure 6a-b the isolines corresponding to discretevalues of annual respiration units in spruce shootsand elm leaves are also plotted. From the exponen-tial relationship between respiration and tempera-ture one would expect that the rise in correspondingannual respiration equivalents would decrease withincreasing July temperature. This is not the case, infact there seems to be an almost linear relationshipbetween t7 and Re (see Figure 6c). The reason isprobably that the vertical temperature decrease ismuch lower in the summer season than in winter,due to increased solar radiation and instability inthe air. According to Werner-Johannessen (1960)this vertical decrease varies from 0.4 °C per 100metres in summer to 0.7 °C in winter. The Julytemperature, like the annual respiration, is alsomore influenced by local topography, the so-called"Massenerhebung", than other temperature measure-ments (Skre 1972).

If now the winter temperatures are raised by 4 °Cand summer temperatures by 2 °C as stated in thescenario, the distribution limits will move towards

25

Re

s

4

3

2

1

METER1000

Figure 5c Annual growth respiration in elm at sheltered localitiesas a function of altitude in inner Troms, North Norway (A1). Thetree line of elm is indicated (dashed line).

more arctic and alpine areas, partly because ofhigher respiration rates in summer and partlybecause of a longer growing season, represented bya higher January temperature. The effect of ahigher winter teniperature will tend to be strongerin a plant with an oceanic distribution and a lowtemperature coefficient for growth like elm (Ulmusglabra) than in plants like Norway spruce (Piceaabies) or mountain birch (Betula pubescens) with ahigh temperature coefficient. This may be seenfrom Figure 7 where the expected temperature riseis for plotted two localities close to the tree lines ofthe last two species. From Figure 6 the increase inspruce respiration was found to be 1.47 units,corresponding to 2.6 °C higher July temperature,and in elm 1.55 units, corresponding to 3.0 °Chigher temperature. From Figure 4 it may be seenthat as a result of the expected climatic change thespruce distribution limit will be raised by about 400m, and the birch limit by 450 m. Because of theexponential increase in annual respiration valueswith temperature, the difference in altitude corre-sponding to one annual respiration unit increases

°C t73 -0.17 .i.;..."1 0.4(+2)._t7

1:10 o o

--- - - - Z--.2 70 0 0- -.: - ... .....oo o 2

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o 0,0 •• o • • •

•• • • • • t• • •• • • • •

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eg <90 90 •0 • • •

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• • aro • • • ••0 -2 -4 -6 -8 -10 -14


PICEA ABIES

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ULMUS GLABRA

t 7.= 0.24 t1 + 13.3 (+3.0 )7 °C

10

• o •

• PRESENTo ABSENT

•o

t

• PRESENT

O ABSENT

5 °C

o -e›.

o 0 o

o o o o

• o14 o o

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0• •

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0 - 2 - 4 -6 -8 -10 -12°C

26

t

Figure 6 The dis-tribution of Piceaabies (a) and Ubnusglabra (b) shownin a therrnospherediagram where themean Janualy tern-peratures (t,) areplotted against thecorresponding Julytemperatures (t,).The distributionlimits (except fornatural regeneratedspruce in WestNorway) coincidewith isolines repre-serning a constantaccumulated annualgrowth respirationequivalent to 2.70and 3.42 units re-spectively, based onthe values in Figure3. Main isolines andthe effects of anexpected temperaturerise of +2 °C in t,and +4 °C in t, onthe distributionlimits are indicated.The relationshipbetween annualrespiration rates inspruce shoots andelm leaves, and thecorresponding Julytemperatures at -5°C January tempe-rantre, are shown ona separate figure (c).

Re

5

4

3

2

1

SPRUCE

ELM

10 14 18

Tree-line Retb (°C)

t1. -5°C

t7

with altitude. The distribution limit of Alnus gluti-nosa, a lowland species with higher temperaturedemands, is expected to rise by only 300 m. InUlmus glabra the low temperature coefficient willcause a relatively large rise in the tree line, about350 m (Figure 5c).

Another result of the greenhouse effect is a longergrowing season and higher winter temperatures, andcorrespondingly higher respiration loss during thewinter. The shortening of the frost-free period isexpected to be much greater at oceanic tree-linelocalities than at continental localities. Because

winter temperatures will increase more than summertemperatures, the effect of climatic change isexpected to be mostly through a shortening of thedormancy period. In Figure 7 the annual tempera-ture distribution is shown at two localities (Bruun1967). One locality, Dagali, is located at an altitudeof 887 m in a continental area in South Norway (60°15'N) close to the spruce timberline while the otherlocality, Tromsø, is located near sea level in NorthNorway (69°39'N). The summer temperatures atTromsø are only slightly higher than at Dagali whilewinter temperatures are about 5 °C higher (see Table1). The growth period varies from 165 to 180 daysat Dagali and from 195 to 220 days at Tromsø whenthe threshold temperatures for growth tb = 2.6 °Cand 1.5 °C in the two species are taken into account.After the expected climatic change has taken placeDagali will have changed to almost the same climateas Tromse has today with slightly higher summertemperatures (t7 = 13.4, t1 = - 4.6) and Tromsø to aclimate similar to Bergen today (t7 = 14.0, t1 = 0.4).The growth period will increase to 210-280 days atDagali and 225-315 days at Tromsø, the highestvalues referring to elm. In the lower part of thefigure the monthly respiration equivalents of the twospecies are shown, based on the diagram in Figure3. Because of the much higher temperature coeffici-ent of the dark respiration function, the expected 2°C temperature increase in summer will have a muchstronger effect on spruce shoots than on elm leaves,as also shown in Table 1. The table also shows that

Table 1 The mean January (t1) and July (t2) temperatures in centigrades (°C),length of the growth period V1 arid V2 in days and annual growth respiration inspruce shoots (Re 1) and elm leaves (Re2) at Dagali and Tromsø before and afterthe expected climatic change (cf. Figure 7). Tree-line respiration values andthreshold temperatures for growth tb (°C) are indicated in the lower part of thetable.

Elm leaves Spruce shoots3.42 2.851.5 2.6

27

20DAGALI

10

f

- 10 - 10

Re Re

1.5

1.0

0.5

SPRUCE

‘4,

20

10

1.5

1.0

0.5

TROMSØ

2 8

JFMAMJJ ASOND J FMAMJJASOND

Figure 7 The annual tempe-rature diatribution at Dagaliand Tromsø (top) comparedwith the monthly respirationequivalents in spruce (centre)and elm (bottom). The conse-quences of a temperature riseof +2 °C in summer and +4°C in winter are indicated(dashed lines). Horizontal linesindicate the threshold tempe-

,t ratures for growth tb (seeTable 1) and the maintenancerespiration Rem in the twospecies.

sss.

•••••••»,

Re

1.5

Re

1.5 •


the temperature rise willhave a stronger effect onrespiration rates in both species at Tromsø than atDagali because of higher temperatures at the formerstation.

As a conclusion, Table 1 and Figure 7 show that theexpected climatic change will bring both stationswell below spruce timberlines (see also Figure 9),and Tromsø will also be situated within the dis-tribution limit of elm.

To investigate the influence of the expected climaticchange on the respiration loss during winter and thephysiological status of the trees, some results areshown from a field experiment comparing mountainbirch seedlings grown in fertilized peat on an ocea-nic lowland site at Fana (50 m) and on a tree-linesite at Kvamskogen (450 m altitude). A comparisonbetween the sites (Figure 8) show approximatelytwice as high growth rates at the former locality.The difference between the lowland and tree-linesites increased as the plants were growing, becausebirch like many other deciduous species (cf. Prud-homme 1983) are rather opportunistic species, inthat a relatively large part of the energy fromrespiration is invested into new growth of structuraland photosynthetic tissue. By increasing theirphotosynthetic capacity, plants are able to replacesome of the carbohydrates that were consumed inthe growth process (see Thornley 1972), this tenden-cy is usually strongest in the fast growing southernecotypes. The second year (1987) growth rates atthe lowland site of Fana had increased to about fourtimes the corresponding growth rates at Kvamskogenin lowland birch and southern ecotypes of mountainbirch seedlings. In the northern ecotype fromFinnish Lapland (BJ), on the other hand, there wasalmost no altitudinal effect, the growth was muchslower and the photosynthetic products were in-vested into storage products and root growth. Thereare also indications that arctic populations "burn ofrpart of their stored energy through alternativerespiration simply to avoid growth and keep a highconcentration of nutrients in their tissue (Chapin1979, Skre 1990). Parallel to the much higher growthrates at the lowland site, however, there was also amuch higher respiration loss during the winter. Theamount of non-structural carbohydrates in rootsdropped from 40 % to 15 % dry weight at Fana andonly to 25 % at Kvamskogen, indicating lower sinkstrength at the former site. The expected tempera-ture rise due to the greenhouse effect would there-fore not only result in much higher growth ratesbut also in lower sink strength and available energy

29

resources, particularly in fast-growing species andecotypes. If the process goes too fast, the time willbe too short for plants to develop new ecotypes thatare adapted to the new climate. The photosynthesiswill take over as the growth-limiting process atambient field temperatures and many plants willtherefore be restricted not only by their upperdistribution limit but also by a lower limit. Printz(1933) suggested that high winter temperaturesmight restrict spruce growth in West Norway, buthis theory was later rejected (Hagem 1947), How-ever, future climatic change might again actualizea situation like the one predicted by Printz (1933).

Summary

In alpine and arctic areas where climate is constantlychanging between a cold and a warm season, mostplants will have evolved methods to survive theunfavourable season. During the year plants aresub jected to many kinds of damage. To repair thisand protect the living tissue against new damage,and for reproduction, growth and active uptake inroots, energy is needed by the production of ATPthrough photosynthesis and respiration. For thisreason plants growing close to their distributionlimits will be restricted by certain high temperaturedemands to complete their life cycle and to produceviable seeds and/or winter buds.

To account for the observed requirements for hightemperature, various empirical parameters have beenintroduced. The most common one is the so-calledheat sum, i.e. the accumulated temperature above acertain threshold value. The tetraterm, Le. the meantemperature during the four warmest months of theyear, has been widely used in forestry to express thehigh temperature demands for seed ripening in trees.However, for a satisfactory explanation of a dis-tribution limit a good correlation, as well as aphysiological mechanism explaining the correlation,is needed. One such mechanism is the dark respira-tion. The respiration rates in growing shoots ofspruce have been found to correlate well with thedaily apical growth at low and medium temperaturesabove a certain threshold value, and similar rela-tionships have been found in leaf discs of birch andelm, and in maize embryos. The existence of analternative, cyanide-resistant respiration in tundraplants and of increasing sink strength with decreas-ing temperatures in a number of plants is furtherevidence for dark respiration as a growth-limitingprocess at low temperatures. On an annual basis,

G DW

4


BJ

o--o—o BH

•

BSo—o--o BAM

BA L

KVAMSKOGEN

JJAS MJJ ASO

1988 1987

30

G OW

24

20

18

12

8

4

lir I

FANA

JJAS MJJASO

1988 1987

Figure 8a Biomass (mgjplant) of mountain and lowland birch seedlings grown in fertilizeJ peat from the 4—leaf stage during the 1986 and 1987seasons at Fana (50 m) and Kvamskogen (450 m altitude). The ecotypes are:

Betula pubescens: BJ Kevo, North Finland (200 m), BH Blefiell, Central Norway (750 m), BS Fana, West Norway (50 m), BAM Løten,East Norway (200 m). R pendula: BAL Løten, East Norway (200 m).

50

40

30

20


KVAMSKOGEN

J J AS

1986

ROOTS

PAJJ ASO

1987

Figure 8b Total non-structural carbohydrate content (% dry weight)1986/87 seasons. See Figure 8a for explanation.

however, photosynthesis may be limiting growthfora short period in spring when the plants are ex-hausted from respiration loss during the winter.

Methods are available for calculating long-termrespiration equivalents based on data published inmeteorological summaries. There is generally a lineardecrease in temperature with increasing altitude.As respiration is an exponential function of tempe-rature, this means that the annual accumulatedrespiration equivalents show a general exponentialdecrease with altitude. In this way maps of annualrespiration at sea level or at low-lying localitieswithin restricted areas throughout Fennoscandia maybe constructed.

When the mean July temperatures are plotted againstthe mean January temperatures, the alpine and arcticdistribution limits of a number of species appear asstraight lines with falling slope when the directionsof the axis are reversed. It can be shown that inspruce shoots and leaf discs of elm these linescoincide with isolines representing certain constantannual respiration equivalents above the mainten-

3 1

50

40 7

30

20

FANA

5

JJAS PAJJASO

1986 1987

in roots of birch seedlings at Fana and Kvarnskogen during the

ance respiration. The reason for the falling slope isthat plants need a higher summer temperature tocomplete their growth in a continental climate withcold winters and a short growing season than in anoceanic climate with mild winters and a long grow-ing season. If the winter temperatures are raised by4 °C and summer temperatures by 2 °C, as stated inthe scenario, the distribution limits will movetowards more arctic and alpine areas, partly becauseof higher respiration rates in summer and partlybecause of a longer growing season, represented bya higher January temperature. The effect of a higherwinter temperature will tend to be stronger in aplant with an oceanic distribution and a low tempe-rature coefficient for growth like elm (Ulmusglabra) than in plants like Norway spruce (Piceaabies) or mountain birch (Betula pubescens) with ahigh temperature coefficient. The expected increasein spruce respiration is 1.56 units, corresponding to2.65 °C higher July temperature, and in elm 1.75units, corresponding to 2.97 °C higher temperature.At tree-line altitudes this corresponds to about 500m vertical difference.

1161.-

1


3 2

Ulmus

glabra

(alrn)

•

Figure 9 Distribution maps of Ulmus glabra (a), Picea abies (b) and Alnus glutinosa (c) showing the present distribution and the annualrespiration equivalent (relative units) corresponding to the present alpine distribution limit (solid line) and the distribution limit after theexpected climatic change (dashed lines).

1 11.-

< • •• t•


14

t--.

18

33

; •

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Picea

abies(gran)

• L.10.1.1/..•••• •• •/ •••••••••••


01.111181, Ilffill•• •••••

3 4

,........... .

...

qr

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glutinosa

(svartor) •

References


Another result of the greenhouse effect, however,is a longer growing season and higher winter tempe-ratures, and correspondingly higher respiration lossduring the winter. The shortening of the frost- freeperiod is expected to be much higher at oceanictree-line localities than at continental localities. Acomparison between mountain birch seedlings grownin fertilized peat on an oceanic lowland site at Fana(50 m) and on a tree-line site at Kvamskogen (450m altitude) showed approximately twice as highgrowth rates at the former localtity. The differencebetween the lowland and tree-line sites increased asthe plants were growing, especially for the fast-growing southern ecotypes. On the lowland site,however, there was also a much higher respirationloss during the winter. The amount of non-structuralcarbohydrates dropped from 40 % to 15 % dryweight at Fana and only to 25 % at Kvamskogen,indicating lower sink strength at the former site. Theexpected temperature rise due to the greenhouseeffect will therefore not only result in much highergrowth rates but also in lower sink strength andavailable energy resources, particularly in fast-growing species and ecotypes. If the process goes toofast, the time will be too short for plants to developnew ecotypes that are adapted to the new climate.The photosynthesis will take over as the growthlimiting process at ambient field temperatures andmany plants will therefore be restricted not only bytheir upper distribution limit but also by a lowerlimit.

Billings, W.D. 1974. Adaptation and origins of alpineplants. - Arctic and Alpine Res. 6: 129-142.

Blackman, V.H. 1919. The compound interest lawand plant growth. - Ann. Bot. 33: 353-360.

Bruun, I. 1967. Standard normals 1931-60 of airtemperature in Norway. - Det Norske Meteorolo-giske Institutt, Oslo. 270 pp.

Chapin, F.S.III. 1979. Nutrient uptake and utilizationby tundra plants. - In Underwood, L.S., Tieszen,L.L., Callaghan, A.B. & Folk, G.E. eds., Com-parative mechanisms of cold adaptation. Acad.press. N.Y.-London-Toronto. pp. 215-234.

Dahl, E. 1951. On the relation between summertemperature and the distribution of alpine vascu-lar plants in the lowland of Fennoscandia. -Oikos 3: 22-52.

Dahl, E. & Mork, E. 1959. Om sambandet mellomtemperatur, ånding og vekst hos gran (Picea abies

35

(L.) Karst.). - Meddr. norske SkogforsVes. 16:81-93. (English summary).

Douce, R. & Day, D.A. 1985. Higher plant cell re-spiration. - Springer, Berlin - Heidelberg - NewYork Tokyo. 522 pp.

Elkington, T.T. 1968. Introgressive hybridizationbetween Betula nana L. and B. pubescens Ehrh.in Northwest Iceland. - New Phytol. 67: 109-118.

Fægri, K. 1960. Maps of distribution of Norwegianplants. 1. The coast plants. - Universitetet iBergen, Skrifter 26: I -134.

Hagem, 0. 1917. Furuens og granens frosætning iNorge. - Meddr. Vestl. forstl. ForsStn. 1,2: 1-188.

Hagem, 0. 1947. The dry matter increase in coni-ferous seedlings in winter. - Meddr. Vestland.forstl. ForsStn. 8,1: 1-317.

Heikinheimo, 0. 1932. Ober die Besamungsfähigkeitder Waldbäume. - Metsätiet. Tutkimuslait. Julk.17,3: 1-61,

Hulten, E. 1971. Atlas Over våxternas utbredning iNorden. - AB Kartografiska Institutet. General-stabens Litografiske Anstalts Förlag, Stockholm.

Hustich, I. 1944. Några synspunkter på skogsgrån-serna i nordligste Skandinavien. - SvenskaSkogsvFOr. Tidskr. 42: 132-141.

Iversen, J. 1944. Viscum, Hedera and Ilex as climateindicators. A contribution to the study of thepost-glacial temperature climate. - Geol. FOren.FOrhandl. 66,3: 463-483.

Junttila, 0. & Heide, O.M. 1983. Shoot and needlegrowth in Pinus sylvestris as related to tempera-ture in Northern Fennoscandia. - Forest Sci. 27,3:423-430.

Kallio, P. 1984. The essence of biology in the North.- Nordia 18,2: 53-65.

Kallio, P. Niemi, S., Sulkinoja, M. & Valanne, T.1983. The Fennoscandian birch and its evolutionin the marginal forest zone. - In Morisset, P. &Payette, S., eds. Tree-line ecology. Proceedingsof the Northern Quebec Tree-Line Conference.Centre d'etudes nordique, Quebec. pp. 101-110.

Kozlowski, T.T. & Gentile, A.C. 1958. Respirationof white pine buds in relation to oxygen availabi-lity and moisture content. - For. Sci. 4: 147-152.

Kramer, P.J. & Kozlowkski T.T. 1960. Physiologyof trees. - McGraw-Hill Book Co. N.Y. - Toron-to - London. 642 pp.

Kujala, V. 1927. Untersuchungen Ober den Bau unddie Keimfähigkeit von Kiefern- und Fichtensa-men. - Metsåtiet, Tutkimuslait. Julk. 12,6: 1-106.

Lambers, H. 1980. The physiological significance ofcyanide-resistant respiration in higher plants. -Plant, Cell and Environment 3: 293-302.


Langlet, 0. 1960. Mellaneuropeiska gransorter isvensk skogbruk. - K. Skogs- Lantbr.- Akad.Tidskr. 99: 259-329. (English summary).

Lindquist, B. 1949. The main varieties of Picea abiesin Europe. - Acta Horti Bergiani 14,7: 249-342.

McCree, K.J. 1970. An equation for the rate ofrespiration of white clover plants grown undercontrolled conditions. - In Prediction and Mea-surements of Photosynthetic Productivity. Pudoc,Wageningen. pp. 221-229

Mooney, H.A., Wright, R.D. & Strain, B.R. 1964.The gas exchange capacity of plants in relationto vegetation zonation in the White Mountains ofCalifornia. - Am. Midl. Nat. 72: 281-297.

Moore, W.J. 1962. Physical Chemistry. 4. ed. -Longmans Green & Co. London. 844 pp.

Mork, E 1933. Temperaturen som foryngelsesfaktori de nord-trønderske granskoger. Meddr. norskeSkogforsVes. 5: 1-144.

Mork, E. 1944. Om sambandet mellom temperaturog vekst. Undersøkelser av de daglige varias joneri granens høydetilvekst. - Meddr. norske Skog-forsVes 8: 1-89.

Mork, E. 1960. Om sambandet mellom temperatur,toppskuddtilvekst og irringens vekst og forved-ning hos gran. - Meddr. norske SkogforsVes. 16:225-262. (English summary).

Opsahl, W. 1952. Om sambandet mellom sommer-temperatur og frømodning hos gran. - Meddr.norske SkogforsVes. 11: 619-662. (English sum-mary).

Penning de Vries, F.W.T. 1972. Respiration andgrowth. In Rees, A.R., Cockshull, K.E., Hand,D.W. & Hurd, J.R., eds. Crop processes in con-trolled environments. Acad. Press, N.Y. - Lon-don. pp 327-347.

Penning de Vries, F.W.T., Brunsting, A.H.M. & vanLaar, H.H. 1974. Products, requirements andefficiency of biosynthesis: A quantitative ap-proach. - J. theor. Biol. 45: 339-377.

Printz, H. 1933. Granens og furuens fysiologi oggeografiske utbredelse. - Nyt. Mag. Naturvid. 73:169-219.

Prudhomme, T.I. 1983. Carbon allocation to antiher-bivore compounds in a deciduous and an ever-green subarctic shrub species. - Oikos 40: 344-356.

Romell, L.G. 1925. Växttidsundersökningar hos talloch gran. - Meddr St. SkogförsAnst. 22: 45-124.

Rutter, A.J. 1957. Studies in the growth of youngplant of Pinus sylvestris L. I. The annual cycle ofassimilation and growth. - Ann. Bot. 21: 399-425.

Skre, 0. 1971. Frequency distributions of monthlyair temperature and their geographical and

36

seasonal variations in Northern Europe. - Meld.Norges Landbr.Högsk. 50,9: 1-54.

Skre, 0. 1972. High temperature demands forgrowth and development in Norway spruce (Piceaabies (L.) Karst.) in Scandinavia. - Meld. NorgesLandbrHøgsk. 51,7: 1-29.

Skre, 0. 1975. CO2 exchange in Norwegian tundraplants studied by infrared gas analyzer technique.- In Wielgolaski, F.E., ed. Fennoscandian TundraEcosystems 1. Plants and Microorganisms.Springer-Verlag, Berlin - Heidelberg - NewYork. pp. 168-183.

Skre, 0. 1979. The regional distribution of vascularplants in Scandinavia with requirements for highsummer temperatures. - Norw. J. Bot. 26: 295-318.

Skre, 0, 1990. The relationship between darkrespiration and growth at low temperatures inecotypes of mountain birch (Betula pubescensEhrh.) and some related species in Fennoscandia,and the application of spruce (Picea abies (L.)Karst.) respiration rates on timberlines through-out Europe. 4. Chemical analysis of birch tissue,grown at varying temperature, light andphotoperiod. - Holarct. Ecol. 13 (in press).

Skre, 0. & Oechel, W.C. 1979. Moss production ina black spruce (Picea mariana) forest withpermafrost near Fairbanks, Alaska, as comparedwith two permafrost-free stands. - Holarct. Ecol.2: 249-254.

Sveinbjörnsson, B. 1983. Bioclimate and its effect onthe carbon dioxide flux of mountain birch (Betulapubescens Ehrh.) at its altitudinal tree-line in theTornetråsk area, Northern Sweden. In Morisset,P. & Payette, S., eds. Tree-line ecology. Pro-ceedings of the Northern Quebec Tree-LineConference. Centre d'etudes nordiques, Quebec.pp. 111-122.

Thornley, J.H.M. & Hesketh, J.D. 1972. Growth andrespiration of cotton bolls. - .1. appl. Ecol. 9:315-317.

Tranquillini, W. 1979. Physiological ecology of thealpine timberline. Tree existence at high latitudeswith special reference to the European Alps. -Ecological Studies 31. Springer Verlag, Berlin-Heidelberg-New York. 137 pp.

Vaaramo, A. & Valanne, T. 1973. On the taxonomy,biology and origin of Betula tortuosa Ledeb. -Rep. Kevo Subarct. Res. Sta. 10: 70-84.

Vowinckel, T., Oechel, W.C., Boll, W.G. 1975. Theeffect of climate on the photosynthesis of Piceamariana at the subarctic line. 1. Field measure-ments. - Can. J. Bot. 53,7: 604-620.


Went, F.W. 1957. The experimental control of plantgrowth. - Chronica Botanica, Waltham, Mass.

Werner-Johannessen, T. 1960. Varmeutvekslingenbygninger og klimaet. - Tanum, Oslo. 258 pp.(English summary).

West, C., Briggs, G.E. & Kidd, F. 1920. Quantitativeanalysis of plant growth. - New Phytol. 19:200-207.

Zelitch, J. 1966. Increased rate of net photosyntheticcarbon dioxide uptake caused by the inhibitionof glycolate oxidase. - Plant Physiol. 41: 1623-1631.

Aalvik, G. 1939. Ober Assimilation und Atmungeiniger Holzgewåchse im westnorwegischenWinter. - Meddr. Vestland. forstl. ForsStn. 6,4:1-266.

Aas, B. 1965. Bjørke- og barskogsgrenser i Norge. -Thesis, University of Oslo (unpublished).

37

Atle Håb jørgDepartment of HorticultureAgricultural University of NorwayBox 22N-1432 As-NLH


Adaptation and adaptability in Scan-dinavian plants

The genetic variability within species is great, bothin morphological and physiological characters (Table1 a, 1 and Figures 2, 3, 4, 5).

Prior to the 1950s, much of the research work in thisfield was concerned with showing that morphologi-cal genotypes were characteristic of differenthabitats. Recently, more research has been directedtowards physiological differences within species andthe development of physiological ecotypes. This typeof research is very important at a time with chang-ing climatic conditions and increased air and soilpollution especially in our cities, industrial areas andso forth.

In addition, modern propagation and productiontechniques combined with efficient marketing havespread homogeneous plant materials over a range ofclimatic regions in Europe (Figure 1). Such plantmaterials may be poorly adapted to environmentalconditions different from those at the origin of thegenotypes. This lack of adaptation again leads toreduced survival and increased maintenance cost forthe plantings. This is a problem of particular impor-tance for the north Scandinavian countries wherethe environmental conditions are so different fromthose in the main part of Europe and because of theextensive import of landscape and ornamental plantsfrom those climatic regions. For instance, in Norwaymore than 90 % of the plant material is of southernorigin thus creating great winter survival problems(Table 1).

Both the changing environmental conditions and theincreased international trade with plants make theadaptability or stability of different genotypes,families or populations to a very important factorboth in natural ecosystems and commercial varieties.Certain habitats, owing to a mixed and rather lowlevel of selection pressure, are able to preserve agreat range of variability within a population and toproduce genotypes which can tolerate variableclimatic conditions, while others will exclude all but

38

Table 1. Winter survival (%) of ecotypesof Betula pubescens Ehrh. cultivatedat lat. 60°N, 64°N and 70°N.

Table la. Family variation in germination, establishment and saleableplants in some important ornamental species.

the specialized, highly adapted variants of thepopulation (Harland & Martin 1938, Håb jørg 1976).The stability of a certain population or genotype orrather its ability to develop satisfactorily underdiffering climatic conditions is a decisive qualifica-tion for native plant populations in a situation withchanging environmental conditions, but also forgenotypes/varieties in countries so sparsely popula-ted and with such great climatic variations as inNorway. Here the growing season can vary from lessthan 3 months in the northeast, with practicallycontinuous light during the growing season, to morethan 9 months in the southwestern part of thecountry and with daylengths varying from 12 to 18hours. In addition, the maritime climate in the westand the continental climate in the east causes greatfluctuations in temperature. In the most continentalareas in the northeast, the maximum differencebetween summer and winter temperature is morethan 80 °C (+30 to -50 °C) and in the maritime areasin the southwest less than 35 °C (+25 to -10 °C).

Adaptation to important climatic and edaphicfactors. During the last 15 years a number ofexperiments have been carried out under controlledclimatic conditions in a phytotron at the AgriculturalUniversity of Norway and in regional field experi-ments at 5-8 different locations in Norway to study

Figure 1 Some climatic data and length of thegrowing season at the most extreme northern,southern, western and eastern towns in Euro-pe.


241

2

16

12

ce 4

O

•

0

u, 24Q-02

01

12• •

the responses of maritime, continental, southern andarctic ecotypes to important climatic and edaphicfactors. So far adaptation to the following environ-mental factors has been found.

1 Climatic factorsLight intensityLight qualityPhotoperiodTemperature (Optimal/Min/Max) for growthDifferences in temp. requirement during thedormancy periodAir humidityAir pollution

2 Edaphic factorsSoil pollution

Photoperiod—6— Max. temperature

Min. temperature

39

SOUTHERN EUROPEAN

.• • LONG. 5 GY4•• • ' LT. PA

L _ LJ: •WESTERN EUROPE

LAT. 52°NLONG,10°WALT. TI.M

J F MA*MJ'J A SON Di F MAMJ J ASOND

MONTH

1111111111111111111

pH (calcium content)Nutritional stageHeavy metal tolerance

Length of growing season

24

20

16

12

rn4

-8 –z

24

— 4

4

- o— 4

-a

Diurnal fluctuation in temperature

In the following only the most important factors willbe discussed.

Photoperiod is obviously the most important factorcontrolling growth and development of most plantspecies in the north temperate and arctic regions,and it is especially so for the onset of growthcessation. In an extensive ecotype study on 13 woodyornamentals and two grass species, all spontaneousto Scandinavia and collected at three differentlatitudes, 56°N, 63°N and 70°N and at different

©Norwegian institute for nature research (NINA) 2010 http://www.nina.no........ ........ Pleaw Q.ontaQjWNA NO-7485 TRONDHEIM, NORWAY for reproduction of tables, figures and other illustrations in this report.

altitudes, it was shown that all species except oneresponded strongly to photoperiod.

v, 24

022

— 20

218

a

•

160

1255 60 65 70

LATITUDE °N

Figure 2 Critical photoperiod for vegetative growth in latitudinaldistant ecotypes of thirteen woody species.

The critical photoperiod for shoot elongation variedconsiderably among ecotypes (Håbjørg 1972a, 1976,1978). It was, however, almost the same for identi-cal ecotypes of different woody species and 1 to 2

LOCAL I TY: 60°N

9\e://.74

• \ FROSTNIAUTU2/.

• /

Ecotype • — 70°N• — 63°N• — 56"N

LOCALITY: 70 °N

• 4\JUNE JULY AUG. SEPT. JUNE JULY AUG. SEPT.

40

hours shorter for grass ecotypes (Figure 2). The verystrong photoperiodic control of growth in Scandina-vian plant materials makes it difficult to grownorthern ecotypes in southern areas. As demonstra-ted in Figure 3, north Scandinavian ecotypes ofBetula pubescens completed growth already in Julywith a shoot growth of 10-12 cm when grown at60°N. Grown at their origin 70°N, they had aseasonal shoot elongation of 45-50 cm or slightlymore than southern ecotypes. Further experimentshave shown that the photoperiodic control of growthand development gradually became less important insouthern and more maritime ecotypes, and it wasalso evident that growth cessation in species with anearly growth cessation like Fraxinus, Syringa andSorbus seemed to be little affected by photoperiod.In fact, field experiments carried out at 59, 63 and71°N showed that northern ecotypes of Sorbusaucuparia had about the same yearly shoot elonga-tion at all localities, 30-35 cm.

Light intensity/quality vary seasonally, diurnallyand with the habitat, latitude, altitude, and aspect.It is evident that great differences exist betweenecotypes in photosynthetic light acclimatisation.Ecotypes native to open habitat and to densely sha-ded areas showed that "shade types" did not acclima-te to high light conditions (B jørkman & Holmgren1963).

I.

• \

\\j,AUTUPANFROST

Fiigure 3 Weekly height growthof three latitudinally distantecotypes of Betula pubescensEhrh. cultivated at two localities— 60°N.

Differences in response to light intensity and lightquality are also found for photoperiodic reactions.In studies under controlled environmental conditions(Håb jørg 1972b), north Scandinavian ecotypes hada critical light intensity for photoperiodic responsesof 250 to 500 lux and south Scandinavian ones 15-100 lux (Figure 4). Northern ecotypes also requireda greater percentage of red light, thus indicating adifference in "measuring" the day-length. Ecotypesfrom northern parts of Scandinavia seem to measurethe day-length from sunrise to sunset while sout-hern ones also include part of the twilight.

Norwegian institute for nature research (NINA) 2010 http://www.nina.noPlease contact NINA, NO-7485 TRONDHEIM, NORWAY for reproduction of tables, figures and other illustrations in this report.

15 100 250 500 100 250 500

Light intensity in lux

Figure 4 Effect of light intensity on shoot growth and dry weightof latitudinal ecotypes of Betula pubescens.

Figure 5 Effect of night tempera—ture on shoot growth and dryweight of latitudinal ecotypes ofBetula pubescens.

5.0 Alta

4.0O 3.0

2.0..ag.; 1.0

8 13 18 8 13 18 8 13 18

Night temperature °C

41

Temperature is an important factor for plantgrowth, and it strongly affects/modifies all lightreactions within the plant (Håb jørg 1972a). Asshown in Figure 1, the vegetation in Europe issub jected to wide seasonal and diurnal temperaturefluctuations. Marked differences are found amongspecies and ecotypes in their response to optimumand minimum temperatures for growth and de-velopment. Ecotype studies on North European treeshave demonstrated adaptation to diurnal tempera-ture fluctuations. Ecotypes from maritime andnorthern areas, where the diurnal - temperaturefluctuations are smaller than in southern and conti-nental areas (Figure 1), also reached their optimumshoot growth when exposed to smaller fluctuationsin diurnal temperatures (Figure 5).

Under Scandinavian conditions, differences amongecotypes in response to low temperature stress iscrucial. As demonstrated in Figure 3 and Table I,the response to low temperature stress in the autumnis always strongly related to the physiological condi-tions of the plant at the moment of the first autumnfrost. However, early autumn frost damage is not theonly crucial moment for winter survival for plantsin Scandinavia. Stability in winter-frost resistanceis, as demonstrated in Table 2, extremely important.

Arctic and continental ecotypes adapted to highlyspecialised and stable winter conditions showed avery strong reduction in winter survival when grownunder maritime and southern conditions or at locali-ties with unstable winter conditions. On the otherhand, the fjord types exposed to a mixed selection

Trondheim Århus 50

4030 5+20

10 c:)


Table 2. Differences in adaptability/stability between ecotypes of Poaprwensis 1% survival).

pressure at their place of origin with both maritimeand continental climate, also produced very stableecotypes which could survive and grow fairly wellunder both maritime and continental conditions. Thedifference in stability in winter-frost resistanceseemed, according to experiments under controlledclimatic conditions, to be related to differences inchilling requirement (Table 3). The maritimeecotypes of Picea abies from coastal areas in Trøn-delag needed about 2 weeks longer chilling treat-ment at 2 °C to break bud dormancy than the morecontinental ecotypes from the same latitude.

Table 3. Ecotype differences in bud-breaking conditions of Picea abies (%bud break)

Weeks at 2°CEcotype 0 1 3 5 7 9

Maritime 0 0 2 26 91 99Continental 0 0 18 98 97 99

The stability in winter-frost resistance obviously isof increasing importance in Scandinavia because ofthe warmer winter climate. The last 2-3 years ofchanging winter climate in the southern part ofNorway has caused severe damage to typical conti-nental species like Ribes alpinum and Berberisthunbergii. In northern Norway, in the town centresof Tromsø and Narvik, a frightening tree damage/-death of local ecotypes of Betula pubescens and Sor-bus aucuparia has been registered. The damage mustpartly be due to the unusually warm and unstablewinter climate and the lack of stability in winter-frost resistance of the local ecotypes. Extensivecambium damage indicated that the ecotypes hadgone through the dormancy period and startedgrowth in late autumn, and were subsequentlydamaged by a succeeding frost period. More mari-time tree species like, for instance, Acer pseudo-

4 2

platanus, which ordinarily are not considered sohardy, showed no damage. Heavy traffic poilutionaffecting the depth of the dormancy may alsoaccount for part of the damage.

Air and soil pollution damage to vegetation isprobably the most important abiotic stress factor inurban and trafficked area.s. For instance, measure-ments of lead accumulation on leaves of differentspecies along highways in Norway showed that plantspecies with hairy and/or strongly wrinkled leaveslike Corylus avellana and Ulmus glabraaccumulated3-4 times more pollutants than species with smoothleaves like Syringa vulgaris. Observations made onvegetation in strongly polluted areas, also indicatedthat those plants, moreover, had lower resistance toair pollution. However, differences within speciesin tolerance to edaphic conditions and to pollutants,as demonstrated in Table 4, are therefore of increas-ing importance and ought to be included in all tree-breeding work for the urban environment.

Summary

Table 4. Ecotype differences inSorbus aucuparia to S02 (g dryweight). Häbjørg 1975.

Locality

S02-exposedUnexposed

Wild S02 resi-type stant type

2,2 4,33,5 3,4

This short review shows that the natural vegetationof Scandinavia is well adapted to the local climaticand edaphic conditions. It also shows that there is agreat difference in adaptability within the species.Moreover, arctic and continental ecotypes seem tobe poorly adapted to southern and maritime condi-tions, as, too, do southern ecotypes to arctic andcontinental conditions. Ecotypes from the fjordareas with a mixed selection pressure showed a wideadaptability. They could grow fairly well undermaritime, arctic and continental conditions.

A possible change in the climate with increasingwinter temperatures to above zero, may causedamage to the highly specialised arctic and conti-

nental ecotypes. The breeders of forestry, agricul-tural and horticultural crops should therefore takethat into consideration in future breeding program-mes.

References

©Norwegian institute for nature research (NINA) 2010 http://www.nina.no

Please contact NINA, NO-7485 TRONDHEIM, NORWAY for reproduction of tables, figures and other illustrations in this report.

B jørgman, 0. & P. Holmgren 1963. Adaptability ofthe photosynthetic apparatus to light intensity inecotypes from exposed and shaded habitats. -Physiol. Plant. 16: 889-914.

Harland, H.V. & M.L. Martin, 1938. The effect ofnatural selection on a mixture of barley varieties.- Jour. Agr. Res. 57: 189.

Håb jørg, A. I 972a. Effects of photoperiod andtemperature on growth and development of threelatitudinal and three altitudinal populations ofBetula pubescens Ehrh. - Meld. Norg. Landbr-Høgsk. 52,26: 1-27.

Håb jørg, A. 1972b. Effects of light quality, lightintensity and night temperature on growth anddevelopment of three latitudinal populations ofBetula pubescens Ehrh. - Meld. Norg. Landbr-Høgsk. 31,26: 1-17.

Håb jørg, A. 1976. Effects of photoperiod andtemperature on vegetation growth of differentNorwegian ecotypes of Poa pratensis L. - Meld.Norg. LandbrHøgsk. 55,16: 1-26.

Håb jørg, A. 1978. Photoperiodic ecotypes in Scandi-navian trees and shrubs. - Meld. Norg. Landbr-Høgsk. 57,33: 1-20.

43

3 Species diversity, plant distributionand vegetation zones

Effects of climate change on speciesdiversity and zonation in Sweden

Lars-Erik LiljelundThe Swedish Society for the Conservation of NatureBox 4510S-102 65 Stockholm

Introduction. Global warming from the increase ingreenhouse gases has become a major scientific andpolitical issue during the last decade. Estimates ofpresent and future effects, however, have significantuncertainties. There have also recently been contro-versial claims that a global warming has beendetected.

Results from most recent climatic models suggestthat average global surface temperature will increaseby some 1.5 to 6 °C during the next century, butfuture changes in greenhouse gas concentrations andfeedback processes not properly accounted for in themodels could produce greater or smaller increases.Forecast of the distribution of variables such as soilmoisture or precipitation patterns have even greateruncertainties.

To make predictions about changes in speciesdiversity and zonation on a regional scale, i.e. inSweden, we should have information not only aboutthe average temperature and precipitation but alsothe distribution of these variables during the year.Since the models are not yet good enough for thesetypes of detailed forecasting, for the sake of thediscussion we need to make some more Of lessprobable assumptions:

- There will be an increase of greenhouse gasesfrom now to 2050 equivalent to a doubling ofcarbon dioxide concentration.

The average temperature in the north of Swedenwill increase by 3-5 °C and in the south by 3-4°C.

Precipitation will increase by 10-30 %. Due to thehigher temperatures the evaporation will increasetoo.


- The length of the vegetative growing period,number of days with an average temperatureabove 5 °C, is prolonged by 50 days.

These assumptions give a climate in the Stockholmregion like we have today in the province of Scania.The inner part of Norrland will have the sameclimate as we have in the Stockholm region. Insouthern Sweden we will have a Mediterraneanclimate (cf. Figure 1).

Changed zonations. In Scandinavia it is primarilythe length of the winter period which limits thedistribution of various plant species. Locally thewater deficiency is more important and also deter-mines the formation of some vegetation types, forexample sand heath, steppes (alvar vegetation), etc.

Even if the average climate is of great importancefor the distribution of different species, extremeclimatic events determine the survival not only ofsingle individuals but also of whole populations.

Studies of climatic changes in the past have clearlyshown how the vegetation zones have changed intime with the temperature in both north-southdirections and upwards-downwards in the alpinearea. Such displaceitents are going on also today. Atthe beginning of this century the average tempe-rature was higher than during the last thousandyears. As a consequence, the mountain coniferousforests were favoured and the timberline advancedover the open alpine areas and tundra. During thelast decades there has been a remarkable deteriora-tion in the climate of this region and there has beenno seedling establishment at all, with the consequen-ce that the timberline is moving downwards again.

Another important aspect is the human influence onvegetation zones through land use. Spruce planta-tions in the deciduous region and deciduous forestsin central Sweden are some examples.

Some important effects of the climatic change inSweden can be expected:

- The timberline will move upwards in the moun-min areas and further north towards the ArcticOcean. In the same way, the borderline betweenthe southern and northern coniferous regions willmove further north but with a delay of 75-150years due to the life span of the trees. Oak(Quercus spp.), hazel (Corylus avellana) and elm

44

C< 800

E 800-900

El900-1100

E 1100-1300

TEMPERATURE ZONES

(number of daydegrees

during the vegetationperiod)

1300-1500

me , 1500

68

66

64

62

60'

58

56

Figure 1 The current abiotic temperature sones in Swedenmeasured as number of day-degrees during the vegetative period.

(U/mus sp.) will gradually become more commonabove the Limes Norrlandicus (see Table 1).


- The alpine ecosystems, especially the subalpineand low alpine, will be influenced by increasedcompetition pressure from immigrants. It is alsoprobable that the limits will move upwards (Table1).

- In southern Sweden the possibilities will be betterfor beech (Fagus sylvatica). Hornbeam (Carpinusbetulus) will establish forests further north andat the same time Norway spruce (Picea abies) willmove its western border eastwards.

- Several new tree species can be expected toimmigrate from the continent, for example silverfir (Abies alba) and sycamore (Acer pseudoplata-nus).

- The distribution pattern of many plant specieswill be affected. Most sensitive are of coursethose which have distribution limits in Sweden.In general, species with a southern distributioncan be expected to advance further north.Examples are Corylus avellana, Hedera helix andherbs like Galium odoratum, Hypericum tetrap-terum, Mercurialis perennis and Orchis mascula.Composites and sedges are expected to be especi-ally favoured by a warmer climate. However, theland use during the last decades, especially inforestry, may have decreased their dispersalpossibilities.

On the other hand, species with a northern oreastern distribution can be expected to declineeither for abiotic reasons or through competition.Examples are Betula nana, Rubus arcticus, Lac-tuca alpina and several alpine species (Table 1).

- It is difficult to speculate about effects on mires.Probably the water balance will change in diffe-rent ways. A lowering of the water table insouthern Sweden will increase the decompositionof organic material in the mires which will havean impact on existing bogs as well as the deve-lopment of new ones.

The ecosystems in southern Sweden are thoughtto be more vulnerable to water deficiency anddrought stress, for example heaths and steppes.This may have an impact on the insect fauna.

- Salt marshes will be flooded by raising of the seawater table. This will have a temporary impact onthe survival of salt marsh plant species. The

45

importance of these biotopes for bird populationswill also be aff ected.

- An increase in temperature can have negativeeffects on vegetation. Storm felling during winteris one example. The flowering of scots pine(Pinus sylvestris) is dependent on a chillingperiod and if the winter becomes warmer thenatural rejuvenation will be cancelled out. Theattack of pathogenes may increase, especiallyduring winter.

Soil formation processes are to a large degreedetermined by climate. In the northern part ofSweden it takes several hundred years for apodzol to develop. With increased temperatureand precipitation the decomposition shouldincrease and more nutrients will be available forthe vegetation.

- During the last decade there has been a constantincrease in nitrogen deposition and in southernSweden today there are several areas which showsymptoms of nitrogen saturation. With increasedtemperature and precipitation, especially duringwinter, nitrification and consequently nitrateleaching and acidification should increase. Therelease of nitrogen in the soil may also favournitrophilous plant species, i.e. the nitrogen impactwill be more obvious than today. Nettles (Urticaspp.), raspberry (Rubus ideaus) and cow parsley(Anthriscus sylvestris) are some examples ofspecies which will be favoured.

The hnportance of rate of change. It is perhapstrivial that another climate in a defined region,warmer or cooler than today, will give anothervegetation. The type of vegetation depends on themagnitude of climatic change. There may be doubtwhen or if a vegetation type of known compositionwill be established. Perhaps more important for theeffects in a short term perspective, especially for thebiological diversity, is the rate in change of climate.The projected climate changes will be much fasterthan the known changes since the last glaciationperiod.

The vegetation changes that will occur will be aresult of an immigration - extinction process, i.e. aplant succession. Immigration is determined byestablishment of seedlings of new species andextinction by death of the last adult individual of aspecies.

Table 1 Some characteristics of competitive, stress-tolerant and ruderal plants.

(i) Morphology

1. Life-forms

2. Morphology of shoot

3. leaf form

(ii) Life-history

4. Longevity of establishedphase

5. Longevity of leaves androots

6. Leaf phenology

7. Phenology of flowering

8. Frequency of flowering

9. Proportion of annualproduction devoted to sccds

10. Perennation

11. Regenerative• strategies

Physiology

12. Maximum potential relativegrowth-ratc

13. Response to stress

14. Photosynthesis and uptakeof mineral nutrients

15. Acclimation of photo-synthesis, mineral nutritionand tissue hardiness toseasonal change in tempera-ture light and moisture supply

16. Storage of photosynthatemineral nutrients

(iv) Miscellaneous

17. Litter18. Palatability to unspecialized

herbivores


Competitive

Herbs, shrubs and trees

High dense canopy of leaves.Extensive lateral spread aboveand below groundRobust, often mesomorphic

Long or relatively short

Relatively short

Well-defined peaks of leafproduction coinciding withperiod(s) of maximurnpotential productivityFlowers produced after (or,more rarely, before) periodsof maximum potentialproductivityEstablished plants usuallyflower each yearSmall

Dorrnant buds and sceds

V, S, W, Bs

Rapid

Rapid morphogenetic responses(root—shoot ratio, leaf area,root surface area) maximisingvegetative growthStrongly seasonal, coincidingwith long continuous periodof vegetative growthWeakly developed

Most photosynthate andmineral nutrients are rapidlyincorporated into vegetativestructure but a proportion isstored and forms the capitalfor expansion of growth in thefollowing growing season

Copious, often persistentVarious

Stress-tolerant

Lichens, herbs, shrubs and Herbstree 5

Extremely wide range of Small stature, lirnited lateralgrowth forms spread

Often small or leathery, or Various, often mesornorphicneedle-like

Long—very long

Long

Evergreens, with variouspatterns of leafproduction

No general relationshipbetween time of flowering life-historyand scason

Stress-tolerant leaves andr00 ts

V. BT

Slow

Morphogenetic responsesslow and small in magnitude

Strongly developed

46

Ruderal

Very short

Short

Short phasc of leaf productionin period of high potentialproductivity

Flowers produced early in the

Intennittent flowering over High frequency of floweringa long life-historySmall Large

Dormant seeds

S, W,

Rapid

Rapid curtailment of vegetativegrowth, diversion of resourcesinto flowering

Opportunistic, often uncoupled Opportunistic, coinciding withfrom vcgetative growth vegetative growth

Weakly developed

Storage stems in leaves, Confined to seedsstems and/or roots

Sparse, sometimes persistent Sparse not usually persistentLow Various, often high

•Key to regenerative strategies (considered in detail in Chapter 3): V — vegetative expansion, S — scasonal regeneration in vegetation gaps, W — numeroussmall wind-dispersed seeds or sporcs, 8, — persistent seed bank, — persistent seedling bank.


Normally, long-living plants are dominant in wellestablished plant communities, i.e. K-species orcompetitive species (Table 1). This is relevant forthe field layer also, many herbs having an averagelife span of 50-150 years. For many species, vegeta-migration rates.

When the environment starts to change, manyexisting species cannot re-establish, but the adultindividuals will keep their place for many years ordecades. At the same time, seeds from new speciescan successively occupy the empty sites. These newspecies are either better adapted to the new environ-ment or have a fast dispersal, i.e. r-species orruderal species (Table 1).

The following can be expected:

The diversity increases since immigration rate ishigher than extinction rate in a qualitative sense.This means also that new species combinations,Le. plant sociological units, will be established.

In general the ecosystems will be more destabili-zed. The environment will be more unpredictablewhich means that species with a life strategywhere more energy is allocated to reproductionthan a long life, will be favoured. There will bea change from competitive species towards moreruderal species. This will also have an influenceon several ecosystem variables.

Due to the rate of change, several ecologicalrelationships can be disturbed: host - parasite,plant - herbivore, predator - prey, etc.

47

Impact of climate change on flora andvegetation in Western Europe withspecial emphasis on the Netherlands

Pieter KetnerDepartment of Vegetation SciencePlant Ecology and Weed ScienceAgricultural UniversityBornsesteeg 696708 PD Wageningen, The Netherlands

Introduction. A global climate change is expected asa result of increased atmospheric CO2 and othertrace gases (the "greenhouse effect"). If there is adoubling of preindustrial CO2 the global meantemperature will rise by 2 to 4.5 °C. This increasewill be larger in the polar regions and less in thetropics, and will be larger in winter than in summer.A global intensification of the hydrological cycle(more precipitation and more evaporation) by 5-10 % is also expected. The most likely climatescenario for Europe is a rise in annual mean tempe-rature that exceeds the rise in global, with uncer-tainty about rise in all seasons. A larger variabilitymight initially result in decreasing winter tempera-tures. As far as precipitation patterns are concernedEurope, will follow the global tendency towardsmore precipitation and more evaporation. The periodof precipitation deficit (in Western Europe, averagesonly a few month per year) could extend fromsummer to spring.

Prediction of climate change on a scale of forexample the Netherlands cannot yet be made. A risein temperature of 2 °C (not only in the annual meanbut also in the seasonal mean, the greatest uncer-tainty in this being the winter temperature) is muchlarger than the actual differences within the Nether-lands. If the actual differences are maintained thetemperature in the southwest of the country will bemore like that in northwest France or southernEngland. An intensification of the hydrological cycleby 10 %, more precipitation and more evaporationcould result in a larger precipitation excess duringwinter and a larger deficit in spring and summer, ifseasonal rainfall patterns remain the same. Anincrease in the length of the growing season willoccur. The number of days increase will differ fromregion to region. For example, in the Netherlandsthe growing season will be lengthened by up to 30days; for the Stockholm area this will be 40 days


(Ingelög 1986), for some parts of Norway even morethan 100 days.

In France, the ecological conditions of. SW Francewill be transferred into the Paris Basin; the ecologi-cal conditions of the latter to the Lorraine. Anincrease of 1 °C will transfer the climate of theLoire Valley into the Paris Basin (Ozenda & Borel1987). Increase in precipitation will probably notcounterbalance the greater dryness (reduction ofwater supply) produced by the warming, especiallyin the regions already affected by a rain deficit (i.e.Mediterranean).

Concerning the impact of the greenhouse effect onplant species, a distinction can be made between:- direct effects as a result of increased CO,- indirect effects through climate change (tempera-

ture, precipitation, evaporation, etc.)- from climate change, derived effects such as sea

level rise, changes in sedimentation and erosionpatterns, etc.

These effects can be synergetic or counteracting.

This paper will concentrate on the indirect effects,i.e. the impact of climate change on flora andvegetation. However, it should be borne in mindthat climate is not the only factor which influencesplant growth and distribution. Not a single climaticfactor, but an interrelative complex set of variables,climatic as well as edaphic and biotic. The influenceof a climate factor can be different for each stageof the life cycle of an individual plant species.

Changes in nature resulting from climate changeswill take place at three levels:1) Direct response of individual species to changing

circumstances2) Response of two or more organisms which

naturally interact3) Response of whole vegetations/ecosystemsOf course these levels are not strictly separate.

Level 1 Direct response of individual species

Phenological response. There are numerousexamples of relations between climate factors(particularly temperature) and phenological featuressuch as date of foliation, flowering, fruit setting.

Change in temperature will give rise to changes inthe phenological features of a plant species, as was

48

well illustrated by Erkamo for certain species inFinland during a warmer period early this century(Erkamo 1952).

Figure 1 gives flowering periods for a number ofspecies in the Netherlands, based on 25 years ofobservation. An increase in temperature will shiftthese times earlier in the year. What the indicationsmay be are difficult to grasp. With an earlier spring,winter rest of flower buds of e.g. fruit trees may bebroken earlier; this might increase the vulnerabilityto frost damage (Landsberg 1981). Also disruptionof relations between flowering and pollinators mayoccur.

Higher temperatures and a longer growing seasonshould be particularly favourable for annual species,which have several life cycles per year (Therophytaepiteia). The number of life cycles may increase andthus lead to increase seed capital contributing to theweed problem, as many of these species are alreadyaggressive weeds, such as Stellaria media, Poaannua, Senecio vulgaris, and Lamium purpureum.

On the other hand, certain short-lived species mayhave greater difficulty in setting seeds underextreme circumstances (e.g. drought). For perennialsthe situation is more complex, as they can oftensurvive unfavourable periods vegetatively.

Warmer conditions and longer summers will promotea generally higher level of flower, seed and sporeproduction.

Two phenomena which are particularly vulnerableto a temperature change are seed dormancy breakingby chilling and germination responses to tempera-ture. In some arable weeds (e.g. Chenopodium album,Polygonum aviculare) requirements for chilling areallied to a need for subsequent exposure to light, orto higher temperature. These weeds form persistentseed banks, suggesting that the chilling requirementmay be implicated, initially in delayed germinationand seed burial, and subsequently in mechanisms ofsecondary dormancy, whereby germination of theburied seeds is favoured only by conditions obtai-ning in the early spring (Grime & Callaghan 1988).It can be expected that many arable weeds willgerminate earlier in the season, adding to the weedproblem. It has also been found that higher summertemperatures promote after-ripening in seeds ofwinter annuals, such as Cardamine hirsuta, Erophilaverna, Capsella bursa-pastoris and Stellaria media(Baskin & Baskin 1986). Some summer annuals like

Figure 1 Average flo-wering period of plantspecies in De Bilt, cen-tral Netherlands, recor-ded over a period of 25

1983). An increase intemperature of 2 *Cmay shift flowering ti-mes by one month tothe left.


JAN

Chenopodium album and Amaranthus hybridus athigh temperatures rapidly gained the ability togerminate at high temperature, while usually re-quiring exposure to low temperature to after-ripencompletely (Baskin & Baskin 1987). An expansionof these weedy species may be a result of climatechange.

Adaptation. Adaptation to temperature change willtake place by evolutionary adaptation, by acclimati-sation and by changes in the distribution area.

Evolutionary adaptation (=genetic adaptation of theenzymatically determined tolerance range) is a slowprocess. It can be expected that annuals and specieswith great genetic variability will react by evolutio-nary adaptation sooner than long-living species.

Acclimatisation: within its genetic tolerance rangethe species can adapt its physiological tolerancewhen it is sub jected to slow changes in its environ-

4 9

MARCH A PR M I JUNE JULY

axac&w,Prvin.s.

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01111111

Rord<;-e„,)

Az.z/es/phinium

7;lial ehlox ;' Cate;odk

DahliaSolidage

14mthchscutn,JAN FES MARCN APR I NRY JUNE I JULY AUG SEP OCT NOV DEC

Re,1 adoro(eat-4,)

Sytviyj IA zakj

Aesculuj ((dhabOn)laburm.rnCr-afaequs (Prd)

AO P T NOV EC

ment. Short-living species will probably respondquicker than perennials.

It can be expected that species with a broad ecologi-cal amplitude (e.g. euroec/eurytherm species) witha wide distribution will adapt easily, while specieswith a narrow amplitude (stenotherm species) willexperience problems.

Changes in distribution. There are numerousexamples of correlations between the occurrence ofa species and one or more climate factors, e.g. snowcover, temperature; the distribution boundary takesa similar course as a certain isotherm (average min.or max. temp. or monthly isotherm, etc. see Grace1987, Woodward 1987). This is not necessarily adirect causal relationship, but can also be a matterof reduction in the ability to compete (competitivepower), as a result of changed physical environ-mental factors (Walter 1979).

At the limits of its distribution area a species oftenbehave, differently from the centre of the area. Itis less abundant, has other environmental require-ments and different performance (including physio-logically) (Haeck & Hengeveld 1979, Grace 1987,Hengeveld 1989).

Good temperature indicators are, for instance, Ilexaquifolium and Hedera helix for which both winterand summer temperatures are important in determi-ning the ranges.

January 0°C

345 daysmaximum >0°C

Europa

•

kin


°

-

t•

q4I

c

The distribution of Hedera helix is related to thetemperature of the coldest month (-2 °C), as well asof the warmest month (ca. 13 °C); the less northerndistribution being attributed to cooler summers. Thisspecies will probably expand further north intoScandinavia, where it has been before in warmertimes (Ingelög 1986). Many examples are known

50

The east boundary of the range of Ilex is determi-ned by the January isotherm of 0 °C; better still bya line demarcating where the maximum temperatureis > 0 °C for at least 345 days per year (or theaverage temperature of the coldest month > -5 °C.In mid Holocene the species did not occur as fareast, which might indicate colder winters. In thethermal maximum after the last Ice Age the speciesoccurred much further north in Scandinavia than atpresent. Figure 2 illustrates, how Ilex may migratenortheastwards under a temperature rise, caused bydoubling atmospheric CO, .

cs

January 0°C2 x CO

Figure 2 Present distribu—tion of Ilex aquijolium.The eastern boundarycoincides well with theJanuary isotherm of 0 °C,even better with the lineshowing where the maxi—mum temperature is above0 °C for 345 days peryear. Tne January isotherrnof 0 °C under doubledCO2 is also given, indica—ting the potential changein distribution of Ilex afterclimate change.

from palynological research of species which havedeclined or increased because of climate changes,e.g. P.Mus silvestris at a marginal site in Swedenslowly declined during the Little Ice Age (1300-1850); because of a change in temperature theregenerative capacity declined and there was highmortality amongst young trees (Kullman 1987).


In the Netherlands and the adjacent part of NWGermany and in parts of England the summers willbecome somewhat continental (higher temperatures,dryness), the winter on the other hand more atlantic(warmer and humid). It is to be expected that plantswith a northern distribution (boreal and boreal-montane elements) which have southern outpostswill retreat. This is likely to be the case with Em-petrum nigrum (southern limit halfway across easternNetherlands), Trientalis europaea, Linnaea borealisand Arnica montana.

Expansion of ranges (expanding within their presentarea as well as expanding their present borders) maybe expected of species with higher temperaturerequirements and a (sub)mediterranean or medi-terranean/atlantic distribution and probably alsosome subcontinental species which may migrate viariver valleys (predominantly the Rhine, see Jongman1989). Species with high temperature requirements,and also species which are more eurytherm, may befavoured at places where they occur under subopti-mal conditions.

Species with high temperature requirements are forinstance C4 species which are adapted to warm anddry conditions, predominantly occurring in thetropics and subtropics, with increasing occurrencein the temperate zone. It is very likely that they willbe favoured by climate change.

At present there are 21 C4 species naturalised in theNetherlands, some are already spreading rapidly; 60C4 species are recorded as casuals (Van Voorst1984). Some of these C4 species are considered asthe worst weeds in the world, e.g. Cynodon dactylon,Echinochloea crus-galli, Portulaca oleracea andCyperus esculentus, some Amaranthus spp. (Holm etal. 1977). The occurrence of C4 plants is related totemperature and human activities. For monocotylesthe temperature limit of min. temp. of 8 °C is given;for dicotyles also plus the availability of water. Theyhave a short life cycle and profit from resistance tocertain herbicides and late germination. With higherspring temperatures, early and increased germinationmay be expected.

Table 1 gives a tentative list of plants which areexpanding or are inclined to do so in the Nether-lands and/or Belgium (see De Langhe et al. 1983;Heukels & Van der Meiden 1983; Van Kampen1989; E. Weeda, Rijksherbarium, pers. comm.).

51

Temperature and continentality values are givenaccording to Ellenberg (1979) or Landolt (1977).Unfortunately these values are not exactly com-parable, as Ellenberg's values apply to plants withthe core of their range in western Central Europeand Landolt's to species occurring in Switzerlandonly. For some plants no indicator values could befound; they are not considered as being naturalisedin these areas. Life form is also given.

The most striking feature is that a large number ofspecies with a mediterranean/submediterranean(south European) or subcontinental distribution, arenow expanding from southwest in a northerly(northeasterly or somewhat northwesterly) direction,a feature which is precisely what may be expectedas a logical adaptation to climate change. Many ofthe species show high temperature indicator values(7 according to Ellenberg; 4 or 5 from Landolt;species from warm places).

Several of the species are therophytes or pioneersand known from more ruderal open sites (variousGramineae). Therefore, further spread of many ofthese species may be enhanced by a gradual tempe-rature increase.

It should be emphasised that human activities suchas eutrophication and increasingly disruptive effectson vegetation (intensive agriculture, urbanisation,deforestation, dereliction and recreational pressure,creation of open spaces) have lead in the recent pastto the explosive spread of many weedy species inWestern Europe.

The ability of a species to expand its area dependson its mobility, i.e. its dispersal capacity and itsmigration rate, as well as the accessibility of thenew area. Rare species with specific environmentalrequirements may not be able to effectively migrate,even when climate change may favour reproductionand vigour. Other species may be too slow tomigrate to new suitable habitats.

Level 2 Interaction between 2 species

Because each species has a different ecologicalrelationship to climate, climate change will elicit animmediate and individualistic response from eachspecies, thus altering the competitive balance amongspecies in a vegetation. What the outcome may be ofthese changes in competitive power is difficult to

Family:

Amaranthaceae

PortulacaceaeCyperaceae

Gramineae

ChenopodiaceaeUrticaceae

Papaveraceae

Cruciferae

ResedaceaePapilionaceae

EuphorbiaceaeLythraceaeUmbelliferae

Balsaminaceae

MalvaceaeGentianaceaeScrophulariaceae

Orobanchaceae

©Norwegian institute for nature research (NINA) 2010 http://www.nina.noPlease contact NINA, NO-7485 TRONDHEIM, NORWAY for reproduction of tables, figures and other illustratibns in this report.

Table I Preliminary list of species which are spreading in the Netherlands and/or Belgiumand surrounding areas. The distribution of these species may be enhanced by a temperatureincrease. L life form; T, K & N = indicator values according to Ellenberg or Landolt(italics): T = temperature, K = continentality and N = nitrogen; F = neophyte; W = weedy.See also footnote.

Species: L TKN F W Remarks:

C4-species:Amaranthus blitoidesAmaranthus retroflexusPortulaca oleraceaCyperus esculentusCyperus fuscusCynodon dactylonDigitaria ischmaenumDigitaria sanguinalisEchinochloa crus-galliEragrostis minorEragrostis pilosaSetaria glaucaSorghum halepense

CR-species:Chenopodium botrysParietaria judaicaParietaria officinalisCorydalis claviculataFumaria muralisCardaminopsis arenosaCardaria drabaCoronopus didymusDescuriania sophiaDiplotaxis tenuifoliaRapistrum rugosumSisymbrium austriacumReseda luteolaMedicago arabicaMedicago minimaMercurialis perennisLythrum hyssopifoliaOenanthe crocataFalcaria vulgarisImpatiens glanduliferaImpatiens balfouriAbutilon theophrastiBlackstonia perfoliataLinaria repensLinaria supinaParentucellia viscosaVeronica peregrinaLathraea clandistina

t 777 t 979 t 837 - - -

t 64 4 g,h 7 3 5

t 643 t 733 t 75

4 t 754 t 7 3 ?

t 7 46 t - - -

t 926 h 727 h 747 t 6 1 ?

- - -h,c X 4 3h,g 7 7 4

t 424 t 6 76 c,h 7 3

4t 4 24 h,t 7 5 7

tb 7 3 3- - -

t 731 h,c 5 3 7

t 753 h,g 5 2 3

h 763 t 727 t 534 t 534

t 73 4 h 444 c 44

2 - - -

t 424 - -

52

x x alienx x N Amer., subcosm.x x trop.x x trop.- -x x subcosm.x x temperatex x subcosm.x xx x trop., warm-temp.x x trop., warm-temp.x x subcosm., warm-temp.x x S Eur., trop.

med., S Eur.S/SW Eur.C & S Eur.W Eur., atl.S & W Eur., ruderalN & C Eur, ruderalS & C Eur.alienruderalS, W & C Eur., ruderalS Eur., ruderalSW & C Eur.S, W & C Eur., ruderalS/SW Eur,S Eur.S & C Eur.subcont.SW Eur.Med./S Euralien, ruderalatienalienW Eur., atl.SW Eur., ruderal

S/SW EuralienSW Eur.



Footnote

L C

53

Herbacecus chamaephyte, herb with buds above the groundHemicryptophyte, buds near the groundGeophyte, buds within the soil, often with storing organsTherophyte, short living "annual" plant

K 1 euoceanic, reaching Central Europe only in the extreme west2 oceanic3 between 2 and 44 suboceanic, main area in whole Central Europe5 intermediate, from suboceanic to subcontinental6 subcontinental, main area in eastern Central Europe7 between 6 and 8

Ellenberg 1979T 5 moderate warm climate

6 intermediate7 mostly in warm climate (more or less rare in northern Central Europe)8 intermediate9 only in very warm climate (mediterranean)

N 1 only in soils very poor in mineral nitroge'n3 mostly in poor soils5 mostly in intermediate soils7 mostly in soils rich in mineral nitrogen8 nitrogen indicator9 only in soils very rich in mineral nitrogen (indicating pollution, manure deposits or similars)

Landolt 1977T 4: Plants occurring chiefly in the colline region in summy places also higher. Plants widely distributed

in the lower regions of Central Europe.Plants occurring only in the warmest situations. Plants chiefly found in Southern Europe.5:

K 2:

3:

4:

N 2:

3:

4:

5:


Plants occurring chiefly in regions with sub-oceanic climate; they cannot stand late frosts or greatextremes of temperature.Plants occurring chiefly outside extreme continental regions. Found almost everywhere in theregion.Plants occurring chiefly in regions with relatively continental climate; capable of withstandingextremes of temperature, low winter temperatures and slight air humidity; not found in placeswhere the snow lies for long periods.

Plants occurring chiefly on poor soils; usually not found on rich to over rich soils, or not able tocompete there. Indicators of poor soil.Plants occurring chiefly on medium poor soil to medium rich soil; neither found on very poor soilnor on over fertilized soils.Plants occurring chiefly on rich soils, hardly found on poor soils. Indicators of rich supply ofnutrients.Plants occurring chiefly on soils with over-rich supply of nutrients (usually nitrogen); never foundon poor soil. Indicators of over fertilization, in water, indicators of pollution.

foresee. It may have immediate impact on thecompetition between crops and weeds, where C3weeds may compete over C4 crops or vice versa.

Other interactions are plant/pathogen and plant/an-imal. Pests and diseases may be enhanced by climatechange, such as rusts in wheat, outbreaks of whichare related to certain temperature levels.

Level 3 Response of natural vegetation

The global distribution of the main vegetation zonesof the world as well as altitudinal zonation arepredominantly determined by rainfall and tempera-ture (Holdridge 1967, Walter 1979). Change inclimate will induce changes in these zonationpatterns.

Several analogies can be mentioned. During theclimate optimum in the Holocene (6500 BP) tempe-rature was 2-3 °C higher; the northern limit of theboreal zone was situated 200-300 km further north.In the Alps the treeline and snow line were situatedabout 400 m higher; in England and Scotland200-300 m. During the warmer period of the MiddleAges, the treeline in northern England lay about150-200 m higher (Ford 1982).

54

An increase of 2-4 °C would mean an altitudinalshift of vegetation zones of up to 700 m. Many plantspecies will be bound to disappear as they will notfind their suitable habitat any longer (see Figure 2in Peters & Darling 1985).

Simulation studies by Emanuel et al. (1985) and DeGroot (1988) show potential shifts in the majorvegetation zones. The largest alterations would takeplace in the tundra and boreal forest zones. Thetundra may disappear almost completely and bechanged to a taiga-like vegetation with birch andconifers, comparable to the present taiga. The borealforest zone may change to another forest typeadapted to a cool temperate climate or change intosteppe, depending on precipitation.

Van Huis & Ketner (1987), in a study about climatesensitivity of natural ecosystems, looked at thepossible vegetation changes in various national parksin Europe, using the GISS climate scenario (Hansenet al. 1984, Bach 1986) to simulate new local clima-tes. For Scandinavia, the Hardangervidda was takenas the example.

Figure 3 shows the hypothetical vegetational changeswhich may occur in this area, assuming the follo-wing climate changes:

Figure 3 Sehematiccross seetion of the ve-getation sonation (hy-po thetical situation) onthe Hardangerviddaplateau, under presentclimatic conditions andunder simulated condi-tions after doubling theCO , content of theatrriosphere (for detailssee Van Huis & Ketner,1987).


»00

1110f

/100

1401)

1141

100

'00A

1,00

800

2 8 13 7 1 3 1

ACTUAL SITUATION

1

SINULATED SITUATION

1 taiga

2 t birch forest

3 .4.4 willow thicket5

1 71

On the mountain plateau at 1000 m a.s.l. awarmer climate will not rule out the frost periodand the probability of extreme weather condi-tions. The frost period will be shortened by 2months from the end of November until thebeginning of April, but there will be more snow.

Hardangerglacee

glacier?

55

1 6 1 4 1 10 16 1 41 g I 2 I 1

4 7It grass heath

S 0 1 dry meadow

.4* wet meadow

7 l 2 110131910 z 1

7 ffiff mire

6 1» moss heath

lichen heath

iO * fjell mark

* Important are the higher mean summer tempera-tures together with the rise in the number of daysabove 10 °C to 50, allowing tree growth.

* A strong increase in precipitation from 730 mmto almost 1000 mm annually with weak peak


values (80-100 mm) in midsummer and in earlywinter.

The precipitation in winter can be expected as snow,resulting in a snow cover that is thicker than thepresent-day one.

Evaporation will not increase parallel to theincreased precipitation under the new conditions(i.e, humid climate). The result will be surpluswater; more runoff can be expected, with conse-quences for the regional hydrological conditions.The effects will be most pronounced in latewinter and spring.

A comparable present-day elimate is found on thewestern mountain slope and fjord coast aroundTrondheim (127 m a.s.1.).

Figure 4 gives the degree of impact of climatechange in natural ecosystems in Europe. For thedetails see Van Huis & Ketner 1987.

Discussion. These studies are all very conjecturaland speculative, and whether all such changes willtake place remains to be seen. However, if thepredictions about climate changes are correct thenthis climate change is already taking place andnature is reacting to it, although this is still notobservable. There is no abrupt climate change noran abrupt response from nature.

There are many factors which cause changes in therange of species. Changes in the occurrence ofspecies take place continuously. It will therefore bedifficult to single out climate change as the drivingforce (Van Kampen 1989). However, the conclusionof Grime & Callaghan (1988) that "The currentland-use policies are conducive to rapid floristicresponse to climate change and will encourageinvasion by thermophilous species (also aliens) witha "weedy" (i.e. fast-growing and fecund) character"is to be taken seriously, as is illustrated in the above.

So far nothing has been said about the time-spanover which these possible changes may take place.It is impossible to make any prediction. One reactionpattern may occur within some decennia (change indistribution area), while the other requires a longertime scale (change of total vegetation composition).Because of the rate at which climate change is goingto take place (doubling of CO 2 in the next 50-100years), a normal gradual course in the processes ofadaptation, acclimatisation and natural migration is

56

less likely, considering the life-spans of manyspecies such as trees.

Lags in the response of the vegetation to climatechange can occur for many reasons, e.g.

* Effective geographical dispersal barriers, such asopen water, high mountain ranges, highly ex-ploited areas such as large agricultural areas.

* Poor accessibility because of unfavourableedaphic conditions. Will a deciduous forest beable to establish on the wet, acid, taiga soils? Orwill a mediterranean vegetation from a calcareoussoil be able to move to northern soils whichpredominantly are humic and acid? "Mismatches"will occur and species will be hampered in theirmigration.

* Low adaptability to additionally changed en-vironmental factors, such as day-length.

* Competition from resident plants that continueto occupy space under the changed clirnateconditions.

* Direct and indirect effects of atmospheric pollu-tion, e.g. accumulation of nitrogenous deposits inthe soil. At higher temperatures, N availabilitywill be enhanced. This process limits plantestablishment and will be favourable for ni-trophilous species with a more ruderal character.

* Ecotypic variation within the range of a species.* Inadequate dispersal capacity and migration rate.

Relatively little is known about migration rates ofplant species. From palynological studies, Davis(1986) has shown that Norway spruce (Picea abies)9000 yrs ago migrated at a rate of 200 km percentury; other tree species migrated far more slowly(10-40 km per century). The predicted temperatureincrease of 2-4 °C in mean temperature over thenext 50 years corresponds to a shift of up to 350 kmin the boundary of a species range. If species are toremain in areas with equitable climate they have tomigrate at rates of the order of I m/hourcited in Dobson et al. 1989).

Changes in flora and vegetation in the coming 50years will therefore probably not be as large asclimate change would allow, because of a highnumber of retarding factors. An immediate responsei.e. an alteration in the competitive balance amongspecies in the vegetation, will occur; some specieswill spread rapidly into new areas, others may notand may decrease in occurrence. The whole compe-tition process in a community itself may take many

z-1


offis vary largeE=3 large

moderateslight

Figure 4 Schematic representation of the impact of climate change on natural ecosystems in Europe (after van Huis & Ketner 1987).

decades to work through into a visible changednatural vegetation (cf. Ingelög 1986).

Extreme climate events may enhance certain de-velopments, e.g. catastrophic die-back of forestscaused by drought or frost.

In vegetation types which are continuously underhuman influence (as is the case with many plant

57

communities in highly agricultural countries) chan-ges may be visible sooner than in natural stablevegetation such as climax forest (see also Van Huis& Ketner 1987).

Vegetation is spatially and temporally non-static.Changes take place continuously. There are externaland internal fluctuations but a striving towards adynamic equiIibrium.


If atmospheric CO, has doubled and if climate haschanged as predicted, then we still have to bear inmind that there will be no equilibrium situation inthe natural environment.

An equilibrium will only be obtained if externalfactors remain relatively constant over a long periodof time, fluctuating around a long-term mean.

Research needs

* Phenological research:- analysing older phenological data

phenology of species within their range overa temperature gradientwhat is known about phenological behaviourduring extreme climatic events?

* Studies on explosive invasion of species, in-cluding aliens.

* Population research of certain species along aclimate gradient.

* Migration studies at the boundary of the range ofa species.Is a threshold value the cause of that boundary?

•

Studies on isolated populations of the samespecies; in what way have ecotypes evolved?

* Temperature requirements for germination;periodicity of seed bank in relation to tempera-ture.

* Dispersal strategies and dispersal rates.

* Impact of corridors (ecological infrastructure) ondispersal of plants.

Conclusions

* There will be an individualistic dynamic responseby plant species to climate change, in growth aswell as in distribution.

* Each species will have its own rate and directionof migration from its present habitat.

* Direction of migration will be determined by thepresence of competitors, local environmentalconditions and human activities.

58

* The ability to compete, i.e. competitive powerdetermined by e.g. a complex of environmentalfactors and surrounding species, will change.

* Some species may be too slow to react and will belimited in distribution or become extinct.

* Other species may vanish because suitable habi-tats are no longer available or cannot be reached.

* Thermophilous species will be favoured bytemperature increase, C4 species may have anadvantage over C3 species; fast-growing andfecund species will be favoured.Many of these types of species are weedy species,thus contributing to a weedification of NWEurope.

* Present land-use policies will add to this weedifi-cation problem.

* New species combinations - new vegetation types- will appear.

* The magnitude of the impact will be stronglydependent on geographical location, habitat type,lag times and the way in which a system will beable to adapt to new circumstances. A temperateclimax forest may experience fewer big changesthan for instance an alpine grassland.

References

Bach, W. 1986. GCM-derived climatic scenarios ofincreased atmospheric CO, as a basis for impactstudies. - In Parry, M.L., Carter, T.L. & Konijn,N.T. eds: Assessment of climate impacts onagriculture. I. High latitude regions. Reidel,Dordrecht.

Baskin, .I.M. & Baskin, C.C. 1986. Temperaturerequirements for after-ripening in seeds of ninewinter annuals. - Weed Research 26,6: 375-380.

Baskin, J.M. & Baskin, C.C. 1987. Temperaturerequirements for after-ripening in buried seedsfor four summer annual weeds. - Weed Research27,5: 385-389.

Davis, M.B. 1986. Lags in the response of forestvegetation to climatic change. - In Rosenzweig,C. & Dickinson, R. Climate-vegetation interac-tions. NASA Conf. Publ. 2440, Greenbelt,Maryland.

De Groot, R.S. 1988. Assessment of potential shiftsin Europe's natural vegetation due to climaticchange and some implicatiOns for nature conser-vation. - IIASA, Laxenburg, Working paper 88-105, 29 pp.

De Langhe, J.E. 1983. Flora van Belgie, het Groot-hertogdom Luxemburg, Noord Frankrijk en de


aangrenzende gebieden. - Uitgave NationalePlantentuin van Belgie.

De Langhe, J.E., Delvosalle, L., Duvigneaud, J.,Lambinon, J. & Vandenberghen, C. 1983. Floravan België, het Groothertogdom Luxemburg,Noord-Frankrijk en de aangrenzende gebieden. -Uitg. Patrimonium van de Nationale Plantentuinvan Belgié, Meise. 970 pp.

Dobson, A., Jolly. A. & Rubenstein, D. 1989. Thegreenhouse effect and biological diversity, -TREE 4,3: 64-68.

Ellenberg, H. 1979, Zeigerwerte der GefIsspflanzenMitteleuropas 2nd edition. - Scripta GeobotanicaIX, Göttingen. 122 pp.

Emanuel, W.R., Shugart, H.H. & Stevenson, M.P.1985. Climatic change and the broad-scaledistribution of terrestrial ecosystem complexes. -Climatic Change 7,1: 29-43.

Erkamo, V. 1953. On plant-biological phenomenaaccompanying the present climatic change. -Fennia 75: 25-37.

Fitter, A. 1972. An atlas of the wild flowers ofBritain and Northern Europe. - Collins, London.272 pp.

Ford, M. J. 1982. The changing climate: responsesof the natural fauna and flora. - Allen & Unwin,London. 190 pp.

Grace, J. 1987. Climatic tolerance and the distribu-tion of plants. - New Phytol. 106 (suppl.): 113-130.

Grime J.P. & Callaghan, T.V. 1987. Direct andindirect effects of climate change on plantspecies, ecosystems and processes of conservationand amenity interest. - Contract report to theDepartment of the Environment, Sheffield, 26PP., aPP.

Haeck, J. & Hengeveld, R. 1979. Biogeografie enoecologie: over verschillen in mate van voorko-men binnen het soortsareaal. - Vakbl. Biol. 59,3:26-31.

Hengeveld, R. 1989. Dynamics of biological in-vasions. - Chapman & Hall. 160 pp.

Holdridge L.R. 1967. Life zone ecology. 2nd Ed. -Trop. Res. Center, San Jose, Costa Rica. 206 pp.

Holm, G.L., Plucknett, D.L., Pancho, J.V. & Her-berger, J.P. 1977. The world's worst weeds: dis-tribution and biology. - Univ. Press Hawaii,Honolulu. 609 pp.

Ingelög, T. 1987. Impact on nature conservation. -In E.A. Koster & H. Lundberg, eds. Impactanalysis of climatic change in the Fennoscandianpart of the boreal and subarctic zone. Reportprepared for the European Workshop on Inter-

5 9

related Bioclimatic and Land-use Changes, Oct.1987, Noordwijkerhout, 69-75.

Jongman, R.H.G. 1989. Regional data for assessingclimate sensitivity. I. The use of climate classifcation. - In Jongman, O.R.H.G. & Boer, M.M.eds. Landscape ecological impact of climaticchange on fluvial systems within Europe. Dis-cussion report prepared for the Europ. Conf. onLandsc. Ecol. Impact of Climatic Change, De-cember 1989, Lunteren, The Netherlands.

KOnnen, G.P. (ed) 1983, Het weer in Nederland. -Thieme Zutphen. 143 pp. -

Kullman, L. 1983. Little ice age decline of a coldmarginal Pinus silvestris forest in the SwedishScandes. - New Phytol. 106: 567-584.

Landsberg, J.J. 1981. Sensitivity of fruit trees toclimatic change. - In Climate change and Euro-pean agriculture. Seminar paper 12: 45-47. 1Centre for European Agricultural Studies.

Landolt, E. 1977. Oekologischer Zeigerwerte zurSchweizer Flora. - Veroeffl. Geobot. Inst. ETHRuebel, Zuerich. 208 pp.

Ozenda, P. & Borel, J-L. 1987. Impacts on vegeta-tion of climatic changes due to increasing tracegas concentrations: scenarios for The WesternEurope. - Paper prepared for the EuropeanWorkshop on Interrelated Bioclimatic and Land-use Changes, Oct. 1987, Noordwijkerhout,Netherlands.

Peters, R.L. & Darling, J.D.S. 1985. The greenhouseeffect and nature reserves. - Bioscience 35,11:707-717.

Van der Meyden, R., Weeda, E.J., Adema, F.A.C.B.& de Joncheere, G.J. 1983. Flora van Nederland.- Wolters-Noordhoff, Groningen. 583 pp.

Van Huis, J. & Ketner, P. 1987. Climate sensitivityof natural ecosystems in Europe. - Discussionpaper, prepared for the European Workshop onInterrelated Bioclimatic and Land-Use Changes,Oct. 1987, Noordwijkerhout, Netherlands. -Dept.Veget. Sc., PLEcol. & Weed Sc. Agric. Univ.Wageningen. 151 pp.

Van Kampen, M. 1989. Mogelijke gevolgen van eenCO -geinduceerde klimaatverandering voor denederlandse flora: een orienterende studie. -M.Sc. thesis, Dept. Veget. Sc., Plantecol. & WeedSc. Agric. Univ. Wageningen, Netherlands. 61 pp.& app.

Van Voorst, A. 1984. Het C4-fotosynthese systeem.Een literatuur studie met speciale aandacht voorC4-species in Nederland. - M.Sc. thesis Dept.Veget. Sc., Pl. Ecol. & Weed Sc. Agric. Univ.Wageningen, Netherlands.


Walter, H. 1979. Vegetation of the earth and ecolo-gical systems of the geo-biosphere. - 2nd ed.Springer Verlag. 274 pp.

Walter, H. & Straka, H. 1970. Arealkunde, flori-stisch-historische Geobotanik. - Verlag EugenUlmer, Stuttgart.

Woodward, F.I. 1987. Climate and plant distribution.- Cambridge University Press. 174 pp.

60

Presuppositions for the effect scenario

In 1978-84, the vertical distribution and habitats of150 taxa, 91 vascular plants, 34 mosses, 8 hepaticsand 17 Iichens, were mapped in a coast-inlandtransect in Central Norway (Figure I). Hypothesesconcerning limiting factors for the distribution ofspecies were put forward. It was suggested that themajor climatic factors determining the distributionpatterns are summer temperature, winter tempera-ture and humidity. In this context, the emphasis isput on summer and winter temperatures, due to thevery uncertain rainfall scenarios.

Figure 1 The location of the area investigated.


Predicted floristic change and shift ofvegetation zones in a coast-inlandtransect in Central Norway

Jarle I. HoltenNorwegian Institute for Nature ResearchTungasletta 2N-7004 Trondheim

61

The taxa mapped in the work of Holten (1986) weregrouped into four main types of vertical distributionbased on the factors suggested.

The coast-inland transect has very steep tempera-ture, moisture and elevation gradients that sharplydefine the western, eastern, upper and lower limitsof species. The transect is found to be very wellsuited for studies of the cause/effect relationshipbetween climatic factors and plant distribution. Inaddition, steep gradients are convenient for thestudy of ecotones and migration of species whenresearch and monitoring programmes on the ecologi-cal effects of climatic change are being carried out.

Climate scenario for Norway

The climate scenario used in the present effectscenario has been worked out by a group of Nor-wegian climatologists (see Grammeltvedt, thisvolume) during the winter of 1990. The generallyaccepted temperature scenario for a 2 x CO2 at-mosphere is:

coast line •

Breidvik Grisvåg

'


- mean temperature increase for December, Janu-ary and February ca 4 °C

- mean temperature increase for June, July andAugust ca 2 °C.

Rainfall will also show a general increase - 5 to15 % spread through the year depending on distancefrom the coast and time of year. The prediction thatground moisture will increase during winter anddecrease during summer is thought to be of greatecological significance, at least for the position ofwestern and eastern limits of continental (xerophi-lous) and oceanic (humidiphilous) plant species (seebelow).

For the specific coast-inland transect in CentralNorway we have made a simple prediction of thetemperature trend through the year, based onmonthly mean temperatures (Figures 2a and 2b). Theoceanic station of Kristiansund has a gentle tempe-rature curve, indicating a high degree of thermicoceanicity. The predicted 2 x CO2 curve indicatesstill higher thermic oceanicity for Kristiansund(Figure 2a). Using a base temperature for growth of6 °C, the growing season in Kristiansund will beextended by 110 days, that is to 303 days. Since 6 °Cis probably a relatively high base temperature, thegrowing season in coastal areas of Western andCentral Norway will be 365 days. Using the samereasoning for Hjerkinn, the growing season wouldbe extended by only 36 days in the new climate, dueto the much steeper temperature curves at continen-tal stations. The extension of the growing season inthe fjord and valley districts will be intermediatebetween the 36 days at Hjerkinn and the 110 daysat Kristiansund.

The warmer climate will certainly have greatconsequences for the distribution of snow in winter.The changed position of the zero degree isotherm(see Figure 3) will give a rough indication of thenew "snow limir. No doubt the position of this"snow limit" will have great significance for ecolo-gy, and therefore for the distribution of plants and,through them, animals. The predicted temperaturescenario for Norway will result in snow-free moun-tains up to about 700-900 m above sea level incoastal and fjord districts, not taking into accountthe very uncertain rainfall scenario.

20

10

62 --

YearKRISTIANSUND (23 m) 1xCO2: 7.0°

=C 1xCO2: 1121 mm

1xCO2

2xCO2

GrowIng season193 da $

303 da $

2xCO2

6°1xCO2

Figure 2a The yearly trend of monthly mean temperatures atpresent and under the 2 x CO2 scenario for the oceanic Kristian-sund station. The growing season indicated by the horisontal barbeing extended by 110 days under the 2 x CO2 seenario.

Figure 2b The yearly trend of monthly mean temperatures atpresent and under the 2 x CO2 cenario for the continentalHjerkinn station. The growing season indicated by the horizontalbar being extended by 36 days under the 2 x CO2 scenario.

Fig-ure 3 The positione of the14 °C isotherm for July andthe 0 °C isotherm for January,under current conditions andunder the Norwegian 2 x CO2climate scenario.


1500

1000

500

Coast

14°C July0°C January

_

Hypotheses for explaining vertical plant distribution

The good correlation between vertical distributionpatterns and climatic parameters (Holten 1986) hasled to the following hypotheses and predictionsregarding the vertical distribution of species andplant communities in a warmer Central Norway.

Basic hypotheses for general plant distribution in thecoast-inland transect are:- low winter temperatures are the main limiting

factor towards inland for frost-sensitive plants(good correlation between eastern distributionlimits (frost limits) and the position of Januaryisotherms has been documented),

- high winter temperatures are an importantlimiting factor for some continental species thatavoid coastal areas with mild winters (goodcorrelation between western distribution limitsand position of January isotherms has beendocumented),low summer temperatures are the main limitingfactor towards higher elevations for more or lessthermophilous plants (good correlation betweenupper limits (ripening limits) and the position ofJuly isotherms has been documented),

63

0°C January (2xCO2

14°C July (2xCO2) •

January (1xCO2)14°C July (1xCO2)

25 50 75 100 125 kmInland

- low humidity (low hygric oceanicity) is the mainlimiting factor for humidiphilous plant species(hygrophytes) towards inland and the lowlands(good correlation between eastern distribution1imits and the position of precipitation isohyetshas been documented),high humidity (high hygric oceanicity) is animportant limiting factor for xerophilous andcontinental plant species towards the more humidcoastal areas (good correlation between westerndistribution limits and the position of precipita-tion isohyets has been documented).

The high degree of coincidence between distributionlimits and limiting ecological factors is schematicallyillustrated in Figure 4 and defines 6 main types ofdistribution:

thermic oceanicity (winter temperatures) definesthe eastern limits of frost-sensitive coastal plantsand the western limits of eastern plants that avoidareas with mild winters ("southwest coast avoi-ders" (Dahl 1951),summer temperature (high temperature demands)defines the upper limits of thermophilous(warmth-demanding) lowland plants and probablythe lower limits of some mountain plants,

COAST

increase- decrease- existence threatened (extinction)

no change


- hygric oceanicity (humidity) defines the easternlimits (and sometimes the lower limits) of humi-diphilous coastal plants and the western limits ofcontinental and xerophilous plants.

The prediction below about plant distribution underthe Norwegian climate scenario (see Grammeltvedt,this volume) is based on the hypotheses above. Inaddition, it is suggested that the predicted change inclimate will not lead to ecosystem collapse, includingthe extensive death of species and communities.Instead, the main response in the ecosystem will bea change in interspecific competition leading tochanges in the floristic composition of plant com-munities.

The response in species groups to climatic change

The response of plants to climatic change is specificfor the individual species. Four main types ofresponse can be distinguished:

sk)Nitt4tøk

0C

'.› k

64

INLAND

Frost - sensitive species (winter-thermophilousspecies). The predicted increase in winter tempera-ture of 4 °C will certainly greatly influence thermicoceanicity (see Figure 3), and theref ore some frost-sensitive coastal vascular plants in the transect. Forthe coastal station of Kristiansund this will result ina January mean temperature of 5-6 °C, comparablewith central parts of England today. Using thedisplacement of January isotherms from Figure 3and the hypothesis for the limitation of frost-sensitive plants (see above), we are able to predictthe potential distribution. Comment We may callthis method correlative modelling of species dis-tribution in relation to climatic change, as it is basedon a more or less good correlation between isothermsor isohyets and distribution limits.

It is predicted that the following frost-sensitiveplants (see Figure 5) will expand eastwards along thefjords in Central Norway and to higher levels (theapproximate limiting January isotherm towardscolder areas is indicated in °C):

Ilex aquifolium 1Chrysosplenium oppositifolium 0.5Asp lenium adiantum- nigrum 0.5Dryopteris borreri 0.5

Figure 4 A schernatical repre-sent ation of the main ecologi-cal factors limiting plant dis-tribution in the coast-inlandtransect.

Sedum anglicumLonicera periclymenumPrimula vulgarisCarex binervisHyperiurn pulchrum (Figure 5)Conopodium majusPolygala serpyllifolia

Figure 5 Present (= mapped)(dots) and predieted (shadedarea) vertical distribution offrost-sensitive species in thecoast-inland transect fromKristiansund to the mainwatershed on the Dovremountain plateau. Verticalaxis: height a.s.l. Horisontalaxis: distance from the coast(after Holten 1986).


M Hypencum pulchnim

1500

1000

500

Eastern and northeastern species (southwest coastavoiding species). Many eastern and northeasternplant species have a distribution that is complemen-tary to that of the frost-sensitive plants, and it issuggested that they have the opposite response tochanges in thermic oceanicity (here expressed asJanuary mean temperatures). The eastern andnortheastern plants in Norway have their maindistribution areas in northeast Europe or even insome cases Siberia. These plant species demand a"real winter rest", that is, in the autumn their stalkswither entirely and the plant has no physiologicalactivity. The underlying physiological mechanismexplaining the lack of eastern and northeasternplants in the winter-mild districts of West Europeis not very well known. However, good correlationsbetween their western distribution limits and thetrend of January isotherms have been shown (Dahl

0 Digitalis purpurea -30 Luzula sylvatica -40

- 1 The prediction indicated in Figure 5 is of course a-1 simplification as we have not considered such- 2 factors as topography, geology, interspecific compe--2.5 tition, etc.

50Coast

65

75 100 125 kmInland

1951, Holten 1986, Salvesen 1988, 1989). In Scandi-navia, at least in Sweden and east of the mainwatershed in Norway, the eastern and northeasternspecies group is rich in species, especially in borealconiferous and subalpine birch forest, boreal miresand arctic/alpine areas (see below). The role playedin the vegetation by these more or less continentalplant species rapidly decreases west of the mainwatershed in Norway. The most important treespecies in Scandinavia, Norway spruce (Picea abies),belongs to this group, although it has no naturaloccurrences in the coast-inland transect. The mostimportant southwest coast avoiders (see Figures 6and 7) in the transect are listed below (see alsoHolten 1988, Salvesen 1988, 1989) (the approximatelimiting January isotherm towards winter-mild areasis indicated in °C):

m Viola

1500-,

1000

500

©No.rwegian institute for nature research (NINA) 2010 http://www.nina.noPlease contact NINA, NO-7485 TRONDHEIM, NORWAY for reproduction of tables, figures and other illustrations in this report.

Coast

Coast

25

• i.

NINNew•

iow wwei

66

50 75 100 125 kmInland

25 50 75 100 125 kmInland

Figure 6 Present (= mapped)(dots) and predieted (shadedarea) vertical distribution ofa southwest coast avoidingspecies (eastern species) in thecoast-inland transect (afterHolten 1986).

Figure 7 Present (= mapped)(dots) and predicted (shadedarea) vertical distribution ofa southwest coast avoidingmountain species in the coast-inland transect.

Carex heleonastesCarex capitataCarex aquatilisEpilobium davuricumBotrychium borealePetasites frigidusSalix starkeanaCarex vesicariaPolemonium caeruleumPoa remotaCarex buxbaumiiScirpus hudsonianusViola mirabilis (Figure 6)Arabis glabraAconitum septentrionaleViola bifloraCalamagrostis stricta s.l.Goodyera repensMoneses unifloraScheuchzeria palustrisCorydalis intermediaCarex digitataHypericum hirsutumLathyrus vernusPyrola chloranthaGagea luteaActaea spicata



0.50.50.51

It is predicted that the western limits of the abovespecies will show a general retreat eastwards in thetransect. Some of the species may have to retreateast of the main watershed to find a sufficiently lowthermic oceanicity for their existence, for exampleCarex heleonastes and Carex capitata.

Humidiphilous coastal species (hygric oceanicspecies). The dampness of air and soil depends onthe relationship between precipitation and eva-potranspiration at a specific site. The rainfallscenario (Eliassen & Grammeltvedt 1990) shows a 5-15 % increase in rainfall, depending on the regionand the time of year. The growing season is likelyto receive an increase in rainfall of about 10 %,according to DNMI and NILU. However, due to theincrease in both summer and winter temperatures,increased evapotranspiration will largely compensatefor this. The net result will probably be drier soilconditions in the growing season, including a lowerwater table in most places.

The preliminary snow cover scenario shows a longerseason without snow, up to 85 days shorter winterfor the simulated west Norwegian climate (N.R.Sælthun, pers. comm.). This is consistent with

-12 predicted extension of the growing season in conti-- 10 nental areas (Figure 2b). The response which the-7 humidiphilous coastal plants will show to the-6 changed humidity is somewhat uncertain. The most-6 typical humidiphilous coastal plants, belonging to- 6 oligotrophic mire, heath and forest vegetation in- 6 western and central parts of the transect are (ap-- 6 proximate limiting yearly rainfall isohyet towards-5 the drier continental areas indicated in mm):

67

Cornus suecicaNarthecium ossifragumBlechnum spicantThelypteris limbospermaScirpus cespitosus ssp. germanicusErica tetralixPedicularis sylvatica

700-800800900

110013001400

The lower limits of humidiphilous coastal plants willprobably retreat in the lowlands of inner districts ofthe transect, because shorter winters and thereforelittle or no snow protection in winter will result inincreasing exposure to occasional frosty periods andto drying out at their lower and eastern limits.

Xerophilous eastern (continental) species (xerophy-tes). The western and in some cases the upper limitsof xerophilous and continental pIant species aredetermined by excessive humidity, (here expressedas annual rainfall), just as the eastern and sometimeslower limits of humidiphilous coastal plants aredetermined by too low humidity. Hence, manyxerophilous species are complementary to manyhumidiphilous ones. The most extreme xerophilousvascular plant species in the transect, in decreasingdegree of xerophili downwards in the table, are(approximate limiting rainfall isohyet towards wetterareas indicated in mm):

Androsace septentrionalisCarex ericetorumThalictrum simplexRanunculus polyanthemusViola rupestrisDianthus deltoidesCarex ornithopodaPuisatila vernalisHeracleum sibiricum spp. sibiricumPlantago mediaAcinos arvensisCotoneaster integerrimusViscaria vulgarisCarex muricataFestuca ovina

600600600600700700800800900900900

1000100012001200

The probable response of xerophilous plants is thatthey will increase and expand westwards andtowards higher levels, due to the predicted decreasein soil dampness in the growing season and shorterwinters.

Thermophilous species (warmth-demanding speei-es). The distribution of thermophilous species(lowland species) is complementary to that ofmountain plants. The summer temperature scenario(ca 2 °C increase) indicates a general expansion ofthis plant group. The most common thermophilousspecies with upper and northern limits in thehemiboreal or southern boreal zones in Scandinavia,but also occurring in the coast-inland transect, arelisted below, arranged according to decreasingtemperature demands downwards (see Figures 10,12, and 13):

Rubus nessensisCephalanthera longifoliaQuercus roburTorilis japonicaAlliaria petiolataLuzula campestrisFestuca giganteaCarex sylvaticaBromus benekeniiBrachypodium sylvaticumEpipactis helleborineSorbus rupicolaAllium ursinumGeranium lucidumAlnus glutinosaFraxinus excelsiorLathyrus nigerFrangula alnusCrataegus monogynaVerbascum thapsusVerbascum nigrumSanicula europaeaUlmus glabraRanunculus ficariaViburnum opulusCorylus avellanaClinopodium vulgare


The general expansion of thermophilous plantcommunities and southern vegetation zones north-wards is indicated on the map of "Potential vegeta-tion regions for Norway" (Holten 1990b).

Mountain plants and northern plants. Part of ourmountain flora has a genetically continental consti-

68

tution. Hence, such plants may belong to the groupof southwest coast avoiders, being absent or in-frequent on coastal mountains, where thermicoceanicity is too high for them. If this hypothesis,that they avoid coastal areas due to too high wintertemperatures, is valid, many mountain plants willexperience this as an additional stress factor toepisodes of high summer temperatures (Dahl 1951,Gauslaa 1984). Many edaphically demanding andfairly continental mountain plants whose optimumis in the Dovrefjell area, Central Norway, have awestern limit in the transect that correlaites well withthe trend of January isotherms, indicating thet theyare southwest coast avoiders (see Figure 7) (approxi-mate limiting January isotherms towards areas withmild winters are shown in °C):

Sagina cespitosa -12Campanula uniflora (Figure 7) -11Draba alpina -10Luzula arctica -10Minuartia rubella -10Poa artica s.l. -10Poa stricta -10Ranunculus nivalis -10Stellaria crassipes -10Vahlodea atropurpurea -9Sagina intermedia -9Phippsia algida -9Draba oxycarpa -9Luzula parviflora -9Silene uralensis -9Carex parallela -8Chamorchis alpina -8Minuartia stricta -8Oxytropis lapponica -7Draba fladnizensis -7Gentianella tenella -7Kobresia myosuroides -7Artemisia norvegica -6Astragalus frigidus (see Holten 1990a, p.26) -6Poa flexuosa -5Astragalus norvegicus -5Salix arbuscula -5Carex microglochin -4Carex misandra -4Carex atrofusca -3Carex adelostoma -2Carex atrata -2Carex saxatilis -2Salix myrsinites -2Pedicularis oederi -2Saxifraga cespitosa -2Juncus castaneus -1


I suggest that species in the list above that have alimiting January isotherm of -10 °C or lower belongto a group of plants that is really threatened ifwinter temperatures are going to increase by about4 °C. The most threatened ones are those having atypical middle alpine distribution, that is, they occurtoday only above about 1400 m on Dovrefjell,Central Norway. This level may also be the approxi-mate potential new timberline. In addition to theimportance of winter temperature for the westerndelimitation of southwest coast avoiding mountainplants, summer temperature and humidity are nodoubt important for the lower limit of many moun-tain plant species in Scandinavia (see Dahl 1951).Therefore both the lower and western limits will beaffected by the climate scenario.

The response of plant communities

With regard to limiting factors we can use the samereasoning for plant communities as for the species.We may also apply the concept of complementaryplant communities to the vertical occurrence ofcommunities in the transect. I suggest that the groupof plant communities belonging to the order Quer-cetalia robori-petraeae (= atlantic oak forests in awide sense) is rather demanding as regards wintertemperature (see Figure 8). The floristic similaritybetween certain coniferous forests and acid oakforests is relatively high. However, in oak forests(mainly Quercus robur) we find a group of ratherfrost-sensitive species, the most important beingHypericum pulchrum, Lonicera periclymenum andHolcus mollis.

It is predicted that the oak forests (Figure 8) willexpand eastwards along the fjords and to higherlevels in the transect, whereas the western limit ofmzny southwest coast avoiding species, many ofwhich have their optimum occurrence in tall herbcommunities belonging to the order Adenostyletalia,will in general retreat eastwards and upwards(Figure 9). The frost- sensitive and southwest coastavoiding communities are in this respect comple-me ntary.

We may expect a floristic change from dominatingtall herbs to dominating tall ferns for the western-most tall herb stands indicated (mapped) in Figure9, towards stands with Athyrium filix- femina forthe southern boreal and middle boreal zones, andtowards stands dominated by Athyrium distentifo-

6 9

lium for the northern boreal and low alpine zones(cf. Holten 1990).

It is predicted that in the transect tall herb commu-nities with Aconitum septentrionale will rarely formstands below about 600 m. However, although thetime vegetation requires to respond is very diff icultto foresee, much more than 50 years is surelyneeded to establish a climax vegetation because thepotential tall fern vegetation will of course need toboth migrate and establish itself following thepotential death of Aconitum septentrionale. Asregards the oak forests (Figure 8), the migration ofthe Oak (Quercus robur) itself will be quite slow,perhaps depending largely on physical transport ofacorns by red squirrels (Sciurus vulgaris), jays(Garrulus glandarius) and other birds and animalsthat forage on acorns.

The thermophilous forests, mainly Ulmus glabra andCorylus forests, are expected to expand their dis-tribution eastwards and upwards in the transect(Figure 10) and in Norway as a whole (see the mapof potential vegetation regions for Norway, Holten1990). The potential uppermost stands of Ulmusglabra and Corylus avellana in the transect, will beat about 800 m in the Oppdal-Drivdalen area. Thenew species limits for Ulmus and Corylus will be at900-1000 m a.s.l. It is predicted that Ulmus will bethe most effective migrator of the two species, andmay during the course of some decades be able toinvade the neighbouring low herb birch forests onsteep south-facing slopes in Central Norway. Suchlow herb sites close to the current Ulmus andCorylus stands should therefore be ideal sites formonitoring vegetation change (permanent plots)including registering the processes of migration,establishment and growth.

The thermophilous plant communities with Ulmusglabra and Corylus avellana will probably invadenorth-facing slopes below 300-400 m in the fjordand valley districts, today inhabited by mesotrophicBetula and Alnus incana forests. The complementaryplant communities to the thermophilous lowlandcommunities are the mountain plant communities.When temperatures are elevated, followed by tim-berlines elevating, the pure mountain plant speciesand communities will retreat. This effect scenario isindicated in Figure 11 for the upper boreal/lowalpine bilberry heaths. It is predicted that thebilberry (Vaccinium myrtillus) itself will decline atits current lower limit because of strong competi-tion from the more thermophilous lowland herbs.

m Quercetaliarobori-petraeae

oak forests1500

1000

500

1500

1000

500

Coast

Coast

•

•


m Adenostyletalia- tall herb communities

• •

25 50 75 100 125 kmInland

• • • •

• • • • • • •

• • • • I I U

•

25 50 75 100 125 kmInland

70

Figure 8 The expansion ofatlantic oak forests belonging tothe order Quercetali robori—petraeae.

Figure 9 The retreat of south—west coast avoiding plant com—munities belonging to the orderAdenostyletalia.

Figure 10 The expansion ofthermophilous plant communities("noble deciduous forests") be—longing to the order Fagetaliasylvaticae.

Figure 11 The predicted eleva—tion of bilberry heaths in a widesense belonging to Phyllodoco—Vaccinion.


m i Fagetalla sylvaticae- Ulmus glabra/Corylus forests

1500-

1000

500

1000

500

Coast

Coast

25

71

50

m Phyllodoce-VacciniumMyrtillus heath(Phyllodoco-Vaocinion)

1500 - Bilberry heaths

75

,;• • • • •

• • • • • •

1011 • • • • 11111111

• • III • •I'• • 111 • • •

• • • 111 • 111111. 111 01,

• • • • • • • •'

• • • • •

III •

100 125 kmInland

25 50 75 100 125 kmInland


Shorter winters, giving very little snow protectionfor Vaccinium myrtillus and drier soils in summer,will lead to more xeric conditions in the eastern partof the transect, resulting in a possible successionfrom Vaccinium myrtillus heaths to Festuca ovinagrass heaths.

Effects on vertical zonation of vegetation

A prediction is made for the whole of Norway forhorizontal vegetation zonation based on the climatescenario made by Eliassen & Grammeltvedt (1990).Since the map of vegetation regions (= zones)(Holten 1990b) did not take into consideration therate of change, migration barriers, etc., the vegeta-tion zones are only potential. The map shows a largequantitative change in the zones, especially for thewarmer lowland zones and the alpine zones. ForNorway as a whole, it is predicted that the tempera-te (= nemoral) zone will increase from 0.7 to 12.8 %of the total land area. The hemiboreal, southern andmiddle boreal zones will increase less. The northernboreal zone (= mountain forests, mainly with Betulapubescens) will be reduced to about a quarter of itscurrent area, from 29.9 to 8.4 %. Almost the sameretreat is predicted for the alpine zone, with areduction from 29.6 to 7.1 % (see Holten 1990a).This prediction is supported by the general principlethat a relatively small elevation of the timberlineresults in a large reduction of the bare alpine area.The potential forested area of Norway is predictedto increase from the current 66 % to about 88 %under the 2 x CO2 scenario. (Comment: We all knowthat the real forested area in Norway today is farbelow 66 %, due to such factors as lack of superfici-al deposits, agriculture, urbanization, etc.).

Qualitative vegetation changes involve death of plantspecies, migration and establishment. All this needtens or hundreds of years, at least the migrationprocess which is hampered in many ways. Forinstance, the thermophilous lowland species on theirmigration northwards across the flat countryside ofSouth Scandinavia and the North European Plainswill in principle meet three kinds of migrationbarriers: 1. cultivated land, 2. open sea, fjords andrivers, and 3. mountains. If the predicted rate ofclimatic change is extremely rapid, the existence ofmany thermophilous plant species will be threate-ned, not directly by the new climate, but by inter-specific competition from other species which arebetter adapted to the new climatic conditions.

7 2

Migration of species is no doubt much easier in hillyor mountainous country. This is the case in thecoast-inland transect in Central Norway. On steepslopes there is a short distance between vegetationzones, and the predicted increase in summer tempe-rature of 2 °C may result in the Betula timberlinebeing elevated about 300 m in the continental partof the transect. Along a slope inclining 30° thiscorresponds to a displacement of the timberline byabout 800 m along the terrain (shorter for steeperslopes). If the predicted climate is realized in 50years, the upward migration of Betula pubescens willbe 16 m/year. This is quite realistic (compareFigures 12 and 13). In horizontal areas in temperateand boreal parts of the world, a 2 °C temperaturerise will correspond to a climatic displacementnorthwards of perhaps 200-400 km, that is, a shiftof 4-8 km/year (compare Cohn 1989). I think thesefigures are too high for most vascular plant speciesto cope with. Under rapid climatic change, moun-tainous topography which includes a large numberof physical niches is no doubt favourable for thesurvival of a high diversity of plant and animalspecies. Roberts (1989) mentions this as an importantphysical factor for the survival of douglas fir(Pseudotsuga menziesii), Ponderosa pine (Pinusponderosa) and western hemlock (Tsuga heterophyl-la) in western North America, as they can moveupslope into the Rockies.

Due to migration barriers, invasion of many newspecies to the transect from the south in the courseof 50 years is not very probable. Some weeds will beexceptions to this (see Table 1 in Ketner, thisvolume). However, a quantitative change in the floraand vegetation, including a shift of vegetation zones,may take place. The most rapid responses willprobably be in vegetation influenced by culturalactivity, which will perhaps become still moreweedy. Efficient migrators with light seeds will befavoured, for example Epilobium angusti folium,species belonging to the family Asteraceae (Taraxa-cum spp., Lapsana cornmunis, Cirsium spp., Seneciospp.), and Salix caprea, Betula pubescens, B. pendulaand Populus tremula.

Nitrophilous species in the new temperate zone andin the hemiboreal zone may also be favoured, dueto the more rapid decomposition rate in the soil(Falkengren-Grerup 1986).

It is predicted that the new temperate zone in thetransect studied (see T in Figure 13) will be bothweedy, thermophilous and nitrophilous in its new


floristic composition, though carrying very few realtemperate species. In addition to the above-mentio-ned species, those which are expected to increase,since they are thermophilous, nitrophilous and alsoefficient migrators, are Arctium spp, Alliaria of fici-nalis. Aegopodium podagraria, Geranium robertia-nium, Sambucus sp, Geum urbanum, Holcus lanatus,Holcus mollis and Rubus spp. There are alreadysigns that some of these species are rapidly in-creasing in Central Norway (own observations), forexample Alliaria of ficinalis, Geum urbanum, Holcuslanatus, Holcus mollis and Rubus spp., so far asmuch a result of changed land use as of on-goingclimatic changes.

Within 50 years it is probable that Ulmus glabra willshow a marked increase in the hemiboreal (HB) andsouthern boreal zones (LB), replacing Betula pube-scens in low herb and some tall herb sites on south-facing slopes. The herb layer of those sites willprobably show a parallel change towards becomingmore thermophilous, involving invasion of Clinopo-dium vulgare, Epipactis helleborine, Brachypodiumsylvaticum, Bromus benekenii , Sanicula europaea, etc.

The current low alpine zone and the lower parts ofthe middle alpine zone will be invaded by Betulapubescens and species from the upper boreal zone(UB) in places with a favourable snow cover.However, the biological processes, including migra-tion of species, will be slower at higher levels.

The predicted milder winters (+4 °C for the wintermonths) will result in much higher thermic oceani-city in the transect. Figure 14 illustrates the verticaldistribution of thermic oceanicity based on phytoge-ographical criteria, that is, on eastern (frost limits)and western distribution limits mainly determinedby winter temperature (see Figures 5-9).

The zone with the currently highest thermic oceani-city, TI, is characterized by a group of plant specieswhich are fairly sensitive to low winter tempera-tures. The most typical ones for the TI section areHypericum pulchrum (Figure 5), Chrysospleniumoppositifolium, Lonicera periclymenum and Ilexaquifolium. Section TI is also defined by Aconitumseptentrionale, Hypericum hirsutum, Scirpus hud-sonianus and Corydalis intermedia among the easternsouthwest coast avoiding plants. Other good in-dicators of the thermic oceanicity sectors are Ericatetralix and Pedicularis sylvatica (boundary TII/IIIfrom the west), Blechnum spicant and Thelypteris

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limbosperma (boundary TIII/IV from the west) andCornus suecica (boundary TIV/V from the west).

The predicted climate defines a thermic oceanicityfor a new section, TO (see Figure 15), in coastalCentral Norway, which today is more characteristicfor the British Isles (January mean temperatureabout 5 °C). Section TO in Central Norway willdevelop potential habitats for extremely frost-sensitive species like Vicia orobus, Erica cinerea,Scilla verna, Endymion nutans, Hypericum elodes,Hypericum androsaemum, Carex laevigata andWahlenbergia hederacea. In addition, due to thepredicted warmer summers (+2 °C), southern atlanticheath species, like Genista anglica and Ulex euro-paeus, will have their climatic demands satisfied inthe new TO section in Central Norway. In theDovrefjell area, the winters will be less severe andthe more extreme southwest coast avoiding borealand alpine plants, which today characterize sectionTV from the east, may be forced to retreat east-wards and upwards, or their existence may bethreatened. In the transect studied, section TV willbe squeezed out and replaced by TIV (see Figures 14and 15).

Summary

A basic study of the phytogeography and autecologyof 150 plant taxa in Central Norway, includingmapping their vertical distribution, has been foundvery suitable for studying the effect of climaticchange. The vertical distribution of the plant taxahas been correlated with the climate factors ofsummer temperature, winter temperature and yearlyprecipitation. This material enables correlativemodelling of future changes in flora and vegetation.The very steep topographic and climatic gradientsin the transect studied also make the material wellsuited for a research and monitoring programme thatincludes studies of ecotones, species migrations anddisplacement of vegetation zones and sections.

Hypotheses for explaining the cause/effect rela-tionship between climate and vertical plant dis-tribution are, in simplified terms:1 thermic oceanicity is decisive for frost-sensitive

coastal plants and complementary southwest coastavoiding continental plants,

2 summer temperature is decisive for thermophi-lous lowland plants and complementary mountainplants,

1 000

500

1500

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m HA High alpine zone1 MA Middle alpine zone

LA Low alpine zoneUB Upper boreal zone

I MB Middle boreal zone15001 LB Lower boreal zone

HB Hemiboreal zone

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HA High alpine zoneMA Middle alpine zoneLA Low alpine zoneUB Upper boreal zoneMB Middle boreal zoneLB Lower boreal zoneHB Hemi boreal zoneT Temperate zone

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Figure 12 The current posi-tion of vertical vegetationsones for south-facing slopesin the coast-inland transect,based on phytogeographicaleriteria.

Figure 13 The predicted posi-tion of vertical vegetationzones for south-facing slopesin the coast-inland transect.

Figure 14 The current posi-tion of thermic oceanicitysections based on easternlimits of frost-sensitive speciesand western limits of south-west coaat avoiding plants.

Figure 15 The predicted posi-tion of thermic oceanieitysections, including the newsection TO and excluding thecurrent section TV (compareFigure 14 and see text).


m TI Oceanic sectionTII Suboceanic sectionTIII Weakly oceanic sectionTIV Subcontinental section

1500 TV Continental section

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m TO Hyperoceanic sectionTI Oceanic sectionTII Suboceanic sectionTIII Weakly oceanic section

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3 humidity is decisive for certain humidiphilouscoastal species and complementary xerophilouscontinental species.

The following predictions of the response of speciesgroupings are made, based on the Norwegian climatescenario (doubled atmospheric CO2 leads to 2 °Ctemperature increase in the summer months and4 °C increase in the winter months).

- Frost sensitive coastal plants will expand east-wards and upwards in the transect (Hypericurnpulchrum).

- Southwest coast avolding continental plants willretreat eastwards (Viola mirabilis); some may bethreatened (Carex heleonastes).

- The fate of humidiphilous coastal plants is moreuncertain. They will probably retreat at theireastern and lower limits (Blechnum spicant).

- Xerophilous continental plants may expand bothupwards and westwards and replace relativelymesic sites dominated by Vaccinium myrtilluswith Festuca ovina heaths.

- Thermophilous plant species and communitieswill expand both eastwards and upwards in thetransect. The response of wych elm (Ulmusglabra) may be rapid and the tree may in a fewdecades invade neighbouring habitats of low andtall herbs with Betula pubescens.Mountain plants will retreat in both area anddiversity due to the predicted elevation of thetimberline. Some middle alpine species arethreatened above about 1400 m (Campanulauni lora).

The total diversity of plants may increase somewhatin the warmer temperate and hemiboreal zones ofthe transect.

The main changes in flora and vegetation will bequantitative, at least for the next 50-100 years.

Migration barriers, mostly physical (open sea, fjordsand mountains), will probably be very effective andretard the invasion of thermophilous temperatespecies from Central Europe and frost-sensitivespecies from the British Isles.

Rapid climatic change may cause strong interspecificcompetition in the currently established vegetationand possibly lead to local extinction of some ecolo-gically specialized and rare species in the transect,for example species with high nutrition demands(Schoenus ferrugineus). The generalists (e.g. Epilo-

7 6

bium angustifolium) are no doubt best adapted torapid climatic change. At intermediate altitudes(500-1000 m), the current northern and alpine plantspecies will probably be replaced by the morecompetitive lowland species at their lower limits.(Example: Cicerbita alpina may in part be replacedby Campanula latifolia).

In central and inner fjord districts it is predictedthat the vegetation zones will be elevated by about200-300 m; in the more continental valleys by about300-400 m. These figures are also valid for thetimberline.

A new temperate lowland zone (T) will allowCentral European species to grow on south-facing,lowland slopes in the transect, and a new thermicoceanic section (TO) will include climatic niches forvery frost-sensitive species which are today con-fined to the British Isles and Southwest Europe. Themiddle and high alpine zones will be greatly reducedin the transect.

References

Cohn, J.P. 1989. Gauging the biological impacts ofthe greenhouse effect. - Bioscience 39,3: 142-146.

Dahl, E. 1951. On the relation between the summertemperature and the distribution of alpinevascular plants in the lowlands of Fennoscandia.- Oikos 3: 145-153.

Eliassen, A. & Grammeltvedt, A. 1990. Scenarios (2x CO2 in Norway). Letter to the Ministry of theEnvironment 1.2 1990. - DNMI.

Falkengren-Grerup, U. 1986. Soil acidification andvegetation changes in deciduous forest in sout-hern Sweden. - Oecologia 70: 339-347.

Gauslaa, Y. 1984. Heat resistance of Norwegianvascular plants. - Holarct. Ecol. 7: 1-78.

Grammeltvedt, A. 1990. Climate change in Norwaydue to increasted greenhouse effect. - NINANotat 4.

Holten, 1.1. 1986. Autecological and phytogeographi-cal investigations along a coast-inland transect atNordmøre, Central Norway. - Dr. philos. thesis.Univ. of Trondheim. 349 pp. 69 plates. Unpubl.

Holten, J.I. 1988. The distribution of eastern plantsand their climatic conditions, with emphasis onScandinavian relationships. - Blyttia 46,3: 105-112.


Holten, J.I., ed. 1990a. Biological and ecologicalconsequences of changes in climate in Norway. -NINA Utredning 11: 1-59. 1 map.

Holten, J.I. 1990b. Potential vegetation regions forNorway. - M1: 3 mill. - Norwegian Institute forNature Research. Map.

Roberts, L. 1989. How fast can trees migrate? -Science 243: 735-737.

Salvesen, P.H. 1988. Comparative cultivation ex-periments with south-west-coast avoiding plantspecies. 1. Garden cultures. Blyttia 46,3: 145-153.

Salvesen, P.H. 1989. Comparative cultivation ex-periments with south-west-coast avoiding plantspecies. 2. Controlled environment. - Blyttia 47,3:143-153.

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4 Summary

GrammeltvedtThe most likely climatic changes in Norway resul-ting from a doubling of atmospheric CO2 are a 3-4°C increase in the average winter temperature andan increase of about 2 °C in the average summertemperature. Precipitation will probably increase inevery season and soil moisture will increase duringwinter, but decrease during summer.

DahlThe predicted climate will result in a longer produc-tion season and higher agricultural production inNorway. Some districts in Norway may becomeimportant areas for the production of fodder androot crops. New cultivars of agricultural plants mustbe developed in response to the changed climaticconditions, with the help of modern plant breedingmethods.

The situation seems likely to be the opposite forforest trees. They have only limited possibilities forgenetic adaptation in the course of 50-100 years,due to the relatively long life span of tree species.For Europe as a whole, the predicted winter tempe-rature conditions wiIl cause the frost-sensitive beech(Fagus sylvatica) to move eastwards from thepresent-day -3 °C isotherm for January to the -7 °Cisotherm. The prospect for Norway spruce (Piceaabies) is the opposite of beech. Its southwesterndistribution limit correlates well with the present-day -2 °C isotherm for January. Under the green-house effect, it is expected that Norway Spruce willcorrelate well with the present-day -6 °C isothermfor January, with the result that spruce may dis-appear from lowland tracts of Northern and CentralEurope. In Northern Europe, spruce and pine willprobably be replaced by beech and oak (mainlyQuercus robur).

The phenological cycle of many plant species maybe disturbed by a rapid climate change, resulting inextinction of local populations.

SkreUnder the predicted greenhouse effect, distributionlimits will generally move towards more arctic andalpine areas because of higher respiration in summerand a longer growing season.

The effect of a higher winter temperature will tendto be greater in a plant with an oceanic distribution.


The expected temperature increase will not onlyresult in much higher growth rates, but also inlower sink strength and available energy resources,particularly in fast-growing species and ecotypes.Photosynthesis may take over as a growth limitingprocess and cause many plant species to have anarrower distribution.

HåbjørgNatural plant species in Scandinavia vary greatly intheir adaptability to changing climatic conditions.Arctic and alpine ecotypes seem to be poorlyadapted to southern and maritime conditions, andsouthern ecotypes are poorly adapted to arctic andcontinental conditions. A change to above zerowinter temperatures may damage highly specializedarctic and continental ecotypes.

LiljelundIn Southern Sweden, the predicted climate willprobably result in increased plant diversity, becausethe immigration rate will be higher than the extinc-tion rate. Vegetation changes will occur as a resultof this immigration/extinction process.

Destabilization of ecosystems will probably takeplace, including a change from competitive speciestowards more ruderal species. Several ecologicalrelationships may be disturbed: host - parasite, plant- herbivore, predator - prey, etc.

KetnerLags in the response of vegetation to change inclimate may occur for many reasons, such as effec-tive geographical dispersal barriers (physical andanthropogenic), poor accessibility because ofunfavourable edaphic conditions, low adaptabilityto the changed length of day, competition fromresident plants, direct and indirect effects of at-mospheric pollution (e.g. accumulation of nitrogen-ous deposits in the soil), ecotypic variation withinthe range of a species and inadequate dispersalcapacity and migration rate.

Because of a large number of retarding factors,changes in flora and vegetation in the coming 50years will therefore probably not be as large asclimatic change would allow. The whole process ofcompetition in a community itself may take manydecades to work through into a visibly changednatural vegetation. Extreme climatic events mayenhance certain developments, for instance cata-strophic death of forests caused by drought or frost.

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In general, thermophilous species will be favouredby the predicted temperature increase. C4 speciesmay have advantages over C3 species; fast-growingand fecund species will be favoured. Many speciesof this type are weedy species, thus contributing toa weedification of northwest Europe.

HoltenA basic work on the phytogeography,autecology andvertical distribution of 150 plant species along acoast-inland transect in Central Norway has beenfound suitable for correlative modelling of futurefloristic gradients. It can form the basis for aresearch and monitoring programme includingstudies of ecotones, species migrations and dis-placement of vegetation zones and sections. Theeffect scenario is based on the Norwegian climatescenario and hypotheses for the explanation ofcause/effect relationship between climate andvertical plant distribution. The hypotheses apply thethree main abiotic factors, thermic oceanicity,summer temperature and humidity, as limitingfactors for vertical plant distribution.

The predicted responses in Central Norway ofdifferent species' groups are:- frost-sensitive coastal plants will expand

southwest coast avoiding plants will retreat or bethreatened

- humidiphilous coastal plants will probably retreat- xerophilous continental plants may expand- thermophilous plants will expand

-

mountain plants will retreat

In the warmer zones, the total diversity of plantsmay increase. During the next 50-100 years, themain change in the flora and vegetation in CentralNorway will be quantitative. Migration barriers willeffectively retard the invasion of temperate speciesfrom Central Europe.

Ecologically specialized and rare species in thetransect may become extinct due to strong inter-specific competition, and typical generalists will befavoured.

The vegetation zones and the timberline will beelevated by 200-300 m in the fjord districts and300-400 m in the inner valley districts.

A new vegetation zone, the temperate zone (T), willdevelop in the lowlands, and a new thermic oceanicsection (TO) will have climatic niches enabling aninvasion of some very frost-sensitive species from


Southwest Europe and the British Isles. However,this migration process will be very slow.

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5 Sammendrag

GrammeltvedtDe mest sannsynlige klimaforandringene i Norge pågrunn av fordobling av CO, -innholdet i atmos-færen, er 3-4 °C økning for vintermånedene desem-ber, januar og februar, og en økning på 2 °C forsommermånedene juni, juli og august. Nedbøren vilsannsynligvis øke i alle årstider, jordfuktigheten viløke om vinteren, og avta om sommeren.

DahlDe forutsagte klimaendringene vil føre til en lengreproduksjonssesong og høyere jordbruksproduksjoni Norge. Noen distrikter i Norge kan bli viktigeområder for produksjon av f6r og rotfrukter. Nyekultivarer av kulturplanter må bli utviklet som svarpå endrete klimaforhold, ved hjelp av moderneplanteforedlingsmetoder.

Situasjonen synes å være motsatt for treslagene. Dehar bare begrensete muligheter til genetisk tilpasningi løpet av 50-100 år, på grunn av relativt langlevetid for treslag. For Europa vil de forutsagtevintertemperaturforholdene forårsake at denfrostømfintlige bøken (Fagus sylvatica) vil forflytteseg østover fra dagens -3 °C-isoterm for januar til -7 °C-isotermen. Utsiktene for gran (Picea abies) erdet motsatte av bøk. Granas sørvestlige utbredelses-grense korrelerer bra med -2 °C-isotermen forjanuar. Under drivhuseffekten er det forventet atgranas sørvestlige utbredelsesgrense i Europa vilkorrelere bra med dagens -6 °C for januar, med detresultat at grana vil forsvinne fra lavlandsområderi Nord- og Sentral-Europa. I Nord-Europa vil granog furu trolig bli erstattet med bøk og eik (vesentlig(Quercus robur) på lavere og midlere høyder.

Den fenologiske syklus for mange plantearter kanbli forstyrret av raske klimaendringer, noe som kanføre til utryddelse av lokale plantepopulasjoner.

SkreUnder den forutsagte drivhuseffekten vil utbredel-sesgrenser generelt forflyttes mot arktiske og alpineområder, på grunn av høyere respirasjon om som-meren og en lengre vekstsesong.

Virkningen av høyere vintertemperaturer vil ha entendens til å være større hos planter med oseaniskutbredeIse.


De forventete temperaturøkningene vil ikke bareføre til høyere vekst- rater, men også til lavere "sinkstrength" og tilgjengelige energiressurser, særlig hosraskt-voksende arter og økotyper. Fotosyntesen kankomme til å overta som vekst-begrensende faktor ogforårsake at mange plantearter får en snevrereutbredelse.

HåbjørgNaturlige plantearter i Skandinavia varierer mye ideres tilpasningsevne til endrete klimaforhold.Arktiske og alpine økotyper synes å være dårligtilpasset til sørlige og oseaniske forhold, og sørligeøkotyper er dårlig tilpasset til arktiske og kontinen-tale forhold. En forandring i vintertemperaturen tilover 0 °C, kan skade de svært spesialiserte arktiskeog kontinentale økotypene.

Lilj elundI Sør-Sverige, vil det forutsagte klimaet sannsynlig-vis føre til økt plante-diversitet fordi "innvand-ringshastigheten" (immigration rate) vil være høyereenn "dødsraten" (extinction rate). Vegetasjonsendrin-ger vil finne sted som et resultat av denne inn-vandrings/døds-prosessen.

Destabilisering av økosystemer vil sannsynligvisfinne sted, dette innebærer en forandring frakonkurransesterke (competitive) arter til "ugrasakti-ge" (ruderale) arter. Flere økologiske relasjoner kanbli forstyrret: Vert-parasitt, plante-graseter, preda-tor - bytte, etc.

KetnerTidsforskyving i responsen hos vegetasjonen tilforandringer i klimaet kan finne sted, slik someffektive geografiskespredningsbarrierer (fysiske ogantropogene), dårlig tilgjengelighet på grunn avugunstige jordbunnsforhold, dårlig tilpasningsevnetil forandringer i daglengden, konkurranse avallerede etablerte arter, direkte og indirekte virk-ninger av atmosfæreforurensing (f.eks. akkumu-lering av nitrogenforbindelser i jorda), økotypevari-asjon innen en arts utbredelsesområde og dårligspredningsevne og migrasjonshastighet.

På grunn av et stort antall av forsinkende faktorer,vil forandringer i flora og vegetasjon de neste 50årene derfor ikke bli så stor som klimaforandringeneskulle tilsi. Selve konkurranseprosessen i et plante-samfunn må sannsynligvis virke flere tiår før mankan se synlige forandringer i den naturlige vegeta-s jonen. Ekstreme klima-episoder kan forsterke visse

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utviklingstendenser, f.eks. katastrofe-død av skogforårsaket av tørke eller frost.

Generelt vil varmekjære arter bli begunstiget av denforutsagte temperaturøkning. C4-arter kan hafordeler framfor C3-arter; raskt-voksende ogfruktbare arter vil bli begunstiget. Mange av disseartene er ugras-arter, som på denne måten bidrar tilen ugras-økning i Nordvest-Europa.

HoltenEt grunnleggende arbeid om plantegeografien,autøkologien og vertikalutbredelsen til 150 plantear-ter langs et kyst-innland-profil i Midt-Norge, erfunnet egnet for korrelativ modellering av framtidi-ge flora- og vegetasjonsgradienter. Arbeidet kanutgjøre grunnlaget for et forsknings- og overvå-kingsprogram som inkluderer studier av økotoner,artsvandringer og forflytting av vegetasjonssoner og- seksjoner. Virkningsscenariet er basert på detnorske klimascenariet og hypoteser for forklaring avårsak/virkning-forholdet mellom klimafaktorer ogvertikalutbredelse av plantearter. Hypotesene basererseg på tre faktorer blant de abiotiske klimafaktorene:Termisk oseanitet (vintertemperatur), sommertem-peratur og humiditet, som begrensede faktorer forvertikalutbredelse av planter.

De forutsagte responsene i Midt-Norge på deforskjellige økologiske plantegrupper er:

- frost-smfintlige kystplanter vil ekspandere- sørvestkyst-skyende plantearter vil gå tilbake

eller bli truetfuktighetselskende kystplanter vil trolig gåtilbake

- xerofile kontinentale planter kan ekspandere- varmekjære arter vil ekspandere- fjellplanter vil gå tilbake, en del arter vil trues

I de varmeste vegetasjonssonene kan den totaleplantediversiteten øke. I løpet av de neste 50-100årene, vil likevel hovedforandringen i floraen ogvegetasjonen i Midt-Norge være kvantitativ. Spred-ningsbarrierer vil effektivt forsinke innvandringenav varmekjære arter fra Sentral-Europa.

Økologiske spesialister og sjeldne arter i vertikal-profilet, kan bli utryddet på grunn av sterk inter-spesifikk konkurranse. Typiske generalister vil blibegunstiget.


Vegetasjonssonene og skoggrensa vil bli hevet ca200-300 m i fjordstrøkene, og 300-400 i indredalstrøk.

En ny vegetasjonssone, den tempererte sonen (T),vil dannes i lavlandet, og en ny termisk oseanitets-seksjon (TO) vil ha klimanisjer som legger til rettefor invasjon av mer frost-ømfintlige arter, som idag bare finnes i Sørvest-Europa og på de britiskeøyer, men denne migrasjons-prosessen vil væresvært treg.

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6 AppendixParticipants

* : lecturer

The Swedish Society for Conservation of Nature,Box 4510, S-10265 Stockholm* Liljelund, Lars E.

Agricultural University of Wageningen, Departmentof Vegetation Science, Bornsesteeg 69, NL-6708 PDWageningen* Ketner, Pieter

Directorate for Nature Management, Tungasletta 2,N-7004 Trondheim

Angell-Petersen, IngeridGynnild, VidarJaren, VernundPaulsen, GunnRfibbert, Sissel

University of Trondheim, Department of Botany,N-7055 Dragvoll

Bruteig, IngaHafsten, UlfRønning, Olaf I.

University of Trondheim, Museum of NaturalHistory and Archaeology, Department of Botany, N-7004 Trondheim

Arnesen, TrondAune, Egil I.Flatberg, Kjell I.Moen, AsbjørnSivertsen, SigmundSingsaas, Stein

University of Trondheim, Museum of NaturalHistory and Archaeology, Department of Zoology,N-7004 Trondheim

Haftorn, SveinJensen, John W.

The Norwegian Polar Research Institute, Rolfstangv.12, N-1330 Oslo Lufthavn

Gulbrandsen, Line

The Norwegian Meteorological Institute, NielsHenrik Abelsv. 40, Oslo 3* Grammeltvedt, Arne

Linge Vista, Sofus


The Norwegian Institute for Air Research, Box 64,N-200I Lillestrøm

Dovland, Harald

The National Committee for Environmental Scien-ces, The Norwegian Research Council for Scienceand the Humanities, Sandakerv. 99, N-0483 Oslo 4

Broch Mathisen, Kirsten

The Ministry of the Environment, Box 8013 Dep.,N-0030 Oslo 1

Slettamark, Brita

Agricultural University of Norway, Department ofBiology and Conservation, N-1432 As-NLH* Dahl, Eilif

Agricultural University of Norway, Institute ofEarth Sciences, N-1432 As - NLH

Naverud, Ståle

Geological Survey of Norway, Leif Erikssons v 39,N-7000 Trondheim

Larsen, Eilif

Norwegian Broadcasting Corporation, NRK Sør-Trøndelag, Otto Nielsens v 2, N-7004 Trondheim

Andersen, Ellen Ingunn

Verdens Gang, Olav Tryggvasons gt. 48, N-7000Trondheim

Bondø, Tor-Hartvig

Adresseavisen, Industriv. 13, N-7080 HeimdalOpland, Egil M.

Norwegian Institute for Forest Research, Fanaflaten4, N-5047 Fana* Skre, Oddvar

Agricultural University of Norway, Department ofHorticulture, Box 22, N-1432 As-NLH* Håbjørg, Atle

Norwegian Institute for Nature Research, Tungaslet-ta 2, N-7004 Trondheim

Brattbakk, IngvarBaadsvik, KarlFremstad, EliFrisvoll, Arne A.Gunnerød, Tor B.Gaare, Eldar

* Holten, Jarle I.Kvam, Tor

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Edited by Jarle I. Holten - NINA naturforskningEffects of climate change on terrestrial ecosystems...

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Transcript of Edited by Jarle I. Holten - NINA naturforskningEffects of climate change on terrestrial ecosystems...