中国西北地区地表植被覆盖特征的时空变化及影响因子分析

Temporal and Spatial Change of Vegetation Cover in the Northwest of China and Factors Analysis Influencing on Vegetations Variation

归一化的植被指数（NDVI）自然正交分解结果显示，自上世纪80年代初期至1994年前后，中国西北部区域地表植被覆盖呈增加的过程；1994～2000年，地表植被覆盖状况开始退化，植被退化强度空间分布不匀．TOVS云覆盖数据与地表特征时间变化的一致性，间接证明1994年之后西北部地区植被退化的事实．通过降水和NDVI的相关分析，划分出西北地区地表植被覆盖变化气候影响显著区域、气候与人为影响共同作用显著区域．并从气候和人为影响2个方面分析了造成西北部地区地表植被覆盖状况下降的原因．在降水和NDVI相关显著区域，气候干旱因素是造成1994年后植被覆盖退化的主要原因；而黄河等流域1994年后植被退化的区域，气候干旱和人为活动因素是造成植被覆盖退化的主要因素．

Spatial eigenvectors and temporal coefficients resulting from decomposed NDVI by EOF show that vegetations cover in the northwest of China presented a significantly upward trend from 1982 to 1994, and decreased after 1994. The temporal consistency between annual variations in clouds cover derived from TOVS and land surface feature implies indirectly the land degradation in the northwest of China. Based on the correlation analysis between NDVI and rainfal], two divisions where climatic factors or human activities influences on vegetation cover are marked off. The areas where the correlations is significant, the drought is a principle reason leading to the degeneration of vegetations cover after 1994; another area, such as Yellow River watershed, the drought and human activities are responsible for land degradation.