Abstract: Soil respiration is an important part of terrestrial carbon cycling. Understanding its response to precipitation changes and nutrient addition can help to assess how global changes affect terrestrial carbon cycling. However, few studies have focused on the interactive effects of precipitation change and nutrient deposition on soil respiration. We conducted a field-manipulated experiment with increasing or decreasing precipitation and adding nutrient to simulate precipitation change and nutrient deposition on a meadow steppe in Hulunber, to explore the main and interactive effects of those two global change factors on soil respiration and the underlying mechanisms. The results showed that increasing precipitation did not affect soil respiration, while drought significantly reduced soil respiration. Nutrient addition had a limiting inhibitory effect on soil respiration, but its interaction with changing precipitation was not significant. Increasing precipitation significantly increased soil moisture, but did not affect soil temperature. Drought significantly reduced soil moisture and increased soil temperature. Nutrient addition significantly increased soluble inorganic carbon, inorganic nitrogen, and aboveground net primary productivity, and reduced soil moisture. Soil respiration was negatively correlated with soil temperature, but positively correlated with soil moisture, microbial biomass carbon and microbial biomass nitrogen. Soil moisture, soil temperature, microbial biomass carbon and microbial biomass nitrogen explained 56.3%, 26%, 16.6%, and 19.6% of the variation in soil respiration, respectively, indicating that soil moisture was the key factor regulating soil respiration. These findings may facilitate the understanding of soil respiration in meadow steppe under scenarios of global change.

Key words: soil respiration, increasing precipitation, drought, nutrient addition, meadow steppe.