Abstract: Forest is a key terrestrial ecosystem type, and plays an important role in regulating the exchange of carbon, water and energy between land surface and atmosphere. Therefore, forestecosystems are vital in mitigating climate change. Understanding the spatiotemporal dynamics of forest ecosystem and its drivers is important to predict its structure, function, and dynamics. Using normalized difference vegetation index (NDVI) dataset from Moderate Resolution Imaging Spectroradiometer (MODIS), we analyzed the vegetation dynamics  and its climatic controls in forested region across Northeast China from 2000 to 2017. The results showed that NDVI increasedin spring, summer, autumn and growing season from 2000 to 2017, with the highest increase rate in autumn and the lowest increase rate in summer. The increase rate of NDVI in the growing season was 0.0025 a^-1 (R²=0.77). Among the three forest types, broadleaved forest had the highest interannual variability, followed by mixed forest and coniferous forest. Results of multiple regression analysis suggested that PDSI (Palmer drought severity index) was the major driver for the forests in Northeast China. PDSI was positively correlated with NDVI, indicating that higher water availability promoted stronger vegetation activity. Under climate warming scenario, increased evapotranspiration due to higher air temperature may increase drought frequency and become a dominant limiting factor for forest vegetation activity and carbon sink in Northeast China.

Key words: NDVI, forest type, climate factor, driving force, Northeast China forest.