Relative contributions of biotic and abiotic factors to the spatial variation of litter stock in a mature subtropical forest

Aims: Dead plant material (i.e. litter) is the major source of soil organic matter and thus plays a fundamental role in regulating soil carbon cycling in global forest ecosystems. The storage of litter is jointly determined by its production from plants and decomposition in a given environment. However, only few studies have explored the relative importance of environmental (i.e. abiotic) and plant (i.e. biotic) factors in driving the spatial variation of litter mass. The objective of this study is to quantify the relative contributions of biotic and abiotic factors in affecting the spatial variation of aboveground litter stock in a mature subtropical forest. Methods: The aboveground litter mass was sampled in 187 grids of a 20-hm forest dynamics plot in a subtropical broad-leave forest in eastern China. The contributions of environmental variables, topographical and species variables on litter stocks were quantified by the boosted regression tree analysis. Important Findings: The mean aboveground litter stock was 367.5 g m^-2 in the Tiantong dynamics forest plot across all the 187 grids. The litter stock ranged from 109.2 to 831.3 g m^-2 and showed a large spatial variation with the coefficient of variance as 40.8%. The boosted regression tree analysis showed that slope elevation and soil moisture were the most influential variables on the spatial variation of litter stock. The relatively influence of abiotic factors (environmental and topographical factors) was 71.4%, which is larger than biotic factors (28.6%). Overall, these findings suggest that abiotic factors play a more important role than plants in driving the spatial variation of aboveground litter stock in the subtropical forest. Given that the global carbon-cycle models have been aiming to refine from the hundred kilometers to sub-kilometer scale, this study highlights the urgency of a better understanding of the spatial variation of litter stock on the fine scale.