Straw chemistry links the assembly of bacterial communities to decomposition in paddy soils

Although increasing number of studies have shown that microorganisms play important roles in plant residue decomposition, an important process for crop productivity and soil fertility in agroecosystems, the underlying ecological processes of microbial community assembly as well as the associated governing factors remain elusive. As such, we conducted three replicate paddy straw decomposition experiments, located across subtropical China. We used ecological null modeling to quantify assembly processes governing bacterial community turnover during straw decomposition. Consistent observations emerged across the experiments that indicated significant associations between bacterial community assembly processes and straw chemistry. Specifically, according to our framework, shifts in straw chemistry were associated with variable selection, which was inferred to drive community turnover between soil and straw surfaces. This resulted in bacterial subgroups from soil being deterministically selected to degrade straw. In turn, patterns were consistent with homogeneous selection governing community composition within straw decomposition stages and ecological drift being important across decomposition stages. Subsequently, shifts in community composition and assembly processes were linked to variation in functional aspects of straw decomposition. This study indicates that straw chemistry strongly influenced assembly processes governing microbial community turnover during straw decomposition. These outcomes are important for mechanistically understanding and predicting microbial-driven plant residue decomposition in terrestrial ecosystem.