## 3 Results
### The Spatial and Temporal Dynamics Analysis of Forest NPP  
To analyze the temporal and spatial trends of forest NPP in the study area, the calibrated Biome-BGCMuSo simulated forest NPP in the study area and calculated the average forest NPP from 2012 to 2018. The results are shown in Figure 7a. The annual mean value of forest NPP ranged from 26.83 to 718.27 g/C/m\({}^{2}\)/year, which was low in the middle and high in the east and west in terms of spatial distribution. Figure 7b shows the forest NPP variation trend from 2012 to 2018. It revealed that the temporal variation trend of forest NPP was not obvious. The variation range of most areas was between \(-\)42.25 and 2.5 g/C/m\({}^{2}\)/year, while the regional change trend was obvious and showed a negative growth trend. Figure 8 shows the time distribution trend of NPP in different forest types in the growing season from 2012 to 2018. The highest NPP value in the growing season is coming from deciduous foreignst (DNF), next was coniferous and broad-leaved mixed forest (MF), the third was deciduous broad-leaved forest (DBF). During the seven-year period, the NPP in the growing season did not change significantly and showed a slow growth trend.  
Figure 9 shows the correlation analysis results of the annual mean value of NPP and climatic factors in the forest growing season in the Greater Khingan Mountains forest area of Inner Mongolia. The correlation coefficient matrix (Figure 9) shows that the annual mean NPP of the forest growing season from 2012 to 2018 has an upward trend with a correlation coefficient of 0.54. The annual mean value of NPP in the forest growing season was positively and strongly correlated with VPD and T\({}_{\rm mean}\), which were 0.82 and 0.81, respectively. The weak correlation with Sard was 0.11 and the negative correlation with PRE was \(-\)0.66.  
Figure 10 shows the statistical results of the annual average forest NPP dynamics and climatic factors in the Greater Khingan Mountains forest area of Inner Mongolia. The statistical data were only calculated for the forest growing season. From 2012 to 2018, the average temperature of the growing season in the study area was between 10.1\(\sim\)12.3 (\({}^{\circ}\)C), the annual precipitation was between 230-770 (mm), the average saturated vapor pressure was between 660-830 (Pa), and the annual shortwave radiation was 1.14-1.95 (106 W/m\({}^{2}\)). Among them, the change trend of forest NPP was basically consistent with the change trend of average vapor pressure and average temperature, which was opposite to the change trend of annual precipitation and the change trend of annual shortwave radiation was not obvious.  
Figure 6: Validation of interannual NPP of the calibrated Biome-BGCMuSo model with NPP from dendrochronological data time series.  
Figure 8: The distribution of different forest types in growing season NPP from 2012 to 2018.  
Figure 7: The spatial distribution of average annual NPP (**a**), and its changing trend (**b**) from 2012 to 2018.  
Figure 10: Interannual NPP and meteorological data statistics for the growing seasons in forested areas over the Greater Khingan Mountains in Inner Mongolia.  
Figure 9: Correlation coefficient (r) matrix of NPP and meteorological data in growing seasons in the Greater Khingan Mountains in Inner Mongolia.