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Plant and soil δ13C and δ15N are linked to community biomass, litter production and litter turnover rate in mature subtropical forests

Enqing Hou1,2, Chengrong Chen2*, Dazhi Wen1*, Yuanwen Kuang1, Fangfang Sun3

1Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650 China;

2Environmental Futures Centre, Griffith School of Environment, Griffith University, Nathan Qld 4111, Australia;

3Institute of Ecology and Sustainable Development, Shenzhen Academy of Environmental Sciences, Shenzhen 518001 China.

*Corresponding authors. Email: (CC); (DW).

Online Resource 1 Monthly variations in precipitation and mean air temperature (a), and litter production (b and c) in mature forests in Dinghushan, China. Graph (a) wasderivedfrom Fang et al. (2009). Graphs(b) and (c) were modified from Zhou et al. (2007), forest names in the brackets were the abbreviationforest names used in this study, see Table 1 for full forest names.

Reference

Fang YT, Gundersen P, Mo JM, Zhu WX (2009) Nitrogen leaching in response to increased nitrogen inputs in subtropical monsoon forests in southern China. Forest Ecology and Management 257:332-342.

Zhou GY et al. (2007) Litterfall production along successional and altitudinal gradients of subtropical monsoon evergreen broadleaved forests in Guangdong, China. Plant Ecology 188:77-89.

Online Resource 2Pearson correlations among the soil water, N, and P axes and the litter production and turnover axis and their Pearson correlations with selected plant and soil parameters.

Parameter / Soil water PCA / Soil N PCA / Soil P PCA / Plant PCA
Axis 1 (The soil water axis) / Axis 1 (The soil N axis) / Axis 1 (The soil P axis) / Axis 1 (The litter production and turnover axis)
The soil N axis / 0.82
The soil P axis / 0.37 / 0.66
The litter production and turnover axis / 0.48 / 0.48 / 0.68
Soil moisture / 0.96 / 0.82 / 0.43 / 0.57
Soil water holding capacity / 0.96 / 0.76 / 0.28 / 0.35
Soil total N / 0.84 / 0.99 / 0.61 / 0.47
Soil extractable N / 0.77 / 0.99 / 0.69 / 0.48
Soil total P / 0.49 / 0.76 / 0.93 / 0.61
Soil extractable P / 0.19 / 0.47 / 0.93 / 0.66
Community biomass / 0.36 / 0.42 / 0.72 / 0.96
Litter production / 0.50 / 0.50 / 0.62 / 0.95
Litter turnover rate / 0.51 / 0.44 / 0.58 / 0.92

The soil water PCA considered mineral soil moisture content and water holding capacity; the soil N PCA considered mineral soil total N and extractable N contents; the soil P PCA considered mineral soil total P and extractable P contents; the plant PCA considered community biomass, litter production, and litter turnover rate.Data in bold indicate significant correlations at the level of P < 0.05, n = 32.

Online Resource 3L layer litterδ13C in relation to F/H layer litterδ13C (a) and the difference inδ13C between the L layer and the F/H layer litters (b).

Online Resource 4 Comparison of leafδ13C and δ15N among the 13 tree species selected in Dinghushan, China.

Species / Site / n / Leaf δ13C (‰) / Leaf δ15N (‰)
Pinus massoniana / PF, PBM1, PBM2, PBM3 / 16 / -29.1(0.7)a / -4.0(0.7)def
Engelhardia fenzelii / MTEB / 4 / -29.3(0.6)a / -2.9(0.3)cde
Ormosia fordiana / REB1 / 4 / -29.7(0.8)ab / -0.2(0.4)a
Rhododendron henryi / MTEB / 4 / -30.5(0.4)abc / -2.5(0.4)bcd
Euodia lepta / PF / 4 / -30.9(0.9)bc / -4.8(0.7)ef
Schima superba / PF, PBM1, PBM2, PBM3, MEB / 20 / -31.0(0.9)bc / -4.3(1.2)def
Aporusa yunnanensis / REB1 / 4 / -31.1(0.5)c / -3.0(0.8)cdef
Castanea henryi / PBM1, PBM2, PBM3, MEB / 16 / -31.3(0.5)c / -4.3(0.5)def
Machilus breviflora / MTEB / 4 / -31.4(0.4)cd / -5.1(0.8)f
Gironniera subaequalis / REB2 / 4 / -32.7(0.9)cd / 0.4(1.4)a
Caryota ochlandra / REB2 / 4 / -33.0(0.5)d / -1.7(2.0)abc
Sterculia lanceolata / REB2 / 4 / -33.5(0.4)d / -0.5(1.6)ab
Cryptocarya concinna / MEB, REB1 / 8 / -33.6(0.4)d / -4.2(1.4)def

Data are mean (SD). The corresponding full names of eight study forest sites are listed in Table 1.

Online Resource 5 Comparison of leaf δ13C and δ15N of the same species among forests.

Species / PF / PBM1 / PBM2 / PBM3 / REB1 / MEB
Leaf δ13C (‰)
P. massoniana / -29.9(0.6)b / -28.9(0.4)ab / -28.3(0.5)a / -29.3(0.4)ab
C. henryi / -31.8(0.3)b / -30.9(0.3)a / -31.2(0.4)ab / -31.3(0.6)ab
S. superba / -31.5(0.6)a / -31.5(0.5)a / -30.3(0.6)a / -31.6(0.5)a / -30.3(1.4)a
C. concinna / -33.8(0.1)a / -33.5(0.5)a
Leaf δ15N (‰)
P. massoniana / -4.9(0.8)b / -3.4(0.4)a / -3.8(0.2)a / -3.7(0.2)a
C. henryi / -4.4(0.5)a / -4.7(0.5)a / -3.9(0.7)a / -4.0(0.2)a
S. superba / -6.2(0.5)c / -4.1(0.4)b / -3.9(0.3)b / -2.8(0.2)a / -4.6(0.6)b
C. concinna / -3.0(0.4)a / -5.4(0.6)b

Data are mean (SD), n=4. Data in the same row with different letters are significantly (P < 0.05) different. The corresponding full names of eight study forests are listed in Table 1.

Online Resource 6 Stepwise multiple regression analysis of plant and soil δ13C and δ15N on the soil water, N and P axes.

Axes / F / Adjusted R2
Soil water / Soil N / Soil P
Leaf δ13C / -0.47** / 8.3 / 0.19
L layer litter δ13C / -0.53** / 11.4 / 0.25
F/H layer litter δ13C / -0.47** / 8.5 / 0.19
Fine roots δ13C a)
Soil δ13C / -0.59*** / 16.2 / 0.33
Leaf δ15N / 0.55** / 13.0 / 0.28
L layer litter δ15N / 0.40** / 0.58*** / 28.6 / 0.64
F/H layer litter δ15N / 0.49*** / 48.9 / 0.61
Fine roots δ15N / 0.70*** / 28.2 / 0.47
Soil δ15N a)

Only for significant predictors the standardized regression coefficient (Beta) are included in the model. F-value and adjusted coefficient of determination (Adjusted R2) are provided. # P < 0.10; * P < 0.05; ** P < 0.01; *** P 0.001.

a)no variables were entered into the model.