高寒草甸植物群落功能多样性对不同生长期干旱的响应机制

植物对干旱胁迫的响应表现为各功能性状的差异化表达。全球气候变化下，青藏高原地区降水格局发生改变，高寒草甸群落功能性状及功能多样性在不同生长期干旱事件下的响应机制对加深高寒草甸适应气候变化认知具有重要意义。以藏北高寒草甸为研究对象，设置截雨棚模拟生长季前期（ED）、中期（MD）和非生长季时期（ND）干旱事件，通过观测群落物种功能性状，分析高寒草甸群落功能多样性对不同生长期干旱的响应机制。结果表明：（1）叶片功能性状对干旱存在差异响应，表现为叶片小而厚且寿命长，同化速率降低，并受氮元素限制加剧；（2）生长季前期干旱对高寒草甸群落功能性状的影响最强，生长季中期干旱次之，非生长季干旱的影响最弱；（3）生长季干旱处理显著改变了群落的功能多样性，ED处理下功能分散度指数（FDiv）和功能分异度指数（FDis）显著降低（P<0.05），而Rao二次熵指数（RaoQ）显著升高（P<0.05），MD处理下功能均匀度指数（FEve）显著降低（P<0.05）；（4）相关性分析得出，群落功能性状与功能多样性对干旱的响应之间存在着联系。本研究发现高寒草甸植物功能性状与群落功能多样性对生长季前期和中期干旱存在差异化响应，指示着高寒草甸植物群落在响应不同时期干旱时可能采取不同的生存策略，即对生长季前期干旱采用耐旱策略、对生长季中期干旱采用避旱策略。探讨了高寒草甸植物群落功能多样性对不同生长时期干旱胁迫的响应机制，为预测未来季节性干旱事件对青藏高原高寒草甸植物功能性状、群落特征和功能多样性的影响提供科学依据。

Responses of functional diversity of plant communities to drought in different growing periods in alpine meadow

The response of plant to drought stress reveals the distinct expression of functional traits. With the global climate change, the precipitation pattern of the Qinghai-Tibet Plateau has been altered. It is of great significance to explore the response mechanism of functional traits and functional diversity of alpine meadow communities in drought events, which would enable an in-depth understanding of the adaptation of climate change in alpine meadows. In this study, we conducted manipulative drought experiments with early growing season drought (ED), middle growing season drought (MD), and non-growing season drought (ND). We observed the functional traits of community species and analyzed the response mechanism of functional diversity of alpine meadow communities to drought in different growing seasons. The results showed that:(1) there were different responses of leaf functional traits to drought, which showed that the leaves were small, thick and long-lived, the assimilation rate was reduced, and it was aggravated by nitrogen restriction. (2) The effect of drought in the early growing season on the functional traits of alpine meadow communities was the strongest, followed by the middle of the growing season, and the weakest effect in the non-growing season. (3) Drought in the growing season significantly changed the functional diversity of the community. The functional divergence (FDiv) and functional dispersion (FDis) were significantly reduced in ED (P<0.05), while the Rao''s quadratic entropy (RaoQ) was significantly increased (P<0.05), and the functional evenness (FEve) was significantly reduced in MD (P<0.05). (4) Correlation analysis showed a link between community functional traits and functional diversity''s response to drought. The study found that the functional traits and community functional diversity of alpine meadows had differential responses to drought in the early and middle growing seasons. This indicates that alpine meadow plant communities may take different survival strategies in response to drought in different periods, that is, the community adopts drought tolerance strategies for drought in the early growing season and drought avoidance strategies for drought in middle growing season. In this study, we investigated the response mechanism of plant community functional diversity to drought stress in different growth periods of alpine meadow. We provided a scientific basis for predicting the effect of seasonal drought events in the future on plant functional traits, community weighted means (CWM) and functional diversity in the alpine meadow on the Qinghai-Tibet Plateau.