1982-2015年蒙古国植被覆盖变化及其与气候变化和人类活动的关系

基于1982-2015年间GIMMS NDVI3g数据、气象数据和植被类型数据，采用趋势分析、偏相关性分析和残差分析等方法，从不同时空尺度上分析蒙古国植被NDVI空间格局、变化趋势及其主要原因。结果表明，过去34年间蒙古国生长季平均NDVI在空间上由南向北逐渐增加，具有显著的纬度地带性分布特征，并随着海拔的升高而降低。生长季NDVI阶段性变化特征明显，1982-1994年和2007-2015年间呈显著增加趋势，而1994-2007年间呈显著下降。从34年的观测尺度看，NDVI以每年0.0005的速率呈显著增加趋势，其变化趋势与降水量的关系较密切，两者之间的偏相关系数为0.74。在空间分布上，植被显著增加的区域主要分布在西部大湖盆地、杭爱山脉、戈壁阿尔泰山脉和北部森林区，其对气候的响应因季节和地区而异。从季节上看，总体上3个季节NDVI均呈增加趋势，其中夏季NDVI波动与生长季的波动一致，主要受降水量的控制，其主要原因为夏季生产力占全年生产力的比重较高有关。春季和秋季NDVI对温度的响应明显。残差分析表明，人类活动是蒙古国植被NDVI变化的另一重要影响因素，特别是在人口密度较大的地区（蒙古国西部高山地区和中部草原地区），植被NDVI的变化受人类活动影响明显。

Variations in vegetation cover and its relationship with climate change and human activities in Mongolia during the period 1982-2015

Dynamics of vegetation change on different spatial and temporal scales in Mongolia were analysed for the period from 1982 to 2015,based on GIMMS NDVI3g data(global inventory monitoring and modeling system normalized difference vegetation index-3rd generation),climate data,and data on vegetation type from 1982 to 2015.Spatial patterns,trends of change in those patterns,and the main reasons for differences in vegetation type were examined using trend analysis,partial correlation analysis and residual analysis.The average NDVI in Mongolia in the growing season increased gradually from the south to the north across Mongolia over the 34-year period,showed significant latitudinal differences,and decreased as the altitude increased.In the growing season,the NDVI displayed characteristic features in particular time periods,notably a significant increase between 1982 and1994 and between 2007 and 2015,and a significant decrease between 1994 and 2007.Across the whole of Mongolia,linear regression model indicated an increasing trend in the values of the NDVI during the growing season at the rate of 0.0005 NDVI per year,and changes in the index were closely related to increasing precipitation,with a partial correlation coefficient of 0.74.In the case of spatial distribution,areas with significant increase in vegetation were distributed mainly in the Great Lakes Region in the west,the Hangayn Mountains,the Gobi Altai Mountains,and the northern forest areas.The responses of vegetation to climatic factors varied with the season and the region.On the whole,the NDVI increased in three seasons,and the fluctuation in the NDVI in summer was consistent with that in the growth season,and the fluctuation in the NDVI in summer was consistent with that in the growth season,which was controlled mainly by precipitation,because summer contributes the most to annual productivity.The effect of temperature on the NDVI was marked in spring and autumn.Residual analysis showed that human activities has a major impact on changes in the NDVI,especially in areas with high population density(western alpine areas and central grassland areas of Mongolia),the decline in the NDVI is obviously caused by human activities.