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Abstract Grazing intensity and global warming are expected to increase in the forthcoming decades, with uncertain consequences for their interaction on grassland ecosystems and their functions. We investigated the effects of warming, grazing and their interaction in a factorial warming (+1.2–1.7 °C) and grazing (moderate intensity with ca. 50% vegetation consumption) experiment in a Tibetan alpine meadow on microbial communities by studying functional genes involved in soil carbon and nitrogen cycles, using GeoChip technology. Our results showed that microbial functional gene structure and abundances were largely affected by the interactive effect of grazing and warming, rather than the main effect of warming or grazing. Compared to the control, grazing alone significantly increased the functional gene alpha diversity, changed the overall functional community structure, and increased the abundances of C fixation, C degradation, N mineralization and denitrification genes, likely due to the stimulating impact of urine and dung deposition. Warming alone did not change these microbial properties, possibly related to the unchanged soil nutrient status. Despite an increase in soil NO 3 − concentrations and the deposition of urine and dung, the combined treatment did not change functional gene alpha diversity, community structure, or C/N cycling gene abundances, possibly resulting from the limiting effect of water depletion in the combined treatment. Our study revealed antagonistic interactions between warming and grazing on microbial functional gene structure and abundances, which remained stable under the moderate intensity of grazing in future warming scenario in the Tibetan alpine meadow, raising potentially important implications for predicting future soil carbon and nitrogen processes in these systems. Highlights • Grazing alone significantly increased abundances of some key soil C/N cycling genes. • Warming alone had no significant effects on them. • Functional gene structure and abundances remained stable in the combined treatment. • Antagonistic interaction between warming and grazing may result from water depletion. [ABSTRACT FROM AUTHOR]

• Soil EEAs and bacterial community composition responded differently to drought. • Soil water content was most important in affecting responses. • Changes in bacterial community composition were more persistent than soil EEAs. Extreme drought can strongly impact belowground communities and biogeochemical processes, including soil microbial community composition and extracellular enzyme activities (EEAs), which are considered key agents in ecosystem carbon (C) and nutrient cycling. However, our understanding of how seasonal timing of drought during the growing season affects soil microbial communities and their activity remains notably poor. In this study, we investigated the responses of soil physicochemical properties, EEAs, and bacterial community composition to extreme-duration drought imposed in the early-, mid-, or late-stages of the growing season in a semiarid grassland ecosystem in Inner Mongolia, China. Compared with the ambient control, the activities of C-, nitrogen (N)-, and phosphorus (P)-acquisition enzymes were significantly decreased in the mid- and/or late-stages of drought. Bacterial community diversity also significantly decreased in the mid- and late-stage drought treatments. Soil water content was the most important factor explaining changes in soil EEAs and bacterial community composition. At the end of the growing season, the activities of C-, N-, and P-acquisition enzymes had mostly recovered, while the bacterial community diversity in the mid- and late-stage drought treatments was still lower than the ambient control. Overall, our study demonstrates that the effects of extreme drought on soil EEAs and bacterial community composition depend on the timing of drought. Our results highlight that understanding the effects of extreme-duration drought at different stages of the growing season may play a vital role in predicting the responses of belowground function to global changes in grassland ecosystems. [ABSTRACT FROM AUTHOR]