Yumiao Sun, Jiaqi Sun, Sijia Wang, Cuicui Qu, Yiwen Hu, Fang Li, Dongmei Geng, Li Xu
The widespread agricultural use of mulch films has raised concerns about their impacts on soil microbial communities. However, how biodegradable and conventional films affect the micro-food web across planting patterns and soil depths remains poorly understood. Here, we conducted a 110-day field experiment to investigate the effects of biodegradable (PBAT) and conventional (PE) mulch films and PE film under film-edge planting (PE_L) on soil bacterial, fungal, and protistan communities. Our results showed that PBAT significantly reduced the diversity and altered the composition of bacteria, fungi, and protists in specific soil layers. Bacteria and protists remained predominantly stochastic across all treatments, whereas fungal assembly shifted to deterministic processes under PBAT. Multitrophic co-occurrence network analysis revealed that PBAT significantly increased network size and overall robustness while lengthening diameter and path length, forming a "long-chain" structure. In contrast, PE substantially reduced network size and robustness, with PE_L being intermediate between the control and PE. Moreover, PBAT enhanced the connective role of fungi in the micro-food web. Vertically, the effects of mulching treatments on microbial communities were mainly concentrated in the surface soil, with network size and robustness decreasing with increasing soil depth. Microbial competition may have intensified in deeper layers, as indicated by increased negative correlations under resource limitation. Furthermore, redundancy analysis and Mantel tests showed that soil physicochemical factors significantly influenced microbial communities, though they explained only a limited fraction of the variation. Overall, biodegradable and conventional films exert different effects on the soil micro-food web across planting patterns and soil depths, implying that agricultural practices require more nuanced risk evaluations.