基于EVI的中国最近10 a植被覆盖变化特征分析

通过对2000—2009年增强型植被指数(EVI)数据的分析发现:在过去的10 a里,中国的植被覆盖度明显增加,植被活动在增强。植被覆盖的年变化和季节变化特征如下:(1)10 a来植被覆盖地区的面积呈增加趋势,植被稀少地区的面积呈减少趋势;(2)无论是植被覆盖区还是全国平均,单位面积EVI年平均值都呈增加趋势;(3)在生长季节(夏季、春季)植被活动增加更明显,EVI增加速率按季节排列如下:夏季春季秋季冬季。植被覆盖的空间变化特征显示,尽管总体上中国植被覆盖呈增加趋势,但存在空间异质性。结合同期的温度、降水和森林资源清查数据,从两个方面初步解释了植被覆盖度增加的原因,即:温度的上升和春季降水量的增加;近年来中国开展的大型林业生态建设工程。

Variation characteristics of vegetation cover in the latest 10 years over China based on EVI

Analysis on the variation data of Enhanced Vegetation Index (EVI) from 2000 to 2009 found that the vegetation coverage was obviously increasing and the vegetation activity was enhancing in China during the past ten years. The characteristics of interannual and interseasonal vegetation coverage variation were as follows:(1) the area of vegetation coverage was increasing while the area of bare land was decreasing; (2) the mean EVI per unit land either in vegetation coverage areas or in the average areas of the whole country was increasing in the past ten years; (3) vegetation activity enhanced obviously in growing seasons (summer, spring), and the growth rate of EVI was ordered according to season as summer > spring > autumn > winter. The spatial variation features of vegetation coverage show that although the vegetation coverage presents increasing trend in China, the spatial difference exists. The increasing of EVI around China could be caused because of:(1) the increasing temperature and precipitation in spring; (2) large forestry ecological construction projects.