Divergent Drivers of Litter Decomposition in Karst and Non-Karst Tropical Rainforests: A Comparison

Litter decomposition is pivotal in nutrient cycling, with this process being influenced by numerous factors. However, the factors and pathways driving litter decomposition in certain heterogeneous ecosystems, such as diverse tropical karst ecosystems, remain unclear. We conducted litter decomposition experiments, both in situ and reciprocal transplants, in the seasonal rainforests of karst (KF) and non-karst (NKF) regions. While the litter N :P emerging was the most determinant influencing factor driving litter decomposition acorss both KF and NKF, other key drivers of in litter decomposition differ significantly between KF and NKF, with. In KF, The topography results in an uneven distribution of water and heat, which drives various factors such as tree diversity, leaf structure, and decomposer feeding, all influencing litter decomposition processes. In NKF, tree diversity, soil nutrients, and other abiotic factors exert relatively uniform effects on decomposition, with no single factor standing out as particularly dominant. The difference between KF and NKF might result from the fact that phosphorus resources are primarily acquired through leaf reabsorption in KF while NKF trees obtain phosphorus through root absorption, which leads to an opposite trend between litter total P and tree diversity in KF and NKF. Even though the decomposition pathways in KF and NKF differ significantly, we did not observe a home-field advantage. This study reveals the driving factors of litter decomposition in karst and non-karst ecosystems, highlighting the pivotal role of nutrient acquisition strategies in shaping decomposition pathways. It provides a foundation for future research aimed at enhancing forest management practices and optimizing nutrient cycling strategies in diverse tropical environments.

凋落物分解（litter decomposition）在养分循环（nutrient cycling）中发挥关键作用，该过程受众多因素调控。然而，在部分异质性生态系统（如多样的热带喀斯特生态系统）中，驱动凋落物分解的因素与路径仍不明晰。本研究在喀斯特（KF）与非喀斯特（NKF）区域的季节性雨林中开展了原位（in situ）凋落物分解实验与互置移植实验。尽管在KF与NKF生境中，凋落物氮磷比（N:P）均为调控凋落物分解的最关键因素，但二者间其他核心驱动因子存在显著差异。在喀斯特生境中，地形导致水热分布不均，进而驱动树木多样性、叶片结构、分解者取食等多种因子共同调控凋落物分解过程。在非喀斯特生境中，树木多样性、土壤养分及其他非生物因子对分解过程的影响相对均匀，无单一因子占据显著主导地位。KF与NKF生境间的差异或源于：喀斯特生境中植物主要通过叶片重吸收（leaf reabsorption）获取磷素，而非喀斯特生境植物则通过根系吸收（root absorption）获取磷素，这使得两地凋落物总磷含量与树木多样性间呈现相反的变化趋势。尽管KF与NKF生境的分解路径存在显著差异，但本研究未观测到分解主场优势（home-field advantage）。本研究阐明了喀斯特与非喀斯特生态系统中凋落物分解的驱动因子，揭示了养分获取策略在塑造分解路径中的关键作用，可为未来旨在优化热带多样生境的森林管理实践与养分循环策略的研究提供理论基础。