Modification by species diversity of effect of soil depth heterogeneity on plant community productivity
Abstract
Fine-scale heterogeneity in soil nutrient availability can enhance plant growth , but that effect in soil depth remain inadequately understood. Previous studies on soil depth gradients have suggested that deeper soils are inherently more productive within herbaceous communities, which is closely related to increased species diversity. Nevertheless, little is known about the interactive effects of soil depth heterogeneity and species diversity on plant community productivity. We conducted a greenhouse experiment in which we grew plant communit ies in three soil treatments (homogeneous, large-patch heterogeneous and small-patch heterogeneous) with two species diversity treatments (low and high) . The community comprised twelve common herbaceous species with varying functional traits and root strategies. Different plants species exhibited varied responses to soil depth heterogeneity. Increased soil depth significantly promoted the growth of legumes and forbs , as well as enhanced overall community productivity . Moreover, elevated s pecies diversity significantly affect ed community productivity and altered the responses of legum es and forbs to variations in soil depth heterogeneity. Forb plants grew more in large-patch heterogene ous and deeper soil within high - diversity communit y ; while legum e plants grew more in these soils with in low - diversity communit y. Legumes tend ed to avoid deep soil layers to alleviate competitive pressures from forbs within high-diversity settings . Therefore, increased species diversity may trigger selection effects within the community that lead to divergent plant growth strategies, thereby modifying the influence of soil depth heterogeneity on plant growth. However, small-patch heterogeneity with reduc ed scales may represent another form of habitat fragmentation within natural plant communities.