Can microplastic mediate soil properties, plant growth and carbon/nitrogen turnover in the terrestrial ecosystem?

Microplastic (MP) pollution, a global environmental problem, has been recently studied in marine and freshwater environments. However, our understanding of MP effect on terrestrial ecosystems, especially carbon (C) and nitrogen (N) turnover remains poor. This review summarizes the sources and distribution characteristics of MPs in terrestrial ecosystems and explores their effects on soil properties, plant growth, C and N turnover. Once entering the terrestrial ecosystem, MPs could involve in sequestrating carbon and nitrogen by changing soil properties (e.g., pH, soil aggregate stability, and soil porosity). MPs could exert direct influences on plants or on soil physical environment and microbial metabolic environment to indirectly affect plant growth, thus altering the quantity and quality of soil C and N inputs by shifts in plant litter and roots. The changes of the dominant bacteria phyla, related functional genes, and enzymes caused by MP pollution could affect C and N cycles. Additionally, the MP effect varies with its properties (e.g., types, shapes, elemental composition, functional groups, released additives). Future researches should unify the standard system of MP separation, detection, and reveal the ecological effects of MPs, especially their impacts on terrestrial carbon and nitrogen cycles in the context of climate changes.