Whole-leaf decomposition rates are the sum of the decomposition rates of each chemical fraction (water-soluble, cellulose, hemicellulose, lignin), but the decomposition rates of each fraction show complicated patterns of covariation. What explains these patterns of covariation? After measuring the k-values of each fraction in 42 different mixtures of tree leaf litters from five species, we tested three alternative causal hypotheses that have been proposed in the literature concerning these mixture interactions using structural equations modeling. All three hypotheses were rejected by the data. We then proposed a new hypothesis, in which rapid decomposition of the labile (water-soluble) fraction stimulates the decomposition of lignin by white-rot fungi and the decomposition of hemicellulose by brown-rot fungi. A more rapid decomposition of hemicellulose then stimulates the decomposition of cellulose. This hypothesis is both consistent with known biology and with our data and is proposed as the most viable current hypothesis.

中文翻译：

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解释不同质量分数落叶物分解率之间相关性的因果假设

全叶分解率是每个化学部分（水溶性、纤维素、半纤维素、木质素）分解率的总和，但每个部分的分解率显示出复杂的协变模式。什么解释了这些协变模式？在测量了来自 5 个物种的 42 种不同树叶凋落物混合物中每个部分的 k 值后，我们使用结构方程模型测试了文献中提出的关于这些混合物相互作用的三个替代因果假设。所有三个假设都被数据拒绝了。然后我们提出了一个新假设，其中不稳定（水溶性）部分的快速分解刺激了白腐真菌对木质素的分解和褐腐真菌对半纤维素的分解。半纤维素更快速的分解然后刺激纤维素的分解。该假设与已知的生物学和我们的数据一致，被认为是当前最可行的假设。