Impact of elevated precipitation, nitrogen deposition and warming on soil respiration in a temperate desert

Soil respiration (<i>R</i>_s) is the most important source of carbon dioxide emissions from soil to atmosphere. However, it is unclear what the interactive response of <i>R</i>_s would be to environmental changes such as elevated precipitation, nitrogen (N) deposition and warming, especially in unique temperate desert ecosystems. To investigate this an in situ field experiment was conducted in the Gurbantunggut Desert, northwest China, from September 2014 to October 2016. The results showed that precipitation and N deposition significantly increased <i>R</i>_s, but warming decreased <i>R</i>_s, except in extreme precipitation events, which was mainly through its impact on the variation of soil moisture at 5 cm depth. In addition, the interactive response of <i>R</i>_s to combinations of the factors was much less than that of any single-factor, and the main response was a positive effect, except for the response from the interaction of increased precipitation and high N deposition (60 kg N ha⁻¹ yr⁻¹). Although <i>R</i>_s was found to show a unimodal change pattern with the variation of soil moisture, soil temperature and soil NH₄⁺-N content, and it was significantly positively correlated to soil dissolved organic carbon (DOC) and pH, a structural equation model found that soil temperature was the most important controlling factor. Those results indicated that <i>R</i>_s was mainly interactively controlled by the soil multi-environmental factors and soil nutrients, and was very sensitive to elevated precipitation, N deposition and warming. However, the interactions of multiple factors largely reduced between-year variation of <i>R</i>_s more than any single-factor, suggesting that the carbon cycle in temperate deserts could be profoundly influenced by positive carbon–climate feedback