Changes in soil respiration after eight years of warming and increased precipitation in a semiarid temperate steppe.

Warming and increased precipitation can affect soil respiration (SR) and plant community variation in grassland ecosystems. Dominant species have important impacts on maintaining grassland landscapes and ecosystem stability, promoting nutrient cycling, and carbon sequestration. However, the mechanisms by which warming and increased precipitation regulate SR through the replacement of dominant plant species remain largely unknown. Here, we conducted an 8-year (2011–2018) manipulative field experiment comprising warming and precipitation addition, as well as a pot experiment simulating different proportions of dominant species (Leymus chinensis and Stipa krylovii), to examine the changes in SR in a temperate steppe in Inner Mongolia, China. Our results indicate that increased precipitation significantly increased SR by 48.9 %, while warming had no significant effect on SR. Warming, increased precipitation, and their interaction did not affect the temperature sensitivity of SR. Warming and increased precipitation were found to increase the biomass of L. chinensis (a rhizomatous grass) and decrease the biomass of S. krylovii (a bunchgrass). SR was significantly positively correlated with community biomass and microbial biomass. Although the proportion of dominant species was not directly significantly correlated with SR, the proportion of dominant species can affect SR by regulating community biomass and subsequently affecting microbial biomass. The pot experiment also showed that community biomass is a key factor affecting SR. This study emphasizes the regulatory role of soil moisture and community biomass in SR. When evaluating the impacts of climate change scenarios on soil respiration and ecosystems, the potential effects of changes in the dominant species should be considered, especially in arid and semiarid regions. • Warming had no significant effect on soil respiration in temperate steppe. • Soil moisture and community biomass are key factors regulating soil respiration in temperate steppe. • Increasing precipitation has a cumulative effect on soil respiration over years. [ABSTRACT FROM AUTHOR]