增温背景下克氏针茅枯黄期物候对降水响应的光合生理机制

基于红外线辐射增温与控水相结合的原位模拟试验资料,分析了克氏针茅(Stipa krylovii)枯黄期对水热变化响应的光合生理机制。结果表明: 增温背景下降水是枯黄期的主要影响因子,增水(减水)导致枯黄始期和枯黄盛期的发生时间均延迟(提前),枯黄期持续时间均延长,减水处理对枯黄期持续时间的延长作用更显著。增温背景下,降水变化显著影响枯黄期的生理生态特性,且在枯黄始期最为显著,净光合速率、气孔导度、蒸腾速率、核酮糖-1,5-二磷酸(RuBP)羧化的最大速率(V_{c max})、RuBP再生能力的最大速率(J_max)均与降水量呈显著正相关。通径分析表明,克氏针茅枯黄期的光合生理机制因水热变化的不同而异。当前环境条件下,枯黄期物候变化的主要影响因子是J_max,主要限制因子是V_{c max}。未来暖干和暖湿气候下枯黄期物候变化的主要影响因子均是V_{c max};但在暖干气候下主要限制因子为J_max,而在暖湿气候下则无限制因子。这表明克氏针茅枯黄期物候的变化取决于气候环境条件变化对其光合能力的影响。

Photosynthetically physiological mechanism of Stipa krylovii withered and yellow phenology response to precipitation under the background of warming

We examined the photosynthetically physiological mechanism of Stipa krylovii response to warming and precipitation changes, based on an experiment with the treatments of warming by infrared radiator and precipitation treatments by irrigation water. Under the warming background, precipi-tation was the main influencing factor of the withered and yellow phenology. Increasing precipitation postponed the occurrence time of both the beginning and the peak of the withered and yellow phenology, and prolonged the duration of the withered and yellow phenology. The effect of decreasing precipitation on prolonging the duration of the withered and yellow phenology was much stronger. Under the background of warming, the changes of precipitation markedly affected the physiological and ecological characteristics of the withered and yellow phenology, with the effect being the most significant at the beginning of the withered and yellow phenology. The net photosynthetic rate(Pn), stomatal conductance(gs), transpiration rate(Tr), and the maximum ribulose 1,5-bisphosphate(RuBP) carboxylation rate(Vc max), RuBP regeneration capacity(Jmax) were positively correlated with precipitation. Results of the pathway analysis showed that the photosynthetically physiological mechanism of withered and yellow phenology of S. krylovii would be different under different conditions of precipitation and temperature. Under the current environmental condition, Jmaxwas the main influencing factor of the withered and yellow phenology, and Vc maxwas the main limiting factor. Under the scenarios of warm and dry climate and warm and wet climate, Vc max become the main influencing factor of the withered and yellow phenology. Jmaxwould be the main limiting factor in the warm and dry climate conditions, and there would be no limiting factor in the warm and wet climate conditions. Our findings indicated that the withered and yellow phenological changes of S. krylovii depend on the photosynthetical capacity limitation resulted from meteorological conditions.