Abstract: Based on the forest inventory data and single tree biomass model, the forest biomass in the sampling plots in Changbai Mountain forest region was calculated, and, by using the estimated forest biomass from four periods’ remote sensing data and based on high accuracy remote sensing models, the changes of regional forest biomass were analyzed. In the meanwhile, the driving factors such as meteorological factors, management factors, and socio-economic factors that caused forest biomass change were selected by bootstrap method, and the driving model of forest biomass change in different time period was set up by using partial least-squares method. The Variable Importance in Projection (VIP) values representing the importance of each of the factors affecting the forest biomass change in study region were calculated. The results showed that the influence of human activity factors (VIP values) on Changbai Mountain forest biomass changes was less than that of natural factors, suggesting that the national forest protection policy for forest regions had played an obvious role. Our research broadened the content of forest biomass change driving analysis, and the introduction of calculating VIP value, which can quantitatively represent the influence of driving factors to forest biomass change, provided a new way for the quantitative analysis on forest biomass change.

Key words: forest biomass, quantitative analysis, VIP value, supplemental irrigation by monitoring soil moisture, wheat, water and nitrogen utilization, soil NO₃^--N content, grain yield.