近30a黄土高原植被覆盖时空演变监测与分析

Detecting and analysis of spatial and temporal variation of vegetation cover in the Loess Plateau during 1982-2009

为监测黄土高原植被建设成效,采用GIMMS和SPOT VGT2种数据集的归一化植被指数作为植被覆盖评价指标,分析了近30a黄土高原植被覆盖时空演变趋势。结果表明,大规模植被建设开始前,黄土高原植被覆盖以小幅波动为主,个别地区有所好转,但大部分区域无显著变化。1999年以后研究区归一化植被指数年度平均值增加显著,并以夏、秋两季增长贡献最大。植被覆盖在空间上呈现出明显的区域性增加趋势,其中黄土高原丘陵沟壑区增加趋势最为明显,植被恢复成效显著。研究区15°～25°和6°～15°坡地植被覆盖状况得到明显改善,对控制水土流失可产生积极影响。大规模植被建设促进了该区植被恢复,但截止2009年,黄土高原处于较低植被覆盖水平的区域面积依然占较大比重,生态环境建设仍须进一步加强。

Time-series GIMMS and SPOT VGT NDVI datasets, which served as an evaluation index of the vegetation cover, were used in this paper to detect and analyze the spatial and temporal variation of vegetation cover in the Loess Plateau from 1982 to 2009. Results showed that before the large-scale implementations of vegetation construction （1982-1998）, the annual mean NDVI of the Loess Plateau fluctuated in a narrow range yearly; most places indicated no significant changes in NDVI except for some improvement in a few places. However, since the large-scale implement of vegetation construction in 1999, the annual mean NDVI of the Loess Plateau has increased significantly. Most regions （covering 66.12% of the total area） on the Loess Plateau showed significant positive correlation between NDVI and time over the past decade, especially in the part traversed by the Loess Hilly-gully Region, where the achievements of vegetation construction were quite noticeable. Moreover, the vegetation cover in 15°～25° and 6°～15° slope areas experienced great improvement from 1999 to 2009, which may be helpful to control soil and water losses. The large-scale implementations of vegetation construction accelerated the vegetation restoration in the Loess Plateau. Nevertheless, regions with sparse vegetation on the Loess Plateau still covered a great part by 2009, so it is necessary to further strengthen the ecological environment construction in the future.