丹江口库区陆地植被物候空间格局及其与海拔的响应关系

SPATIAL PATTERNS IN THE TERRESTRIAL VEGETATION PHENOLOGY OF DANJIANGKOU RESERVOIR AREA AND ITS RELATION WITH ELEVATION

海拔高度变化对区域温度、降水都起着至关重要的作用,从而会对植被物候特征产生影响。以丹江口库区为研究区,分析库区植被物候随海拔变化特征,该工作的开展对进一步认识库区植物物候空间特征,进而监测库区土地覆盖变化具有重要实践意义。研究采用Savitzky-Golay滤波算法重建库区2001~2012年MODIS 16天最大合成EVI时序影像数据,对重建后的时间序列影像采用动态阈值法提取库区陆地植被关键物候特征信息,并对库区陆地植被物候特征随海拔梯度变化特征进行分析。研究结果表明,丹江口库区陆地植被生长季为4月上旬至10月上旬,南部山区林地生长季最长,而库区中部、东部耕地生长季较短。植被物候特征随海拔梯度变化呈现两个较为明显的区域,低海拔区域植被生长季开始时间（Start of Season,SOS）随海拔升高而提前,生长季结束时间（End of Season,EOS）随海拔升高而推迟,进而导致生长季长度（Length of Season,LOS）随海拔升高而延长。而在海拔较高山区,林地植被物候呈现完全相反变化趋势。受丹江口水库和人类活动的影响,丹江口库区植被分布随海拔变化呈现两个较为明显的区域。

Greater spatial variation occurred in vegetation phenology, which may be due to the spatial distribution of rainfall and temperature as a function of elevation. In this study, taking the Danjiangkou reservoir as study area, we assessed the spatial variation in key vegetation phenology parameters in relation to elevation. This work will has important practical significance on further vegetation phenological analysis, and thus is helpful for land cover change detection in the reservoir. We employed the Savitzky-Golay filter to rebuild the Moderate Resolution Imaging Spectroradiometer（MODIS）Enhanced Vegetation Index time-series dataset, and then a dynamic threshold method was used to investigate the spatial distribution of terrestrial vegetation phenology in Danjiangkou reservoir during 2001–2012. The results showed that the vegetation growing season spans from early April to early October, and the average length of growth season ranges from100 days to 200 days. The spatial patterns of the vegetation phenology indicated that the relatively longer length of season（LOS） in the south resulted from an early start of season（SOS） and later end of season（EOS）. Regression models and correlation analysis indicated that elevation is moderately related to vegetation phenology. However, the relation between vegetation phenology and elevation displayed different variation trends above or below 474 m. In the land area where elevation below 474 m, there was generally an advanced SOS, and delayed EOS of vegetation growing season, due to warmer temperatures at higher elevation. However, the elevation-phenology relationship was reversed where the elevation was above 474 m, which coincides with colder temperatures at higher elevations.