Rodent Bioturbation Significantly Enhances Annual Methane Uptake by Tibetan Alpine Grasslands.

Tibetan alpine grasslands (AG) serve as critical methane (CH) 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 CH uptake remain poorly understood. Among the first, we combined paired year-round CH flux measurements from Plateau zokor mounds (ZM) and surrounding healthy meadow (HM) patches in Tibetan alpine meadow with collated CH 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 CH uptake (HM: -0.91 ± 0.08 kg C ha vs. ZM: -1.80 ± 0.19 kg C ha, mean ± standard error, negative values indicate uptake). Notably, 67% of this net increase (-0.89 ± 0.10 kg C ha year) 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) CH uptake contributed 45% and 39% to annual CH uptake for HM and ZM, respectively, falling into the ranges of 12%-64% NGS CH uptake contributions from TG to AG of China. The TrG showed significant (p < 0.001) lower annual CH 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 CH flux changes and highlight soil moisture as a key driver for global CH sink variations. These results emphasise the need for long-term monitoring to better assess the ecological consequences of bioturbation in climate-sensitive alpine ecosystems.