Microplastics positively mediate soil multifunctionality in dryland

Soil multifunctionality (SMF) denotes soil capability to concurrently offer diversified functions. Here, we unveiled the long-term effects of polyethylene microplastics (MPs) on SMF along their physical forms and concentrations in dryland. General linear model showed that eight major function groups (across 21 functions) explained 78.6 % of SMF variation. Direct or indirect productive functions of soil, including plant productivity and its physical property stability, contributed to SMF by 8.65 % and 13.68 %, respectively. Ecological functions, including microbial activity (12.73 %), bacterial composition diversity (10.69 %), bacterial functional diversity (11.71 %), carbon storage (9.98 %), nitrogen storage (3.54 %) and pollutant metabolism function (7.62 %), exhibited positive contributions to SMF. These were somewhat dependent on MPs physical forms and concentrations, and mostly attributed to the foam-modified effects of MPs on soil bulk density, and functional trade-off between conservation and services. Overall, MPs induced positive effects on SMF, challenging the widespread viewpoint that MPs only produced negative impacts in dryland.