Diminished positive effects of warming on stability of plant productivity over time in an alpine meadow

Warming can alter the temporal stability of aboveground net primary productivity (ANPP) in grasslands. However, it remains unclear how ANPP stability responds to long-term warming. Through a 10-year in-situ manipulative warming experiment conducted in an alpine meadow on the Qinghai-Tibetan Plateau, we found warming initially enhanced ANPP stability and the positive effects of warming on ANPP stability tended to decline as the duration of the experiment was extended. Increased community height primarily enhanced ANPP and its stability under warming. However, declining sedge cover and reduced ecosystem carbon and water use efficiency under prolonged warming increased annual ANPP fluctuations, thereby negating the positive effects of warming on ANPP stability. Our findings provide the evidence that carbon and water use efficiency crucially maintain ANPP stability under long-term warming. These results highlight the necessity of a continuous long-term monitoring of ecosystem responses to warming.