Inter-annual precipitation variability alters the effects of soil resource enrichment and mycorrhizal suppression on plant communities in desert steppe

Questions: In desert steppes, plant community productivity and species composition are primarily co-limited by soil water and nitrogen availability. However, how the addition of resources and arbuscular mycorrhizal fungi interactively influence plant community performance has not been investigated in detail.

Location: Desert steppe, China.

Methods: We performed a field study to examine the effects of levels of increased water, nitrogen and arbuscular mycorrhizal (AM) fungal suppression on plant communities in 2 year with contrasting inter-annual precipitation variability in desert steppe.

Results: We found that inter-annual precipitation variability altered plant community composition and productivity in responses to water and nitrogen addition and mycorrhizal suppression. AM fungal suppression had few effects on aboveground plant productivity, whereas the primary effects of water and nitrogen addition were significant across all two years. The addition of water and nitrogen altered plant community composition and productivity primarily by increasing the abundance and biomass of annual species only in normal year (2019), but decreasing the abundance of perennial grasses regardless of the presence of AM fungi across two years with contrasting precipitation conditions. Moreover, the addition of water alone slightly increased the species richness and Shannon diversity compared with the control.

Conclusions: Our findings highlight the importance of inter-annual precipitation variability rather than that of soil resource enrichment and plant–arbuscular mycorrhizal fungi interactions in plant community composition within the desert steppe.