Environmental heterogeneity is thought to promote plant species coexistence, but we lack the convincing evidence. Here, I examined the effects of spatial variation in soil nutrients, soil pH and plant-soil feedbacks on plant species coexistence.
I found that soil nutrient heterogeneity can promote species coexistence through equalizing the competitive ability between competing plant species, and reduce plant species diversity by promoting the dominance of particular plant species. Heterogeneity in soil pH may promote plant diversity when the patch size of soil heterogeneity is large by proving refuges for subordinate species. The negative density-dependent plant-soil feedbacks can promote species coexistence by preventing the predominance of particular species. The spatial variation in plant-soil feedbacks also has the potential to promote coexistence by reducing the growth inequalities between the competing plant species.
Therefore, soil heterogeneity had an important influence on plant species coexistence. However, the effects varied depending on the type of soil factors that were manipulated, as well on the spatial scales at which species diversity and soil heterogeneity were measured.