Nutrient cycling in tropical forests has a large importance for primary productivity, and decomposition of litterfall is a major process influencing nutrient balance in forest soils. Although large-scale factors strongly influence decomposition patterns, small-scale factors can have major influences, especially in old-growth forests that have high structural complexity and strong plant-soil correlations. Here we evaluated the effects of forest structure and soil properties on decomposition rates and stabilization of soil organic matter using the Tea Bag Index (TBI) in an old-growth riparian forest in southeastern Brazil. These data sets were described separately using Principal Components Analysis (PCA). The main axes for each analysis, together with soil physical properties (clay content and soil moisture), were used to construct structural equations models that evaluated the different parameters of the TBI, decomposition rates and stabilization factor. The best model was selected using Akaike’s criterion. Forest structure and soil physical and chemical properties presented large variation among plots within the studied forest. Clay content was strongly correlated with soil moisture and the first PCA axis of soil chemical properties, and model selection indicated that clay content was a better predictor than this axis. Decomposition rates presented a large variation among tea bags (0.009 and 0.098 g·g− 1·d− 1) and were positively related with forest structure, as characterized by higher basal area, tree density and larger trees. The stabilization factor varied between 0.211–0.426 and was related to forest stratification and soil clay content. The old-growth forest studied presented high heterogeneity in both forest structure and soil properties at small spatial scales, that influenced decomposition processes and probably contributed to small-scale variation in nutrient cycling. Decomposition rates were only influenced by forest structure, whereas the stabilization factor was influenced by both forest structure and soil properties. Heterogeneity in ecological processes can contribute to the resilience of old-growth forests, highlighting the importance of restoration strategies that consider the spatial variation of ecosystem processes.

中文翻译：

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热带古河沿岸森林中有机物的分解和稳定：土壤性质和植被结构的影响

热带森林中的养分循环对于初级生产力非常重要，凋落物的分解是影响森林土壤养分平衡的主要过程。尽管大尺度因素强烈影响分解模式，但小尺度因素可能会产生重大影响，尤其是在结构复杂度高且植物与土壤相关性强的老龄林中。在这里，我们使用茶袋指数（TBI）评估了巴西东南部一个古老的河岸森林中森林结构和土壤特性对分解速率和土壤有机质稳定的影响。使用主成分分析（PCA）分别描述了这些数据集。每种分析的主轴，以及土壤物理性质（粘土含量和土壤水分），用来构建结构方程模型，以评估TBI的不同参数，分解速率和稳定因子。最佳模型是使用Akaike准则选择的。森林结构和土壤理化性质在所研究的森林中各样地之间存在很大的差异。粘土含量与土壤水分和土壤化学性质的第一个PCA轴密切相关，模型选择表明，粘土含量比该轴更好。分解率在茶袋中表现出较大的差异（0.009和0.098 g·g−1·d-1），并且与森林结构成正相关，其特征在于较高的基础面积，树木密度和较大的树木。稳定因子在0.211-0.426之间变化，与森林分层和土壤黏土含量有关。所研究的旧林在较小的空间尺度上表现出较高的森林结构和土壤特性异质性，这影响了分解过程，并可能导致了养分循环的小范围变化。分解速率仅受森林结构影响，而稳定因子受森林结构和土壤特性影响。生态过程中的异质性可以促进旧林的复原力，突出了考虑生态系统过程空间变化的恢复策略的重要性。分解速率仅受森林结构影响，而稳定因子受森林结构和土壤特性影响。生态过程中的异质性可以促进旧林的复原力，突显了考虑生态系统过程空间变化的恢复策略的重要性。分解速率仅受森林结构影响，而稳定因子受森林结构和土壤特性影响。生态过程中的异质性可以促进旧林的复原力，突显了考虑生态系统过程空间变化的恢复策略的重要性。