Variation in the chemical composition of green leaves and leaf litters from three deciduous tree species growing on different soil types

Forest Ecology and Management 210 (2005) 303–319 www.elsevier.com/locate/foreco

Variation in the chemical composition of green leaves and leaf litters from three deciduous tree species growing on different soil types T. Sariyildiz *, J.M. Anderson School of Biological Sciences, Hatherly Laboratories, University of Exeter, Exeter EX4 4PS, UK Received 6 April 2004; received in revised form 13 December 2004; accepted 13 February 2005

Abstract The chemical composition of green leaves and leaf litters of sweet chestnut (Castanea sativa), oak (Quercus robur) and beech ( Fagus sylvatica) were determined for 26 sites grouped into high fertility (HF) and low fertility (LF) soils according to base saturation and N-mineralization potentials. Measurements were made of total carbon, acid detergent fibre (ADF), Klason lignin, holo-cellulose, sugar constituents of hemicellulose and phenylpropanoid derivatives of lignin, and nutrient concentrations (N, Ca, P, Mg, K and Mn). Leaf and litter constituents varied within and between species according to soil groups, but beech showed contrasting responses to oak and chestnut. Beech leaves had lower ADF, lignin and cellulose on HF soils than LF soils, whereas oak and chestnut leaves had higher ADF, lignin and cellulose on HF than the LF soils. Conversely, the same constituents in beech leaf litter were higher on HF soils than LF soils, but lower in oak and chestnut leaf litter on HF soils than LF soils. The phenylpropanoid derivatives of lignin and sugar constituents of hemicellulose also showed similar variations in relation to soil groups with contrasting patterns for in leaves and litters. Re-absorption of N from leaves before litter fall was negatively correlated with soil N mineralization potential for beech (highest on LF soils) but showed an unexpected, positive relationship for oak and chestnut (highest on HF soils). These intra-specific differences of leaf and litter chemistry in relation to soil fertility status are unprecedented and largely unexplained. The observed patterns reflect phenotypic responses to soil type that result in continuum of litter quality, within and between tree species, that have been shown in related studies to significantly influence litter decomposition rates. # 2005 Published by Elsevier B.V. Keywords: Leaves; Leaf litter; Soil fertility; Broad-leaf trees; Lignin; Phenylpropanoids; Hemicellulose; Nitrogen; Nutrient translocation

1. Introduction ¨ niversi* Corresponding author. Present address: Kars Kafkas U tesi, Artvin Orman Faku¨ltesi, 08000 Artvin, Turkey. Tel.: +90 543 831 4696/+90 466 212 6842; fax: +90 466 212 6951. E-mail addresses: [email protected], [email protected] (T. Sariyildiz), [email protected] (J.M. Anderson). 0378-1127/$ – see front matter # 2005 Published by Elsevier B.V. doi:10.1016/j.foreco.2005.02.043

The mineralogy of parent soils is important in determining the general structure and functioning of forest ecosystems. In natural forests, tree species or functional groups, such as broadleaves or conifers, are

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characteristically associated with different parent soil materials even at quite fine scales (e.g. Wessmann et al., 1988; Cunningham et al., 1999). These tree/soil relationships are reflected in nutrient concentrations and biochemical constituents of leaves and litter that influence herbivory, litter quality, decomposition processes and hence the development of soil properties that feed back to plant production through nutrient availability (Stachurski and Zimka, 1975; Bryant et al., 1983; Pastor et al., 1984; Zak et al., 1993; Aerts and Chapin, 2000). Tree species on fertile soils tend to produce leaves and leaf litters with high nitrogen concentrations, low concentrations of carbon-based plant protection compounds such as tannins and lignin mainly associated with vascular tissues. The high quality litters decompose rapidly and support high plant production through fast turnover of the nutrient pools. Trees on soils of low inherent fertility generally produce leaf litters that decompose slower, reducing the rates nutrient turnover, because of low nitrogen, higher tannins and polyphenol concentrations, and greater lignification of leaf tissues (often associated with longer leaf life spans; Davies et al., 1964; Cornelissen and Thompson, 1997; Tresender and Vitousek, 2001; Hattenschweiler et al., 2003). An important feed-back mechanism is the extent of nutrient re-absorption from leaves before abscission, that can amount to 50% or more of foliar N concentrations under limiting conditions and hence affect litter quality and decomposition rates (Staaf, 1982; Killingbeck, 1996; Cherbuy et al., 2001; Cote et al., 2002). Most of the literatures on these plant/soil relationships involve comparisons of natural systems that generally differ in plant taxa, soil types and climate. On the other hand, it has long been recognised that the same tree species growing on different soil types can develop underlying forest floor characteristics that vary in the mass of carbon and nutrient pools, pH and humus forms (Swift et al., 1979). These relationships are particularly evident for where forestry trials have involved planting different species on the same soil or the same species on different soils within a geographical area (Ovington, 1962). However, few studies have systematically investigated this intraspecific variation in leaf and litter quality across soil types. Sanger et al. (1996, 1998) found changes in hemicellulose and lignin constituents of needles from Scots pine (Pinus sylvestris) growing on soils with

different exchangeable calcium concentrations. Similarly, Sariyildiz and Anderson (2003a) showed that beech ( Fagus sylvatica L.) and oak (Quercus robur L.) growing on three different soil types showed significant variation in the quality and decomposition rates of leaf litters. Here we report a more extensive study investigating changes during senescence in the leaf and litter chemistry of three deciduous tree species growing in woodlands on a wide range of soil types developed on different parent materials under similar climatic conditions. This study was possible because the South West of England was not glaciated in the last Ice Age. Consequently, Devon has complex combinations of different soils and vegetation types within a small geographical area that are less apparent in regions where natural associations of trees and soils are relatively homogeneous at much larger scales.

2. Materials and methods 2.1. Sampling sites The study was carried out in the county of Devon, South West England. The location, parent material, soil series and soil types of the sampling sites are shown in Table 1. The altitude of the sites studied varied from 30 to 405 m above mean sea level. Mean annual temperatures across the sampling area range between 10.2 and 10.9 8C. Precipitation decreases from about 1000 mm in the west (on the edge of the Dartmoor plateau) to 850 mm in the east (Met Office averages 1971–2000) (Met Office, 2002). The soils in this area belonged to four major soil types namely; brown earths (BE), gleyed brown earths (GBE), ochreous brown soils (OBS) and podsols (P). Of the 26 sites studied, 7 were located on brown earths, 9 on gleyed brown earths, 5 on ochreous brown soils and 5 on podsols. The physical and soil characteristics of the sites are summarised in Table 1. Of these sites, 13 had mixed stands of beech ( Fagus slyvatica), oak (Q. robur) and chestnut (Castanea sativa), 8 had mixed stands of oak and beech, 2 sites had mixtures of chestnut and beech and only 3 sites were single stands of chestnut or oak. At all sites, the beech, oak and chestnut trees were selected of approximately the same height, girth and growth form, and were therefore assumed to be of approximately the same age.

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Table 1 Sites and soil characteristics of the woodlands used as sources for green leaves and leaf litters and soil samples Site name

Soil types (U.K)

pH (H2O)

BS (%)

CEC N-mineralization (m eqiv 100 g 1) (mg N g/(soil day))

Brown earths

6.1

99

19.0

22.2

Brown Brown Brown Brown Brown

earths earths earths earths earths

5.9 5.9 5.9 5.9 6.5

66 66 65 65 59

17.3 17.3 17.0 17.0 8.6

21.0 15.0 12.2 5.62 4.14

Brown earths

4.6

7

16.2

3.72

5.8 (0.22)

61.0 (10.3) 16.1 (1.28)

12.0 (2.95)

Culm shale Culm shale Permian breccia and Conglomerate Permian Breccia

Gleyed brown earths Gleyed brown earths Gleyed brown earths

7.1 7.1 6.8

79 79 78

9.2 9.2 16.3

5.63 7.77 17.5

Gleyed brown earths

6.8

78

16.3

13.7

Permian Permian and Trias sand stone Cretaceous Sand Permian and Trias sand stone Loamy head over permian and slate

Gleyed brown earths Gleyed brown earths

6.1 6.1

71 71

19.0 19

14.1 16.4

Gleyed brown earths Gleyed brown earths

6.1 4.4

71 38

19 23.6

18.8 4.3

Gleyed brown earths

6.3

61

15.7

18.2

6.3 (0.28)

69.6 (4.40) 15.4 (0.87)

Granite Granite Granite Granite Granite

Ochreous Ochreous Ochreous Ochreous Ochreous

4.9 4.7 4.7 4.7 4.3

14 9 11 11 11

4.7 (0.98)

11.2 (0.80) 12.1 (1.20)

3.61 (0.27)

Podzols Podzols

4.5 4.8

6 23

11.3 3.9

3.06 3.60

Podzols

4.1

8

11.5

3.15

Podzols

4.5

7

4.9

3.01

Podzols

4.5

7

4.9

4.15

7.30 (0.05)

3.39 (0.22)

Parent material

Knowles Wood (KW)

Permian breccia and conglomerate Dunchideock Wood (DC) Dolerite and basalts Higher Horrells Wood (HH) Dolerite and basalts Newton Wood (NW) Dolerite and basalts Killerton Wood (KT) Dolerite and basalts Hayes Wood (HY) Permian and Trias sand stone Stoke Wood (ST) Culm shale Mean Ashclyst Forest-1 (AF-1) Ashclyst Forest-2 (AF-2) Whitedown Copse Wood (WD) Higher Comberoy Wood (HC) Pinhill Wood (PH) Big Wood (BW) Colwell Wood (CW) Harpford Wood (HF) Hawkerland Valley Wood (HK) Mean Netton Wood (NT) Fernworty Forest (FW) Bellever-1 Wood (BL-1) Bellever-2 Wood (BL-2) Bridford Wood (BF)

brown brown brown brown brown

Mean Woodbury Wood (WB) Yarner Wood (YN) Danes Wood (DN) Haldon Forest (HD) Ashcombe Tower Wood (AC)

Granite Gravelly head over culm Permian and Trias sand stone Gravel over flinty clay Gravel over flinty clay

Mean

soils soils soils soils soils

4.48 (0.11) 10.2 (3.22)

12.3 10.5 10.5 10.5 16.7

12.9 (1.87) 3.04 3.47 3.40 3.54 4.62

Data are from Clayden (1971) except for N-(anaerobic) mineralization potential and soil pH (this study). Standard errors of mean are given in parentheses. BS, base saturation; CEC, cation exchange capacity.

2.2. Sampling and preparation of materials Green leaves of beech, oak and chestnut trees were collected from the study sites in September 1996.

Materials were sampled from 25 stands of beech, 22 stands of oak and 15 stands of chestnut. The green leaf samples were collected by hand from five mature trees chosen at random from each site in early September

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before any visible signs of senescence. Leaves were collected from the lower braches that showed typical ‘shade leaf’ characteristics. The ‘sun’ and ‘shade’ leaves and litter from the same trees can be differentiated by shape, colour, texture, tissue morphology and physiology (Niinements et al., 1998). These extremes of leaf types, and intermediate categories, can be operationally defined by their mass per unit area (Sariyildiz and Anderson, 2003b). The leaves were air-dried in the laboratory for 3 weeks and then oven-dried at 40 8C for 48 h. The oven-dried leaf materials were then lightly crushed by hand, the largest fragments of petioles removed and stored in plastic bags at 5 8C until needed for chemical analyses. Soil samples for N-mineralization potentials were collected in September under the same trees (2 m from the base of the trunk) from which the fresh leaves were sampled. Samples for soil characterisation were taken from the mineral B-horizon at a depth of 20 cm from a 50 cm  50 cm area of soil. For each category, samples were sieved (<2 mm) and bulked to give a single representative soil sample from each site. In mid December 1996, leaf litters of the same species were collected from the same sites and similar locations from which the green leaves were sampled. The leaf litters were carefully chosen from the surface litter layers to conform to the same shade-leaf morphotypes as the green leaves (Sariyildiz and Anderson, 2003b). Any leaves showing discolouration or indicating fungal activity were discarded. In the laboratory, the leaf litter samples were prepared in the same way as for the green leaf samples and stored at 5 8C until needed for chemical analyses. 2.3. Chemical composition of leaves and leaf litters The leaf and litter samples were oven-dried at 85 8C and ground in a laboratory mill to a mesh fraction less than 1 mm. Analyses were carried out for N, P, K, Ca, Mg, Mn, carbon, acid detergent fibre (ADF), lignin and cellulose as well as the phenylpropanoid derivates from lignin (PPDs) and trifluoro acetic acid (TFA)-carbohydrate (mainly sugar constituents of hemicellulose). Three replicates were analysed for mineral elements and two replicates PPD and TFA determinations. Organic C was analyzed using a Leco HF 10 gravimetric carbon analyzer (Leco Corporation, St.

Joseph, MI, U.S.A.). Total-N was determined by Kjeldal digestion (Allen, 1989) followed by analysis of ammonium by the indophenol method using an auto-analyzer (Bemas, Burkhard Ltd., Uxbridge, UK). Acid detergent fibre, cellulose and lignin were determined using the sulphuric acid/CTAB method of Rowland and Roberts (1994). Sugar constituents of hemi-celluloses were determined after hydrolysis, using 4 M trifluoro acetic acid, and preparation for GC analysis according to the method of Guggenberger and Zech (1994). Sugar concentrations were analysed using a Shimadzu GC 14-A capillary GC, with a BPS 25 m  0.25 mm i.d. column with standards of xylose, arabinose, fucose, mannose, galactose and maltose (Sanger et al., 1998). Phenypropanoid moieties of uncondensed lignins were determined after alkaline CuO oxidation (Hedges and Ertel, 1982; Ko¨ gel and Bochter, 1985) using the modified procedure of Hetherington and Anderson (1998). The concentrations of PPDs were determined using a Shimadzu GC 14-A capillary GC, with a BPS 25 m  0.25 mm i.d. column with standards of phydroxyl ( p-hydroxybenzaldehyde, p-hydroxybenzoic acid, p-hydroxyacetophenone), vanillyl (vanillin, acetovanillone and vanillic acid), syringyl (syringaldehyde, acetosyringone and syringic acid), coumaric acid and ferulic acid (Sanger et al., 1996). The sub-samples used for the determination of total N in leaf and leaf litter samples by Kjeldahl digestion were also used for the determination of mineral elements Ca, Mg, Mn, K and P. Concentrations of Ca, Mg and Mn were determined in the acid digest solution by atomic absorption spectrophotometer (AAS), K by flame emission spectrophotometer (FES) and P by continuous flow colorimetry using the molybdenum blue method (Allen, 1989). 2.4. N-mineralization potential and soil chemistry Assays for anaerobic N-mineralization potential (after Anderson and Ingram, 1993) were set up with the fresh top-soils on the same day of sampling. The dry weight of soils was also calculated by weight loss after drying 1 g of soil for 48 h at 80 8C. Three replicates were used per site. The pH of the mineral (B-horizon) soil was measured in deionised H2O using a glass calomel electrode, after equilibration for 1 h in a solution to

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soil paste ratio of 10 to 1. A small number of soil samples, from a random selection of sites, were also analysed to determine percentage base saturation (% BS), cation exchange capacity (CEC) and concentrations of exchangeable Ca, Mg and K to compare with soil survey values Clayden (1964, 1971). The results showed no significant differences from the published values for these soil types and so the extensive data in Clayden (1971) were used for soil characterisation. 2.5. Statistical analysis Principal component analysis (PCA) was carried out to investigate relationships between soil types, tree species and litter quality parameters. A component with eigenvalues of less than 1 was discarded (Frey and Pimental, 1978). The eigenvectors of each PC indicated the loadings of each of the variables contribute to a PC and negative values indicated inverse relationship between the value and that PC. PCA was carried using the computer package MINITAB Version 7.2 Silicon Graphics. Relationships between soil types, tree species and litter quality parameters were determined by the Scheffe method of multiple pair-wise comparison at a = 0.05 using SPSS 9.0 for Windows.

3. Results 3.1. Soil chemistry Soil pH, percentage base saturation, cation exchange capacity, exchangeable Ca and N-mineralization potential of the 26 sites and their mean values for the four soil types are shown in Table 1. The gleyed brown earths had the highest mean pH, percentage base saturation, CEC, exchangeable Ca and N mineralization potential (Nmin). In contrast, the podsols were more acidic with lower percentage BS, CEC, exchangeable Ca and Nmin. The brown earths and ochrous brown soils were located along a fertility gradient between these extremes. Exchangeable Mg, K and Na showed no differences between soil types. Principal component analysis of soils data (not shown) revealed that the first two PCs explaining 92% of the variation were strongly affected by Ca, BS, Nmin, pH and CEC. The four soil types were

307

separated into a group consisting of the BE and GBE soils with high base status and Nmin, and a second group of the podsols and OBS soils with low base status and Nmin. Soil type did not explain significant variation within these two groups of soils and so these are referred to below as the ‘high fertility’ (HF) and ‘low fertility’ (LF) soils, respectively. The exceptions to this grouping were Stoke Woods (BE) and Harpford Wood (GBE) that clearly belonged to the LF and HF soils respectively on the basis of their soil properties, despite their classification in Clayden (1971). 3.2. Green leaves Concentrations of carbon, nitrogen, mineral elements, ADF, lignin and cellulose, TFA-carbohydrates and phenylpropanoid derivatives of lignin in green leaves are shown in Table 2. The PCA for individual sites and species produced two components (PC1 and PC2) with eigenvalues of greater than 1 explaining the percentage of total variance (Table 3). The explained total variation (cumulative variances) of the PCA between the soil types and contribution of each green leaf properties to the variation is given in Table 3. The PC1 versus PC2 plots for the three tree species (Fig. 1) showed that the leaf properties were differentiated along the PC1 or PC2 axis into the HF and LF soil groups, but there was no consistent variation with the groups according to soil type. Further analysis of green leaf properties will therefore be considered in relation to the HF and LF groups rather than to individual soil types. 3.3. Green leaves: C, N, ADF, lignin and cellulose concentrations The loadings (the coefficients of correlation between parameters and the PCA scores) showed that variations in PC1 or PC2 were correlated with N, ADF, lignin and cellulose, whereas differences in carbon concentrations (reflecting ash contents) did not contribute significant effects (Table 3). The PC1 versus PC2 plots for the tree species also showed separation of these parameters along the PC1 or PC2 axis according to their origin in the HF and in the LF soils. In all the three species, N, ADF, lignin and cellulose varied significantly (P < 0.01) between the

308 Table 2 Concentrations of mineral elements, carbon, acid detergent fibre (ADF), lignin and cellulose and ratios of C-to-N and lignin-to-N in green leaves of beech, oak and chestnut growing on the different soil types with different characteristics Chemical composition

Soil types Beech

Oak

HF sites (15)

LF sites (10)

Chestnut

HF sites (14)

LF sites (8)

HF sites (11)

HF sites (4)

GBE (8)

OBS (5)

P (5)

BE (4)

GBE (8)

OBS (4)

P (4)

BE (4)

OBS (5)

P (4)

N (%) Ca (%) Mn (%) K (%) Mg (%) P (%)

2.39a (0.07) 0.77ab (0.04) 0.23bc (0.02) 1.03b (0.11) 0.18a (0.02) 0.18b (0.01)

2.46a (0.09) 0.75ab (0.03) 0.20bc (0.03) 0.97b (0.05) 0.17a (0.01) 0.17b (0.01)

2.66b (0.08) 0.83bc (0.09) 0.07a (0.01) 0.67a (0.04) 0.25b (0.03) 0.11a (0.01)

2.65b (0.07) 0.89bc (0.04) 0.13a (0.05) 0.85a (0.13) 0.25b (0.02) 0.15a 0.02)

2.87c (0.15) 0.86b (0.04) 0.16b (0.02) 1.19c (0.04) 1.17a (0.01) 0.26d (0.02)

2.91c (0.08) 0.83b (0.05) 0.18b (0.02) 1.23c (0.03) 0.15a (0.01) 0.25d (0.01)

2.32a (0.02) 0.74ab (0.05) 0.11a (0.02) 1.02b (0.10) 0.23b (0.02) 0.16ab (0.01)

2.37a (0.06) 0.77ab (0.03) 0.06a (0.01) 1.00b (0.06) 0.22b (0.03) 0.17ab (0.01)

2.36a (0.10) 0.75a (0.09) 0.25c (0.03) 0.94b (0.07) 0.32c (0.02) 0.25c (0.03)

2.45ab (0.06) 0.70a (0.06) 0.27c (0.06) 0.91b (0.05) 0.28c (0.02) 0.17c (0.02)

2.72bc (0.08) 0.96c (0.02) 0.10a (0.03) 0.71a (0.02) 0.22b (0.01) 0.13a (0.01)

C (%) C-to-N ADF (%) Lignin (%) Cellulose (%) Lignin-to-N

46.7 (0.30) 19.5:1b 44.8d (1.05) 18.8c (1.22) 25.4c (0.46) 7.87:1c

47.0 (0.32) 19.1:1b 43.4d (1.27) 17.4c (0.94) 25.5c (0.50) 7.07:1c

45.3 (0.48) 17.0:1a 50.5e (3.47) 20.6d (2.06) 29.0d (1.60) 7.74:1c

46.8 (0.09) 17.7:1a 47.8e (0.85) 20.4d (0.36) 26.7d (0.84) 7.70:1c

46.8 (0.28) 16.3:1a 36.2c (1.55) 16.4c (1.08) 18.8b (0.76) 5.71:1b

47.9 (0.64) 16.2:1a 37.0c (1.06) 16.8c (0.87) 19.3b (0.42) 5.77:1b

45.3 (0.48) 20.3:1b 31.5b (0.40) 14.2b (0.21) 16.7a (0.13) 6.12:1b

45.3 (0.48) 20.0:1b 31.8b (0.57) 13.8b (0.38) 17.1a (0.44) 5.82:1b

47.0 (0.44) 19.7:1b 32.7b (1.00) 12.7b (0.57) 19.5b (0.79) 5.38:1b

47.9 (0.64) 19.6:1b 32.0b (1.17) 12.9b (0.57) 19.1b (0.77) 5.27:1b

45.9 (0.92) 16.9:1a 26.5a (1.32) 9.35a (0.32) 16.9a (1.20) 3.44:1a

70.7b (1.79) 26.9c (0.36) 9.60b (0.40) 3.13b (0.20) 7.98a (1.00) 35.4b (1.31)

79.9b (3.05) 22.9b (0.20) 7.15a (0.15) 2.15a (0.05) 4.55b (0.05) 23.9a (0.40)

84.1b (2.46) 23.4b (0.38) 8.42a (0.04) 2.30a (0.12) 4.63b (0.20) 23.8a (0.56)

51.3a (5.08) 34.9d (1.40) 8.93a (0.90) 2.48a (0.12) 3.73c (0.36) 38.1b (1.76)

43.5a (2.09) 33.5d (0.66) 7.15a (0.93) 2.33a (0.10) 3.40c (0.27) 35.9b (124)

47.0a (3.80) 40.2e (1.10) 13.3d (0.75) 3.25bc (0.05) 4.52b (0.17) 45.4d 0.60)

53.9a (3.73) 40.3e (1.30) 14.2d (0.83) 3.37bc (0.13) 4.37b (0.22) 44.3d (0.76)

46.8a (3.85) 22.0a (0.49) 11.4c (0.39) 3.39bc (0.05) 3.28c (0.19) 40.8c (0.40)

50.4a (2.20) 21.3a (0.40) 12.4c (1.20) 3.40bc (0.20) 4.20c (0.50) 41.7c (3.40)

48.9a (1.30) 24.4b (1.10) 14.4d (0.75) 3.55c (0.45) 4.45b (0.45) 43.5cd (2.65)

Sugars (mg g 1) Xylose 79.3b (1.43) Arabinose 26.1c (0.39) Rhamnose 9.70b (0.51) Fucose 3.19b (0.20) Mannose 6.95a (1.39) Galactose 38.2bc (1.09) Total

163.4b (2.12)

153.7b (2.25)

140.6b (4.05)

146.7b (2.40)

139.4a (3.18)

125.8a (5.35)

153.7b (2.22)

160.4b (2.65)

127.7a (4.19)

133.4a (3.25)

139.2ab (3.15)

PPDs (mg g 1) p-Hydroxyl Vanillyl Syringyl p-Coumaric Ferulic acid

4.29c (1.02) 28.8b (0.29) 20.4b (0.34) 3.52 (0.37) 2.19 (0.15)

4.68c (0.31) 31.0b (1.90) 21.1b (0.45) 4.30 (0.18) 2.2 (0.15)

3.95c (0.06) 35.2c (5.00) 26.7d (0.95) 3.40 (0.09) 2.05 (0.06)

4.43c (0.41) 35.8c (1.09) 27.2d (0.55) 4.41 (0.37) 2.45 (0.15)

2.26ab (0.34) 34.5c (1.66) 22.6bc (0.60) 3.41 (0.95) 1.81 (0.52)

1.57ab (0.06) 33.0c (1.32) 22.1bc (0.46) 2.87 (0.63) 1.55 (0.28)

2.30ab (0.77) 23.3a (0.48) 17.4a 1.42) 4.22 (1.22) 2.42 (0.31)

1.61ab (0.10) 26.2a (2.24) 15.7a (0.33) 2.63 (0.45) 1.62 (0.40)

2.39b (0.64) 36.8c (2.74) 24.4c (1.74) 3.74 (0.32) 2.99 (0.31)

2.15b (1.00) 34.1c (5.97) 22.9c (2.40) 3.28 (1.67) 2.57 (0.55)

2.26ab (0.09) 29.8b (1.01) 21.1b (1.04) 2.97 (0.44) 2.31 (0.37)

Total

59.2b (1.80)

63.3b (2.79)

71.3d (6.00)

74.3d (1.18)

64.5bc (1.54)

61.2bc (0.87)

49.6a (3.23)

47.8a (1.22)

70.3cd (5.43)

65.0cd (6.57)

58.4b (1.21)

BE (Brown earth) and GBE (Gleyed brown earth) represent for the High Fertility (HF) Sites and OBS (Ochreous brown earth) and P (Podzols) for Low Fertility (LF) sites. Values in parentheses indicate the number of sampling sites within each soil type. Standard error of the mean is given in parentheses. The Scheffe test is used for multiple comparisons. Means with the same superscript letters (a–d) are not significantly different by lines.

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BE (7)

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Table 3 Summary of the PCA for litter quality variables in chestnut (a), oak (b) and beech (c) green leaves and leaf litters collected from sites on each soil types Eigenvalues

Eigenvectors

PC Value PrVar Cum Var C (a) Chestnut Green leaves 1 2 Leaf litters

1 2

ANOVA N

ADF

Lignin

Cellulose

F

P-values

2.70 1.11

0.54 0.22

0.54 0.76

0.02 0.87

0.35 0.42

0.59 0.08

0.59 0.26

0.53 0.02

43.9 <0.001 1.64 n.s

2.50 1.42

0.50 0.28

0.50 0.78

0.15 0.29

0.21 0.71

0.42 0.39

0.50 0.42

0.49 0.41

3.15 n.s 6.02 <0.05

Xylose

Arabinose Rhamnose Fucose

Mannose Galactose Total

Green leaves 1 2

4.12 1.50

0.59 0.21

0.59 0.80

0.19 0.72

0.42 0.28

0.33 0.10

0.42 0.22

0.42 0.34

0.34 0.43

0.25 0.38

55.6 <0.001 0.72 n.s

Leaf litters

1 2

3.53 1.38

0.50 0.20

0.50 0.70

0.49 0.23

0.31 0.51

0.45 0.03

0.45 0.16

0.34 0.24

0.36 0.16

0.28 0.32

7.54 <0.05 1.97 n.s

Green leaves 1 2

6.58 1.95

0.35 0.20

0.35 0.55

0.23 0.25

0.35 0.05

0.36 0.28

0.28 0.09

0.18 0.20

0.32 0.08

5.65 <0.05 0.69 n.s

Leaf litters

6.67 2.21

0.47 0.16

0.47 0.63

0.23 0.25

0.37 0.04

0.32 0.20

0.28 0.09

0.18 0.20

0.35 0.10

5.35 <0.05 1.93 n.s

p-Hydroxyl Vanillyl

1 2

Ca

Mn

Syringyl

K

p-Coumaric Ferulic

Mg

Total

P

Green leaves 1 2

2.33 1.21

0.47 0.24

0.47 0.71

0.36 0.51

0.06 0.84

0.45 0.31

0.27 0.40

0.03 0.61

5.40 <0.05 53.0 <0.001

Leaf litters

1 2

2.02 1.48

0.40 0.30

0.40 0.70

0.50 0.11

0.45 0.49

0.51 0.44

0.38 0.35

0.53 0.04

78.8 <0.001 4.27 <0.05

(b) Oak Green leaves 1 2

0.32 1.47

0.46 0.30

0.46 0.76

0.01 0.71

0.12 0.46

0.65 0.07

0.54 0.34

0.52 0.40

11.0 <0.01 3.12 n.s

0.32 1.47

0.46 0.30

0.46 0.76

0.01 0.71

0.46 0.24

0.65 0.07

0.54 0.34

0.52 0.40

11.0 <0.01 3.12 n.s

Leaf litters

1 2

Xylose

Arabinose Rhamnose Fucose

Mannose Galactose Total

Green leaves 1 2

2.12 1.83

0.30 0.26

0.30 0.56

0.25 0.43

0.44 0.63

0.48 0.22

0.46 0.07

0.36 0.44

0.35 0.42

0.26 0.18

31.0 <0.01 1.31 n.s

Leaf litters

2.12 1.83

0.3 0.26

0.30 0.56

0.39 0.43

0.35 0.63

0.48 0.22

0.46 0.07

0.35 0.44

0.31 0.42

0.33 0.28

5.31 <0.05 1.31 n.s

1 2

p-Hydroxyl Vanillyl

Syringyl

p-coumaric Ferulic

Total

Green leaves 1 2

4.21 2.58

0.40 0.15

0.40 0.55

0.23 0.26

0.32 0.35

0.31 0.33

0.01 0.31

0.23 0.15

0.35 5.18 0.31 6.32

<0.05 <0.05

Leaf litters

5.31 2.74

0.38 0.20

0.38 0.58

0.25 0.38

0.42 0.10

0.39 0.18

0.09 0.01

0.23 0.02

0.39 4.51 0.23 3.46

<0.05 n.s

1 2

Ca

Mn

K

Mg

P

Green leaves 1 2

1.65 1.15

0.33 0.23

0.33 0.56

0.25 0.60

0.12 0.51

0.17 0.63

0.58 0.35

0.10 0.67

10.5 34.4

<0.05 <0.001

Leaf litters

1.65 1.15

0.33 0.23

0.33 0.56

0.37 0.51

0.35 0.42

0.17 0.53

0.58 0.35

0.10 0.67

10.5 34.4

<0.01 <0.001

1 2

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Table 3 (Continued ) Eigenvalues

Eigenvectors

PC Value PrVar Cum Var C (c) Beech Green leaves 1 2 Leaf litters

1 2

ANOVA N

ADF

Lignin

Cellulose

F

P-values

2.38 1.34

0.48 0.27

0.48 0.75

0.69 0.17

0.03 0.53

0.54 0.64

0.39 0.54

0.32 0.51

5.23 <0.05 5.00 <0.05

2.25 1.25

0.45 0.25

0.45 0.70

0.11 0.18

0.01 0.66

0.65 0.32

0.53 0.40

0.53 0.36

2.04 n.s 54.4 <0.001

Xylose

Arabinose Rhamnose Fucose

Mannose Galactose Total

Green leaves 1 2

3.13 1.56

0.45 0.22

0.45 0.67

0.19 0.54

0.36 0.42

0.35 0.55

0.47 0.33

0.32 0.14

0.50 0.20

0.21 0.39

50.5 <0.001 0.51 n.s

Leaf litters

1 2

2.23 1.86

0.32 0.27

0.32 0.59

0.57 0.05

0.42 0.60

0.31 0.51

0.36 0.18

0.30 0.15

0.35 0.50

0.26 0.29

23.3 <0.001 1.64 n.s

Green leaves 1 2

4.39 2.76

0.43 0.2

0.43 0.63

0.26 0.13

0.51 0.26

0.42 0.25

0.28 0.21

0.23 0.33

0.41 0.29

Leaf litters

5.51 2.86

0.39 0.20

0.39 0.6

0.36 0.27

0.39 0.12

0.33 0.19

0.28 0.21

0.28 0.35

0.40 13.8 0.29 9.2

p-Hydroxyl Vanillyl

1 2

Ca

Mn

Syringyl

K

p-Coumaric Ferulic

Mg

8.32 <0.01 2.05 n.s <0.001 <0.01

P

Green leaves 1 2

1.68 1.19

0.34 0.24

0.34 0.58

0.22 0.79

0.58 0.39

0.49 0.37

0.59 0.39

0.11 0.33

Leaf litters

2.10 1.20

0.42 0.24

0.42 0.66

0.61 0.31

0.19 0.72

0.32 0.23

0.62 0.15

0.37 0.56

1 2

Total

6.63 <0.05 9.92 <0.01 22.9 16.9

<0.001 <0.001

For each of the highest two principal components (PC) the eigenvalues and the proportional variance (PrVar) and cumulative variance (CumVar) it explains, are shown with the eigenvectors and loading each variable contributes to that PC.

two soil groups but showed contrasting trends (Table 2). For example, lignin and cellulose concentrations in beech were lower in the HF soils than in the LF soils but oak and chestnut showed the opposite pattern with higher concentrations in the HF than LF soils. However, beech and chestnut had lower N concentrations and higher C:N ratios in the HF soils than in the LF soils in contrast to oak. 3.4. Green leaves: mineral element concentrations The PC1 versus PC2 plots showed that the mineral element concentrations in the leaves were separated along the PC2 axis into the groups of sites with high and low fertility soils (Fig. 1a). Beech and chestnut had lower Ca concentrations in the HF than the LF soils, while oak had higher Ca concentrations in the HF soils than in the LF soils. The three tree species showed similar responses to soil properties for Mn, K and P with higher concentrations

in the HF soil than in the LF soils. Mg in beech and oak had lower concentrations in the HF soils than in the LF soils but chestnut had higher Mg concentrations in the HF soils than in the LF soils. 3.5. Green leaves: TFA-extractable sugars The PC1 versus PC2 plots for all the three trees showed separation of the sugar constituents along the PC1 axis according to their origin in the HF and in the LF soils (Fig. 1b). The tree species showed inter-specific variations in the individual sugars between soil types (Table 2). Arabinose, rhamnose, fucose, mannose and galactose in beech had significantly (P < 0.01) higher concentrations on the HF soils than on the LF soils. Oak and chestnut showed the opposite relationships to beech with lower arabinose, rhamnose, fucose, mannose and galactose in the HF than LF soils. Xylose concentrations in beech were 1.5 times higher

T. Sariyildiz, J.M. Anderson / Forest Ecology and Management 210 (2005) 303–319

311

Fig. 1. Plots of axes 1 and 2 for PC analysis of chemical constituents in green leaves from beech (circles), oak (squares) and chestnut (triangles) trees growing on soils of high fertility (solid symbols) and low fertility (open symbols) soils. The dashed line was fitted by eye to delimit the high and low fertility sites. (a) Low fertility soils, (b) TFA-extractable carbohydrates and (c) CuO-extractable phenylpropanoid moieties.

312

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(P < 0.01) for the HF and LF soils than oak and chestnut leaves in the same soil groups. Concentrations of rhamnose, fucose and mannose showed smaller differences between tree species. Chestnut had higher galactose in the HF soils than beech and oak (P < 0.01), but on the LF soils chestnut and oak both had two-fold more galactose than beech (P < 0.01). 3.6. Green leaves: CuO-extractable PPDs The PC1 versus PC2 plots showed separation of these parameters along the PC1 axis for chestnut and beech and along the PC2 axis for oak according to their origin in the HF and in the LF soils (Fig. 1c). For all three trees species, total PPDs, vanillyl and syringyl concentration explained most of the variation between the two groups of soils, whereas phydroxyl, p-coumaric and ferulic acid had less influence. Concentrations of total PPDs, vanillyl and syringyl showed contrasting responses for the three trees species between the HF and the LF soils. Beech had significantly (P < 0.01) lower concentrations in the HF soils than in the LF soils. However, oak and chestnut showed the opposite trends with higher (P < 0.01) vanillyl, concentrations in the HF soils than LF soils. Beech, oak and chestnut also showed significant intra-specific differences between the HF and the LF soils. For example, on the HF soils, beech contained lower concentrations of total PPDs, vanillyl and syringyl than oak and chestnut. 3.7. Leaf litters Table 4 shows the concentrations of mineral elements and cell wall constituents in leaf litters for beech, oak and chestnut growing on different soil types. The results of PCA anaysis of soil types and litter constituents are given in Table 3. Leaf litter chemical properties were differentiated along the PC1 or PC2 axis into the HF and the LF soil groups and showed no consistent variation with the groups according to soil types (Fig. 2). Intra-specific variation in leaf litter properties is therefore discussed in relation to the HF and the LF soil groups rather than individual soil types.

3.8. Litter: total carbon, nitrogen, ADF, lignin and cellulose concentrations The PC1 versus PC2 plots showed separation of these parameters along the PC1 axis for oak and along the PC2 axis for beech and chestnut according to their origin in the HF and in the LF soils (Fig. 2a). Beech had higher (P < 0.01) concentrations of N, ADF and lignin in the HF soils than in the LF soils, whereas oak and chestnut showed the opposite trends with lower (P < 0.01) concentrations in the HF soils than the LF soils. However, there were lower concentrations of cellulose in beech and oak in the HF than in the LF soils but chestnut showed the opposite response. In the HF soils, chestnut showed the highest C:N ratios followed by beech and oak, whereas in the LF soils beech showed the highest C:N ratios followed by chestnut and oak. 3.9. Litter: mineral element concentrations Mineral element concentrations were separated along the PC1 axis for chestnut and along the PC2 axis for beech and oak into the HF and LF soil groups (Fig. 2b). Calcium concentrations in beech were lower (P < 0.01) in the HF than LF soils. However, oak and chestnut showed the opposite trends to beech with higher (P < 0.01) Ca concentrations in the HF soils. All three species showed similar trends for Mn with higher (P < 0.01) concentrations in the HF soil than in the LF soils. K, Mg and P in beech litter were also present in significantly (P < 0.01) lower concentrations on the HF soils than in the LF soils, while oak and chestnut showed the opposite responses. 3.10. Litter: TFA–extractable sugars Total and individual sugars in each tree species showed significant (P < 0.01) differences between the HF and the LF soils (Fig. 2c). Total sugar concentrations in all species were lower in the HF soils than LF soils (Table 4). Most individual sugars showed similar trends to total sugars with lower concentrations in the HF soils than in the LF soils. The exception of this were arabinose and galactose in beech, mannose and galactose in oak, and xylose and mannose in chestnut

Table 4 Concentrations of mineral elements, carbon, acid detergent fibre (ADF), lignin and cellulose and ratios of C-to-N and lignin-to-N in leaf litters of beech, oak and chestnut growing on the different soil types with different characteristics: BE (Brown-earth) and GBE (gleyed brown-earth) comprised the high fertility (HF) sites and OBS (ochreous brown earth) and P (Podzols) the low fertility (LF) sites Litter quality variables

Soil types Beech

Oak

N (%) Ca (%) Mn (%) K (%) Mg (%) P (%) C (%) C-to-N ADF (%) Lignin (%) Cellulose (%) Lignin-to-N

LF sites (10)

Chestnut

HF sites (14)

LF sites (8)

HF sites (11)

LF sites (4)

BE (7)

GBE (8)

OBS (5)

P (5)

BE (6)

GBE (8)

OBS (4)

P (4)

BE (6)

GBE (5)

P (4)

1.23bc (0.03) 1.00ab (0.08) 0.14bc (0.02) 0.19bc (0.02) 0.16ab (0.01) 0.08ab (0.01) 46.1 (0.45) 37.5:1ab 73.9e (1.67) 42.9d (1.45) 28.9d (0.78) 34.9:1c

1.35bc (0.03) 0.87ab (0.14) 0.14bc (0.01) 0.17bc (0.02) 0.13ab (0.03) 0.06ab (0.01) 44.6 (0.91) 33.0:1ab 74.5e (1.89) 41.0d (1.23) 30.5d (0.42) 30.4:1c

1.14a (0.04) 1.36cd (0.07) 0.05a (0.01) 0.26de (0.02) 0.25c (0.01) 0.17d (0.01) 44.4 (0.88) 38.9:1cd 69.8d (1.29) 37.9c (0.80) 31.1e (0.98) 33.2:1c

1.01a (0.03) 1.14cd (0.09) 0.09a (0.01) 0.24de (0.01) 0.25c (0.01) 0.15d (0.01) 45.0 (0.95) 44.6:1cd 71.4d (0.91) 37.7c (0.69) 32.8e (0.74) 37.3:1c

1.39cd (0.04) 1.45d (0.09) 0.14c (0.03) 0.25e (0.04) 0.16b (0.02) 0.12c (0.02) 48.0 (0.47) 34.5:1b 61.2b (2.71) 33.8b (2.35) 25.4a (1.28) 24.3:1b

1.41cd (0.07) 1.33d (0.04) 0.18c (0.02) 0.29e (0.04) 0.16b (0.01) 0.14c (0.01) 47.6 (0.22) 33.8:1b 57.9b (1.25) 33.0b (0.69) 23.6a (0.90) 23.4:1b

1.49d (0.09) 0.97bc (0.06) 0.09ab (0.02) 0.15ab (0.05) 0.12aa (0.01) 0.05a (0.01) 47.3 (0.74) 31.7:1a 65.8c (1.45) 36.2c (2.01) 28.3cd (1.64) 24.3:1b

1.53d (0.18) 1.18bc (0.08) 0.08ab (0.04) 0.13ab (0.01) 0.12a (0.01) 0.05a (0.01) 47.4 (0.47) 32.0:1a 66.3c (2.76) 36.7c (0.89) 27.7cd (1.48) 24.8:1b

1.10ab (0.06) 1.12bc (0.08) 0.22d (0.03) 0.23cd (0.01) 0.24c (0.02) 0.09b (0.01) 47.0 (0.36) 42.7:1d 49.8a (2.42) 21.3a (1.47) 27.0bc (1.34) 19.4:1a

1.14ab (0.10) 1.02bc (0.06) 0.29d (0.06) 0.17cd (0.02) 0.20c (0.02) 0.08b (0.02) 47.1 (0.12) 41.3:1d 49.9a (1.38) 21.8a (1.74) 27.4bc (0.29) 19.1:1a

1.23abc (0.04) 0.80a (0.02) 0.08ab (0.02) 0.11a (0.01) 0.16b (0.01) 0.05aa (0.01) 47.5 (0.41) 38.6:1bc 52.4a (1.00) 22.9a (1.72) 25.5ab (1.27) 18.6:1a

72.1d (2.20) 24.7b (0.85) 7.04a (0.48) 2.84a (0.10) 7.33d (0.31) 30.7b (1.42)

83.3e (0.98) 21.0a (0.29) 8.94b (0.32) 3.48b (0.14) 8.64e (0.15) 23.0a (1.09)

79.7e (0.86) 21.1a (0.49) 8.86b (0.27) 3.76b (0.16) 8.46e (0.20) 23.4a (1.12)

47.5b (2.64) 33.9d (0.86) 9.10b (0.65) 2.75a (0.17) 5.90bc (0.37) 34.4c (1.09)

50.0b (1.57) 31.3d (0.86) 9.39b (0.47) 2.92a (0.14) 6.00bc (0.31) 34.7c (1.09)

58.6c (0.50) 37.6e (0.87) 10.7c (0.06) 3.60b (0.12) 5.23a (0.26) 30.7b (0.26)

57.1c (0.61) 36.9e (1.21) 11.5c (0.30) 3.43b (0.13) 4.75a (0.21) 31.0b (0.33)

54.2c (3.28) 23.4b (0.91) 12.1 (1.00) 3.52b (0.12) 6.15c (0.37) 36.4c (1.00)

56.7c (4.83) 23.8b (0.99) 10.9c (0.45) 3.48b (0.08) 6.98c (0.67) 35.0c (1.24)

44.0a (1.13) 26.4c (0.41) 13.8d (0.10) 4.35c (0.09) 5.50ab (0.30) 43.5d (1.36)

Sugars (mg g 1) Xylose 66.7d (3.17) Arabinose 24.3b (0.66) Rhamnose 6.74a (0.41) Fucose 2.76a (0.16) Mannose 7.10d (0.30) Galactose 30.4b (1.09)

138.0bc (4.12) 144.7bc (2.56) 148.4c (1.68) 145.3 (2.15)

133.6a (3.24) 134.3a (2.30) 146.4c (2.31) 144.7c (1.85) 135.8ab (3.42) 136.9ab (2.12) 137.6ab (2.37)

PPDs (mg g ) p-Hydroxyl Vanillyl Syringyl p-Coumaric Ferulic acid

6.32b (0.58) 66.2c (1.73) 37.8c (2.01) 4.50b (0.66) 2.03b (0.21)

4.94b (0.18) 59.4c (1.51) 32.1c (1.38) 3.36b (0.35) 1.77b (0.14)

7.36c (0.43) 50.8ab (2.51) 27.5b (1.58) 4.10b (0.39) 1.98b (0.19)

6.77c (0.45) 52.4ab (2.22) 27.1b (2.09) 3.89b (0.42) 1.80b (0.19)

2.01a 54.3b 20.8a 2.33a 1.47a

(0.14) (5.20) (1.82) (0.27) (0.12)

1.89a (0.07) 58.2b (0.98) 20.4a (0.97) 2.42a (0.15) 1.51a (0.06)

2.20a (0.32) 71.2c (3.21) 26.2b (0.83) 2.73a (0.47) 1.35a (0.21)

1.85a (0.07) 65.4c (0.56) 28.3b (0.56) 2.38a (0.12) 1.60a (0.10)

1.42a (0.07) 50.2a (3.71) 20.4a (1.12) 2.05a (0.14) 1.93b (0.07)

1.59a (0.12) 43.5a (2.51) 19.4a (1.92) 2.14a (0.24) 2.22b (0.20)

1.51a (0.06) 62.3c (4.38) 24.7b (0.67) 2.17a (0.04) 1.86b (0.14)

Total

116.9d (3.75)

101.6d (2.29)

91.7c (4.13)

92.0c (3.35)

80.9b (7.13)

84.4b (1.58)

103.7d (3.52) 99.5d (0.68)

76.0a (4.84)

68.9a (4.13)

92.5c (4.64)

Total 1

T. Sariyildiz, J.M. Anderson / Forest Ecology and Management 210 (2005) 303–319

HF sites (15)

Values in parentheses indicate the number of sampling sites within each soil type. Standard error of the mean is given in parentheses. The Scheffe test was used for multiple comparisons. Means with the same superscript letters (a–d) are not significantly different by lines.

313

314

T. Sariyildiz, J.M. Anderson / Forest Ecology and Management 210 (2005) 303–319

Fig. 2. Plots of axes 1 and 2 for PC analysis of chemical constituents in leaf litters from beech (circles), oak (squares) and chestnut (triangles) trees growing on soil of high fertility (solid symbols) and low fertility (open symbols). The dashed line was fitted by eye to delimit the high and low fertility sites. (a) Total C, N, ADF, lignin and cellulose, (b) mineral elements, (c) TFA extractable carbohydrates and (d) CuO extractable phenylpropanoid moieties.

T. Sariyildiz, J.M. Anderson / Forest Ecology and Management 210 (2005) 303–319

315

Fig. 2. (Continued ).

that had higher concentrations in the HF soils than in the LF soils (Table 4). 3.11. Litter: CuO-extractable PPDs The PC1 versus PC2 plots showed separation of these parameters along the PC1 axis in relation to the

HF and LF soil types (Fig. 2d). The total PPDs, vanillyl and syringyl, explained most of the variation between the two groups of soils, whereas phydroxyl, p-coumaric and ferulic acid had little influence. The total PPDs, vanillyl and syringyl showed contrasting but significant (P < 0.01) inter-specific

316

T. Sariyildiz, J.M. Anderson / Forest Ecology and Management 210 (2005) 303–319

Fig. 3. Quotients for ratios of N in leaf litters to N in green leaves from beech (circles) oak (squares) and chestnut (trianges) trees growing on soils of high fertility (solid symbols) and low fertility (open symbols) in relation to soil N-mineralization potential. An increasing proportion of N translocated before leaf abscission is reflected by a lower quotient of N-litter/N-leaf. (a) Beech, (b) oak and (c) chestnut.

T. Sariyildiz, J.M. Anderson / Forest Ecology and Management 210 (2005) 303–319

responses between the HF and the LF soils. Beech showed higher concentrations in the HF soils than in the LF soils, while oak and chestnut showed the opposite relationships (Table 4). There were also inter-specific differences in total PPDs, vanillyl, syringyl concentrations between soil groups. In the HF soils, beech contained the highest vanillyl concentrations followed by oak and chestnut. On the LF soils, oak had the highest vanillyl concentrations followed by chestnut and beech. Beech and oak contained similar syringyl concentrations that were higher than chestnut. Beech had three-fold higher phydroxyl concentrations than oak and chestnut on both the HF and the LF soils. However, p-coumaric and ferulic acid showed differences between tree species.

Table 5 Percentage changes in concentrations of mineral elements between green leaves and leaf litters of beech, oak and chestnut trees growing on different soil types Soil types

N

Beech Brown earths (seven sites) 49 Gleyed brown earths (eight sites) 46 Mean

Ca

Mn K

30 39 16 30

Mg P

82 11 83 24

56 65

47

23 35

83 17

60

Ochreous brown soils (five sites) 57 Podzols (five sites) 62

63 29 52 21

61 15 72 13

60 50

Mean

60

46 30

66 14

55

52 52

69 13 60 12

79 6 76 12

54 64

52

64 13

78

9

59

Ochreous brown soils (five sites) 36 Podzols (five sites) 35

31 18 43 11

85 11 87 10

69 71

Mean

36

42 15

86 11

71

53 53

49 12 46 6

76 25 81 29

64 53

Oak Brown earths (six sites) Gleyed brown earths (nine sites) Mean

Chestnut Brown earths (six sites) Gleyed brown earths (five sites)

317

3.12. Differences in the concentrations of mineral elements before and after leaf abscission in relation to soil types Percentage changes in foliage concentrations of mineral nutrients before and after leaf abscission in beech, oak and chestnut trees are shown in Table 5. Nitrogen and potassium concentrations decreased substantially during senescence, whereas Ca concentrations increased. The other nutrients did not show differences between green leaves and leaf litters. Nitrogen showed significant translocation, while losses of potassium were probably a consequence leaching during leaf senescence (and are not considered further). The three tree species showed significant (P < 0.01) differences in the N-translocation between the HF and LF (Fig. 3). For beech, N-translocation was higher on the LF soils (60%) than on the HF soils (47%), whereas oak and chestnut showed lower Ntranslocation (36 and 45%, respectively) on the LF soils than on the HF soils (52 and 53%, respectively). Increases in Ca concentrations in litters were significantly different between the HF and LF soils (P < 0.01) but beech showed greater increases on the LF soils, whereas oak and chestnut showed the opposite pattern with larger increases on the HF soils.

4. Discussion

Mean

53

48

9

78 27

58

Podzols (five sites)

45

18 14

85 27

62

Mean values for the high fertility (HF) and low fertility (LF) sites are indicated. Values in parentheses indicate the number of sampling sites within each soil type. Positive values indicate a reduction in concentrations before leaf abscission; negative values indicate that mineral concentrations were higher in leaf litters than green leaves.

We have shown that plant structural compounds of green leaves and litter from beech, oak and chestnut varied qualitatively and quantitatively, within and between species in relation to the mineral nutrient status and N-mineralization potential of 26 soils grouped into high fertility and low fertility types. Concentrations of plant nutrients also varied with soil type, but N re-absoption efficiency in relation to Nmineralization potential showed a contrasting response by beech to that of oak and chestnut. We are unaware of any comparable studies of intraspecific variation in this suite of constituents over such a range of soil types, though there is quite extensive literature on N re-absorption and litter quality by tree species growing on high and low fertility soils. The general hypothesis is that N (and P) re-absorption from

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leaves before abscission increases as an inverse function of soil nutrient availability. Cote et al. (2002) reported 56–71% N re-absorption efficiency for eight hardwood species on two sites of contrasting fertility. However, no relationships between Ntranslocation efficiency and soil factors was found by Staaf (1982) for beech trees on 24 sites, and a review by Aerts (1996) concluded that trees and shrubs showed poor intra-specific responses to soil nutrient availability with 63% of experiments reporting no response by 60 plant species. In the present study, we found significant intra-specific differences in N re-absorption but different inter-specific responses to soil fertility. Beech on 12 low-fertility soils re-absorbed about 60% leaf N before abscission but this decreased with increasing N-mineralization potential to 47% on the most fertile soil; a pattern consistent with the nutrient recovery hypothesis. Paradoxically, oak and chestnut showed the opposite trends. Both of these species exhibited greater variation than beech in N re-absorption on the low fertility soils, with similar N availability, but showed consistent trends of increasing N re-absorption with increasing N rates of mineralization potential. The exact quantitative basis of these relationships might have been influenced by errors in selecting similar litter-morphotypes for comparison with shade leaves. However, the differences in responses between the tree species were large, statistically significant and reflected by other constituents. Since beech, oak and chestnut are all slow-growing species these responses are not explicable in terms of differences in N allocation to growth. Increased concentrations of calcium in litter relative to leaves are most likely to have resulted from a differential loss of labile constituents, such as K and simple sugars, that are subject to rapid leaching after autolysis of the cells during senescence. Mean Klason lignin concentrations were highest in beech, lowest in chestnut and intermediate in oak but showed different intra-specific responses to soil type. The PPD derivatives of lignin from CuO oxidation mainly comprise the peripheral moieties around the condensed lignin core, and about 10–25% of the total mass of lignin (sensu strictu) (Ko¨ gel, 1986). Total PPDs, vanillyl and syringyl in beech were highest on LF soils for leaves, but highest on HF soils for litter. Conversely, in oak these PPDs were higher on HF for

leaves and lower for litter. An extensive study by Wessmann et al. (1988) showed that hardwood and conifer stands showed an inverse relationship between Klason lignin in the tree canopy and N-mineralization potential of the forest floor. This relationship is complicated not only by conifers showing greater lignification associated with longer needle retention on poor soils of (Flanagan and van Cleve, 1983) but Klason lignin also contains non-lignin compounds, such as suberins and cutins, that are associated with leaf sclerotisation under the physiologically stressing conditions often associated with soils of low inherent fertility. The leaves of temperate deciduous hardwoods have a life span of about 7–8 months and hence lignin mainly occurs in vascular tissues with additional lignification in ‘sun’ leaves because of their exposure to environmental conditions in the canopy. The differences in the chemical composition of ‘shade’ leaves and litters shown here therefore reflect intrinsic responses of these tree species to soil types. In conclusion, we have demonstrated that beech, oak and sweet chestnut trees respond to soil type with consistent qualitative and quantitative differences in hemicellulose and lignin composition in leaves and litter, and N translocation before leaf fall. We are unable to explain the different responses of tree species to soil chemistry. Tresender and Vitousek (2001) showed genetic variation associated with differences in foliar chemistry in a tropical tree species on a soil fertility gradient. Given that most mixed woodlands in England have been planted, and replanted, over many centuries it is unlikely that the provenance of tree species in this study were site specific. The observed patterns therefore reflect phenotypic responses to soil types that result in continuum of litter quality, within and between species, that have been shown to influence litter decomposition rates (Sariyildiz and Anderson, 2003a), and possibly herbivory and susceptibility to pathogens.

Acknowledgements This study was carried out while TS was supported by a postgraduate bursary from Kafkas University in Turkey. We are grateful for the helpful comments from two reviewers in the revision of this paper.

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