Nitrogen Deposition Drives Response and Recovery in the Context of Precipitation Change and Its Reversal in an Arid Ecosystem

Abstract

AbstractClimatic change profoundly impacts terrestrial ecosystem function and structure. However, it remains unclear how an entire ecosystem responds to precipitation fluctuations in relation to nitrogen (N) deposition, especially in arid ecosystems. A field experiment was conducted in a desert steppe over the course of 4 years to determine plant community and belowground responses to precipitation alteration and a subsequent precipitation regime reversal treatment under increased N addition, with an initial 3‐year precipitation regime manipulation period followed by a fourth‐year reversal. The aboveground net primary production (ANPP) significantly increased with increased precipitation, particularly at high N levels. However, the precipitation regime reversal treatment in the final year reversed the ANPP effects induced by the previous precipitation alteration. Soil microbial carbon and N content significantly increased with increasing precipitation, whereas the precipitation reversal in the final year partly eliminated the soil microbial effects produced by this previous precipitation alteration. Plant community composition shifted under both the precipitation and N treatments, with a few critical species playing crucial roles. The response ratio (initial treatment vs. control) of ANPP increased with increased precipitation during the first 3 years. Both the resilience (precipitation regime reversal treatment vs. control) and the limitation or promotion index (LPI, precipitation reversal treatment vs. initial treatment) of NPP were relatively high under the initial low precipitation and the final high precipitation regimes. Structural equation modeling in particular illustrated that the precipitation alteration treatments made greater contributions to the response ratio, resilience and LPI of the NPP than did N deposition via either the soil microbial levels or the plant diversity index. We should therefore consider both vegetation productivity and its compositional shift, as well as the associations with soil microbes under contrasting environmental changes, to accurately assess and predict the responses of terrestrial ecosystems to climate change.