# Spatiotemporal Dynamics of Net Primary Productivity in China's Urban Lands during 1982-2015
## 3 Results
### The Importance of Multiple Variables to the NPP of the Three Urban Agglomerations  
Moreover, we evaluated the importance of the annual cumulative precipitation, the annual average air temperature, the annual cumulative sunshine duration, and the proportion of vegetation to the NPP in the urban lands, 5 km buffer zone, 10 km buffer zone, and 20 km buffer zone of the BTHUA, the YRDUA, and the PRDUA (Figure 11).  
In the BTHUA, the importance of the annual cumulative sunshine duration to the NPP of urban lands, which was 0.33, was significantly higher than that of other environmental variables. The importance of the three meteorological variables to NPP in urban lands was dominant, with a sum of 0.56. The importance of the proportion of vegetation here was 0.44. However, in the \(\sim\)5-20 km buffer zones, the importance of the three meteorological variables to NPP gradually decreased, while the importance of the proportion of vegetation increased. Among them, the importance to NPP of both the annual cumulative precipitation and the annual average air temperature in the 20 km buffer zone was less  
Figure 11: The importance to NPP of the annual cumulative precipitation, the annual average air temperature, the annual cumulative sunshine duration, and the proportion of vegetation in urban lands in 2015, also including the 5 km buffer zone, 10 km buffer zone, and 20 km buffer zone of (**a**) the BTHUA, (**b**) the YRDUA, and (**c**) the PRDUA.  
than 0.1 (0.065 and 0.073 respectively), and the importance of the proportion of vegetation reached 0.6.  
In the YRDUA, the importance of the three meteorological variables to NPP increased linearly with the expansion of the buffer zones. The corresponding change in the importance of the proportion of vegetation was opposite to that in the BTHUA and gradually decreased. In urban lands, the proportion of vegetation was the most important of all variables for NPP, and its importance reached 0.87. In the 20 km buffer zone, its importance decreased significantly, reaching 0.46. Noticeably, the importance of the annual average air temperature increased significantly among the three meteorological variables. In urban lands, its importance was only 0.04, but in the 20 km buffer zone, its importance to NPP rose to 0.3.  
In the PRDUA, the changing trend of the importance to NPP of the meteorological variables and of the proportion of vegetation were similar to those in the YRDUA. However, the importance of the proportion of vegetation decreased with the expansion of the buffer zone, but its importance was still 0.72 in the 20 km buffer zone. In urban land, its importance to NPP was as high as 0.94, occupying an absolute dominant status. Among meteorological variables, although the importance of the annual cumulative precipitation and the annual average air temperature increased with the expansion of the buffer zone, their importance was still less than 0.1 in the 20 km buffer zone (0.07 and 0.04, respectively). Compared with the other two meteorological variables, the importance to NPP of the annual cumulative sunshine duration increased the most, from 0.02 to 0.17.