Changes of Vegetation Coverage in Northeast China from 1982 to 2003

Based on the remote sensing data,GIMMS-NDVI,technology of GIS and statistical processing,the paper conducted quantitative analyses of spatial-temporal changes of vegetation coverage from January 1982 to December 2003 in the Northeast China.The results showed that:(1) the average annual NDVI curves of vegetation had a single peak in those regions such as forest,grassland and cropland.The NDVI peaks of different vegetation occured in summer.The NDVI peak of forest was highest,cropland took second place and grassland was the lowest.(2) The NDVI variation trends of forest were decreased,the trends of grassland and cropland were decreased,but trends of grassland of Xi Liao River Plain and cropland of Song Nen Plain were increased.For the same type vegetation,the vegetation coverage change of forest in the northeast part of Changbai Mountain,grassland in Xi Liao River Plain and cropland in Song Nen Plain were stable.(3) The changes of vegetation coverage were slowly decreased during the past 22 years in whole area.From 1982 to 1992,the vegetation coverage increased in the Northeast China.The coverage increased areas were(545 435) km2,accounted for 43.91% of Northeast China.The coverage decreased areas were 96 491 km2,accounted for 7.77% of Northeast China.From 1993 to 2003,the vegetation coverage of Northeast China decreased.The coverage decreased areas were 626 839 km2,accounted for 50.45% of Northeast China.The coverage increased areas were 27 025 km2,accounted for 2.18% of Northeast China.The main reasons of decrease of vegetation coverage were the effect of human activities and natural factors in Northeast China.