Temperature-mediated responses of carbon fluxes to precipitation variabilities in an alpine meadow ecosystem on the Tibetan Plateau.

Effects of climate warming and changing precipitation on ecosystem carbon fluxes have been intensively studied. However, how they co-regulate carbon fluxes is still elusive for some understudied ecosystems. To fill the gap, we examined net ecosystem productivity (NEP), gross ecosystem productivity (GEP,) and ecosystem respiration (ER) responses to multilevel of temperature increments (control, warming 1, warming 2, warming 3, warming 4) in three contrasting hydrological growing seasons in a typical semiarid alpine meadow. We found that carbon fluxes responded to precipitation variations more strongly in low-level warming treatments than in high-level ones. The distinct responses were attributable to different soil water conditions and community composition under low-level and high-level warming during the three growing seasons. In addition, carbon fluxes were much more sensitive to decreased than to increased precipitation in low-level warming treatments, but not in high-level ones. At a regional scale, this negative asymmetry was further corroborated. This study reveals that future precipitation changes, particularly decreased precipitation would induce significant change in carbon fluxes, and the effect magnitude is regulated by climate warming size.