Soil nutrient heterogeneity alters productivity and diversity of experimental plant communities under multiple global change factors

Plant communities in nature are often challenged by multiple global change factors (GCFs) and also ubiquitously encountered with soil nutrient heterogeneity. So far, however, we know little about the interactive effect of multiple GCFs and soil nutrient heterogeneity on plant communities. We conducted an outdoor mesocosm experiment in which a plant community was either grown in heterogeneous soils consisting of high- and low-nutrient patches, or in homogeneous soils where the same amount of nutrients was evenly distributed. These plant communities were exposed to none (control), single, or a combination of two or four GCFs (i.e. drought, nitrogen deposition, microplastic and cadmium). Biomass of the plant community exposed to drought and nitrogen deposition were greater in heterogeneous than in homogeneous soils, but evenness of the plant community exposed to microplastics was lower. Increasing the number of GCFs increased community biomass more in heterogeneous than in homogeneous soils, but it generally reduced community evenness, independent of soil nutrient heterogeneity. These contrasting responses were related to changing competitive hierarchies and root foraging responses under different treatments. Our results suggest that soil nutrient heterogeneity can alter community productivity and diversity via changing competitive interactions of the component species, depending on both the identity and the number of GCFs acting on the community. These results have important implications for the maintenance of ecosystem functions and services under rapid and complex ongoing global changes.