江河源区植被水分利用效率遥感估算及动态变化

Estimating and dynamic change of vegetation water use efficiency in Yangtze and Yellow River headwater regions

为了获取高寒地区在资料短缺条件下的陆地生态系统碳循环和水循环的变化特征,该文以遥感数据、气象数据和实际观测数据相结合,利用基于光能利用率的CASA(carnegie ames stanford approach)模型和FAO Penman-Monteith方法对江河源区2000–2010年植被水分利用效率进行估算和动态分析,得出以下结论:1)所选模型较好的反应了区域植被水分利用效率的时空分布特征。近11 a来,长江源区和黄河源区多年平均水分利用效率(以C质量计,下同)分别为0.54 g/(mm·m^2)和0.56 g/(mm·m^2),江河源区植被水分利用效率呈减少趋势,其中黄河源区植被水分效率减少速度大于长江源区。2)江河源区典型高寒草甸和高寒草原水分利用效率年际变化总体呈下降趋势,其中黄河源区减少趋势较长江源区更明显。长江源区高寒草甸和高寒草原水分利用效率呈现明显单峰现象,黄河源区呈现为阶梯增加和减少现象,表明长江源区在单位面积上植物消耗单位水分的固碳能力要好于黄河源区。3)主成分分析表明:江河源区植被水分利用效率变化与NDVI、温度、降水、太阳辐射以及蒸发密切相关;长江源区以NDVI、降雨为主导,黄河源区以NDVI、降雨和温度为主导。该研究可为江河源区水资源合理利用,实现区域生态环境可持续发展提供科学参考。

The alteration of water and carbon cycles can produce great influence on the terrestrial ecosystem, as far as to the whole earth. Vegetation water use efficiency （WUE） is the important variable on the contact of a carbon cycle and hydrological cycle in the vegetation ecosystem. In addition, study of vegetation WUE, in Yangtze and Yellow River Headwater Region, can provide important support for region ecological environment development. Therefore, in order to obtain the change characteristics of the hydrologic and carbon cycle within the terrestrial ecosystem under a data shortage condition, this manuscript, focused on the advantages and applicability of light energy utilization model （CASA model） and a FAO Penman-Monteith model, estimated the vegetation WUE and analyzed the dynamic change situation from year 2000 to 2010. Furthermore, test data which consisted of several vegetation types were subject to verification. The results revealed that a CASA model could reflect vegetation WUE distribution characteristics preferable in time and space. During the study phase, a decrease trend of vegetation WUE was obvious. Moreover, a changing rate of partition, in the Yellow River headwater Region and Yangtze headwater region, was relatively different. In terms of these two area, the alpine grassland in the Yellow River headwater Region showed more obvious expression to reducing than that of the Yangtze headwaters region. As far as the regulation was concerned within the year, continuous mono-peek distributions mainly appeared in the Yangtze headwaters region. In addition, changes by leaps and bounds turned up in the Yellow River Headwater Region. These cases showed that carbon sequestration capacity in the Yangtze headwaters region was much better during the calculation period. In addition, studies of principal component analysis indicated that the factors, such as NDVI, temperature, precipitation, solar radiation, and evaporation are closely related to vegetation WUE. Especially the NDVI, precipitation, and temperature were the main influencing factors in the study area.