Divergent drivers of litter decomposition in karst and non-karst tropical rainforests: a comparison

Litter decomposition is a key process in nutrient cycling, shaped by both environmental factors and litter quality. However, in complex karst ecosystems, where shallow soils, high rock exposure, and fragmented terrain create strong abiotic and biotic heterogeneity, the dominant drivers of decomposition remain unclear. To explore these effects, we conducted two litter decomposition experiments, using litter deposited in situ and through reciprocal litter transplants, in the seasonal rainforests of karst (KF) and non-karst (NKF) regions. Although we observed no differences in litter mass loss rates or evidence of a home-field advantage (i.e., faster decomposition of litter in its native environment due to local adaptation of decomposer communities) between KF and NKF, the primary drivers of litter decomposition appeared to differ between the two areas. Notably, the litter nitrogen-to-phosphorus ratio (N:P) was the most significant factor influencing litter decomposition in both KF and NKF. In KF, structural equation modelling showed that topographical factors were significantly correlated with leaf quality and soil elemental nutrient content, which in turn indirectly influenced litter decomposition. In NKF, tree diversity, soil elemental content, and other abiotic factors had quantitively similar effects on decomposition, with no single factor standing out as particularly dominant. Overall, our results suggest that nutrient acquisition strategies, particularly N:P and phosphorus acquisition, play a key role in shaping litter decomposition pathways. Additionally, in karst forests, topography significantly influences other factors, further affecting decomposition processes. These findings provide a basis for improving forest management approaches, optimizing nutrient cycling, and guiding species selection for afforestation and restoration in karst ecosystems.