Soil homogenization and microedges: perspectives on soil-based drivers of plant diversity and ecosystem processes

Disturbance caused by agriculture and resource extraction has resulted in widespread homogenization of soils at the local (within-site) scale. Here, we describe how experimental manipulation of heterogeneity at the local scale has had inconsistent effects on plant species diversity. Moreover, we discuss how soil homogenization per se typically has not been accounted for in the study of heterogeneity-diversity relationships, and how disturbance, often viewed as an artifact in soil heterogeneity experiments, can be a key driver of soil homogenization. We propose a conceptual model for describing the relationship between plant size, patch size, and diversity, and we discuss how factors such as disturbance, productivity, and competition among species cither should be controlled or accounted for in soil heterogeneity-plant diversity experiments. Finally, we consider the concept of soil patch microedges, which may provide unique micrositcs for increased plant diversity, and how these biogeochemical and hydrological interfaces could potentially drive ecosystem processes in a manner unique from the adjacent patches. Overall, this synthesis integrates perspectives on the functional links between plant-driven processes, and soil patterns and processes.