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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]

Grazing exerts a significant influence on greenhouse gases (GHGs) fluxes within temperate grasslands. While previous studies have explored the impact of varying grazing intensities on GHGs fluxes in meadow steppe, typical steppe, and desert steppe, there remains a knowledge gap regarding how grazing intensities affect GHGs fluxes across different grassland types and seasonal variations. In this study, we conducted a meta-analysis of Inner Mongolia grasslands involving 38 published reports and aggregating 143, 160, and 118 records for the CO 2 , CH 4 , and N 2 O, respectively. Our results demonstrated that grazing reduced annual mean CO 2 emission, CH 4 uptake, and N 2 O emission by 15.29%, 10.56%, and 24.73%, respectively (P < 0.05). Specifically, during the freeze-thaw period, grazing induced a decrease of 28.06% and 58.41% in CH 4 uptake and N 2 O emissions, respectively, compared to ungrazed treatments (P < 0.05). Further dissecting the impact, we found that grazing reduced CO 2 emissions in desert steppe, typical steppe, and meadow steppe by 20.28%, 15.54%, and 11.79%, respectively. In addition, grazing decreased CH 4 uptake in typical steppe by 15.14% and decreased N 2 O emission in typical steppe, meadow steppe, and sown pasture by 20.25%, 24.18%, 52.91%, respectively. Crucially, the alteration in plant biomass due to grazing-induced changes underlying drivers that govern the responses of GHGs fluxes. These results furnish compelling evidence that grazing, particularly in non-growing season, holds the potential to mitigate grassland GHGs fluxes in temperate grasslands. Our results can deepen the understanding of the grazing effects on GHGs and offer valuable insights for refining grazing management strategies in pastoral regions. [ABSTRACT FROM AUTHOR]

• Warming and water addition increase L. chinensis biomass and reduce S. krylovii. • Community biomass is remained unchanged under warming and water addition. • Warming increases L. chinensis biomass by affecting SA and GA. • S. krylovii steppe may be replaced by L. chinensis in warmer and wetter future. Dominant species play a crucial role in regulating plant community structure and productivity. Climate change affects community productivity by changing plant traits and resource use efficiency. However, the response of the productivity of a dominant species to warming and precipitation addition and the related effects on community biomass production in semi-arid grasslands remain unclear. We conducted a ten-year warming and precipitation addition study of a semi-arid steppe in Inner Mongolia, China. We examined the responses of community composition, biomass production, and trait and resource use efficiency of two dominant species, Leymus chinensis (rhizome grass) and Stipa krylovii. The results show that warming and precipitation increased the biomass of L. chinensis and decreased the biomass of S. krylovii. Community biomass production was unchanged under warming and precipitation from the contrasting changes in the two dominant species. Warming significantly increased the leaf area (LA) of L. chinensis and S. krylovii compared to that in ambient conditions, while it decreased the specific leaf area (SLA) and δ13C of S. krylovii. Increases in temperature stimulated biomass production of L. chinensis by affecting salicylic acid (SA) and GA (gibberellin), and they increased its competitive ability compared with that of S. krylovii. Our results highlight the different responses of L. chinensis and S. krylovii to environmental changes, which stabilised community productivity under warming and precipitation. Our study provides evidence that S. krylovii may be replaced by L. chinensis in steppe climates in the warmer and wetter future. [ABSTRACT FROM AUTHOR]

Microorganisms are the basis for sustaining ecosystem function and are extremely sensitive to global warming and altered precipitation. Nevertheless, the seasonal pattern of the microbial response to a coupled effect of warming and increased precipitation is largely unknown. We set up a six-year manipulative experiment to verify changes in microbial response to warming (approximately 2 °C), increased precipitation (20 %), and their interactive effect in a semiarid steppe in Inner Mongolia. We detected changes in microbial species richness, diversity, community structure, and microbial interactions during different periods of the growing season. The results suggest that warming and increased precipitation had a stronger impact on the microbial community in the early growing season than in the mid- and late growing seasons. In the early growing season, warming significantly decreased bacterial diversity, while increased precipitation did not significantly affect the microbial community. The interactive effect of increased precipitation and warming significantly increased bacterial richness but decreased fungal richness and amplified the dissimilarities among bacterial and fungal communities. Compared to the early growing season, less microbial taxa significantly responded to warming and increased precipitation in the mid- and late growing seasons. Warming weakened species interactions, as evidenced by fewer nodes and links and lower complexity and robustness in the network. Increased precipitation strengthened species interactions and eased the warming-induced negative effect under the interactive effect. Our findings emphasize that more attention should be given to the changes in the microbial community in the early growing season of grassland in Inner Mongolia under future climate change scenarios. • Climate change impacts were more obvious in the early growing season. • The interactive effect increased bacterial richness but reduced fungal richness. • Fewer taxa respond to climate change in the mid and late growing seasons. • Species interactions weakened by warming but enhanced by precipitation addition. [ABSTRACT FROM AUTHOR]