退耕还林工程以来黄土高原植被覆盖与地表湿润状况时空演变

Spatiotemporal Evolution of Vegetation Cover and Surface Humidity Since Implementing the Grain for Green Project in the Loess Plateau

基于2000—2014年的MODIS数据和Landsat数据,利用温度植被干旱指数反映地表湿润状况,分析了退耕还林工程以来黄土高原地表湿润状况与植被覆盖的时空变化特征及其相互关系。（1）2001—2014年黄土高原归一化植被指数增速为6.3%·（10a）^-1,温度植被干旱指数降速为-4.5%·（10a）^-1,植被覆盖与地表湿润状况均呈增加趋势,分布呈＂东南高、西北低＂的特征,大体上可以看出两者具有正的空间相关性。（2）从TVDI和NDVI的变化趋势来看,黄土高原植被覆盖与地表湿润状况整体上呈现出增加趋势。空间分布上反映出,植被覆盖变化基本上与地表湿润状况变化分布一致,但是仍然存在区域性差异。（3）从相关系数来看,黄土高原植被覆盖与地表湿润状况呈现出正相关。从变化趋势对应关系来看,14 a间黄土高原东北—西南一线山地地区植被覆盖与地表湿润状况变化有利于生态环境改善。人类活动强烈的平原地带极不利于生态环境改善。值得注意的是,退耕还林重点区是未来生态环境变化监测和管理的重点区域,以免引起再次退化。

Based on the MODIS data and Landsat data during the period from 2000 to 2014,the temperature vegetation drought index was used to reflect the surface humidity,and the temporal and spatial changes of surface humidity and vegetation cover on the Loess Plateau since implementing the Grain for Green Project were analyzed.The findings suggested as follows：（1）The growth rate of normalized vegetation index in the Loess Plateau during the period from 2001 to 2014 was 6.3%·（10a）^-1,the temperature vegetation drought index was decreased by-4.5%·（10a）^-1,the vegetation cover and surface humidity were increased,the vegetation coverage was high in the southeast but low in the northwest,and it could be generally seen that there was a positive correlation between the surface humidity and the vegetation coverage;（2）According to the change trend of TVDI and NDVI,the vegetation cover and surface humidity were in an increase trend in the Loess Plateau.The spatial change of vegetation cover was in accordance with the variation of surface humidity perfectly,but there was a regional difference;（3）The correlative coefficient indicated that there was a positive correlation between the vegetation cover and the surface humidity in the Loess Plateau.From the perspective of the change trend,the changes of vegetation cover and surface humidity in the northeast-southwest zone of the Loess Plateau in 14 years were beneficial to the improvement of ecological environment.Intensive human activities in the plain are very unfavorable to the improvement of ecological environment.It is worth to pay attention to the key areas where the Grain for Green Project is implemented because they are critical for monitoring and managing the ecological environment change in the future so as to avoid degenerating again.