Conspecific negative density dependence decreases with increasing species abundance

Abstract

Conspecific negative density dependence (CNDD) is often involved in explaining the maintenance of species diversity in forest communities given that it may suppress the common species. Recent studies, in contrast, suggested that CNDD had a stronger effect on rare species than on common species and thus shaped the current tree abundance pattern. However, this finding was obtained mainly in the tropical forest and mixed results also occurred in the similar area. In addition, experimental test of the role of soil biota in maintaining this relationship is rare. In this study, two parallel manipulative shade‐house and field experiments were conducted in a subtropical evergreen broad‐leaved forest to test whether abundant species showed weaker CNDD than rarer species and whether susceptibility to soil biota was sufficient to maintain this relationship. The shade‐house experiment provided strong evidence for negative density‐dependent effects, and the strength of the density effect was significantly decreased along with the increase of the tree abundance. In the field experiment, a similar result was obtained. The density effect did not correlate with tree abundance after the sterilized treatment in the shade‐house experiment and the fungicide treatment in the field. Our results indicated that CNDD was negatively corrected with tree abundance in this subtropical forest and that soil biota played an important role in maintaining the relationship.