克氏针茅物候对气候变暖和水分变化的响应及其光合生理生态机制

Photosynthetically ecophysiological mechanism of Stipa krylovii phenology in response to climatic warming and precipitation alteration

物候对气候变化具有重要指示作用,然而现有研究主要关注植物物候变化与环境因子的关系,对于物候变化的生理生态机制研究较为缺乏。基于内蒙古自治区克氏针茅草原红外线辐射增温与控水相结合的原位模拟试验资料,探究了克氏针茅物候变化的光合生理生态机制及其对水热环境因子的响应。研究结果表明:(1)增温使克氏针茅返青期和抽穗期提前2.8 d和7.8 d、枯黄期推迟6.8 d;水热协同作用主要影响抽穗期,增温增水(气候暖湿化)较增温减水(气候暖干化)提前7.4 d。(2)增温增水使得克氏针茅返青期和抽穗期的净光合速率、气孔导度和蒸腾速率显著高于增温减水,而对水分利用效率的影响则相反(P<0.05),增温增水与增温减水对克氏针茅枯黄期的光合生理生态特征影响无显著差异。(3)净光合速率是影响克氏针茅物候变化的决策因子,温度是影响克氏针茅植物返青期和枯黄期的限制因子,水分则是影响克氏针茅植物抽穗期的限制因子。研究发现克氏针茅物候与其光合生理生态特征和环境因子密切相关,研究结果可为植物物候模型发展和物候机理研究提供理论支撑。

Phenology plays an important role in indicating climate change. However, current researches mainly focus on the relationship between phenological changes and environmental factors. There is a lack of research on ecophysiological mechanisms which cause phenological changes. Based on a simulation experiment on Stipa krylovii in the Inner Mongolia Autonomous Region under different treatments of infrared radiation heating and water control, the photosynthetic ecophysiological mechanism of Stipa krylovii in response to climate change was examined.(1) The green-up date and heading date were advanced(2.8 d & 7.8 d) under increasing temperature treatment, while the wilting date was delayed(6.8 d). The interaction of temperature and precipitation mainly affected the heading date. Compared with Stipa krylovii under increasing temperature and decreasing precipitation treatment(climate warming and drying), those under increasing temperature and increasing precipitation treatment(climate warming and wetting) were 7.4 days earlier.(2) The net photosynthetic rate, stomatal conductance and transpiration rate of Stipa krylovii were significantly higher at green-up stage and heading stage under the increasing temperature and increasing precipitation treatment, while water use efficiency was lower than those under increasing temperature and decreasing precipitation treatment. There was no significant difference in photosynthetic ecophysiological characteristics between increasing temperature and precipitation treatment and increasing temperature and decreasing precipitation treatment at wilting stage.(3) Net photosynthetic rate was the decision-making factor affecting the change of plant phenology. Temperature was the limiting factor affecting green-up date and wilting date, while precipitation was the limiting factor affecting heading date. The results showed that the phenology of Stipa krylovii was closely related to both photosynthetic ecophysiological characteristics and environmental factors. This study could provide a theoretical support for the development of plant phenological model and the understanding of phenological mechanism.