优势种功能性状在干旱导致的高寒草原植物群落构建中的作用机制研究

草地植物群落组成对极端干旱事件的响应是全球变化生物学研究的热点话题。干旱导致草地植物群落组成变化主要体现在优势种的更替上，对其生物学机制目前还不清楚。植物功能性状及其根际过程在植物群落构建中起着极其重要作用，但由于原位监测草地植物群落根系、根际存在诸多困难，以往的研究主要集中叶片功能性状，对地下部分，尤其是发生相互更替的优势种根系性状及其根际过程如何响应干旱的生理生态过程还不清楚。本项目在青藏高原高寒草原控雨试验长期观测结果的基础上，以长期干旱导致常见种赖草取代优势种紫花针茅为切入点，通过针对性的设计紫花针茅和赖草的同质园试验，并结合两个试验平台，比较紫花针茅和赖草叶片性状、根系性状、根际过程响应干旱胁迫的差异，从根系吸收水分策略、叶片控制水分散失的策略、根际活化矿质养分策略等方面揭示赖草取代紫花针茅的生物学机制，为高寒草原植被群落适应未来环境变化的演替提供理论依据。

The responses of grassland community composition to drought events have been a hot topic in the study of global change biology. It has been well established that drought-induced shifts in plant community composition occurred across different types of grasslands worldwide by re-ordering in the dominant species, while little is known of how root traits and rhizosphere of dominant species respond to prolonged drought due to technical challenge in determination of root traits and rhizosphere. A long-term observation from manipulated precipitation platform in Alpine steppe of the Tibetan plateau is shown that the dominant species Stipa purpurea was replaced by common species Leymus secalinus under prolonged drought. To address the key issues, a common garden experiment will be established to specifically compare their leaf traits, root traits and root exudation, and further understand their contrasting strategies on water acquisition by root systems, water-loss reduction by leaves, and nutrition activation by rhizospheres under the drought. The proposed project aims to unravel the mechanisms underlying the drought-induced re-ordering of dominant species. The outcomes of the projects will contribute to our effective management of grasslands under the scenarios of global changes of precipitation pattern.