Journal Article Tibetan Plateau 7440-44-0 Carbon Research Support, Non-U.S. Gov't Soil alpine meadow asymmetric warming community stability context dependency ecosystem respiration freeze-thaw events labile carbon limitation microbial community response moderate grazing number and frequency of freeze-thaw cycles plant functional group precipitation addition semi-arid with ice-poor permafrost soil heterotrophic respiration soil incubation soil respiration acclimation species asynchrony species diversity warming gradient