Mixing effect of polylactic acid microplastic and straw residue on soil property and ecological function.

Microplastics have become a contaminant of increasing concern in soils. Although biodegradable plastics were considered as alternatives of traditional plastics, some evidence showed that biodegradable plastics might produce more microplastics. Until now, the effect of biodegradable microplastics on soil functions and processes, as well as microbial communities is uncertain. Based on high throughput sequencing, enzymatic activity assay and dynamic analysis of soil carbon and nitrogen, we investigated the effects of biodegradable polylactic acid microplastics (PLA MPs) on soil microbiota and related ecological processes under conditions of high or low carbon content. The results showed that PLA MPs had no significant effect on the overall diversity and composition of bacterial communities or related ecosystem functions and processes. However, co-occurrence network analysis revealed that PLA MPs impacted the interactions between constituent species, which might have legacy effect on soil bacterial communities and functions. Our data also revealed that PLA MPs could trade off the priming effect of carbon source. Our results provided an integrated picture in understanding the effects of PLA MPs on soil microbes, properties and ecological functions, which will help to further understand the effects of MPs on terrestrial ecosystems.