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[Display omitted] • Severely altered precipitation regime induced NO 3 – and DOC redistribution between soil layers in the alpine meadow. • Topsoil microorganisms are more sensitive to severe changes in precipitation regime in the alpine meadow. • The main edaphic regulators of microbial communities are heterogeneous in soil layers in the alpine meadow. • Microbes at different soil layers have divergent modes of regulating GHG fluxes in the alpine meadow. How soil microbial communities regulate greenhouse gas (GHG) emissions as precipitation events are "repackaged" from many small events to a few larger events has received significant attention. Previous studies have quantified the net fluxes of GHG across the soil/atmosphere interface; however, they have not investigated GHG fluxes in soil profiles under altered precipitation regimes. This study investigated the joint regulation of topsoil and subsoil microorganisms on GHG emissions under changes in precipitation regime in an alpine meadow. Severely altered precipitation regimes have led to changes in NO 3 –, DOC, and soil moisture among different soil layers, which can be attributed to a combination of substrate migration and changes in carbon and nitrogen mineralization rates. Topsoil microorganisms exhibit high sensitivity to severe changes in the precipitation regime, which can affect their biomass, microbial composition, and metabolic activities. In contrast, the activity of subsoil microorganisms remains relatively stable. This was likely due to the heterogeneity of dominant regulators across soil layers. Under the severely altered precipitation regime, carbon dioxide (CO 2) emissions significantly decreased by approximately 11.08%. This decrease was primarily due to a reduction in microbial respiration in the topsoil. The decrease in both topsoil and subsoil methane (CH 4) uptake likely caused the inhibition of the CH 4 sink from the surface (by approximately 11.60%). While a 1.75-fold increase in nitrous oxide (N 2 O) emissions under the severe changes in the precipitation regime might be primarily related to the increase in subsoil N 2 O emissions caused by the increasing abundance of subsoil denitrifiers, as well as the addition of subsoil nitrate content and soil moisture. This study revealed the divergent modes of microbial communities at different soil layers regulating GHG fluxes, which could guide the improvement of ecological models predicting GHG emissions in response to altered precipitation regimes. [ABSTRACT FROM AUTHOR]

• Droughts increased CH 4 uptake in a wet year in the semiarid grassland. • Magnitude and pathways of drought effects on CH 4 uptake depend on seasonal timing. • Positive effects of early drought on CH 4 uptake were the least. • Plant composition regulated CH 4 uptake in response to droughts. Increasingly frequent and severe droughts are occurring in multiple seasons of a year in many dryland ecosystems, with unknown impacts on the role of drylands in cycling of methane (CH 4), a potent greenhouse gas. In particular, there is limited understanding of how drought occurring at different times within the growing season regulates biological CH 4 uptake, and how these responses are mediated by plant community composition. Here, we quantify how drought timing and plant community composition regulate CH 4 uptake in a semiarid grassland. We employ a field experiment in which droughts were imposed in early, middle, or late growing season in three different communities (two graminoids, two shrubs and their mixture), respectively. All three droughts increased CH 4 uptake, but the effect size and pathway varied with seasonal timing. Early and middle drought increased CH 4 uptake through increasing both soil pomA abundance and diffusivity resulting from reduced soil water content (SWC), while late drought increased CH 4 uptake only by reducing SWC. Overall, early drought had the least positive effects on CH 4 uptake because it excluded the least precipitation and therefore had smaller impacts on SWC. Besides, plant composition did not affect CH 4 uptake under normal environment but regulated CH 4 uptake in response to droughts due to different response of plant composition to droughts. Early and middle drought had larger positive effects on CH 4 uptake in shrub communities than the other two communities, consistent with larger reductions in SWC and larger increases in pomA abundance, respectively. In contrast, late drought had consistent effects on CH 4 uptake across three communities. Our results suggest that the magnitude and pathways of extreme drought effects on CH 4 uptake are strongly co-regulated by seasonal timing and plant composition. [ABSTRACT FROM AUTHOR]