Warming stabilizes alpine ecosystem in face of extreme rainfall events by changing plant species composition

Climate warming and extreme climatic events are threatening ecosystem processes and functions. However, it remains unclear how climate warming changes ecosystem stability in facing extreme rainfall events. Here, we investigated the temporal stability of above-ground net primary productivity (ANPP) in an alpine meadow via a 5-year warming experiment, during which two flooding events occurred, in an alpine meadow. We first found that warming significantly increased the temporal stability of ANPP in facing flooding events by increasing resistance to and decreasing recovery from flooding events. Second, we found that warming shifted the plant community structure by increasing the dominance of grasses and reducing species richness and asynchrony. Last, we detected the higher temporal stability of ANPP under warming, which was mainly ascribed to the warming-induced increase in dominant species stability (Deschampsia caespitosa). Synthesis. These findings indicate that climate warming may mitigate the shock of flooding events on the temporal stability of community productivity via altering plant community structure in alpine grasslands. Our study highlights that to buffer ecosystems from climatic extremes, we should focus on promoting the maintenance or selection of dominant species rather than only focusing on increasing species richness. <br>气候变暖与极端气候事件正威胁着生态系统的过程与功能。然而，目前尚不清楚气候变暖如何改变生态系统在极端降雨事件下的稳定性。本研究依托高寒草甸开展的5年增温实验（实验期间发生两次洪涝事件），探究了地上净初级生产力（above-ground net primary productivity, ANPP）的时间稳定性。首先，研究发现增温通过提升生态系统对洪涝事件的抗性、降低其灾后恢复力，显著提升了洪涝事件下ANPP的时间稳定性。其次，增温通过提升禾本科植物的优势度、降低物种丰富度与物种异步性，改变了植物群落结构。最后，本研究观测到增温处理下ANPP的时间稳定性更高，这主要归因于增温诱导的优势种（Deschampsia caespitosa）稳定性提升。综合分析表明，上述研究结果证实，在高寒草地中，气候变暖可通过改变植物群落结构，缓解洪涝事件对群落生产力时间稳定性的冲击。本研究强调，若要使生态系统抵御气候极端事件，应着重促进优势种的维持或筛选优势种，而非仅关注提升物种丰富度。