景天酸代谢（CAM）植物广泛分布于干旱环境中，具有多种适应水分胁迫的独特形态特征和光合节律。近年来，全球CAM植物出现了丰度和分布范围增加的趋势，但引起该变化的植物水分利用策略与适应特征尚不明确。为此，本项目利用氢氧稳定同位素技术，结合植物生理生态学指标和土壤理化性质，首先在内蒙古高原西部开展样带调查，揭示典型CAM植物瓦松的水分利用来源及其影响因素；而后通过温室控制降水总量、降水变异程度和种间竞争引起的三种水分胁迫梯度，揭示CAM植物氢氧稳定同位素特征及其与水分胁迫的定量表达关系；在此基础上，最终揭示CAM植物对水分胁迫的响应与适应策略。本项目将为气候变化下的CAM植被动态与群落演替机制提供新的见解，并为干旱半干旱地区的生态系统管理提供重要的理论支撑。

Crassulaceae acid metabolism (CAM) plants are widely distributed in arid environment and have a variety of unique morphological characteristics and photosynthetic rhythms adapted to water stress. In recent years, the abundance and distribution range of CAM plants gradually increased, but the mechanisms of water use strategy and adaptation characteristics causing this change was still unclear. To this end, this project uses stable hydrogen and oxygen isotope technology, combines with ecophysiological indicators and soil physical/chemical properties. Firstly, a sample survey will be carried out in western Inner Mongolia plateau to reveal the water use sources and influencing factors of typical CAM plant (Orostachys fimbriatus). Afterwards three kinds of water stress gradients caused by precipitation amount, precipitation variation and inter-species competition will be controlled in the greenhouse. The characteristics of the stable hydrogen and oxygen isotopes of CAM plants and their quantitative expression relationship with water stress will be revealed. Finally, the response and adaptation strategies of CAM plants to water stress will be revealed. This project will provide new insights into CAM vegetation dynamics and community succession mechanisms under climate change and provide important theoretical support for ecosystem management in arid and semi-arid regions.