Growth of Pinus Pinea and Pinus Halepensis as Affected by Dryness, Marine Spray and Land Use Changes...

7/27/2019 Growth of Pinus Pinea and Pinus Halepensis as Affected by Dryness, Marine Spray and Land Use Changes in a Me

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Corresponding author: J. Ravents - e-mail: [email protected] 1

Growth of Pinus pinea and Pinus halepensis as affected

by dryness, marine spray and land use changes in a

Mediterranean semiarid ecosystem

Jos Ravents*, M. De Lus*, M.J Gras*, Katarina Cufar**, J.C. Gonzlez-Hidalgo***,

A. Bonet*, J.R. Snchez*

* Departamento de Ecologa, Universidad de Alicante - Spain

**Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana - Slovenia

*** Departamento de Geografia y Ordenacin del Territorio, Universidad de Zaragoza - Spain

Abstract

Pine afforestations located on sand dunes, are among the most threatened coastal woodlands of semiarid western Mediter-

ranean areas. In the recent time, dryness and land use changes seem to have caused a considerable degradation of these

ecosystems. The marine spray affects their development as well. Our objective was to examine the possible effects of

these ecological factors on tree-ring variation ofPinus pinea L. and Pinus halepensis Mill. We selected altogether 30 trees

of both species from a sand dune stand located in the Guardamar Pine Woodland, Alicante, Spain. For both species we

selected five trees per each of three canopy damage levels and analysed four cores per tree. The results of dendrochrono-

logical analysis show that there exists a correlation between tree-ring widths and September-June precipitation and it is an

inverse relationship between the growth-climate correlation and the degree of canopy damage. Moreover, trees showed

an increased number of missing-rings during the 1990s which was strongly related to severity of canopy damage due to

marine spray. Synergistic effect of defoliation produced by the marine spray and dryer conditions due to limited water

availability seem to have strong affect on variation of tree-ring widths.

Keywords: dendroecology; tree-ring records, dune ecosystem, missing rings, canopy damages, rainfall series

Preliminary research report

Introduction

In the Western Mediterranean areas, the rainfall

variability in space and time is one of the most

relevant characteristics (Romero et al. 1998). For

these areas, where water availability is the main

limiting factor for forest development, General

Circulation Models (GCMs) predict a significant

decrease in rainfall for next decades. Two recent

studies based on historical rainfall records seemto agree with this prediction. Annual rainfall

during 1961-1990 has significantly decreased and

interannual variability has significantly increased

(De Lus et al. 2000). Moreover, a significant

change in seasonal distribution has been detected

(Gonzlez-Hidalgo et al. 2001). All this together

allowed Lavorel et al. (1998) to hypothesise that

Mediterranean regions, as transitional climate zones,

are areas where climatic changes may have the

greatest effects.

In this context, pine afforestations located

in coastal areas, belong to the most threatened

woodlands of semiarid western Mediterranean areas

(Barnes et al. 2000). The main species used

in afforestations in Mediterranean semiarid dune

ecosystems are Pinus pinea L. and Pinus halepensis

Miller. These pine species are not native in the

dune systems (Bols 1967), and have to survivein hard environmental conditions, with a limited

water resource and exposed to a constant threatening

effect of marine spray (Garrec 1994).

The Guardamar Pine Woodland is a good exam-

ple of this kind of afforested dune ecosystem. This

area, located in the Valencian Region (SE Spain), is

characterised by a semiarid climate and a clear gra-

dient of canopy damage due to marine spray from

coastal to inland areas (Gras et al. 2000). More-

over, the conservation of this ecosystem is highly

Dendrochronologia 19 (2) - 2001:


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related to the dynamics of the nearby Segura River

(Aldeguer et al. 1997). Furthermore, dryness (De

Lus 2000) and changes in water and land uses

could have affected water supply to woodland.

The objective of this study was to produce a pre-

liminary chronology for these pine species in rela-

tion to its degree of canopy damage. Thereafter, we

related them with precipitation series and discuss

our results in relation to ideas exposed above.

Materials and Methods

Study area

The Guardamar Pine Woodland is located in the

Valencian Region (SE Spain) (Fig. 1). This area is

characterised by a semiarid climate with a mean

annual rainfall of 304 mm, concentrated mainly in

autumnal season. Mean annual temperatures range

from 12C in the coldest month January, to 23C in

the warmest August (Fig. 2).

Between 1900 and 1920 the sand dunes were

afforested with two pine species (Pinus pinea and

Pinus halepensis) to fix the dune along the coastal

line (Mira 1906). Presently, forest density is about

500 ind/ha, composed of approximately 45% ofP.pinea and 55% ofP. halepensis with wide range of

sizes (DBH from 15 cm to more than 55 cm) (Gras

et al. 2000).

Experimental Design

During the first months of 2000, samples of

Pinus pinea (PIPI) and Pinus halepensis (PIHA)

were collected from different microtopographies

and sea expositions (Tab. 1). Trees were classified

according to degree of marine spray injury usinga three-level scale: healthy, moderately damaged

(25-60% of the canopy injured), and severely defo-

liated (60-99% of the canopy injured) (CEC-CEPE,

1996) (Fig. 3).

From each species and level of injury, five

trees were selected and four cores were extracted

from each of them on the north, south, east, and

west direction. The cores were sampled at breast

height with an increment borer. Then, the cores

were mounted, dried, and fine-sanded. After that,

Ravents, De Lus, Gras, Cufar, Gonzlez-Hidalgo, Bonet and Snchez

Fig. 1 - Location of the sampling site Guardamar Pine Woodland, Valencian Region, SE Spain.

Fig. 2 - Climate diagrams for Guardamar. Temperature in

(C) (thin line) and rainfall (mm) (bold line).

Month

J F M A My Jn Jl Ag S O N D

0

5

10

15

20

25

30

0

10

20

30

40

50

60

Temperature

Rainfall


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3


Fig. 3 - Different degree of canopy damage in this Pinus spp. (a) Healthy Pinus pinea. (b) Moderately damaged Pinus

halepensis, (c) Severely damaged Pinus halepensis. Notice the typical flag shape of the crown.

B C

A


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the ring-widths were measured to the nearest 0.01

mm using a LINTAB (Rinn 1996) measuring table.

Tree-ring analysis

The tree-ring series were visually cross-dated.

The cross-dating was verified statistically by using

the TSAP and the COFECHA programmes (Rinn

1996; Holmes 1994). The ring-width series con-

taining less than 50 years were not considered in

analysis. The cores where we could not confidently

assign every ring to a specific calendar year, werenot used to construct a chronology.

The ring-width series of individual trees were

standardised using the ARSTAN programme (Cook,

Peters 1981; Holmes 1994). The long-term trend

was removed from each time series of ring width

measurements by fitting a curve and calculating an

index defined as actual ring-width for each year

divided by the curve-fit value. This allowed us to

remove the non-climatic age and size trend, and the

effects of stand dynamics (Cook, Kairiukstis 1990).

The first step stage de-trending used a modified neg-

ative exponential curve. At the second stage, a more

flexible fit of the curve to the data was achieved by

using a cubic smoothing spline, designed to remove

variability on the time scales of 50 years or more.

Finally, each individual series was combined

into a single non autoregressive chronology by a

technique known as biweight robust estimate of

the mean designed to reduce the influence of iso-

lated outlayer values (Cook 1985) (Tab. 2).

Rainfall Data

Monthly rainfall data between 1950-1999 were


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Tab. 1 - Basic data on tree-ring chronologies from Guardamar. The site is located at Latitude 0 41 09 W, Longitude 38

4 47 N, Elevation 5 m.s.s.l..

Time Span Total No. Total No. of

Tree Species Damage Chronology Lenght Number of Cores Cores Used in

Name earliest latest (years) of Trees Sampled Chronologies

Healthy PIPI_1 1918 1999 82 5 20 17

Pinus pinea Moderate PIPI_2 1918 1999 82 5 20 18

Severe PIPI_3 1921 1999 79 5 20 10

Pinus halepensis Healthy PIHA_1 1927 1999 73 5 20 13

Moderate PIHA_2 1911 1999 89 5 20 14

Severe PIHA_3 1913 1998 87 5 20 7

Tab. 2 - Summary statistics for the six chronologies from computer program ARSTAN.

Total Chronology Common Intervals

Chronology Mean Standard Time spanAgreement

Total nMean Variance in

name sensitivity deviation Skewness Kurtosis (AD)with population

of yearscorrelation first principal

chronology among radii component (%)

PIPI-1 0.24 0.29 0.44 0.02 1939-1999 0.94 61 0.47 51

PIPI-2 0.24 0.32 0.91 1.06 1936-1999 0.92 55 0.44 49

PIPI-3 0.22 0.29 0.47 0.39 1943-1993 0.85 51 0.36 44

PIHA-1 0.28 0.32 0.23 -0.53 1942-1990 0.93 49 0.55 60

PIHA-2 0.28 0.32 -0.33 0.86 1932-1991 0.73 60 0.25 45

PIHA-3 0.25 0.25 -0.45 0.08 1934-1987 0.59 54 0.17 31


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collected from the Guardamar weather station (0 41

09 W, 38 4 47N, 5 m.s.s.l., code 7261-O Mete-

orological National Agency, INM). Monthly and

seasonal data were checked for inhomogenities withAlexandersson test (Alexandersson 1986; Peterson

et al. 1998).

Results

Comparison of Chronologies

The tree-ring index variations for three groups

of canopy damages in both species are shown in

Figs. 4 and 5. The average correlation coefficient

among the trees from each species and canopy dam-

ages demonstrated similarities in growth charac-teristics. The correlation coefficients for P. pinea

chronologies were 0.89, (healthy vs moderate);

0.72, (healthy vs severe) and 0.73 (moderate vs

severe). For P. halepensis chronologies, correlation

coefficients were 0.68 (healthy vs moderate); 0.67

(healthy vs severe) and 0.62 (moderate vs severe).

All comparisons were significant at p 0.001.


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Fig. 4 - Tree-ring index variations for Pinus pinea with different degree of canopy damage.

0.0

0.5

1.0

1.5

2.0(a) Pinus pinea (HEALTHY)

0.0

0.5

1.0

1.5

2.0 (b) Pinus pinea (MODERATE)

Year

1920 1930 1940 1950 1960 1970 1980 1990 2000

0.0

0.5

1.0

1.5

2.0

(c) Pinus pinea (SEVERE)


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Tree Rings and Rainfall

Both studied species showed a high sensitivity

to climatic variations in mean sensitivity sensu

Douglas (1936) denoted by S for Mediterranean

species. In P. pinea, S value was 0.24 and in P.

halepensis 0.28.

The correlation between tree-ring indices (TRI)

and normalised standard deviation of September-

June precipitation (i.e. departure) are shown in Figs.

6 and 7. In five cases a highly to moderately corre-

lation was found between TRI and September-June

precipitation (Tab. 3).

There was an inverse relationship between the

growth-climate correlation and the degree of canopy

damage. This was true for both species with anexception of moderately damaged P. pinea.

Missing Rings and Damages

Although tree-ring index variation of P. pinea

and P. halepensis did not show any abrupt changes

in the period of 1950-1990, occurrence of missing-

rings was mainly concentrated in the last years.


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Fig. 5 - Tree-ring index variations for Pinus halepensis with different degree of canopy damage.

0.0

0.5

1.0

1.5

2.0 (a) Pinus halepensis (HEALTHY)

0.0

0.5

1.0

1.5

2.0 (b) Pinus halepensis (MODERATE)

Year

1920 1930 1940 1950 1960 1970 1980 1990 2000

0.0

0.5

1.0

1.5

2.0 (c) Pinus halepensis (SEVERE)


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Fig. 6 - The relationship between tree-ring growth and

precipitation in Guardamar. (a) The relationship between

Pinus pinea index for healthy trees and September-June

precipitation; (b), (c) the same relationship for moder-

ately and severely damaged Pinus pinea trees. All series

are normalised.

Fig. 7 - The relationship between tree-ring growth and

precipitation in Guardamar. (a) The relationship between

Pinus halepensis index for healthy trees and September-

June precipitation; (b), (c) the same relationship for mod-

erately and severely damaged Pinus halepensis trees. All

series are normalised.

Tab. 3 - Relationship between chronologies ofPinus pinea and Pinus halepensis and precipitation. R = Coefficient of

Correlation;p=probability value; N = 49.

PIPI-1 PIPI-2 PIPI-3 PIHA-1 PIHA-2 PIHA-3

R 0.48** 0.18 0.36** 0.57** 0.46** 0.30*

p 0.000 0.103 0.008 0.000 0.000 0.018


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The Tab. 4 shows the statistics on missing

rings in the 1950-1999 period. In both species we

observed no missing-rings from 1950 to 1988, but

the trees showed an increased number of missing-

rings during the 1990s. Their frequency was greater

in P. halepensis. It increased in the last years of

the decade (Fig. 8, Tab. 4) and was strongly corre-

lated with severity of canopy damage due to marine

spray. While healthy trees in average had 0 and 3.5

missing rings, the number was significantly higher

in severely damaged trees (2.4 and 4.9 in P. pinea

and P. halepensis, respectively).

The frequency of missing rings was not related

to the core aspect (F=0.83, p=0.494).

Discussion and Conclusions

The Mediterranean regions are complex land-

scapes where high recurrences offire, extreme rain-

fall events and human activities used to be the main

ecological and evolutionary forces. This is espe-

cially true in the Valencian Region (East Spain)where strong changes in land use have occurred in

the last 70 years.

Previous studies (Richter, Eckstein 1990; Rich-

ter et al. 1991) in Pinus spp. in mountain forest sites

showed a widespread common climatic signal in

tree-ring widths of the Southern Spain. In coastal

areas, the two investigated species show also a

high sensitivity to rainfall variations. Boreux et al.

(1988) reported similar results for P. pinea from the

Provence Region in France (S = 0.26).

Tab. 4 - Statistics Missing rings in Pinus pinea and Pinus halepensis for different canopy damage.

Mean number of missing ringsCores with

Mean number of missing rings per tree and decadeper tree on relation to the Aspect

missing

rings (%)

50-59 60-69 70-79 80-89 90-99 WE EW SN NS

PIPI_1 0 0 0 0 0 0 0 0 0 0

PIPI_2 0 0 0 0 1.2 2 1.2 0.2 1.8 28

PIPI_3 0 0 0 0 2.4 2 5 2.3 2 70

PIHA_1 0 0 0 0 3.5 1 2.5 3.3 3 46

PIHA_2 0 0 0 0 2.9 0 2.4 2 5.5 57

PIHA_3 0 0 0 0.3 4.9 1 7.7 10 1 100

Fig. 8 - Presence of missing rings in cores in the last 15

years. (a) Pinus pinea, (b) Pinus halepensis.

The high correlation between tree growth (with

independence of damage class) and rainfall pointed

out that water availability is the main factor influ-

encing tree growth of both pine species in semiarid

dune Mediterranean conditions.

Touchan and Hughes (1999) who intended to

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make a P. halepensis chronology in Jordania where

weather conditions are similar, report on generally

high frequency of missing rings. In Guardamar Pine

Woodland, despite persistently high dryness, thetrees did not show any missing rings between 1950

and 1988 but from 90s, a increasing number of

missing rings has been found.

Probably on the early decades, a extra water

supply from the Segura catchtment was available.

On the last decade, water demand for human activi-

ties (tourism, agriculture, high rate of urbanisation)

has increased greatly on this area and could affected

the availability of water for the pine woodland.

Moreover, the Guardamar Pine Woodland is

affected harmfully by chemical components of themarine spray, as reported in other parts of the Med-

iterranean coast of Spain (Diamantopoulos et al.

2000) and Italy (Bussotti et al. 1995).

Synergistic effect of both factors (defoliation

produced by marine spray and lower water avail-

ability) seems to have strongly affected woodland

persistence.

Presently, P. pinea, and particularly P. halepensis

are the most representative tree species of the Span-

ish Mediterranean coastal landscapes. These species

seem to have a high potential to study the relation-ship between effects of climate, water supply and

damage on tree growth in the region. We intend

to address the aforementioned needs in our future

research.

Acknowledgements

This work has been supported by a FEDER European

project (1FD97-1117-C05-01) and by a CICYT Spanish

project (CLI99-0957). Jos Ravents wants to thank the

Sabbatical Program of the Universidad de Alicante that

provided funds to stay at the LTRR Lab. (University ofArizona, Tucson) and at the Dept, of Wood Science and

Technology (University of Ljubljana, Slovenia).

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