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 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 (), stomatal conductance (), transpiration rate (), and the maximum ribulose 1,5-bisphosphate (RuBP) carboxylation rate (), RuBP regeneration capacity () were positively correlated with precipitation. Results of the pathway analysis showed that the photosynthetically physiological mechanism of withered and yellow phenology of would be different under different conditions of precipitation and temperature. Under the current environmental condition, was the main influencing factor of the withered and yellow phenology, and was the main limiting factor. Under the scenarios of warm and dry climate and warm and wet climate, become the main influencing factor of the withered and yellow phenology. would 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 depend on the photosynthetical capacity limitation resulted from meteorological conditions.