forest Soil Survey and Mapping of the Nutrient Status of ...

Working Report 2007-78
forest Soil Survey and Mapping of the Nutrient Status of the Vegetation
on Olkiluoto Island Results from the first Inventory on the ffH Plots
Pekka Tamminen
Lasse Aro
Maija Salemaa
September 2007
Fl-27160 OLKILUOTO, FINLAND
Tel +358-2-8372 31
Fax +358-2-8372 3709
Working Report 2007-78
forest Soil Survey and Mapping of the Nutrient Status of the Vegetation
on Olkiluoto Island Results from the first Inventory on the ffH Plots
Pekka Tamminen
Lasse Aro
Maija Salemaa
Working Reports contain information on \11/ork in progress
or pending completion.
are those of author(s) and do not necessarily
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FOREST SOIL SURVEY AND MAPPING OF THE NUTRIENT STATUS OF THE VEGETATION ON OLKILUOTO ISLAND. RESULTS FROM THE FIRST INVENTORY ON THE FEH PLOTS
ABSTRACT
The aim of the inventory was to determine the status of the forest soils and to map the current nutrient status of forest vegetation on Olkiluoto Island in order to create a basis for monitoring future changes in the forests and to provide data for a biospheric description of the island. The study was carried out on 94 FEH plots, which were selected from the forest extensive monitoring network (FET plots) on the basis of the forest site type distribution and tree stand characteristics measured on the island during 2002-2004. Forest soils on Olkiluoto are very young and typical of soils along the Finnish coast, i.e. stony or shallow soils overlying bedrock, but with more nutrients than the forest soils inland. In addition to nutrients, the heavy metal concentrations are clearly higher on Olkiluoto than the average values for Finnish forest soils. The soil in the alder stands growing along the seashore is different from the other soils on Olkiluoto and the control soils inland. These soils are less acidic and have large reserves of sodium, magnesium and nitrogen. Macronutrient concentrations in vascular plant species were relatively similar to those reported for Southern Finland. However, it is obvious that the accumulation of particulate material on the vegetation, especially on forest floor bryophytes, has increased due to emissions derived from the construction of roads, drilling and rock crushing, as well as the other industrial activities on Olkiluoto Island. Leaf and needle analysis indicated that the tree stands had, in the main, a good nutrient status on Olkiluoto Island. The surveying methods used on Olkiluoto are better suited to detect systematic changes over a larger area or within a group of sample plots than the changes on individual plots.
Keywords: bioindicators, conifers, deciduous trees, nutrition, soil profile description, soil properties, understorey vegetation
MAANNOSKUVAUS JA KASVILLISUUDEN RAVINNETILAN KARTOITUS OLKILUODON FEH-ALOILLA
TIIVISTELMA
Avainsanat: aluskasvillisuus, bioindikaattorit, havupuut, lehtipuut, maannoskuvaus, maan ominaisuudet,ravinnetila
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2.2 Sampling ...................................................................................................... 13
2.2.2 Vegetation sampling .................................................................... 15
2.2.3 Foliage sampling ......................................................................... 16
2.3.1 Soil samples ................................................................................ 17
2.3.2 Vegetation samples ..................................................................... 18
2.4 Statistical analysis ....................................................................................... 19
3.2 Soil acidity .................................................................................................... 22
3.4 Total carbon and nitrogen in the soil ............................................................ 26
3.5 Total element concentrations and amounts in the organic layer .................. 30
3.6 Soil and peat types on Olkiluoto .................................................................. 32
3.7 Variation in soil properties ............................................................................ 34
3.8 Chemical composition of the understorey vegetation .................................. 40
3.8.1 Carbon and macronutrients (N, P, K, Ca, Mg and S) ................... 40
3.8.2 Micronutrients (B, Mo, Cu, Zn, Mn, Ni and Fe) ............................ 45
3.8.3 Non-essential elements (Cd, Cr, Pb and AI) ................................ 45
3.8.4 Sample plot ordinations according to the elemental
composition of bryophytes and Vaccinium myrtillus ............................. 49
3.9 Nutrient status of the tree stands ................................................................. 49
4 CONCLUSIONS ....................................................................................................... 59
Appendix 1. Main characteristics of the studied FEH plots ......................................... 71
Appendix 2. Field forms used in the soil survey .......................................................... 75
Appendix 3. Amounts of exchangeable base cations (kg ha-1) in the organic layer on the mineral soil plots by site type and by tree species ........................................... 79
Appendix 4. Amounts of exchangeable base cations (kg ha-1) in the 0-10 and 1 0-30 cm mineral soil layers on the mineral soil plots by site type and by tree species .............................................................................................................. 81
Appendix 5. Amounts of organic matter, carbon (Mg ha-1) and nitrogen (kg ha-1)
in the organic layer on mineral soil sites by site type and by tree species .................. 83
Appendix 6. Amounts of organic matter, carbon (Mg ha-1) and nitrogen (kg ha-1)
in the mineral soil layers 0-10 and 10-30 cm on mineral soil sites by site type and by tree species ..................................................................................................... 85
Appendix 7. Total (wet-digestion) amounts of elements (kg ha-1) in the organic layer on mineral soil sites by forest site type ............................................................... 87
Appendix 8. Peat types of each sub-plot by studied peat layers on peatland sites ..... 89
Appendix 9. The mean C, Nand macronutrient concentrations (mg g-1) in vascular plant, bryophyte and lichen species in different site types .......................................... 91
Appendix 10. The mean micronutrient concentrations (mg kg-1) in vascular plant, bryophyte and lichen species in different site types .................................................... 95
Appendix 11. The mean Cd, Cr, Pb and AI concentrations (mg kg-1) in vascular plant, bryophyte and lichen species in different site types .......................................... 99
Appendix 12. Element concentrations and carbon content in needles and leaves ... 103
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FOREWORD
Soil sampling and soil profile description were carried out in the field by forestry engineers Teuvo Levula, Raino Lievonen, Pekka Viilikangas and Ari Ryyniinen. The understorey vegetation survey and plant tissue sampling were carried out by Leila Korpela, PhD, and Ari-Pekka Huhta, PhD. Leaf and needle samples were taken by forestry engineer Ari Ryyniinen, forestry technician Sulo Lehtinen and field foremen Pauli Alavataja, Pertti Niemi and Markku Nikola. Pretreatment of the soil samples from mineral soil sites were organized by Pekka Viilikangas and Reijo Hautajiirvi at the Salla office of Rovaniemi Research Unit. Pretreatment of the peat, leaf and plant tissue samples was performed by the staff ofParkano Research Unit. Arja Tervahauta, MSc, at Metla's Central Laboratory in Vantaa, laboratory superviser Arja Ylinen at Parkano Research Unit and laboratory technician Ulla Raatikainen at Salla were in charge of all the laboratory analyses. John Derome revised the English language. The report was checked by Reija Haapanen from Haapanen Forest Consulting. Tuire Kilponen was responsible for the layout. We gratefully acknowledge the contribution of all the persons mentioned in the above, as well as other staff from Metla.
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9
IIODDN
Almost all of the natural processes taking place in forest ecosystems are either directly or indirectly connected to the soil. The soil provides plants with mechanical support and an anchorage, as well as water and nutrients. The detritus of dead animals, plants and microbes are decomposed in the soil, and the nutrients that are released through mineralization become available for re-utilization by living organisms or are transported down into deeper soil layers. Forest soil also acts as a filter protecting the underlying groundwater and surface waters.
The soil mantle in Finland primarily dates back to the last ice age and the melting of the continental ice sheet, and is therefore relatively young, on the average 10,000 years. Land uplift is continuously producing new land especially along the coastline of the Gulf of Bothnia. Owing to the relatively rapid rate of land uplift at Olkiluoto (6 mm per year, Eronen et al. 1995), and the flat topography, the soils on Olkiluoto Island are, on the average, only 500 to 2,000 years old.
Soils can be described on the basis of their physical and chemical properties. Physical properties include soil thickness, i.e. how much loose soil is lying on top of the bedrock, the volume of stones and boulders, particle size distribution, proportion of organic matter, the quality and thickness of the organic layer on top of the mineral soil, soil moisture and the upper level of the groundwater. Chemical characteristics include acidity, i.e. the concentration of acidic cations such as H+ and AP+, and the concentrations and amounts of elements that act as plant nutrients, as well as trace elements, heavy metals and other elements.
Soils can be classified according to their external appearance into soil types. In Finland, most of the soils are podzolized (Podzols ), i.e. leached and acidic with a mor layer overlying the mineral soil, peat soils with a peat layer of varying thickness (Histosols ), very shallow soils (Leptosols), young soils (Arenosols or Regosols) and fine-textured soils (Cambisols). Soil classification and detailed soil description form a sound basis for deciding which phenomena are the most relevant for the development of a specific soil.
Olkiluoto Island is low-lying, with an altitude mainly below 10 m above sea level. According to the bedrock map (Simonen 1980), the bedrock is mainly composed of migmatic gneiss with granitic veins. On the basis of visual, microscopic and lithogeochemical investigations of outcrops, investigation trenches and core samples on Olkiluoto Island, the bedrock is consisted mainly of various biotite-rich migmatitic mica gneisses of metasedimentary or metavolcanic origin (Vaittinen et al. 2003). In addition to migmatitic rocks, various more homogenous high-grade metamorphic gneisses and granite pegmatites occur at Olkiluoto (Vaittinen et al. 2003). According to the quaternary deposit map (113206+09), moraine and bedrock with a thin moraine blanket cover over 90% of the area of the island. There are also peat, sand and clay soils on the island (Rautio et al. 2004, Lahdenperii et al. 2005). The thickness of overburden is usually 2-4 meters, although even up to 12-16 meter thick layers have been observed at Olkiluoto (Lahdenperii et al. 2005).
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The properties and condition of the soil are reflected in the species composition of the vegetation, and the growth and chemical composition of the vegetation. Vascular plants mainly take up elements via their roots from the soil, although the foliar uptake of gases (e.g. N0
2 , NH
3 and SO) and soluble elements may also be substantial (Marschner 1995).
The bioavailability of elements in the soil is regulated by many physical, chemical and biological properties and processes. For instance, the mobility and toxicity of heavy metals are strongly related to the acidity and organic matter content of the soil (Alloway 1995). The foliar uptake ofheavy metals has been demonstrated in many crop plants (e.g. Haslett et al. 2001) but, in evergreen species, the thick epidermis and waxy cuticle of the leaves provide external protection against toxic elements. Large amounts of metal containing dust become attached to the leaf surfaces of trees growing near the emission sources (Kozlov et al. 2000), and particles may also become embedded in the cuticular waxes (Rautio & Huttunen 2003).
Cryptogams (bryophytes and lichens), on the other hand, have no real roots, epidermis or continuous cuticle layer, and they absorb water and dissolved elements directly across their surface. Most of the bryophyte and lichen species obtain the majority of their water and nutrients from atmospheric deposition; some species also obtain nutrients from water that has been in contact with the substrate (Garty 2001). The following element compartments occur in both taxons: 1) trapped particulate matter, 2) intercellular soluble elements, 3) extracellular elements, bound to the cell wall on charged exchange sites, and 4) intracellular elements (Garty 2001). Both bryophytes and lichens (especially the mycobiont partner) have a high ion exchange capacity on their cell walls, and the dead tissues also have an ability to bind ions (Zechmeister et al. 2003).
After being selected for the site of spent nuclear fuel repository, increasing attention has been paid to the environmental monitoring of the Olkiluoto area. Besides the monitoring, data from prevailing ecosystems is needed in order to describe the current biosphere on Olkiluoto Island. Hitherto, vegetation types (Miettinen & Haapanen 2002) and species coverage (Huhta & Korpela 2006), forest resources (Rautio et al. 2004) and the state of the forests (Saramiiki & Korhonen 2005), and microbial community structure in the organic layer of forest soils (Potila et al. 2007) have been reported on forest ecosystems of the Olkiluoto Island. In addition, Roivainen (2006) studied stable element and some radionuclide concentrations in shoreline alder stands in 2005.
The aim of the soil survey was to determine the status of the forest soils on Olkiluoto Island in 2005 (absolute state), to compare the soils on Olkiluoto with similar soils on the mainland of South Finland (relative state), and to create a basis for monitoring future changes in the soils (more than one composite samples/soil layer). The aim of carrying out nutrient analyses on the ground vegetation and tree foliage was to map the current nutrient status of forest vegetation on Olkiluoto Island. Chemical composition of plant species, especially mosses, can be used as a bioindicator of deposition level of harmful elements or wind-blown dust. In addition, both the soil survey and the vegetation nutrient inventory provide data for a biospheric description of the island.
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2.1 Forest extensive high-level plots (FEH)
The monitoring of forests and mires on the island is based on a systematic grid with a density of 1 plot/ha (e.g. Haapanen 2006). The number of plots included in this grid is 560, and they are called Forest ExTensive monitoring plots (FET, Haapanen 2006). Originally, 100 plots ofthe FET network were selected for more in-depth studies, including soil profile descriptions and ground vegetation surveys, and the analysis of nutrient concentrations in different compartments of the forests. FEH plot selection was based on the forest site type distribution and tree stand characteristics measured on Olkiluoto Island during 2002-2004 (Miettinen & Haapanen 2002, Rautio et al. 2004, Saramiiki & Korhonen 2005). In the classification of tree species coverage, the proportion of the dominant tree species had to be 65-75% at least. However, due to the limited number of plots fulfilling this requirement, the proportion of the dominant tree species was decreased to 45-55% on a number of plots. The selection criteria are briefly described in Huhta and Korpela (2006), but more detailed information is given in Table 1. The aim of the FEH
Table 1. Criteria applied in selecting the forest extensive high-level (FEH) plots.
Tree species Soil type Site type 11 Mean Target number Accepted
stand age of plots
Norway Mineral soil MT, bedrock :::; 50 yrs 10 10 spruce MT >50 yrs 10 11
OMT :::; 50 yrs 10 9 OMT >50 yrs 10 10
Scots pine Mineral soil VT,MT :::; 50 yrs 10 10
ClT, CT, MT, bedrock >50 yrs 10 10 OMT :::; 50 yrs 10 10
Peatland various 21 15-20 21 10 2
Birch Mineral soil MT-Lh 5-50 21 10 10 Peatland various 21 15-26 21 0 5
Common alder Mineral soil various 21 20-60 21 5 5 Peatland various 21 35- 55 21 5 2
Total 100 94
11 The forest site types according to Cajander (1949) in descending order of site fertility: Lh (the most fertile, herb-rich sites), OMT (Oxalis acetosella- Vaccinium myrtillus), MT (Vaccinium myrtillus), VT (Vaccinium vitis-idaea), CT (Calluna vulgaris), ClT (Cladina type) and bedrock sites with no or very shallow mineral soil layer.
21 Not a selection criterion.
e Scc::Q pile stand
e Norway spruce !land
..
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plot selection was to include the most common forest types with a representative age distribution while, at the same time, ensuring that the spatial distribution of the plots was sufficiently representative (Fig. 1). In addition, some of the peatland plots on the island, as well as plots in alder forests close to the shoreline, were also included due to their importance in ongoing modeling projects. The final number ofFER plots was 94 (Table 1, Appendix 1).
2.2 Sampling
2.2.1 Soil sampling and soil profile description
Soil samples were collected during May and June, 2005, on 94 sample plots, of which 85 were situated on mineral soils. Three composite samples were taken of the organic layer, two composite samples of the 0- 10 cm mineral soil layer, and one composite sample of the 10-30 cm mineral soil layer (Table 2). Samples of the organic layer were taken on all the plots. Organic layer samples only were taken on 9 peatland plots and 9 bedrock plots. In addition to the Olkiluoto plots, corresponding soil samples were also taken from 9 control plots at sites in Ikaalinen (western central Finland), Tuusula and Vantaa (close to Helsinki), and Kiihtelysvaara (eastern Finland) (Table 3). The control plots were picked up from the 9th National Forest Inventory network (Metsiintutkimuslaitos 1998).
Table 2. Number of soil samples per sampled layer on Olkiluoto.
Layer Samples/layer/plot Sampled plots
Organic 3 94 0-10 cm 2 76 10-30 cm 1 75 50-60 cm pi 62
11 Only one sample, not a composite sample as from the other soil layers.
Table 3. Rectangular Finnish coordinates (E27a = 3 500 000 m) of the control plots.
Plot Town Northing, m Basting, m
1 Vantaa 6692250 3392000 2 Vantaa 6694000 3392750 3 Tuusula 6700000 3393000 4 Ikaalinen 6860250 3296000 5 Ikaalinen 6862000 3298250 6 Ikaalinen 6873500 3290000 7 Kiihtelysvaara 6946500 3662300 8 Kiihtelysvaara 6947100 3662000 9 Kiihtelysvaara 6947700 3662000
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Ten circular sub-plots were marked out systematically in a circle (r = 7 m) inside the FEH plot for soil sampling (Fig. 2). If the plot was not homogeneous enough for representative soil sampling, a new centre point was marked and its direction and distance from the original center point recorded (Appendix 1). On the mineral soil sites three composite samples, each consisting of 10 sub-samples, were taken from the organic layer with a cylinder ( d = 60 mm). Living (green) vegetation was removed from the top of the sub sample and its thickness measured (mm). The type of organic layer was determined at the same time (0 = organic layer missing, 1 = mor, 2 = moder, 3 = mull, 4 = peat, 5 = mull-like peat). The proportion of stones and boulders (d > 2 cm), i.e. stoniness, was estimated in the soil on the circular sampling circles by attempting to push a steel rod (d = 10 mm) down to a depth of 40 cm at 20 points (2/sampling circle) (Viro 1952). The actual penetration depth was recorded. The proportion of stones, boulders and bedrock in the 0-30 cm mineral soil layer was calculated using an empirical equation (Viro 1952, Tamminen 1991):
Stone volume percentage= 83-2.75 x mean penetration (cm) (1)
The mineral soil samples from the 0- 10 cm layer consisted of composite samples, each comprising five sub-samples from the 1st, 3rd, 5fh, 7th and 9th, or respectively the 2nd, 4th, 6th, 8th and 1Oth sub-plots. The mineral soil sample from the 10 to 30 cm layer consisted of a composite sample comprising five sub-samples from every second sub-plot. The
N
f s
=Vegetation square e = Humus sample • = Peat sample :• =Soil sampling pit f = Needle sampling tree
M1neral soil site r =2m
Figure 2. Sampling design on the 300m2 circular plot.
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deepest mineral soil sample (50 to 60 cm) was taken from one soil pit, the coordinates of which were determined by GPS. In the case of shallow bedrock or if the groundwater was too shallow, samples were taken down to the depth of this obstacle, e.g. 10- 15 cm, 50-55 cm etc.
The soils were classified, and samples were taken from the first and second genetic mineral soil horizons in the deepest pit: in most cases down to a depth of 60 cm, with a range of 0 to 60 cm. The uppermost horizon sampled was at least a 2.5 cm-thick E or A horizon. The second sampled horizon was taken from the B, BC or C horizon, but not more than 10 cm down from the upper limit. The deepest soil pits were photographed with a digital camera. The field forms used in the soil survey are given in Appendices 2a and 2b.
Nine FEH plots represented peatland sites (Fig. 1, Table 1). Peat samples were collected from three sampling points on each sub-plot to form three separate composite samples for each 0- 10 cm, 10-20 cm and 20-30 layer (Fig. 2). Thus each composite sample consisted of ten sub-samples. However, the sub-samples were not pooled until after the bulk density had been determined in the laboratory. The distance between each sampling point on each sub-plot was one metre (Fig. 2). Sampling was carried out on flat surfaces and the sampling point could not be located near the bank of a ditch or on a hummock that was clearly separated from its surroundings. If the systematically located sampling point did not fulfil these requirements, or there was e.g. a tree stem, stump, fallen dead wood or forest road at the specific point, the sampling point was primarily moved 0.5 m forwards to the centre point of the FEH plot, secondarily outwards, and then to the left or then to right. If any of these re locations was not suitable for sampling, peat samples were not taken at that point.
Peat samples were taken using a stainless steel peat sampler after any green (living) vegetation had been removed. The removed vegetation was taken as a separate sample for future studies. The sampler had a surface area of 27 mm x 63 mm ( 1701 mm2
) and a length of about 60 cm. The actual length of each sub-sample was measured. In most cases the length of the peat samples was 10 cm, but on some sites with a very shallow peat layer samples with a length of 5 cm were collected. The total thickness of the peat layer at each sample point was determined to an accuracy of 1 cm using a 2 m metal rod. Before cutting the individual peat layers, each peat profile was photographed with a digital camera (Fig. 3). All the relevant information was recorded on a field form (Appendix 2c ).
2.2.2 Vegetation sampling
Fresh plant samples were collected for chemical analysis inside each plot, but not from the actual vegetation quadrats, in the summer 2005 (Huhta & Korpela 2006). When possible, shoot samples of the most abundant or frequent evergreen and deciduous dwarf shrub, herb, grass, bryophyte and lichen species were collected from each plot. Only living above-ground biomass was sampled. The number of collected plant samples varied greatly depending on the vegetation type, because not all of the above-mentioned vegetation groups were present within every plot. The total number of plant samples was 343, representing 7 dwarf shrub, 16 herb, 10 grass, 7 bryophyte and 4 lichen species (Appendices 9- 11 ). The most frequently samples were taken from Vaccinium myrtillus
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9 ) J -3
Figure 3. An example of how the peat profiles were photographed before cutting the peat layers. The peat profiles were always in the same order in the photos, i.e. sampling point 1 was closest to the camera (Photo: A. Ryynanen/Metla).
(n =58), V vitis-idaea (n =50), Dryopteris expansa (n = 23), Deschampsiafiexuosa (n = 19), Pleurozium schreberi (n = 47) and Hylocomium splendens (n = 33). Shoot samples were subjectively selected evenly from different parts of the plot, placed in plastic bags, and stored frozen up until chemical analysis.
2.2.3 Foliage sampling
Leaf samples were collected for chemical analysis in August 2005, and needle samples in March 2006. Separate samples were taken from 4-10 dominant or eo-dominant trees of the dominant tree species on each plot. The sample trees were selected from a circle (r = 9.77±2 m) around the FEH centre point, which was the same as that used in soil profile description (Fig. 2). The samples were collected from southern and western aspects in the upper third section of the crown in accordance with the Pan-European Forest Condition Monitoring Programme (Manual on methods ... 2002). The samples were collected using an extendable branch cutter ( 18 m), each sample branch of conifer trees including at least two needle age classes (C =current-year, C+ 1 =previous-year needles). During sampling the location of the tree was determined and the diameter at breast height (DBH) of the tree measured. The average DBH of the sample trees was 183 mm for Scots pine, 188 mm for Norway spruce, 95 mm for birch, and 179 mm for common alder. The sample trees were marked with a number painted at breast height on the tree (conifers) or by attaching a number plate with copper wire (deciduous trees, Fig. 4).
The total number of pine foliage sample plots was 30, spruce 39, birch 15 and common alder 6. The total number of individual sample trees was 279, 325, 132 and 50 for pine, spruce, birch and alder, respectively. Samples could not be collected on all the FEH plots owing to the changes in land use or the forest management activities carried out on some of the plots. Furthermore, the number of individual sample trees per FEH plot varied
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due to the lack of dominant or eo-dominant trees representative of the prevailing site conditions (Appendix 12).
2.3 Pre-treatment and analysis of the samples
2.3.1 Soil samples
Soil samples from mineral soil sites were delivered immediately to the pre-treatment station of the Finnish Forest Research Institute at Salla, Lapland, where they were weighed as field fresh, and then air dried and weighed as air-dry. The peat samples were dried at a temperature of +60 oc in the laboratory of the Parkano Research Unit. Peat type was determined from the individual layers from one sampling point on each sub-plot before drying. Peat type classification was based on macroscopic determination of the relative occurrence of individual peat components in the peat samples (Laine & Vasander 1986, Laine et al. 2000). After drying, the peat samples were weighed and the bulk density (g cm-3
) calculated for each sub-sample. Peat and organic layer samples were ground in a mill to pass through a 2 mm bottom sieve, and the mineral soil samples were sieved with a 2 mm sieve. All the analyses were performed on the < 2 mm fraction.
The pH in a water suspension ( 10 ml of sample and 25 ml of distilled water) and the particle size distribution of the mineral soil samples (0.06<d<20 mm), were determined at Salla. In the latter analysis, the mineral soil samples were boiled in water + H
2 0
2
to destroy organic matter, and the fine fractions (d<0.06 mm) then washed through a 63 )liD sieve. The rest of the sample was dried and the coarse fractions (63>d>2000 )liD)
determined using 63, 200 and 630 )liD sieves in a sieving machine (see Heiskanen & Tamminen 1992).
The particle size distribution of all the fine-textured and some of the medium-textured mineral soils was determined on a Coulter LS230 laser diffraction analyser in the laboratory of the Department ofForest Ecology, University ofHelsinki.
Figure 4. Labelled sample trees on FEH plots: a) conifers (e.g. Scots pine) and b) deciduous trees (e.g. common alder; Photos: A. Ryynanen/Metla).
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Most of the other analyses were performed at the Central Laboratory of the Finnish Forest Research Institute in Vantaa. The concentrations of exchangeable cations were determined by extracting the samples with 0.1 M BaC1
2 (15 ml of sample to 150 ml of extractant),
shaking for 2 hours, followed by filtration and analysis by inductively coupled plasma atomic emission spectrometry (ICP/AES). Exchangeable acidity was determined on an aliquot of 50 ml by titrating the filtrate to pH 7 with 0.05 M NaOH. Total carbon and nitrogen concentrations were determined on all the samples, except for the 50-60 cm and genetic horizon samples, on a Leco CHN-1000 analyser (the peat samples were analysed on a Leco CHN-2000 at the Parkano Research Unit). Total elemental concentrations were determined by wet digestion (H
2 0
2 + HNOJ The elemental concentrations were then
analysed by ICP/AES. The pH in a 0.01 M CaC1 2
suspension was determined on 20 organic layer and 20 mineral soil samples. The pH(CaCl) values for the rest of samples were calculated using an equation generated on the basis of the above 40 samples:
pH(CaCl) = -2.035+ 1.33**pH(H 2 0); (R2 = 0.90) (2)
In addition, pH(CaC1 2
) was measured on all the peat samples. The genetic horizon samples were analysed for aluminium and iron using acid ammonium oxalate extraction (Loeppert & Inskeep 1996).
The cation exchange capacity (CEC) was estimated as follows:
(3)
where H+ is exchangeable acidity, and the base cations (Ca, Mg, K, Na) are expressed as mmol( +)/kg. Base saturation was calculated as the proportion of base cations out of CEC:
(4)
2.3.2 Vegetation samples
Current-year (2005) shoots of the dwarf shrubs (evergreen species mainly Vaccinium vitis-idaea and deciduous one Vaccinium myrtillus) were separated and the leaves were detached for chemical analysis. In the case of Calluna vulgaris and Lycopodium annotinum, the sample consisted of young shoots (stems and leaves). On the other hand, for small herbs (e.g. Maianthemum bifolium and Trientalis europaea) the sample consisted of the whole above-ground shoot, excluding inflorescences, whereas for tall herbs (Filipendula ulmaria, Rubus idaeus and Rubus saxatilis) only the leaves were taken. The grass sample consisted ofleaves and stems, excluding inflorescences. The bryophyte samples consisted of the three youngest annual segments (C, C+ 1, C+ 2). For reindeer lichens ( Cladina) the upper, light-coloured part was separated from the darker (decomposing) lower part for the sample. The plant material was not washed before chemical analysis and thus included elements in particles adhering to the surface of the material. All the plant samples were handled using plastic gloves.
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The chemical composition was determined separately for each plant species. The samples were oven-dried ( + 60 ac) and homogenized. The carbon and nitrogen concentrations of the plant samples were analysed on a CHN analyser (Leco CHN-2000) in the laboratory of the Parkano Research Unit. The element concentrations (P, K, S, Ca, Mg, B, Cu, Zn, Mn, Na, Fe, Al, Cd, Cr, Ni, Pb and Mo) were determined by wet digestion (HNO/H
2 0
2 ) and
analysed by ICP-AES in the Central Laboratory of the Finnish Forest Research Institute. Wet digestion was carried out in a microwave oven. The results were expressed on a dry matter basis (determined by drying at + 105 °C).
2.3.3 Needles and leaves
The sample branches were stored in sealed plastic bags in a freezer (-20 ±4 °C) until pre-treatment. Pre-treatment of the needle and leaf samples was performed separately for each sample tree. The current (C) and previous-year (C+ 1) branch sections with the needles still attached were first separated from each other and then dried at a temperature of +60 °C. After drying, the needles were removed from the branch sections. The leaves including petioles were separated from the branches before drying ( +60 °C). The sample for the needle or leaf analyses was prepared by combining an equal amount in weight of dried needles or leaves from each sample tree to form a composite sample before homogenising in an ultracentrifuge mill.
During pre-treatment, the dry weight ( + 105 °C) of 100 needles or leaves was determined for each FEH plot. The foliar element concentrations were analysed in the same way as for the vegetation samples (see Ch.2.3.2).
2.4 Statistical analysis
The differences in soil properties were tested between site types or tree species using one way anova in which pair-wise comparisons were made using the Bonferroni test.
Site type -specific means and standard error of means (se) of the C concentration and the element concentrations of the plant species and life-forms (evergreen dwarf shrubs, deciduous dwarf shrubs, herbs, grasses, bryophytes and lichens) were calculated. Pair wise differences in the element concentrations of the life-forms within the site types were tested by the LSD (Least Significant Difference) method.
The data for elemental concentrations of bryophytes and Vaccinium myrtillus were analysed by global nonmetric multidimensional scaling (NMDS) in order to determine the main chemical gradients of the plots where the species grew (R programme version 2.2.1, Vegan package, Oksanen 2007). The two-dimensional solution using the Bray Curtis coefficients as a measure of dissimilarity in the chemical composition between the plots was chosen for the final method. The Fe concentration of the plants, indicating soil dust and particle deposition, was fitted (Generalized Additive Model) to the ordination configurations of the sample plots in order to find the plots receiving the highest deposition level.
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3.1 Physical properties of the soil
There were a considerable amount of stones, boulders and exposed bedrock on the plots. The mineral soil layer was missing, or was less than 10 cm thick, on nine plots. The 0-30 cm mineral soil layer contained, on the average, 21% stones or bedrock on the control plots, while the corresponding figure on Olkiluoto Island was 61%. There was also gravel far less on the control plots, 8%, than on Olkiluoto, 28%. The groundwater on Olkiluoto occurred within a depth ofO to 40 cm on 15 plots. The depth of24 of the 85 deep profile pits was less than 50 cm owing to the presence ofbedrock, large boulders or groundwater.
The organic layer on the mineral soil sites was classified in most cases on both the Olkiluoto and control plots as mor, but on Olkiluoto the organic layer was also quite often peat or mull-like peat (Table 4). The organic layer was thicker on the Olkiluoto mineral soil sites than on the control plots, mainly due to the high proportion of peat and mull-like peat (Table 5). The organic layer type on all the peatland plots was peat (organic matter content >40%, Table 6). The peatland sites had shallow peat layers (Table 5), which is typical for young soils in coastal areas of western Finland. Peat density increased in the order: pine < birch< alder (Table 6).
The mineral soil on both the Olkiluoto and control plots was coarse-textured (Table 7), as is normally the case on Finnish forest sites (Tamminen 2000). The medium particle size class was very fine sand (63 to 200 )liD) on both the Olkiluoto and control plots, corresponding to the average values for all Finnish forest soils (Tamminen 2000).
Table 4. Organic layer types on the mineral soil sites.
Organic layer type1 1 Total 0 1 2 3 4 5
Olkiluoto 3.9 56.1 4.1 0.2 7.2 28.5 100.0
Control 0.7 92.6 4.1 1.1 1.5 100.0
11 0 missing, 1 mor, 2 moder, 3 mull, 4 peat, 5 mull-like peat.
Table 5. Distribution of the thickness (cm) of the organic layer by percentiles.
M in 25% 50% 75% Max
Olkiluoto, mineral soil sites 2.3 3.8 5.4 7.0 21.1
Control, mineral soil sites 2.6 3.0 3.6 4.9 5.6
Olkiluoto, peatland sites 6.0 12.0 23.0 30.0 115.0
22
Table 6. Organic matter content (OM) and bulk density of the peat layers by dominant tree species.
Layer (cm) OM(%) Density (g cm-3)
Pine Birch Alder Pine Birch Alder
0-10 Mean 95.1 85.5 74.0 0.128 0.179 0.251
M in 93.7 79.7 59.6 0.094 0.147 0.204
Max 96.5 91.3 88.3 0.163 0.227 0.297
10-20 Mean 95.2 83.0 0.126 0.193
M in 93.8 78.1 0.078 0.155
Max 96.7 87.5 0.175 0.250
20-30 Mean 92.8 82.2 0.146 0.197
M in 89.7 77.6 0.093 0.150
Max 95.9 84.7 0.200 0.281
Table 7. Distribution of the proportion (%) of clay (d<2 11m) and fine fractions (d< 63 11m) in the 10-30 cm mineral soil layer.
Clay Fines
M in 25% 50% 75% Max M in 25% 50% 75% Max
Olkiluoto 0.3 1.5 3.1 4.0 16.8 3.0 14.9 26.2 33.2 61.0
Control 0.9 2.0 3.5 7.7 11.4 9.5 18.1 42.7 57.4 66.9
3.2 Soil acidity
The acidity of the soils on Olkiluoto was, as a whole, similar to the corresponding values for forest soils in Finland (Tables 8 and 9, Laine & Vasander 1996, Tamminen 2000). Exchangeable acidity was, on corresponding types of plot (site type and tree species), higher in the organic layer and lower in the 0- 10 cm mineral soil on Olkiluoto than on the control plots. The plots were classified approximately into classes based on the pH of the organic layer as follows:
1) the least fertile sites on Olkiluoto (i.e. CT forest site type, bedrock sites) pH 3. 7-3 .8, 2) all VT and MT sites, pH 4.1-4.2, 3) all OMT sites, pH 4.4, 4) birch stands on Olkiluoto, pH 4.5, 5) and alder stands on Olkiluoto 5.1.
23
Table 8. Mean exchangeable acidity (H+, mmol(+ )/kg) and pH(H 2 0) in the organic layer
by forest site type and by dominant tree species. Values for the control plots (n = 9) are in italics.
Forest site type11
Lh+OMT MT VT CT Bedrock All
83 47 93 75 95 183 180 98 4.4 4.4 4.2 4.1 4.1 3.7 3.8 4.3
Dominant tree species Pine Spruce Birch Alder All
113 65 96 66 94 34 98 4.1 4.2 4.2 4.2 4.5 5.1 4.3
11 Lh "" the most fertile, herb-rich sites, OMT = Oxalis acetosella- Vaccinium myrtillus sites, MT = Vaccinium myrtillus sites, VT = Vaccinium vitis-idaea sites, CT = Calluna vulgaris sites, CIT = Cladina sites, Bedrock = sites with no or a very shallow mineral soil layer.
Table 9. Mean pH in the peat layers by dominant tree species.
Layer (cm) pH Tree species
Pine Birch Alder All
CaC1 2
CaC1 2
CaC1 2
4.0 4.0 4.0
The organic layer in alder stands growing near the seashore was much less acid than in the other classes.
3.3 Exchangeable base cation concentrations
The concentrations of exchangeable Ca, Mg and Na in the surface soil were higher on Olkiluoto than on the control plots (Table 1 0). The maximum concentrations ofNa and Mg
24
Table 10. Distribution of base cation concentrations (Ca::+, K+, Mg::+, Na+, mmol(+)/kg), cation exchange capacity (CEC, mmol(+ )/kg) and base saturation (BS, %) by soil layer. Values of the control plots (n = 9) are given in italics.
Soil type Ca K Mg Na CEC BS
Layer
Organic (n=85)
M in 60 72 9 9 21 13 1.5 1.1 261 150 35 64 Median 200 158 18 21 49 34 3.3 1.9 378 294 75 74 Max 620 234 30 34 283 56 145 3.1 749 358 99 91
0-10 cm (n=76)
M in 1.3 1.7 0.3 0.6 0.9 0.6 0.2 0.2 23 27 11 10 Median 12.1 5.9 1.2 1.0 5.0 1.7 0.5 0.3 49 47 40 17 Max 182 16 3.4 2.3 32.7 6.3 22.0 0.9 216 79 99 32
10-30 cm (n=75)
M in 1.4 2.2 0.3 0.2 0.7 0.4 0.2 0.2 14 8 10 18 Median 10.2 2.7 1.1 0.5 3.9 0.5 0.4 0.3 30 16 54 34 Max 35.0 16.2 3.2 1.4 19.3 11.2 11.5 1.0 75 49 99 54
50-60 cm (n=56)
M in 0.5 0.5 0.1 0.2 0.4 0.1 0.1 0.2 1.6 2.2 11 20 Median 10.6 1.5 1.5 0.2 4.3 0.4 0.4 0.3 23.0 6.4 85 53 Max 54.4 79.8 4.3 3.5 39.5 102 4.0 4.2 80.2 191 100 99
Peatland sites
Median 212 12.9 61.6 5.9 431 69
Max 534 21.3 204 23.0 799 97
10-20 cm (n=6)
Median 217 7.0 60.3 8.3 428 71
Max 453 18.2 197 27.3 707 98
20-30 cm (n=5)
Median 287 3.4 69.9 10.7 457 80
Max 312 11.3 127 18.8 476 97
25
especially were high on Olkiluoto. In conifer stands on MT and OMT sites the base cation concentrations in the organic layer were, apart for K, significantly higher on Olkiluoto than on the control plots.
The concentrations of base cations, especially Ca, correlated with the forest site type, which was used to estimate site fertility (Table 11 ). On peatland sites, base cations did not correlate with the site type (Table 12). The results for Na and Mg on Olkiluoto differed the most from the control material, the values being clearly higher on Olkiluoto (Table 11).
The concentrations ofbase cations, especially those ofNa and Mg, were on the alder plots as much as 30 to 60 times higher than on the control pine plots (Table 13). These alder soils are the youngest in the material. They emerged from the sea only a few centuries ago and still contain sea salts rich in sodium and magnesium, and probably still receive sea salts as droplets or spray during storms. The differences between Olkiluoto and the
Table 11. Mean exchangeable base cation concentrations (mmol(+ )/kg), cation exchange capacity (CEC, mmol(+ )/kg) and base saturation (BS, %) by soil layer and by forest site type. Values of the control plots (n = 9) are given in italics.
Layer n Ca K Mg Na CEC BS Site type
Organic 1+21) 37 249 207 16.2 20.8 76.2 39.8 16.3 2.0 441 316 78 85
3 37 229 139 20.0 22.5 52.9 29.7 4.3 2.1 399 269 76 71
4 2 161 23.8 44.5 3.1 327 71
5+6 3 100 20.3 41.0 5.0 350 47
7 6 76 18.6 27.2 3.1 305 41
0-10 cm
1+2 37 22.0 9.9 1.4 1.4 8.4 3.1 2.2 0.54 56 58 54 24
3 37 14.2 4.7 1.2 0.9 4.9 1.5 0.5 0.40 50 44 40 16
4 2 10.9 1.3 5.6 0.4 52 34
10-30 cm
1+2 36 13.2 7.9 1.3 0.8 6.2 4.4 1.40 0.55 33 33 63 38
3 37 10.7 5.1 1.1 0.4 4.3 1.9 0.55 0.40 33 20 52 35
4 2 9.9 1.2 5.6 0.35 37 50
50-60 cm
1+2 32 14.2 27.8 1.6 1.3 6.3 34.2 0.73 1.59 26 68 82 64
3 29 10.0 6.1 1.5 0.4 5.3 2.8 0.59 0.34 25 13 69 53
4 8.1 1.7 8.2 0.40 26 70
11 Forest site type: 1 = Lh, 2 = OMT, 3 = MT, 4 = VT, 5 = CT, 6 = CIT, 7 = bedrock sites (see the
footnote below Table 1 ).
26
Table 12. Mean exchangeable base cation concentrations (mmol(+ )/kg), cation exchange capacity (CEC, mmol(+ )/kg) and base saturation (BS, %) by peat layer and by site type on the peat/and sites.
Layer (cm) Site type n Ca K Mg Na CEC BS
0-10 211 5 285 14.4 91.1 10.6 485 78
3 3 145 14.7 46.0 6.6 409 50
5 1 212 12.2 64.0 8.3 427 69
10-20 2 2 353 12.5 134 16.3 575 87
3 3 142 6.4 46.4 8.9 384 52
5 1 239 7.2 64.6 8.6 431 74
20-30 2 2 265 6.9 98.3 11.9 436 87
3 2 254 4.5 77.1 11.0 418 82
5 1 300 3.1 63.5 7.5 468 80
11 Site type: 2 = OMT and corresponding mire and drained peatland site types, 3 = MT and corresponding mire and drained peatland site types, 5 ~ CT and corresponding mire and drained peatland site types (see the footnote below Table 1 and Laine & Vasander 2005).
control plots seemed to decrease on moving towards deeper soil layers. The amounts of exchangeable base cations (kg/ha) in the soil layers on the mineral soil sites are presented by site type and by tree species in Appendices 3 and 4.
3.4 Total carbon and nitrogen in the soil
Olkiluoto and the control plots had higher nitrogen concentrations and lower C/N ratios than the average for Finnish forest soils, indicating somewhat higher soil fertility (Table 15, Tamminen 2000). Nitrogen concentration in the peat varied between 1.36 and 2.92% (Table 15). According to Pietiliiinen et al. (2006), a total nitrogen concentration of 1.5-2.0% in peat ensures a satisfactory nitrogen mineralisation rate for trees growing on peatland when the effective temperature sum is 950-1100 d.d. The long-term (1971- 2000) average temperature sum on Olkiluoto Island ( 1301 d. d., based on the data provided by the Finnish Meteorological Institute and calculated according to Ojansuu & Henttonen, 1983) is considerably above this range. The C/N ratios in the peat, which in most cases were below 25-30 (Table 15), also indicated conditions favourable for nitrogen mineralisation (Pietiliiinen et al. 2006).
As expected, the nitrogen concentration increased and the C/N ratio decreased from poor to more fertile site types (Tables 16 and 17, Tamminen 1993, Pietiliiinen et al. 2006). On
27
Table 13. Mean exchangeable base cation concentrations (mmol(+ )!kg), cation exchange capacity (CEC, mmol(+)lkg) and base saturation (BS, %) by soil layer and by dominant tree species. Values of the control plots (n = 9) are given in italics.
Layer n Ca K Mg Na CEC BS
Tree species
Organic Pine 30 184 118 16.9 20 41.2 20 3.0 1.8 358 225 66 70 Spruce 40 234 184 20.4 23 60.0 39 6.8 2.2 417 314 75 79 Birch 10 258 15.9 59.1 3.8 431 76 Alder 5 258 15.7 185.6 79.8 573 92
0-lOcm Pine 22 17.4 4.6 1.2 0.8 5.2 1.0 0.4 0.3 51 35 47 18 Spruce 39 15.2 7.4 1.3 1.2 5.9 2.5 0.9 0.5 52 56 42 19 Birch 10 28.6 1.2 6.6 0.6 57 48 Alder 5 19.9 2.2 18.5 10.0 59 84
10-30 cm Pine 22 12.6 3.0 1.0 0.3 4.2 0.5 0.4 0.3 33 11 56 37 Spruce 39 10.8 7.5 1.2 0.7 4.6 3.8 0.6 0.5 31 31 54 35 Birch 9 11.5 1.3 4.8 0.8 33 53 Alder 5 17.8 2.6 15.5 6.1 45 94
50-60 cm Pine 18 10.0 1.5 1.3 0.4 3.7 0.2 0.4 0.2 20 6 73 54 Spruce 32 10.7 19.3 1.5 0.9 5.4 19.9 0.5 1.0 24 44 75 58 Birch 8 13.4 1.9 9.3 0.9 34 70 Alder 4 30.3 2.7 11.9 2.5 48 100
Table 14. Mean exchangeable base cation concentrations (mmol(+)/kg), cation exchange capacity (CEC, mmol(+ )/kg) and base saturation (BS, %) by peat layer and by dominant tree species.
Layer (cm) Tree species n Ca K Mg Na CEC BS
0-10 Pine 2 373 14.2 134.0 15.6 613 83 Birch 5 158 15.4 52.0 5.5 400 56 Alder 2 268 11.7 64.4 11.1 425 82
10-20 Pine 2 346 12.7 130.8 17.9 569 86 Birch 4 170 6.5 52.6 8.0 399 58 Alder 0
20-30 Pine 2 293 7.2 95.1 13.1 463 88 Birch 3 250 3.8 74.7 9.0 417 80 Alder 0
28
Table 15. Distribution of the total carbon and nitrogen concentrations (%dry weight) and C/N ratio. Values of the control plots (n = 9) are given in italics.
Soil type n c N C/N
Layer
Median 39.5 40.2 1.62 1.34 23.2 25.4
Max 48.7 41.6 2.71 1.73 36.6 35.2
0-10 cm 76
Median 1.7 3.4 0.11 0.15 15.7 20.6
Max 7.3 5.2 0.46 0.31 22.3 24.3
10-30 cm 75
Median 0.6 1.8 0.06 0.1 11.4 18.3
Max 5.8 2.5 0.45 0.13 22.9 20.3
Peatland sites
Median 47.1 2.11 20.3
Max 52.7 2.88 34.3
Median 46.5 2.21 19.6
Max 52.8 2.81 35.7
Median 48.2 2.53 17.9
Max 54.3 2.92 25.3
29
Table 16. Mean total carbon and nitrogen concentrations (% dry weight) and the C/N ratio by soil layer and by forest site type. Equality of the site type means on Olkiluoto was tested by one-way anovan. Equal mean values are marked with the same letter (Bonferroni test). Values of the control plots (n = 9) are in italics. Levels of significance: * p<O. 05, ** p<0.01, *** p<0.001.
Layer n c N C/N
Site type
Organic 1+221 37 36.2a 34.5 1.78 1.42 20.9a 24.4
3 37 39.3ab 35.5 1.62 1.27 24.4b 28.0
4 2 41.0ab 1.37 30.0bc
5+6 3 47.4b 1.41 33.8c
7 6 40.9ab 1.57 26.3b
F value11 3.55* 2.10 19.47***
0-10 cm
3 37 2.0 2.7 0.12 0.14 17.2b 20.2
4 2 2.3 0.11 22.0b
F value11 0.16 1.62 11.91***
10-30 cm
3 37 1.0 1.5 0.07 0.08 12.8b 18.2
4 2 1.4 0.08 16.7b
F value11 2.16 0.48 5.90**
21 Forest site type: 1 = Lh, 2 = OMT, 3 = MT, 4 = VT, 5 = CT, 6 = CIT, 7 = bedrock sites (see the footnote below Table 1 ).
the mineral soil sites on Olkiluoto, the C/N ratio in the organic layer was the best indicator of the fertility level of the forest site types (Table 16).
The C/N ratio of the organic layer also reflected the tree species, as for the site types (Tables 18 and 19), but there were no statistical differences between tree species in the mineral soil layers. The soil in the alder stands contained plenty of nitrogen and had a very low C/N ratio. However, the nitrogen status in the conifer stands growing on mineral soil was also better than the average for Finnish forest soils (Tamminen 2000), the C/N ratio in the organic layer being 27 on the OMT sites and 37 on the MT sites. The amounts of organic matter, carbon (Mg ha-1) and nitrogen (kg ha-1) in the organic and 0-10 and 10-30 cm mineral soil layers on the mineral soil sites are given by site type and by tree species in Appendices 5 and 6.
30
Table 17. Mean total carbon and nitrogen concentrations (%) and the C/N ratio by soil layer and by site type on the peat/and sites. Equal mean values are marked with the same letter. Levels of significance: * p<0.05, ** p<O.Ol, *** p<O.OOJ.
Layer (cm) Site type n c N C/N
0-10 211 5 44.2 2.20 21.3
3 3 45.2 2.11 21.5
5 1 52.7 1.63 32.3
F value 0.73 0.61 1.36
10-20 2 2 49.7a 2.09 27.0
3 3 43.0a 2.28 18.9
5 1 52.8a 1.65 32.0
F value 15.72* 0.42 1.53
20-30 2 2 48.3a 2.49 21.0
3 2 44.0a 2.53 17.4
5 1 54.3a 2.15 25.3
F value 23.49* 0.29 1.67
11 Site type: 2 "" OMT, 3 = MT, 5 ""' CT (see the footnotes below Tables 1 and 12).
In the pine stands on peatland, both the low nitrogen concentration and the high C/N ratio in the peat indicated poorer nutrient status than in the deciduous tree stands (Table 19). The amounts of soil carbon and nitrogen clearly increased from pine peatland sites to alder forests, but the difference between the pine and alder sites was significant only in the amount of nitrogen in the 0-10 cm peat layer (Table 19). The amount of nitrogen in the 30 cm-thick peat layer of the pine sites was approximately the same as the values presented by Kaunisto and Paavilainen (1988), Kaunisto and Moilanen (1998) and Westman and Laiho (2003).
3.5 Total element concentrations and amounts in the organic layer
Total element concentrations were determined only on the organic samples. The analysed elements treated can be classified as macronutrients (Ca, K, Mg, P, S), micro-nutrients (B, Cu, Fe, Mn, Zn), heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) and other elements (Al, Na), although the classes are partly overlapping.
All the elements, except for Mn, appeared to have higher concentrations on the Olkiluoto mineral soil sites than on the control plots (Table 20). The average Cu concentration was
31
Table 18. Mean total carbon and nitrogen concentrations (%) and the C/N ratio by soil layer and by dominant tree species. Equal mean values are marked with the same letter. Values of the control plots (n = 9) are in given italics. Levels of significance: * p<0.05, ** p<0.01, *** p<0.001.
Layer
Organic
Birch 10 36.9 1.73a 21.4b
Alder 5 36.0 2.32b 15.5a
F value 1.19 13.79*** 13.74***
0-10 cm Pine 22 2.0 1.8 0.12 0.09 16.8 19.5
Spruce 39 2.2 3.6 0.14 0.18 16.2 20.6
Birch 10 2.1 0.14 15.0
Alder 5 2.0 0.15 13.2
F value 0.05 0.47 2.03
10-30 cm
Birch 9 0.8 0.06 11.8
Alder 5 0.7 0.07 10.0
F value 1.04 0.47 1.04
2.8 times higher on Olkiluoto, while the Mn concentration was only 27% of that on the control plots. Heavy metal concentrations were all higher on Olkiluoto than in Finnish forest soils, on the average (Tamminen 2000). The Cu concentration was as much as four times higher on Olkiluoto compared to the average Cu concentration in Finland in 1986- 1989 (Tamminen 2000). The total amounts of individual elements (kg ha-1) in the organic layer on the mineral soil sites are presented by forest site type in Appendix 7.
The total P, Ca and Mn concentrations in peat (Table 22) were relatively similar to the values reported by Kaunisto and Paavilainen ( 1988) and Kaunisto and Moilanen ( 1998) for corresponding drained peatland types and peat layers in southern Finland (P 327-1363, Ca 534-7141 and Mn 5-104 mg kg-1). In contrast, the K, Mg, Cu, Zn, B and Fe concentrations in the peat in Olkiluoto ranged from about 2- to 40-fold the values reported by Kaunisto and Paavilainen (1988) and Kaunisto and Moilanen (1998) for drained peatlands (K 56-321, Mg 99-741, Cu 1.6-15.2, Zn 1.2-19.2, B 0.2-2.3 and Fe 1540-8833 mg kg-1).
32
Table 19. Mean total carbon and nitrogen concentrations(%) and the C/N ratio, and the amounts of carbon and nitrogen (kg m-2
) by soil layer and by dominant tree species on the peat/and sites. Equal mean values are marked with the same letter. Levels of significance: * p<0.05, ** p<O.Ol, *** p<O.OOJ.
Layer n C,% N,% C/N C, kgm-2 N, kgm-2
Tree species
0-10 cm Pine 2 50.6 1.52 33.3a 6.565 0.199a Birch 5 45.7 2.23 20.6b 8.166 0.402ab Alder 2 39.8 2.39 16.6b 9.557 0.574b
F value 1.80 4.20 44.31*** 1.66 9.22*
10-20 cm Pine 2 50.5 1.50a 33.8a 6.489 0.197 Birch 4 45.0 2.41b 18.7b 8.796 0.474 Alder 0
F value 2.42 15.77** 105.68*** 0.75 4.40
20-30 cm Pine 2 51.3 2.10a 24.4a 7.655 0.310 Birch 3 45.4 2.66b 17.1a 9.056 0.535 Alder 0
F value 3.83 10.77* 75.12** 0.14 1.21
The alder sites differed from the other sites in the total element concentrations, as was the case for exchangeable cation concentrations (Tables 13 and 21). The alder sites had about three times higher Mg, about five times higher B and about 10 times higher Na concentrations. The total Mg, B and Na concentrations on the peatland sites were not elevated (Table 22). However, the total Al, Cr, Cu and Fe concentrations in the two uppermost peat layers especially were clearly higher in the birch and alder stands than in the pine stands (Table 22). The amounts of plant nutrients, excluding P and Mn in 30-cm thick peat layer (Table 23), were clearly higher than the values reported by Kaunisto and Paavilainen (1988), Kaunisto and Moilanen (1998) and Westman and Laiho (2003) for corresponding peatland sites; the amounts of P and Mn were at about the same level as those reported in the above-mentioned studies.
3.6 Soil and peat types on Olkiluoto
The soils on Olkiluoto were poorly developed due to the short time span of about 500 to 2,000 years. It takes from 500 to 1,500 years for a Podzol to develop on sorted sands along the coasts of Gulf ofBothnia (Jauhiainen 1973, Starr 1991 ). Therefore, the lack ofPodzols
33
Table 20. Distribution of total element concentrations (mg kg1 ) in the organic layer of
the mineral soil sites. Equality of the means in the Olkiluoto and the control material was tested by the t testn. Levels of significance: * p<0.05, ** p<O.Ol, *** p<O.OOJ.
Element Olkiluoto Control plots
M in Median Max M in Median Max t value11
Al 1607 4823 13430 1357 2510 10020 1.29***
B 3.0 6.5 73.6 3.8 4.3 8.8 2.94**
Ca 1277 4633 15430 2420 4077 6483 1.85
Cd 0.24 0.58 2.06 0.31 0.36 0.63 6.23***
Cr 3.3 11.1 30.5 5.0 7.8 18.3 1.75
Cu 17.8 28.1 70.4 8.4 9.9 17.7 12.92***
Fe 1937 5897 15730 1353 2910 9937 2.19
K 805 1333 3820 965 1207 2153 1.14
Mg 496 1237 6820 651 726 2743 1.95
Mn 35 235 1383 165 872 2580 -2.39*
Na 66 129 3473 63 91 163 2.83**
Ni 7.9 12.7 29.0 5.1 6.9 12.9 6.90*** p 686 1038 2260 636 911 1217 2.53*
Pb 19.2 36.5 158.7 22.5 32.5 162.3 -0.77
s 1049 1737 4583 773 1317 1727 4.79***
Zn 22.6 71.0 142.2 30.1 61.6 104.9 1.76
on Olkiluoto was expected (Table 24). On the other hand, seven of the nine control plots were Podzols. The most common soil types on Olkiluoto were poorly developed (often podzolized) coarse to medium coarse arenosols (Figs. 5 and 6) or fine-textured Regosols, shallow Leptosols and Gleysols (Fig. 7), characterized by a shallow groundwater (Table 24).
Lithic Leptosols are bedrock sites covered by less than 10 cm layer of mineral soil. Gleysols are fine to medium fine soils having reducing conditions or an average groundwater table within 50 cm from the mineral soil surface. Umbric Gleysols have a peat layer 11 to 39 cm thick, and Dystric Gleysols have an organic layer not more than 10 cm thick. Gleyic Arenosols have reduced conditions or an average groundwater table within 50 to 100 cm of the mineral soil surface, Cambic Arenosols have a mull layer, an Ah horizon instead of a leached E horizon, and Haplic Arenosols form the rest of Arenosols and are often poorly developed Podzols. Regosols are finer-textured, undeveloped soils with no horizons. Podzols are soils which fulfil the texture, carbon, pH and leaching- accumulation criteria of the FAO system. The criteria for Podzols are a Spodic B horizon, which must have at least 0.5% of aluminium+ 0.5%·iron extracted with acid ammonium oxalate, and the ratio of between the B and E horizon must be at least 2, i.e. B AI+oi,F/E AIW,Fe> 2. On Olkiluoto
34
Table 21. Mean total concentrations (mg kg1 ) in the organic layer of the mineral soil sites
by dominant tree species. Values of the control plots (n = 9) are given in italics.
Element Pine Spruce Birch Alder
Al 4890 3550 4760 3970 5600 8170
B 5.5 4.0 7.5 5.5 6.6 31.3
Ca 4430 3310 5620 4900 6230 6960
Cd 0.76 0.34 0.63 0.41 0.61 0.54
Cr 13.2 10.2 10.9 9.3 14.0 20.1
Cu 29.2 9.5 29.7 12.1 34.2 41.6
Fe 5540 3990 5790 4040 7410 10200
K 1430 1220 1480 1420 1440 2380
Mg 1250 898 1400 1130 1610 4290
Mn 284 575 322 1110 379 477
Na 117 105 201 101 145 1950
Ni 12.4 6.0 13.3 8.0 15.3 23.2 p 1110 789 1070 1010 1190 1150
Pb 47.5 38.9 38.5 58.4 34.8 27.4
s 1570 1030 1810 1420 2070 3020
Zn 78.0 61.2 73.9 62.0 69.6 69.6
these chemical criteria were not fulfilled. Gleyic Cambisols have reduced conditions or an average groundwater table within 50 to 100 cm from the mineral soil surface, and Dystric Cambisols have a potential base saturation under 50% (determined using neutral ammonium acetate extraction). Cambisols must have in the B horizon at least 8% of clay and at least a moderately developed secondary structure and more colour in the B horizon than in the underlying BC or C horizon.
Carex peats with peat components of Cyperaceous, Sphagnum, Phragmites australis, Lignum and Equisetum dominated in the area of Olkiluodonjiirvi (FEH plots 918278, 919276, 920274, 921272 and 921273, Appendix 8). On the alder peatlands the dominating peat types were woody and Carex peats, i.e. c:_vperaceous-Lignum or Lignum-c:_vperaceous peat (FEH plots 911275 and 921245). Sphagnum peat was typical for Liiklansuo (FEH921257), and Sphagnum-lignum and Lignum-Sphagnum peat type for FEH plot 917263 (Appendix 8).
3.7 Variation in soil properties
An attempt was made to estimate the variation in the properties of the surface soil on the basis of the collected samples. Three composite samples, each comprising 10 sub samples, were collected from the organic layer. The sampling error was estimated as the
35
Table 22. Distribution (m in, median, max) and mean value of total element concentrations (mg/kg) in the individual peat layers on the peat/and sites. Mean values are presented by dominant tree species.
Layer Element n M in Median Max Mean values (cm) Pine Birch Alder
n = 2,2,2 IJ n = 5,4,3 IJ n=2
0-10 AI 9 710 3947 7757 1567 4755 3335
B 9 4.2 5.5 10.2 7.2 5.4 7.7
Ca 9 1278 4613 12833 8723 3516 6028
Cd 9 0.28 0.53 0.81 0.47 0.60 0.34
Cr 9 1.6 6.2 12.4 2.4 8.0 5.9
Cu 9 12.7 29.1 71.4 16.2 41.0 33.6
Fe 9 1900 7130 15330 2750 9756 6782
K 9 498 784 1044 651 859 705
Mg 9 684 1007 2803 1852 956 1272
Mn 9 26.3 40.1 148.7 73.0 60.7 51.3
Mo 3 0.92 1.86 3.00 1.4 3.0
Na 9 69.2 151.3 578 384 158 300
Ni 9 4.9 14.9 29.9 9.9 18.1 12.5 p 9 635 937 1270 668 1026 871
Ph 9 14.4 23.8 31.0 21.0 26.6 21.9
s 9 2060 5210 11151 5907 6698 2580
Zn 9 21.7 35.2 76.1 55.8 41.7 28.9
10-20 AI 6 638 4887 9173 1049 6173
B 6 3.3 5.2 8.1 5.7 5.3
Ca 6 985 5007 10733 8005 3921
Cd 6 0.30 0.49 1.33 0.39 0.67
Cr 6 0.99 8.9 17.4 1.7 12.0
Cu 6 7.3 37.7 93.4 9.8 52.8
Fe 6 1573 5295 30467 1705 12229
K 6 292 654 936 522 636
Mg 6 793 990 2587 1723 1086
Mn 6 10.8 23.9 80.9 45.9 29.7
Mo 4 1.0 1.5 2.9 1.7
Na 6 102 213 667 427 219
Ni 6 4.1 13.3 32.8 7.3 21.1 p 6 453 748 1153 507 877
Ph 6 15.0 17.9 27.2 16.0 20.5
s 6 3237 10784 14015 7016 10100
Zn 6 13.8 29.5 87.0 45.9 39.9
36
Table 22. Distribution (m in, median, max) and mean value of total element concentrations (mg/kg) in the individual peat layers on the peat/and sites. Mean values are presented by dominant tree species (cant 'd).
Layer Element n M in Median Max Mean values (cm) Pine Birch Alder
n = 2,2,2 IJ n = 5,4,3 IJ n=2
20-30 AI 5 1197 5470 9853 2120 6984
B 5 3.6 8.1 8.8 5.9 6.8
Ca 5 4713 6570 7800 6600 5994
Cd 5 0.24 0.51 1.38 0.53 0.76
Cr 5 1.7 7.0 18.0 4.0 12.5
Cu 5 10.8 35.9 80.7 19.1 52.5
Fe 5 2417 3920 7677 2588 5326
K 5 128 577 817 373 528
Mg 5 818 1693 1823 1321 1459
Mn 5 9.6 42.2 53.0 29.4 38.1
Mo 3 0.9 1.3 3.3 1.9
Na 5 107 284 483 322 238
Ni 5 6.1 16.0 40.9 11.0 27.0
p 5 504 733 1000 597 854
Ph 5 9.6 12.7 23.5 12.4 16.1
s 5 4810 11765 15456 9049 11004
Zn 5 10.2 65.9 118 62.9 65.1
1ln for the 0-10 cm, 10-20 cm and 20-30 cm layers, respectively.
coefficient of variation, and the smallest observable change (d) was estimated as follows (Tables 25 and 26).
d(%)=loo.lxl ~x21, (5) xl
where x1 and x2 are the mean values of a soil property at the first and second sampling time. The smallest observable change (d) was estimated using the formula:
d~t·lO~·Sl · fi, (6) xl V3
where t 005
J= 2
= 4.30, x1 is a mean of three composite samples at the first sampling time,
s1 is the corresponding standard deviation, and the term 10~· s1 is the coefficient of xl
variation (Vasama & Vartia 1973, p. 623). It is hypothesized that the variances are equal at the first and second sampling time.
37
Table 23. Total amounts (kg ha-1 ) of macro- (P, K, Ca, Mg, S) and micronutrients (B, Cu,
Mn, Zn, Fe) in the peat layers by dominant tree species.
Layer (cm) Element Pine Birch Alder n = 2,2,2 li N = 5,4,3 n n=2
0-10 B 0.819 0.949 1.889
Ca 978 626 1405
Cu 1.954 7.058 7.740
Fe 324 1720 1625
K 79 154 178
Mg 205 171 317
s 634 1164 622
Zn 6.468 7.481 7.524
10-20 B 0.599 0.984
s 703 1840
Zn 4.325 6.997
s 1177 1891
Zn 6.385 10
1in for the 0-10 cm, 10-20 cm and 20-30 cm layers, respectively
38
Soil type Olkiluoto Control
Lithic Leptosol 9 0
Umbric Gleysol 3 0
Dystric Gleysol 1 0
Gleyic Arenosol 17 0
Cambic Arenosol 4 0
Haplic Arenosol 44 0
Regosol 6 0
Haplic Podzol 0 7 Gleyic Cambisol 1 1 Dystric Cambisol 0 1
Total 85 9
Figure 5. The most common soil type on the Olkiluoto Island was Haplic Arenosol (an example from FEH plot 914260, where the soil was fine sand). The soil layers are H, Eh, Bh and BC without a Cg layer free of oxygen. Photo: S. Levula/Metla.
39
Figure 6. An example of a Gleyic Arenosol from FEHplot 914273. The soil layers are H, Eh and Cg, and the sub-soil is gravel. (Photo: S. Levula/Metla).
Figure 7. An example of a Dystric Gleysol from the FEH plot 922247. The soil layers are H, Eh and Cg with a sub-soil of fine sand. (Photo: S. Levula/Metla).
Although the plot-wise sampling errors were relatively small, possible plot-wise changes have, on the average, to be large in order to be statistically observable (Tables 25 and 26). The possibility of observing changes within plot groups will increase along with . . . mcreasmg group s1ze.
Two composite samples were taken from the 0 to 10 cm mineral soil layer. The sampling error, i.e. the coefficient of variation, was estimated on the basis of these sample pairs for the whole material, and not for single plots as in the organic layer (see Youden 1951, 1975, Minkkinen 1995, Tamminen 2003) (Table 27).
Owing to the high variation and large sampling errors, possible changes in the 0-10 cm mineral soil layer will have to be very large and will only be observable for groups of several plots (Table 27). Because the distributions of the variances and sampling errors were skewed to the right (see Table 27), the arithmetic mean values tend to exaggerate the average sampling errors and the observable changes. Therefore, median values better describe the average situation.
40
Table 25. Sampling error estimated as the coefficient of variation based on three composite samples and the smallest observable change at a probability of 95% for exchangeable acidity and exchangeable cations in the organic layer.
Soil Sampling error, % Observable change, % variable M in Median Max M in Median Max
H+ 1.3 10.0 43 4.6 35 149
Ca 0.7 8.9 36 2.6 31 127
K 1.3 8.3 34 4.4 29 119
Mg 2.3 7.7 34 7.9 27 119
Na 1.3 9.5 49 4.5 33 171
Table 26. Sampling error estimated as the coefficient of variation based on three composite samples and the smallest observable change at a probability of 95% for total element concentrations in the organic layer.
Soil Sampling error, % Observable change, % variable M in Median Max M in Median Max
c 0.2 4.7 17 0.7 16 59
N 0.6 4.8 23 2.0 17 79 Ca 0.9 10 33 3.0 35 115
Cu 1.0 8.0 31 3.6 28 110
K 0.5 8.4 44 1.6 30 153
Mg 0.5 8.9 48 1.8 31 168
Na 0.8 8.7 31 2.8 31 109
Ni 0.3 7.0 23 1.2 25 80 p 0.8 6.3 44 2.9 22 156
Pb 1.0 8.3 121 3.4 29 424
s 0.7 6.5 22 2.4 23 78 Zn 0.9 7.8 30 3.0 27 107
3.8 Chemical composition of the understorey vegetation
3.8.1 Carbon and macronutrients {N, P, K, Ca, Mg and S)
The C concentration was the highest in the leaves of evergreen dwarf shrubs (mean 53%), followed by Vaccinium myrtillus (51%) and other species ( 46-48%) (Appendix 9).
In general, the concentrations of macronutrients were higher in vascular plants (dwarf shrubs, herbs and grasses) than in bryophytes and lichens (Figs. 8a- f). An exception was
41
Table 27. Sampling error estimated as the coefficient of variation based on tvvo composite samples and the smallest observable change at a probability of 95% for total carbon and nitrogen concentrations and for exchangeable acidity and cations in the 0- 10 cm mineral soil layer.
Soil Sampling error,% Observable change, % variable Mean Median Mean Median
c 27.2 16.8 346 213 N 22.0 12.1 280 153 H+ 25.9 12.6 329 160 Ca 30.6 22.0 388 280 K 16.5 8.4 210 107 Mg 22.8 16.7 290 212 Na 22.7 11.6 289 147 pH 2.9 1.5 37 19
P, bryophytes having higher P concentrations than dwarf shrubs in the fertile site types (Fig. 8b ). Lichens always had lower concentrations than bryophytes. Within the group of vascular plants, herbs or grasses had the highest P, K and Mg concentrations, whereas Vaccinium myrtillus had the highest Ca concentrations. In most cases the macronutrient concentrations of Vaccinium myrtillus were higher than those ofthe evergreen dwarf shrubs (mainly Vaccinium vitis-idaea). Grasses had higher S concentrations in the peatland than in the mineral soil sites, which might be due to the occurrence of Phragmites australis, which had a higher S concentration than the other grass species (Appendix 9).
In the case of individual species, high N concentrations(> 2.5%) occurred in Filipendula ulmaria, Lysimachia vulgaris, Melica nutans, Rubus idaeus and Phragmites australis (Appendix 9). All these species indicated fertile growing sites. Macronutrient concentrations in Vaccinium myrtillus at Olkiluoto (e.g. N 2.02%, P 1.34 mg g-1 and K 9.19 mg g-1 in MT sites) were approximately at the same level as measured in an old growth spruce forest (Hylocomium-Myrtillus type, HMT) in Oulanka, northern Finland (N 1.5%, P 1.9 mg g-1 and K 7.0 mg g-I, Kubin 1983). Correspondingly, the mean N concentration of the herb species on OMT sites at Olkiluoto (N 2.2%) was close to that measured in an OMT forest site at Heinola, southern Finland (N 2.4%, Miikipiiii 1994). On the other hand, the macronutrient concentrations in Vaccinium vitis-idaea at VT sites at Olkiluoto were slightly higher (N 1.56%, P 1.89 mg g-1 and K 7.06 mg g-1) than those measured at Mekrijiirvi, eastern Finland (N 0.93%, P 1.14 mg g-1 and K 4.71 mg g-I, Salemaa et al. 2004). In the Mekrijiirvi data, both stems and leaves of current-year shoots were included in the samples, and this may explain the lower values. Compared to the nationwide bryophyte data (Poikolainen et al. 1998), theN concentration of Hylocomium splendens (0.97 -1.41 %) andPleurozium schreberi (0.92 -1.26%) atOlkiluoto represented well the range found in southern Finland in 1995.
a)
3
2.5
2
I 1- - I- -
c a.l:! a Ill c l bc aa l! c 1 aa bx c l aa be. b e I aaa OMT+ MT VT- CIT Rock s Alder Birch
Upland sites Peatland sites
Phosphorus (P) in plants
1- - L I
- - fE""- i- 1-
I l c " a c l:l a aaa GO i a a tl
Alder I aaa I OMT+ MT VT- CIT Rocks Birch
1:11 Lichens
Figure 8a- b. Site type specific means of macro nutrient concentrations in the different plant groups at Olkiluoto. OMT+ includes one herb rich stand (Lh, see footnote in Table 1) in additition to the herb rich heaths. The same letter indicates that there are no significant differences (p > 0.05) benveen the means within the site type (Least Significant Difference Test).
c)
30
25
20
n· I
h - d e b a tl 1 e L aae I bb a bp e a a ll<
I aa i:J 1
Magnesium (Mg) in plants
[ 1 od J a tl e
l e a d e I ab a e b e b e d
I a bb
IJ Lichens
Figure 8c-d. Site type specific means of macronutrient concentrations in the different plant groups at Olkiluoto. OMT+ includes one herb rich stand (Lh, see footnote in Table 1) in additition to the herb rich heaths. The same letter indicates that there are no significant differences (p > 0.05) benveen the means within the site type (Least Significant Difference Test).
e)
3500
3000
2500
I
c ab a b: c I t> a a ,t;. b l b a e<: c tl l a ti c I
aaa I OMT+ MT VT - CIT Rocks Alder Birch Oligotr
Calcium (Ca) in plants
- - 1-
lA. i r , ea LHl c I baac b ~ ~ ~ a ~ c rJ Li a d cO
I a PJ a
Upland s1tes Peatland s1tes
Cl Lichens
Figure 8e-f Site type specific means of macro nutrient concentrations in the different plant groups at Olkiluoto. OMT+ includes one herb rich stand (Lh, see footnote in Table 1) in additition to the herb rich heaths. The same letter indicates that there are no significant differences (p > 0.05) benveen the means within the site type (Least Significant Difference Test).
45
3.8.2 Micronutrients {B, Mo, Cu, Zn, Mn, Ni and Fe)
Boron (B) belongs to the metalloid group of elements, whereas Mo, Cu, Zn, Mn, Ni and Fe are commonly referred to as heavy metals. These metals are essential micronutrients to plants, but are toxic at high concentrations (Marchner 1995). The B concentrations were high in dwarf shrubs and herbs, but low in grasses, bryophytes and lichens (Fig. 9a). Vaccinium myrtillus had a higher B concentration than evergreen dwarf shrubs.
The Mo concentrations were below 0.01 mg kg-1 (limit of quantification for the analysis) in all the studied species, except for the value of 0.02 mg kg-1 in a grass Deschampsia cespitosa on a herb rich site (Lh). In general, vascular plants had lower metal concentrations than bryophytes (Figs. 9b-f). Bryophytes accumulated Cu, Ni and Fe especially. On the other hand, Vaccinium myrtillus had high Mn and herbs high Zn concentrations. Of the individual species, a herb Melampyrum sylvaticum appeared to have the ability to accumulate relatively large amounts of metals (Appendix 10).
The Cu (9.8 mg kg-1) and Ni (6.9 mg kg-1) concentrations in bryophytes (Hylocomium splendens) in the VT sites at Olkiluoto (Appendix 10) were slightly higher than those in the "clean" background area at Mekrijiirvi (Pleurozium schreberi: Cu 6.5, Ni 3.7 mg kg-1;
Salemaa et al. 2004). In the bryophyte data representing the whole Finland the mean Cu concentration has decreased from 6.0 to 4.0 mg kg-1 and that ofNi from 2.2 to 1.8 mg kg-1 during 1985-2000 (Poikolainen et al. 2004). The Fe concentration in bryophytes (1595 mg kg-1 in VT, 2550 mg kg-1 in CT, and 1010-2220 mg kg-1 in mires) and lichens (553 mg kg-1 in CT) were especially high compared to Mekrijiirvi (283 mg kg-1 in Pleurozium schreberi, and 100-340 mg kg-1 in lichens). In the nationwide data the Fe concentration ofbryophytes was 259 mg kg-1 in the year 2000 (Poikolainen et al. 2004). In actual fact, the Fe concentrations in bryophytes and lichens at Olkiluoto were as high as those recorded at a distance of 4-8 km from the Harjavalta Cu-Ni smelter in the beginning of 1990's (Salemaa et al. 2004). It is obvious that accumulation of particulate material on the vegetation, especially in the case of forest floor bryophytes, has increased due to emissions caused by the construction of roads, drilling and crushing of rock, as well as other industrial activities on Olkiluoto Island.
3.8.3 Non-essential elements {Cd, Cr, Pb and AI)
Cadmium, Cr and Pb are heavy metals, but non-essential elements for plants. They may be toxic or lethal for plants even when absorbed in small amounts. Cadmium especially is potentially harmful in the environment because it has a tendency to accumulate in mammals. Aluminium is also a non-essential metal, which is however taken up in relatively large amounts by plants, and may have toxic effects on plant growth at high concentrations (Marchner 1995).
The Cd concentrations were the highest in herbs (Rubus chamaemorus in pine mire plots) and bryophytes (Fig. 1 Oa, Appendix 11 ). In addition, high Cd concentrations were found in evergreen dwarf shrubs (especially Vaccinium oxycoccos) on the birch and pine mire plots (Appendix 11 ). As was the case for other heavy metals, the Cr concentrations were also high in bryophytes (Fig. 1 Ob), and relatively high Cr concentrations occurred in grasses,
a)
b)
40
35
30
25
15
10
5
0
12
10
8
4
2
0
46
rt ir 1 1• --
flr; ri ~ a ace b aacc I a a ~~fl a b
Alder I a b to 1
OMT+ MT VT- CIT Rocks Birch
Copper (Cu) in plants
I
c i:J b f:lt; a bab tl'C a I:Jb c a bo b a c
I aaa
1:1 Lichens
Figure 9a- b. Site type specific means of micronutrient concentrations in different plant groups at Olkiluoto. OMT+ includes one herb rich stand (Lh) in additition to the herb rich heaths. The same letter indicates that there are no significant differences (p > 0.05) benveen the means within the site type (Least Significant Difference Test).
c)
140
120
100
40
20
0
d)
2500
2000
- ,_ ~ ~ ,;rl !!: r:Jll
c ~~-c""'!T +---.-l e c-~ ... ~-'!'b.__lr"!'1J ~~~T ~~~;,~Idee~ B:,;~ ~ Pine
Manganese (Mn) in plants
lir l - 1- -
ll rL n-. r ~ ~ t.l ac oa I b ab cc I b a ;!Q CC I a a b: I abb
I OMT+ MT VT- CIT Rocks Alder Birch Pine
III Lichens
Figure 9c- d. Site type specific means of micronutrient concentrations in different plant groups at Olkiluoto. OMT+ includes one herb rich stand (Lh) in additition to the herb rich heaths. The same letter indicates that there are no significant differences (p > 0.05) benveen the means within the site type (Least Significant Difference Test).
e)
f)
8
7
6
5
3
2
0
2500
2000
d ,_ Il fl ~ ~ 1- ri I
cc !J!J a I cc tr b a I till tr a b IJ a D aaa OMT+ MT VT- CIT Rocks Alder Birch Pine
Iron (Fe) in plants
·r::m: ,..,_ r.:ll r- a. .., l J ~ rE-
btl ll b a I !'I tl tit a Dl:l boo b tJ
Alder I ob t a
OMT+ MT VT- CIT Rocks Birch Pine
C Lichens
Figure 9e-f. Site type specific means of micronutrient concentrations in different plant groups at Olkiluoto. OMT+ includes one herb rich stand (Lh) in additition to the herb rich heaths. The same letter indicates that there are no significant differences (p > 0.05) benveen the means within the site type (Least Significant Difference Test).
49
too. The Pb concentrations were higher than the limit of quantification for the analytical equipment only in bryophytes and lichens (Appendix 11). Compared to the background area at Mekrijiirvi (year 1992: Pleurozium schreberi 9.44 mg kg-I, Cladina rangiferina 4.79 mg kg-I, Salemaa et al. 2004), the Pb concentrations in bryophytes (3.0-4.8 mg kg-1) and lichens (3.3 -1.8 mg kg-1) were lower at Olkiluoto in 2005. This may reflect the effect of the decrease in Pb deposition resulting from the ban on leaded petrol in vehicular traffic. In the nationwide monitoring the mean Pb concentration ofbryophytes has decreased from 15.5 to 3.4 mg kg-1 during 1985-2000 (Poikolainen et al. 2004).
The Al concentrations were the highest in bryophytes (Pleurozium schreberi: max 1450 mg kg-1 in CT) and lichens (Cladina stellaris: max 267 mg kg-1 on rock sites) (Fig. 10d, Appendix 11 ). Ofthe dwarf shrubs, Lycopodium annotinum accumulated relatively highAl concentrations ( 696 mg kg-1
) on one birch mire plot. The Al concentrations in bryophytes and lichens were clearly higher at Olkiluoto than at Mekrijiirvi (Pleurozium schreberi: 304 mg kg-1
, Cladina stellaris: 117 mg kg-1 ; Salemaa et al. 2004), which may be due to the
presence of wind-blown soil dust derived from construction work at Olkiluoto.
3.8.4 Sample plot ordinations according to the elemental composition of bryophytes and Vaccinium myrtillus
Two different ordinations of the sample plots were carried out according to the chemical composition of bryophyte thalli and leaves of Vaccinium myrtillus. Bryophytes possess many properties that make them suitable for monitoring atmospheric deposition. Bryophytes have no real roots and they absorb water and dissolved elements directly through their surface. They obtain the majority oftheirwater and nutrients from atmospheric deposition, and some species bind nutrients from water that has been in contact with the substrate. Bryophytes have a high ion exchange capacity on their cell walls and a high tendency to accumulate heavy metals especially. The bryophyte samples had three annual growth segments, thus indicating cumulative deposition of elements. On the other hand, the element concentration of the current-year leaves of Vaccinium myrtillus indicated in addition to the site fertility also recent deposition.
The more similar the element composition of the plants growing on the plots, the closer the plots were located to each other in the ordination configuration (Fig. 11 ). The ordination pattern was strongly related to the heavy metal (Fe, Cr, Ni) andAl concentrations in both plant groups (Fig. 11). Those sample plots with high Fe concentrations in bryophytes (> 2000 mg kg-1) and in Vaccinium myrtillus (> 250 mg kg-1) were located near the sites where drilling or road construction has caused considerable particulate emissions (Fig. 12). The Al, Cr and Ni concentrations had very similar patterns to Fe in the ordination configurations.
3.9 Nutrient status of the tree stands
TheN, P, K and S concentrations in the current-year needles (C) of the pine stands, grouped by site fertility and stand age, varied between 1.45 -1.7%, 1.5-1.7 mg g-1, 5.4-5.8 mg g-1
and 902-1018 mg kg-I, respectively (Fig. 13). These mean values indicated that the pine
a)
b)
50
0.6
0.4
10
9
8
7
3
2
0
Rocks Pine
'
-
rl ----rl 1\ h 1---rl!J rtf · r cc t, b a bb 1\ a b b a b b fl :T a I
MT VT- CIT Rocks Alder Birch Pine
o Lichens
Figure 1 Oa- b. Site type specific means of non-essential elements in different plant groups at Olkiluoto. OMT+ includes one herb rich stand (Lh) in additition to the herb rich heaths. The same letter indicates that there are no significant differences (p > 0. 05) benveen the means within the site type (Least Significant Difference Test).
c)
5
4.5 -
4 -
3.5 -
51
r-
I I VT- CIT a a I I MT Rocks Alder Birch Pine
Aluminium (AI) in plants
rl ~ ~ rt n rn. ~ L I bl:lb l'l a
MT b ll b a b I b a b VT- CIT Rocks Alder I Birch I Pine
[J Lichens
Figure 1 Oc- d. Site type specific means of non-essential elements in different plant groups at Olkiluoto. OMT+ includes one herb rich stand (Lh) in additition to the herb rich heaths. The same letter indicates that there are no significant differences (p > 0. 05) benveen the means within the site type (Least Significant Difference Test).
N Cl) 0 :::2: z
0
c::i
I 925252 L()
NMDS1
Figure 11. Ordination (NMDS) of the sample plots according to the chemical concentration of a) bryophytes (n = 88) and b) Vaccinium myrtillus (n =58). Iron (Fe) concentration (mg kg1
) of the plant species fitted as a surface to the ordination configuration.
V1 N
53
Figure 12. Location of the FEH plots with high Fe concentration in bryophytes (red circles) and in Vaccinium myrtillus (vellow triangles).
stands had an adequate supply of N, P, K and S (Reinikainen et al. 1998; optimal N, P, K and S concentrations for pine growing on mineral soils are 1.5-2.1%, 1.4-1.8 mg g-I, 5.0-7.0 mg g-1 and >900 mg kg-I, respectively). The Mg concentrations were higher (1.14-1.24 mg g-1
) than those reported by Reinikainen et al. (1998) for Scots pine (optimal Mg concentration 0.5-1.0 mg g-1). TheCa concentrations (2.32-2.57 mg g-1)
were below the optimal value (> 3.1 mg g-1 , Reinikainen et al. 1998), but did not indicate
severe Ca deficiency in the pine stands.
TheN and P concentrations in the current (C) needles of the spruce stands varied between 1.25-1.45% and 1.42-1.63 mg g-1
, respectively (Fig. 13), indicating an adequate supply ofN and P to the spruce trees (Reinikainen et al1998; optimal Nand P concentrations for Norway spruce growing on mineral soils are 1.3-1.5% and 1.2-1.5 mg g-1
, respectively). The K, Ca and Mg concentrations were higher (6.4-7.3, 3.9-4.8 and 1.07-1.17 mg g-I, respectively) than those reported by Reinikainen et al. (1998) as optimal values for Norway spruce (K 4.5-6.0 mg g-I, Ca 2.0-3.0 mg g-1 and Mg 0.8-1.0 mg g-1). The S concentrations in the needles were below the optimal level (>900 mg kg-1
, Reinikainen etal.1998).
54
Needle B concentration in pine indicated an optimal boron nutrient status (>8 mg kg-1
according to Reinikainen et al. 1998). The concentrations of other micronutrients (Cu, Zn, Mn) and Fe in C needles were also above the deficiency limits (Fig. 14; Reinikainen et al. 1998: >3, >30, >5 and >30 mg kg·I, respectively). In spruce, the B, Zn and Mn concentrations in C needles indicated an optimal nutrient status (Fig 14; Reinikainen et al. 1998: optimal values for B, Zn and Mn are 8-25, >25 and 80-500 mg kg·I, respectively). The Fe concentration in spruce needles was above the deficiency limit (> 17 mg kg·I, Reinikainen et al. 1998), but the Cu concentration was below the optimal level in most cases (>3 mg kg·I, Reinikainen et al. 1998).
2.0
1.&
.::IC
• 3
2
Scots pine
Norway spruce
2.0 1.8
1.8 1.4
0.6
0.4
0.2
'i 100 R'soo e500
400 300 200 100
0.4
0.2
0.0
_r"" r=~"' z,=
Scots pine
NoJWay spruce
.. . ~
70 5(J
30 ~
10
0
800
;:r:. .X ,I ""'
Norway spruce
Scots pine
Norway spruce
Figure 14. Needle boron (B), copper (Cu), iron (Fe), zinc (Zn) and manganese (Mn) concentrations (+standard error) in current (C) and previous-year (C+ 1) needles of Scots pine and Nonvay spruce stands grouped by site fertility and stand age. For MI' and OMI', see Table 13.
The differences in nutrient concentrations of current (C) and previous-year (C+ 1) needles were typical for pine and spruce compared to the values reported e.g. for the ICP Forest Level II plots (Raitio et al. 2001). The P, K, Mg and Cu concentrations in both species, and N in spruce and B in pine, were higher in the C needles than in the C+ 1 needles (Figs. 13 and 14). TheCa, Fe and Mn concentrations in both pine and spruce, and B in spruce and Zn in pine, were lower in the C than in the C+ 1 needles (Figs. 13 and 14). The S concentration in both species, and the N in pine, were about at the same in the C and C+ 1 needles, but the difference in the Zn concentration of spruce varied between the site fertility and age groups (Fig. 14).
The P and K concentrations in birch leaves on both mineral soil and peatland sites (Fig. 15) were below the average values (P 2.67 for birch and K 9.6 mg g-1 on mineral soil, and 1.99 and 8.8, respectively, on peatland) reported for downy birch by Perm & Markkola
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(1985, see also Reinikainen et al. 1998). TheN, Ca and Mg concentrations in birch leaves on the mineral soil plots were above the average values (N 22.4, Ca 6.6 and Mg 2.39 mg g-I, Perm & Markkola 1985). The B, Zn and Mn concentrations were markedly higher, and the Cu concentration below the average values presented by Perm and Markkola ( 1985), and were not dependent on the soil type (Fig. 16).
The average carbon concentration was 52.8% in the C needles and 53.4% in the C+ 1 needles of pine. The respective figures for spruce were 51.4 and 51.6%. Carbon concentrations in the leaves of birch and alder were 53.2% for birch and 51.9% for alder on peatland plots and 52.5% and 51.8% on mineral soil plots, respectively.
The dry mass of 100 needles or leaves, the element concentrations and carbon concentration in needles and leaves are presented for each FEH plot in Appendix 12.
.. 2..5 Mineral N
Ul
0..5
10 3..0
6 2..5
Birch Alder Birch Alder
Figure 15. Foliar nitrogen (N), phosphorus (P), potassium (K), sulphur (S), calcium (Ca) and magnesium (Mg) concentrations (+standard error) of birch and alder on mineral soil and peat/and plots.
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- Pealland 14 150 12
~ ~0 lr10 E ~8
Fe Zn 120
40 200
140
Birch Alder
Figure 16. Foliar boron (B), copper (Cu), iron (Fe), zinc (Zn) and manganese (Mn) concentrations (+standard error) of birch and alder on mineral soil and peat/and plots.
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4 CONCLUSIONS
The forest soils on Olkiluoto Island are very young compared to inland soils. They are typical soils for Finnish coasts, i.e. stony or shallow soils overlying the bedrock, but contain more nutrients than average inland soils. On the other hand, one quarter of the soils on Olkiluoto have groundwater table within 1 m from the mineral soil surface. In addition to nutrients, the heavy metal concentrations are clearly higher on Olkiluoto than on the control plots or the average values for Finnish forest soils. The soil in the alder stands growing near the seashore are different from the other soils on Olkiluoto and the control soils inland. These soils are less acidic and have large reserves of sodium, magnesium and nitrogen.
The surface soil layers, which can be expected to be more susceptible to changes than the deep

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