Distribution pattern and factors affecting litter stocks at the slope-scale in a karst forest in subtropical China

Abstract

Litter distribution significantly affects nutrient cycling, energy transfer, and various ecosystem services. However, little is known about how microtopography affects litter accumulation and distribution on the forest floor. Distribution characteristics of litter stocks at the slope-scale and their relationship with topography and rock exposure rate (RER) in a typical subtropical karst forest in China were determined by measuring the litter stock and RER of 300 grids of1 × 1 m in a 10 × 120 m square on a limestone hill. The results showed that (1) the average litter stock of karst forest was 691.54 ± 332.60 g∙m-2, among which 65.81% was undecomposed litter; (2) the spatial distribution of litter stocks was uneven with moderate variation, presenting five aggregated areas and four sparse areas on the entire slope; (3) there was a significant negative correlation between RER and litter stock (R = −0.37, P < 0.01), which increased with increasing slope gradient and slope position; and (4) the RER coupled with topography in karst areas directly affected litter accumulation via the redistribution process and indirectly affected the decomposition rate by altering the microenvironment, which reshaped the slope-scale distribution pattern of litter stocks. Our research highlights the importance of the complex slope-scale morphology of karst ecosystems in altering nutrient cycling and energy transfer by mediating litter redistribution, providing new insights into the formation of the high environmental heterogeneity in karst habitats.