1982-2006年华北植被指数时空变化特征

利用1982-2006年GIMMS/NDVI数据,研究华北近25 a来植被指数在时间和空间上的变化。结果表明:①植被指数的年内变化呈单峰型,最大值出现在夏季,其中北京市NDVI最大,森林NDVI比农田和草地NDVI大;②华北年平均NDVI呈增加趋势,河北省植被指数增加最快,北京市次之,不同土地覆盖类型中,农田NDVI增加最快,草地次之,森林最小;③空间趋势分析结果显示,华北植被指数改善的面积占整个地区面积的15.96%,退化面积占11.86%,其中,河北省改善面积最大,内蒙古退化较明显,不同土地覆盖类型中,农田植被改善最明显;④基于华北近年暖干化发展趋势下,人类活动对该区域NDVI变化起到了重要作用。

Spatiotemporal Variation of Vegetation Coverage Index in North China during the Period from 1982 to 2006

In this paper,the spatiotemporal variation of normalized difference vegetation index(NDVI) values in north China was analyzed based on the GIMMS data during the period of 1982-2006.The preliminary results were as follows:(1) The average annual NDVI curves of vegetation were unidomal in north China.The NDVI peaks of vegetation occurred in summer,the NDVI peak in Beijing was the highest,then in Hebei Province,and it was the lowest in Inner Mongolia.The NDVI peak of forests was higher than that of grasslands and farmland;(2) In recent 25 years,the average annual NDVI in north China was increased.The average annual NDVI in Hebei Province was increased significantly,and the trend was the most significant(P<0.01).The average annual NDVI in Beijing was also increased significantly.In different land cover types,the highest increase of average annual NDVI occurred over farmland,than over grasslands,and it was the slowest in forests;(3) Based on the spatial trend analysis,the proportion of NDVI increase in the study area was 15.96%,and that of NDVI decrease was 11.86%.In different provinces,the NDVI increase occurred mainly in Hebei Province,and the NDVI decrease occurred mainly in Inner Mongolia.In three land cover types,NDVI in farmland was increased more significantly than that in forests and grasslands;(4) Based on the background of warming and drying climate in north China,human activities were the main causes resulting in the NDVI variation.