## 3 Results
### The Spatial and Temporal Distribution of the Forest NPP in the Yangtze River Basin  
The spatial distribution and changing trends of the annual mean NPP and accumulated NDVI for the forests in Yangtze River basin during 1982-2013 were analysed (Figure 3a,b). The results indicated that the spatial distribution of the forest NPP was characterized by a gradually decreasing trend from the southeast to the northwest in the Yangtze River basin from 1982 to 2013. This demonstrates that the spatial distribution of the forest NPP was relatively consistent with the pattern of temperature and precipitation in the basin. However, the east of the basin had the highest NDVI value, which was different from the distribution of NPP. This indicates that the forest NPP in the foothills of the Qinghai-Tibet Plateau and most areas of Jiangxi Province was relatively high, whereas the forest NPP in the Yangtze River delta, the middle reaches of the Yangtze River and the Qinghai-Tibet Plateau was relatively low during the period of 1982-2013. This distribution was closely related to the vegetation type and urbanization level of the entire Yangtze River basin. The hydrothermal conditions in the foothills of the Qinghai-Tibet Plateau were better and thus the forest NPP was relatively higher. For parts of the mid-lower Yangtze, although natural conditions such as photosynthesis, temperature and precipitation were superior, human activities driven by economic interests have resulted in great damage to vegetation in recent years. There was then a comparison between the annual forest NPP and NDVI anomalies in the Yangtze River basin. As shown in Figure 3c, compared to 1982-2013, the NPP in the northern and southern edge regions of the Yangtze River were gradually decreasing from 1982 to 2000. The NDVI in parts of the east showed the decreasing trends (Figure 3d). Compared to 1982-2013, the NPP and NDVI were increasing generally from 2001 to 2013 in the Yangtze River basin (Figure 3e,f). This demonstrates that the NPP in the north of the Yangtze River basin from 2001 to 2013 increased significantly compared to the period 1982-2013. Figure 2: Spatial distribution of annual mean NPP in Yangtze River basin in 2000 and 2010. The forest NPP and NDVI exhibited a generally increasing trend in the Yangtze River basin from 1982 to 2013 (Figure 4a,b). According to the calculations, the pixels representing forest NPP that presented increasing trends in the entire region were as high as 69% of the total number of pixels, of which 13% of the pixels exhibited significant increasing trends. Moreover, 25% of the Yangtze River basin remained relatively stable. Meanwhile, the pixels representing forest NDVI that took on increasing trends in the entire region were as high as 71% of the total number of pixels, of which 38% of the pixels showed significant increasing trends. In addition, 18% of the Yangtze River basin remained relatively stable. The difference between NPP and NDVI could be due to the influence of human activities, which could not be reflected by the LPJ model. Hanjiang River basin presented the decreasing trend for the annual forest NPP during 1982-2000 (Figure 4c). However, the annual forest NDVI exhibited the increasing and stable trends in the Hanjiang River basin during 1982-2000 (Figure 4d). While Dongting Lake basin displayed the increasing and stable trends for the annual forest NPP during 2001-2013 (Figure 4e) and the annual forest NDVI took on the decreasing trend in the Dongting Lake basin during 2001-2013 (Figure 4f). The annual mean forest NPP and accumulated NDVI were analysed in the Yangtze River basin from 1982 to 2013 (Figure 5). The results show that both the NPP and NDVI in mid-lower Yangtze River was higher than that in upper Yangtze River. As presented in Figure 5b, the trends of the forest NDVI in the upper Yangtze reaches took on the same pattern. This phenomenon does not show up in Figure 5a. It should be noted that the patterns of NPP and NDVI are quite different.