Effects of polyethylene microplastics on soil microbial assembly and ecosystem multifunctionality in the remote...

Microplastics (MPs) are ubiquitously present in almost every ecosystem globally, including the remote mountains. To date, the effects of MPs on the properties and functioning of soils in remote mountainous ecosystems have been less explored. This study aimed to investigate the ecological impacts of polyethylene (PE) MPs at ∼0.2 % (w/w) on soils in three typical altitude zones of Changbai Mountain, China, including the mixed coniferous and broad-leaved forest (MF) zone, birch forest (BF) zone, and alpine tundra (AT) zone. The results showed that PE MPs exerted diverse effects on soil carbon and nitrogen nutrients across altitude zones but consistently increased soil pH. PE MPs enhanced the humification of soil dissolved organic matter (DOM) and the α-diversity of the bacterial community in the lower-altitude MF zone but exerted negligible effects in the higher-altitude BF and AT zones. Phyla Proteobacteria and Actinobacteria dominated bacterial communities under all treatments but exhibited opposite variation patterns on exposure to MPs. PE MPs contributed to the enrichment of a larger number of carbohydrate-active enzymes (CAZy) gene families in the BF and particularly MF zones. Soil ecosystem multifunctionality was significantly improved by PE MPs in the AT and MF zones but was less affected in the BF zone. The soil bacterial diversity, pH, organic carbon, DOM chemodiversity, and climatic factors (i.e., mean annual temperature) were the pivotal predictors of soil ecosystem multifunctionality. This study provides new insights for evaluating the ecological impacts of MPs on soils in remote mountains.