高寒草甸植物光能利用效率及其对气温升高的响应

Alpine meadow is the major vegetation type in the plateau cold area. Due to the impact such as climate change and grazing intensity, it’s obviously strengthened that the trend of high quality forage grass and sedge are being replaced by dicotyledonous weeds. Light use efficiency (LUE) is the efficiency of plant utilizes the solar energy to assimilate CO2. Understanding the LUE in alpine meadow plants (alpine plants) is the key to keep its productivity stable and prevent degradation. The study will be performed in the alpine meadow which located in the eastern of Tibetan plateau and northern of Zoige plateau, and based on the alpine meadow comprehensive observation field and the open-top chamber (OTC), which have been monitoring. Through the positioning observation under natural environment and the simulated warming in situ, to carry out the study on the leaf LUE and its physiological regulatory mechanisms, the canopy LUE and its ecological regulatory mechanisms, and the response of both leaf and canopy LUE to warming. Combining with the meteorological data and the observation analysis on soil physical and chemical properties, the relationships between the LUE changes and the variations of climate and soil factors in different alpine species, dominant populations, and mixed communities will be recognized, the effects of climate warming on the carbon assimilation ability and the LUE of alpine plants will be analyzed, and the response mechanisms of alpine plants to climate warming will be elucidated. The results will provide the scientific base for further understanding and predicting the impact of global warming on alpine meadow ecosystem productivity, and alpine vegetation conservation and adaptive management.

高寒草甸是高原寒区植被的主要类型，由于气候变化和放牧强度等因素影响，优质牧草禾草和莎草被双子叶杂草代替的趋势明显加强。光能利用效率(LUE)是植物利用太阳能同化CO2的效能，认识高寒草甸植物(高寒植物)LUE是保持其生产力稳定和防止退化的关键。本项目以青藏高原东部若尔盖高原北部高寒草甸为研究对象，基于已经监测的高寒草甸综合观测场和开顶式气室(OTC)，通过自然环境下定位观测和原位模拟增温试验，开展高寒植物叶片LUE及生理调控机制、群体LUE及生态调控机制、叶片和群体LUE对气温升高的响应等研究。结合气象资料和土壤理化性质的观测分析，认识不同高寒植物种、优势种群和混生群落LUE变化与气候和土壤的关系，探讨升温对高寒植物碳同化能力、LUE的影响，揭示高寒植物对气温升高的响应机制，为深入理解与预测全球气候变暖对高寒草甸生态系统生产力的影响，以及高寒植被保育和适应性管理提供科学依据。

高寒草甸是高原寒区植被的主要类型，近年来，由于气候变化和放牧强度等因素，优质牧草禾草和莎草被双子叶杂草代替的趋势明显加强。光能利用效率(LUE)是植物利用太阳能同化CO2的效能，认识和改善光能利用效率是提高高寒植被生产力的关键。本项目以青藏高原东部若尔盖高原北部高寒草甸为研究对象，通过自然环境下野外观测和控制条件下人工模拟相结合的方法，开展高寒植物叶片气体交换、光能利用效率及其调控机制；高寒植物群体碳同化、光能利用效率及其对气候变化的响应；叶片和群体观测资料的整合分析等研究。主要结论如下：（1）模拟增温使高寒草甸空气温度平均升高0.7 °C，空气相对湿度增加了0.5 %，5 cm土层土壤温度增加1.7 °C；同时，模拟增温使0-10 cm，10-20 cm土层土壤含水量下降，土壤孔隙度、PH值和土壤硬度也有所下降，而土壤硬度下降更有利于植物生长；（2）连续3年增温使叶片全碳含量显著增加，同时减少了叶片全氮、全磷含量；气温升高提高了高寒优势种植物垂穗披碱草和蕨麻的光能利用效率，且对高寒植物的光抑制有所改善；（3）增温提高了高寒草甸的地上生物量，降低了高寒植物的根冠比，且提高了高寒优势种植物的优势度。同时，模拟增温下高寒草甸群落水平净光合速率、群落光能利用效率均有所提高；（4）通过高寒优势种植物叶片和群体水平光能利用效率比较，得出叶片水平光能利用效率显著高于群体水平。将叶片光合速率与群落光合速率线性拟合，发现高寒植物叶片和群落光合具有很好的相关性；同时，通过叶片光合速率，结合3种易测的叶片性状指标推导出的群落光合速率与实测的群落光合也有很好的相关性。（5）初步探讨了模拟增温对土壤微生物的影响，发现土壤细菌数量的变化表现为增温土壤细菌数显著低于对照土壤细菌数。研究结果为预测未来气候变化对高寒草甸生产力的影响、以及高寒植被保育和适应性管理提供理论依据。