中文摘要：

当前人类活动的加剧显著地影响着全球大气循环的格局。大气循环的多个模型均预测未来全球气候变化的显著特征是极端降水事件和极端干旱事件发生的频率会显著增加。水分是干旱、半干旱区草原植物生长发育的限制性资源，而草原生态系统是陆地生态系统中对降水格局变化非常敏感的系统。但是，关于极端降水事件和极端干旱事件对草原生态系统结构和功能的影响还是以分散的个案研究为主，甚至关于极端气候事件的定义迄今也不尽相同。为此，该文在分析极端气候事件定义及其研究方法的基础上。总结了极端降水事件和极端干旱事件对草原生态系统土壤水分和养分状况、植物生长发育和生理特性、群落结构、生产力和碳循环过程的影响，并提出了未来极端气候事件研究中应重点关注的5个重要方向，以及控制试验研究的2个关键科学问题，对开展全球变化背景下草原生态系统对极端气候事件响应机制的研究具有指导意义。

英文摘要：

Global atmospheric circulations are greatly affected by anthropogenic activities. Several atmospheric circulation models predict that the frequencies of extreme rainfall events and extreme droughts will increase in the lustre. Water is one of the most limiting resources for growth and development of plants in arid and semi-arid ecosystems. Furthermore, grassland ecosystems have been proven to be very sensitive to changing precipitation regimes. However, our understanding on the effects of extreme climatic events on the structure and functioning of grass- land ecosystems is inadequate. By far, the definitions of extreme climatic events are still inconsistent. Therefore, based on analyses of the definitions of extreme climatic events and research methods in literature, we synthesize the effects of extreme rainfall events and extreme droughts on soil water and nutrient availability, individual plant development and physiological characteristics, community structure, ecosystem productivity and carbon cycling. In addition, we put forward five scientific questions on research concerning the impacts of extreme climatic events and identify two key issues on manipulative precipitation experiments to help with understanding the mechanisms on how grassland ecosystems respond to extreme climatic events in the context of global change.