Rodent Bioturbation Significantly Enhances Annual Methane Uptake by Tibetan Alpine Grasslands

Tibetan alpine grasslands (AG) serve as critical methane (CH₄) sinks, yet face degradation from anthropogenic and climatic disturbances that promote subterranean rodents (e.g., Plateau zokor [Myospalax baileyi] and pika [Ochotona curzoniae]) activities. Although rodent bioturbation (e.g., burrowing, foraging and excreting) alters soil structure, soil physico-chemical properties and productivity from AG, its impacts on CH₄ uptake remain poorly understood. Among the first, we combined paired year-round CH₄ flux measurements from Plateau zokor mounds (ZM) and surrounding healthy meadow (HM) patches in Tibetan alpine meadow with collated CH₄ fluxes from meta- and synthetic analyses across Tibetan AG, temperate grasslands (TG) and tropical grasslands (TrG) globally. We observed that rodent bioturbation significantly (p < 0.001) doubled annual CH₄ uptake (HM: -0.91 ± 0.08 kg C ha^-1 vs. ZM: -1.80 ± 0.19 kg C ha^-1, mean ± standard error, negative values indicate uptake). Notably, 67% of this net increase (-0.89 ± 0.10 kg C ha^-1 year^-1) due to rodent bioturbation occurred during the growing season. Meta-analysis results revealed this phenomenon associated with significantly (p < 0.001) decreased topsoil moisture and increased functional gene abundances of pmoA for methanotrophs. Non-growing season (NGS) CH₄ uptake contributed 45% and 39% to annual CH₄ uptake for HM and ZM, respectively, falling into the ranges of 12%-64% NGS CH₄ uptake contributions from TG to AG of China. The TrG showed significant (p < 0.001) lower annual CH₄ uptake than TG and AG globally, due to the fact that significant (p < 0.05) greater precipitation and soil moisture from the former than the latter. Our findings elucidate mechanisms underlying rodent-mediated CH₄ flux changes and highlight soil moisture as a key driver for global CH₄ sink variations. These results emphasise the need for long-term monitoring to better assess the ecological consequences of bioturbation in climate-sensitive alpine ecosystems.