沙生植被生态系统是对气候变化最为敏感的生态系统之一。沙生植物经常遭受光强、极端温度、水分亏缺等环境胁迫的影响。然而，沙生植物适应环境波动（胁迫）的生理生态过程、内在机制与策略仍不清楚。由于光系统Ⅱ叶绿素荧光对环境波动的高度敏感性，是当今研究植物胁迫的重要探针。本项目以宁夏盐池半干旱沙区典型种沙蒿、杨柴为研究对象，通过原位长期自动监测光系统II叶绿素荧光与环境因子,结合原位控制实验手动测定光合荧光参数，运用大数据集数据整合分析方法、统计回归模拟等手段，分析沙蒿、杨柴PSII叶绿素荧光各参数昼夜、季节、年际变化及其对非生物环境因子波动响应和生物因子对其的调控机制，发现控制PSII光化学效率的关键因子及其阈值，建立沙蒿、杨柴光系统II光化学效率模型，定量揭示沙蒿、杨柴对环境胁迫的响应过程、机制、适应策略，为沙区林业生态建设、应对气候变化提供科学支撑。

Desert ecosystem is one of the most sensative terrestrial ecosystems to climate change.Desert vegetations are exposed to high radiation,extreme temperature,water deficit, and other climatic anomalies. However,the responses and acclimation stratagies of desert vegetation to environmental stresses remain unclear.Chl fluorescence has been widely accepted as a indicator of plant stress due to its highly sensitivity to environmental stresses.The program aims to minitor continuously PSII Chl fluorescence of Artemisia ordosica and Astragalus mongolicum in situ and environmental factors simultaneoustly,combining manual measurements of Chl fluorescence in manipulated experiments. The data is analyzed using mathmatical integration and statistical regression analysis, computer and statistical fitting as well. The objectives are:(1) to demonstrate changes of Chl fluorescence parameters diurnally, seasonally, and interannually, (2) to understand the controlling factors of Chl fluorescence parameters and their thresholds, (3) to create a model of effective quantum yield of PSII photochemistry, (4) to examine the mechanism and strateges of responses and acclimation of two shrub species to environmental stresses.