Biodegradable film mulching increases soil microbial network complexity and ecological stochasticity and decreases nitrogen cycling genes

Biodegradable plastic films have emerged as an alternative to conventional plastic films. However, responses of plant-associated microbiome to the application of biodegradable film mulching in field scale have received little attention. A field experiment was performed to assess the influence of different film mulching on the multiple microbial attributes and nitrogen (N) cycling functional genes in bulk and rhizosphere soils. We found that biodegradable film mulching increased bacterial Shannon index in bulk soils, but not in rhizosphere soils. Biodegradable film mulching increased the complexity and connectivity of microbial network, and increased positive association of microorganisms owing to raised soil nutrient and crop roots. In biodegradable film-treat soils, both bacterial and fungal communities were driven by stochastic processes mainly belonging to dispersal limitation. Moreover, conventional plastic film mulching raised denitrification, anammox, N fixation and dissimilatory nitrate-reduction (DNRA) gene abundances in bulk soils, but in rhizosphere soils, biodegradable film mulching declined nitrification, denitrification, anammox, N fixation, DNRA gene abundances. Furthermore, keystone genus (e.g. Nitrosospira, Truepera, Adhaeribacter, Opitutus, Fusarium) were affected by edaphic variables, contributing to decreased N-cycling gene abundances in biodegradable film-treat soils. Collectively, biodegradable film mulching transformed soil microbiome assembly and functional adaptation, and soil nutrient availability and plant biomass were the critical factor influencing microbial community. These results provide a new perspective on effects of conventional and biodegradable film mulching on the soil microbiome and N cycling processes.