Responses of Vegetation Growth to Climate Change in Permafrost Distribution Region in Northeast China

LI Yunyun, LIU Hongyan†

Laboratory for Earth Surface Processes (MOE), College of Urban and Environmental Science, Peking University, Beijing 100871; † Corresponding author, E-mail: lhy@urban.pku.edu.cn

Abstract The interannual change rate of the normalized vegetation index (NDVI) and its correlation with climate factors were compared under different permafrost degradation and vegetation types. The results indicated that NDVI of the coniferous forest accelerated, which was positively correlated with the temperature and negatively with the precipitation in the growing season. As the permafrost active layer deepens, the rate of increase in NDVI of coniferous forests gradually decreases from north to south. The grassland NDVI accelerated in non-permafrost regions, which was positively correlated with growing season precipitation. There is a clear difference between the response of mixed forests to climate in permafrost and non-permafrost regions. In permafrost regions, mixed forest NDVI is positively correlated with growing season temperature and negatively correlated with growing season precipitation. As the permafrost active layer deepens, the correlation coefficient between the NDVI of mixed forest and growing season temperature shifts from positive to negative, and the correlation coefficient with growing season precipitation shifts from negative to positive. This may be related to the different water supply caused by different active layer thickness. The results imply that under the coupling effects of climate and permafrost, climate warming will lead to gradual northward shifting of coniferous forests and mixed forests, and occupation by grasslands in non-permafrost regions. Key words permafrost; active layer thickness; vegetation growth; climate warming