Leaf morphology versus chemical parameters

4.7.1.1 δ¹³C versus other leaf attributes

δ¹³C showed weak but significant correlations with leaf size (positive) and length-width ratio (negative) in the complete random sample, comprising four land use types, as well as within the secondary forest sample. Looking at some families and species, δ¹³C showed a strong, negative correlation to the leaf length-width ratio in the Euphorbiaceae and Urticaceae families (Figure 4.28 B, C).

1 2 3 4

Figure 4.28 A. δ¹³C versus C/N ratio in the complete random sample, comprising trees from four different land use types (for specification of random sample, see Table 3.2). B & C. δ¹³C versus leaf length-width ratio in a sample of individuals from two large-leaved families. The Euphorbiaceae sample is based on 85 individuals of 10 species (B) and the Urticaceae on 57 individuals of 10 species (C).

A positive correlation of δ¹³C to SLA was detected in the complete random sample of four land use types and in the agroforestry system, whereas the family Urticaceae showed a negative correlation between δ¹³C and SLA. A negative correlation with total carbon concentration was found in the complete random sample and in the natural forest.

δ¹³C also correlated positively with N and P in certain samples. Correlations to N were found in the complete random sample, the natural and secondary forests, the agroforestry system and within the families Euphorbiaceae and Fabaceae. Correlations to P were detected in the complete random sample of four land use types, within the secondary forest, in the Euphorbiaceae and Urticaceae families and in the species Litsea sp.1. Figure 4.28 A shows the relation between δ¹³C and C/N ratio in the complete random sample, which yielded a higher r²-value than correlations with C or N in that sample. A strong correlation between

4 RESULTS

total carbon and δ¹³C was observed in the late-successional species Litsea sp.1 (Lauraceae), which was the species with the most negative δ¹³C among all species investigated.

All correlation parameters for the relation between δ¹³C and other leaf traits in different samples are given in Table 4.12 and Appendix 3.

4.7.1.2 SLA versus other leaf attributes

SLA showed a negative correlation with leaf length-width ratio in the complete random sample, the natural forest and agroforestry system, as well as within the families Fabaceae and Euphorbiaceae. In contrast, the predominantly late-successional family Lauraceae and the widespread, but mainly pioneer-species family, Urticaceae showed positive correlations between SLA and length-width ratio.

A significant negative relation of SLA to leaf size was found in the complete random sample, the agroforestry system, and the families Lauraceae and Urticaceae.

Further, there was a clear positive correlation between SLA and leaf phosphorus and, more pronounced, nitrogen concentrations in the complete random sample, within each of

0

Figure 4.29 Leaf nitrogen and phosphorus concentrations versus specific leaf area (SLA) of trees in random samples from four different land use types. For specification of the random samples, see Table 3.2. (p < 0.01 in all eight correlations)

65

behind the r² value. p-values < 0.05 are marked bold. (No. ind. – Number of individuals, Compl. – Complete random sample, NF – Natural forest, SF – Secondary forest, FG – Forest garden, AF – Agroforestry system, LW – length-width ratio, SLA – specific leaf area)

Compl. NF SF FG AF Compl. NF SF FG AF Compl. NF SF FG AF

No. ind. 354 119 160 25 49 354 119 160 25 49 354 119 160 25 49

Leaf size SLA δ¹³C

0.01 (-) 0.03 (-) 0.005 (-) 0.002 (-) 0.25 (-) 0.02 0.002 0.05 0.002 0.05 (-) Leaf size

0.04 0.11 0.35 0.86 <0.01 0.01 0.72 <0.01 0.84 0.14 LW <0.001 (-) 0.05 0.11 (-) 0.004 0.11 (-) 0.05 (-) 0.05 (-) 0.02 (-) 0.12 (-) 0.11 (-) 0.04 (-) 0.001 0.08 (-) 0.02 0.02 (-)

0.66 0.02 <0.01 0.78 0.04 <0.01 0.03 0.06 0.08 0.02 <0.01 0.74 <0.01 0.53 0.29

SLA 0.01 (-) 0.03 (-) 0.005 (-) 0.002 (-) 0.25 (-) 0.08 0.005 0.002 0.02 (-) 0.13

0.04 0.11 0.33 0.86 <0.01 <0.01 0.45 0.62 0.51 0.01

Ca 0.005 0.04 0.002 (-) 0.10 (-) 0.04 (-) 0.002 (-) 0.03 0.03 (-) 0.07 0.06 (-) 0.02 0.01 0.07 0.10 0.10 (-)

0.17 0.05 0.63 0.08 0.19 0.35 0.08 0.03 0.22 0.09 <0.01 0.24 <0.01 0.13 0.02 K <0.001 (-) 0.03 <0.001 (-) 0.06 (-) 0.21 (-) 0.04 0.06 <0.001 (-) 0.13 0.22 0.01 <0.001 0.01 0.21 0.27 0.68 0.09 0.93 0.27 <0.01 <0.01 <0.01 0.96 0.08 <0.01 0.05 0.8 0.2 0.02 <0.01

Mg 0.001 0.05 0.002 0.08 (-) 0.10 0.02 (-) 0.01 0.02 (-) <0.001 0.18 (-) 0.03 (-) 0.02 0.01 0.38 0.22 (-)

0.54 0.02 0.66 0.17 0.02 <0.01 0.23 0.11 0.97 <0.01 <0.01 0.1 0.16 <0.01 <0.01

P 0.008 0.01 <0.001 0.06 (-) 0.17 (-) 0.24 0.24 0.10 0.36 0.43 0.27 0.006 0.01 0.001 (-) 0.25

0.09 0.22 0.88 0.26 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 0.37 0.13 0.89 <0.01

N 0.006 (-) <0.001 (-) 0.008 0.07 (-) 0.72 (-) 0.42 0.29 0.26 0.40 0.57 0.16 0.04 0.11 0.006 0.22

0.13 0.84 0.27 0.21 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 0.03 <0.01 0.71 <0.01 C 0.03 (-) 0.005 (-) 0.04 (-) 0.02 (-) 0.27 (-) 0.01 0.004 (-) 0.03 0.17 (-) 0.14 0.02 (-) 0.05 (-) 0.01 (-) 0.01 (-) 0.01 <0.01 0.45 0.02 0.5 <0.01 0.07 0.56 0.03 0.04 <0.01 0.01 0.01 0.11 0.63 0.5 C/N 0.001 (-) 0.005 (-) 0.02 (-) 0.004 0.68 0.34 (-) 0.21(-) 0.26 (-) 0.39 (-) 0.49 (-) 0.20 (-) 0.08 (-) 0.18 (-) 0.03 (-) 0.12 (-) 0.63 0.49 0.05 0.76 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 0.39 0.01

δ¹³C 0.02 0.001 0.05 0.002 0.05 (-) 0.08 0.005 0.002 0.02 (-) 0.10

0.01 0.72 <0.01 0.84 0.14 <0.01 0.46 0.63 0.51 0.01 N/P 0.04 (-) 0.03 (-) 0.002 0.001 (-) 0.37 (-) 0.006 (-) 0.008 (-) 0.02 0.02 (-) 0.01 0.06 (-) 0.02 0.04 0.008 0.002 (-) <0.01 0.11 0.63 0.88 <0.01 0.14 0.32 0.06 0.55 0.49 <0.01 0.09 0.01 0.66 0.77 C/P 0.02 (-) 0.03 (-) 0.01 (-) 0.002 0.08 0.26 (-) 0.23 (-) 0.10 (-) 0.29 (-) 0.42 (-) 0.26 (-) 0.008 (-) 0.04 (-) 0.01 (-) 0.29 (-) <0.01 0.09 0.2 0.83 0.05 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 0.32 <0.01 0.59 <0.01 δ¹⁵N <0.001 0.006 (-) 0.003 0.05 (-) 0.25 <0.001 (-) <0.001 0.005 0.05 0.24 (-) 0.006 0.02 (-) 0.05 0.14 0.06 (-) 0.7 0.41 0.55 0.26 <0.01 0.97 0.84 0.36 0.27 <0.01 0.14 0.15 <0.01 0.05 0.1

4 RESULTS

the four land use types (Figure 4.29). This relation was also visible in the families Euphorbiaceae and Lauraceae. Leaf phosphorus and nitrogen concentrations showed a strong interrelationship in all samples (r² = 0.51 (NF), r² = 0.53 (SF), 0.28 (complete sample), p < 0.01).

Parameters for all correlations between SLA and other leaf traits in different samples are given in Table 4.12 and Appendix 2.

4.7.1.3 Leaf size versus other leaf attributes

Leaf size was found negatively correlated to specific leaf area in the complete random sample, the agroforestry system and in the Urticaceae and Lauraceae families, but not within natural or secondary forest (Table 4.12, Appendix 1). Generally, leaf size was found closer related to length-width ratio than to specific leaf area in the various samples studied. Leaf size was negatively correlated to length-width ratio in SF and AF (Figure 4.30) and within four of the five most frequent families, indicating that round leaves were generally larger

1 10

Secondary forest

1 10 100

1000 Natural forest

1 10 100 1000

1 10

Agroforestry system Forest garden

logLeafsize[cm2]

log Length-width ratio

r²=0.11 (-) p=0.04 r²=0.11 (-) p<0.01 For x<10:

r²=0.08 (-) p<0.01

r²=0.05 p=0.02

Figure 4.30 Leaf size versus leaf length-width ratio in the random samples of four different land use types. Including three species with very large length-width ratios in the natural forest gave a positive correlation within that land use type, whereas excluding them gave a negative. For numbers of individuals and species included, see Table 3.2.

67

than lanceolate leaves. In the natural forest leaf size and leaf length-width ratio showed a negative correlation only if three species with very high length-width ratios were excluded, whereas including them gave a positive relation (Figure 4.30, Table 4.12, Appendix 1).

Leaf size further showed a negative relation to total carbon concentration in the complete random sample, SF and AF. Significant correlations between nitrogen

concentration and leaf size were only found in the agroforestry system and within the family Lauraceae. These correlations were strong and negative. The N/P ratio though, was shown to decrease with increasing leaf sizes in the complete random sample.

Leaf size showed a negative correlation with calcium in the two agroforestry species Theobroma cacao and Gliricidia sepium.

Parameters for all correlations between leaf size and other leaf traits in different samples are presented in Table 4.12 and Appendix 1.

4.7.2 Relations between leaf physiology and morphological or chemical parameters