Mycorrhizal suppression and phosphorus addition influence the stability of plant community composition and function in a temperate steppe

Abstract

Nutrient enrichment can reduce ecosystem stability, typically measured as temporal stability of a single function, e.g. plant productivity. Moreover, nutrient enrichment can alter plant–soil interactions (e.g. mycorrhizal symbiosis) that determine plant community composition and productivity. Thus, it is likely that nutrient enrichment and interactions between plants and their soil communities co‐determine the stability in plant community composition and productivity. Yet our understanding as to how nutrient enrichment affects multiple facets of ecosystem stability, such as functional and compositional stability, and the role of above–belowground interactions are still lacking.We tested how mycorrhizal suppression and phosphorus (P) addition influenced multiple facets of ecosystem stability in a three‐year field study in a temperate steppe. Here we focused on the functional and compositional stability of plant community; functional stability is the temporal community variance in primary productivity; compositional stability is represented by compositional resistance, turnover, species extinction and invasion. Community variance was partitioned into population variance defined as community productivity weighted average of the species temporal variance in performance, and species synchrony defined as the degree of temporal positive covariation among species.Compared to treatments with mycorrhizal suppression, the intact AM fungal communities reduced community variance in primary productivity by reducing species synchrony at high levels of P addition. Species synchrony and population variance were linearly associated with community variance with the intact AM fungal communities, while these relationships were decoupled or weakened by mycorrhizal suppression. The intact AM fungal communities promoted the compositional resistance of plant communities by reducing compositional turnover, but this effect was suppressed by P addition. P addition increased the number of species extinctions and thus promoted compositional turnover.Our study shows P addition and AM fungal communities can jointly and independently modify the various components of ecosystem stability in terms of plant community productivity and composition.