中文摘要：

通过测定不同季节蒙古沙冬青的气体交换参数,探讨其光合作用的日变化和季节变化特征,旨在为蒙古沙冬青天然种群的保护和恢复工作提供理论依据和参考。结果表明：蒙古沙冬青光合作用具有显著的季节变化特征,总体呈春夏高、秋冬低的趋势;3—9月期间,蒙古沙冬青净光合速率（Pn）在10：00—13：00时均显著下降,但其机制具有季节差异;多元线性回归结果表明,影响蒙古沙冬青Pn的主要生理因子是气孔导度、胞间CO2浓度和气孔限制值,主要环境因子是空气湿度、大气CO2浓度和光照强度。本研究认为,蒙古沙冬青生长关键季节是春夏两季,干旱引起的气孔关闭是其光合作用的主要限制因子;建议利用春夏两季进行蒙古沙冬青种群的恢复和重建工作,重点关注其旱季和冬季的保护工作。

英文摘要：

In order to provide theoretical reference for the protection and recovery of Ammopiptanthus mongolicus population, the diurnal and seasonal variation patterns of the photosynthetic characteristics in A. mongolicus were investigated by measuring the foliar gas exchange in the field.The results showed that the photosynthesis of A. mongolicus showed significant seasonal variations. In general, the photosynthesis was higher during spring and summer compared with that in fall and winter. The net photosynthetic rate （Pn） in A. mongolicus decreased during 10：00-13：00 from March to September, but its underlying mechanisms were seasonally specific. The results of multiple regression analysis showed that the major physiological factors affecting Pn in A. mongolicus were stomatal conductance, intercellular CO2 concentration, and stomatal limitation to CO2. Meanwhile, the environmental factors affecting Pn were air relative humidity, air CO2 concentration and photosynthetic photon flux density. In conclusion, A. mongolicus grew rapidly during spring and summer, and the main limiting factor of its photosynthesis was the droughtinduced stomatal limitation. It was suggested that the restoration of A. mongolicus population should be conducted during spring and summer, and the protection of A. mongolicus population should be emphasized during drought season and winter.