Increased frequency of extreme climatic events weakens the community stability of natural grassland under directional climate changes by reducing resilience

<b>Aim: </b>Chronic directional climate changes in temperature and precipitation are predicted to increase the frequency of extreme climatic events (ECEs), however, their co-occuring effects on the temporal stability of community productivity (i.e., ANPP stability) is still unclear. Here, we evaluate whether the increased frequency of ECEs reduces ANPP stability, and how it modulates the effects of chronic directional climate factors on ANPP stability in natural grassland.<b>Location: </b>Twenty-two sites in Asia and fourteen sites in the North America.<b>Time period: </b>1980s-2010s.<b>Major taxa studied: </b>Herbaceous plant.<b>Methods: </b>We collected 36 long-term observational and consecutive ANPP data (at least 10 years), and resampled yearly ANPP via a consecutive resampling method of a series of nested time windows for each field. We used linear mixed-effect models, partial regression analysis and structure equation model to explore the interplayed effects climatic factors on ANPP stability and their associated intermediate process.<b>Results: </b>The increased frequency of ECEs was observed within the long-term rising temperature and elevating precipitation trend across sites in the past several decades. Elevating precipitation rather than rising temperature was the primary driver influencing ANPP stability. Elevating precipitation increased ANPP stability through increasing mean ANPP and decreasing the standard deviation (i.e., SD) of ANPP due to a decrease in sensitivity of ANPP to precipitation. The increased frequency of ECEs decreased ANPP stability mainly by increasing the SD of ANPP, and it reduced the positive effect of elevated precipitation on ANPP stability via a decrease in resilience.<b>Main conclusion:</b> Our results demonstrated the recurrent and discrete ECEs has cumulatively negative effects on ANPP stability, and the decreasing resilience was the primary intermediate process in accelerating the destabilization of natural grassland under long-term climate change, highlighting the potential risks of increased frequency of ECEs for grassland ecosystem functions.<br>