Milk vetch (Astragalus sinicus L.) affects microbial-driven rice straw decomposition in multiple stages

Although variations in microbial communities and residue components have been detected during the decomposition of monospecific and mixed plant residue in soils, little is known about the response of specific taxa to different residue types and their interactions with other microorganisms. We compared the decomposition dynamics, recruited microbial community, and lignocellulolytic genes during the decomposition of leguminous milk vetch (MV), non-leguminous rice straw (S), and their mixed residue (SMV) to reveal the mechanisms of microbial-driven residue decomposition in soil. The residue remaining weight and main lignocellulose component contents exhibited varied periodic dynamics during decomposition. The SMV treatment maintained a relatively high decomposition rate, particularly at the early stages. Actinobacteria, Alphaproteobacteria, Gammaproteobacteria, and Sordariomycetes were enriched in S treatment. Eurotiomycetes and Bacilli were enriched in MV treatment, while Mucoromycetes was enriched in SMV treatment. Co-decomposition of residues increased the alpha diversity of the microbial community and enriched the Mucorales by increasing its niche breadth. Redundancy analysis (RDA) revealed that Mucorales was a key functional taxon with high lignocellulolytic potential. Our study indicated that co-decomposition could widen the niche breadth of specific microbial species facing competitive condition during decomposition. Also, they could recruit more functional groups, maintain decomposition efficiency, and promote residue decomposition.