增温对金露梅灌丛冻土水热过程影响的试验研究

With a warming climate, cold regions ecosystems undergo significant ecological changes such as encroachment of canopy-forming shrubs into tundra communities (termed as shrubification) using repeat photography, long-term ecological monitoring and dendrochronology over past decades. Recent researches have documented that shrub expansion around the cold regions influence the local scale hydrological cycle. shrubification is becoming the important parts, and aroused general interest in cold region hydrological research. However, the effects of this process on freeze-thaw processes and water and heat processes of frozen soil still are unclear. Therefore, we will select the Hulu watershed in Qilian Alpine Ecology and Hydrology Research Station of Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences as experimental area. Based on Open-top chamber stimulated warming method, this program will take Potentilla fruticosa as test object to detect effects of warming and Shrubification on freeze-thaw processes and water and heat processes of frozen soil under shrub cover in Qilian Mountains. The differences of water and heat balance and transfer processes between simulated warming and shrub cover will be analyzed by using experimental data. Then, the CoupModel model will be used to simulate the gradients and transfer characteristic of water and heat in frozen soil under different shrub cover and warming scenarios. Analysis of the impact of shrub cover on pattern and process of water and heat transfer under warming scenarios also will be documented. Finally, we will make a preliminary quantitative assessment for difference of impacts of Shrubification and warming on water and heat transfer processes of frozen soil, and forecast the response of frozen soil water and heat transfer process of frozen soil to the Shrubification process under warming scenarios. The results will provide important parameters and theoretical foundation for large scale hydrological research in cold regions, land surface processes and model research, and global climate change research.

在气候变暖背景下，近几十年来全球寒区出现灌丛化过程，这将改变地表水热状况，影响局地水文循环，是寒区水文研究的热点，但是灌丛化过程对冻土冻融过程及水热传输过程的影响机理、程度还不清楚，相关研究极为薄弱。本项目拟在祁连山中科院寒旱所祁连站葫芦沟试验流域，以不同盖度金露梅灌丛为研究对象，采取开顶式生长室（Open-top chamber，OTC）模拟增温装置，基于野外试验数据，分析灌丛盖度和增温情景下冻土水热平衡及传输过程的差异，以此确定灌丛化过程对冻土冻融过程的影响；结合CoupModel冻土-植被-大气水热耦合模型，探讨升温情景下不同盖度灌丛区冻土分层水热梯度变化及传输特征，分析升温情景下灌丛对冻土水热传输过程的影响，初步定量评估灌丛化与升温引起冻土水热传输过程的时空差异性，预估气温升高后，冻土水热传输对灌丛化过程的响应，为大尺度寒区水文、陆面过程和气候变化相关研究提供相关参数和理论基础。

在气候变暖背景下，近几十年来全球寒区出现灌丛化过程，这将改变土壤水热状况，影响局地水文循环，但是灌丛化过程对冻土冻融过程及水热传输过程的影响机理、程度还不清楚，相关研究极为薄弱。在祁连山中科院寒旱所黑河上游站葫芦沟试验流域，选取高盖度金露梅灌丛（70%）、中盖度灌丛（40%）、高寒草甸（对照样地）3个试验样地，代表不同程度的灌丛化情景，采取开顶式生长室（Open-top chamber，OTC）模拟增温装置，分析了增温对灌丛化冻土水热过程的影响。通过实测数据，设计的OTC可使气温升高约1.65℃，验证了OTC（Open-top Chamber）模拟增温装置在祁连山高寒灌丛区的适用性，可为高寒山区生态水文模型预测和验证提供关键参数。对比分析了灌丛化对祁连山金露梅灌丛冻土水热过程的影响，模拟增温后灌丛冻土地温明显高于控制样地，增温效应在4月下旬之后更为显著，表层土壤温度对模拟增温的响应最为明显。模拟增温后土壤冻结时间延后，融化时间提前，表层土壤表现更为明显，在彻底融化后，增温样地土壤水分含量小于控制样地。低盖度灌丛土壤水分含量高于高盖度灌丛，低盖度灌丛地表最先消融。夏季灌丛具有遮蔽效应，冬季能够吸收更多太阳辐射，灌丛覆盖降低了植被下地表温度的变化剧烈程度，起到降低地温波动振幅的效应；日尺度上，高温时灌丛覆盖降低地表温度，低温时使地表降温过程减缓。CoupModel模型是更适合高寒山区灌丛草甸区的一维水热传输模型。利用Lysimeter实测了祁连山区灌丛草甸的蒸散发，对比了冻融过程中蒸散发的差异，对比了不同植被类型的蒸散发和水量平衡，利用模型敏感性分析，初步探讨了气候变暖对高寒山区水量平衡的可能影响。项目发表论文5篇，其中SCI收录4篇，完成发明专利1项，完成了预设目标。