# Spatial and Temporal Variation of GPP and Its Response to Urban Environmental Changes in Beijing
## 4 Discussion
### Influence of Environmental Factors on AGPP in Beijing  
In terms of environmental factors, LST has significant and varying impacts on AGPP in Beijing. LST exerts a negative influence in the northern, central, and southeastern regions, where high surface temperatures likely limit plant productivity. However, in certain areas, such as those extending eastward and westward from the central parts, LST's impact shifts to a more positive influence, suggesting that moderate temperatures may benefit plant growth in these regions. This result highlights temperature as a key driving factor for vegetation productivity in Beijing. Within an optimal range, higher temperatures promote photosynthesis and boost plant productivity. However, excessive heat increases respiration and transpiration, causing dehydration and reducing productivity. These findings align with existing research [39; 40; 41].  
The impact of precipitation (PRE) on AGPP in Beijing is relatively less significant, and its impact varies in different regions of Beijing. The negative impact of precipitation on AGPP in Beijing is attributed to the region's temperate semi-humid continental monsoon climate, which is marked by summer precipitation and a dearth of precipitation in spring and winter. This seasonal precipitation pattern induces water stress in vegetation during early growth stages, consequently affecting AGPP [42; 43]. Additionally, extreme weather events, such as rainstorms and droughts, can exacerbate the decline in vegetation productivity. Rainstorms can lead to soil erosion and nutrient depletion, while droughts impede plant water uptake and photosynthesis [43]. As shown in Figure 6, the PRE in the Beijing area fluctuates greatly, and the intense fluctuations in PRE have caused obvious disturbance to vegetation growth. In the central regions of Beijing, human activities are capable of regulating water resources. Therefore, PRE exerts a positive influence on the  
Figure 5: Spatial variation trend of AGPP and LUCC of Beijing from 2000 to 2020. (**a**) shows the results of LUCC in Beijing, and (**b**) shows the slope of AGPP interannual variation.  
AGPP. On the periphery, however, human activities exhibit a limited ability to manage water resources effectively. Consequently, erratic precipitation patterns and the occurrence of extreme weather phenomena result in a negative impact of PRE on AGPP. In essence, the suppressive effect of precipitation on Beijing's AGPP is likely due to the seasonal distribution of precipitation and the frequency of extreme weather events.  
Figure 6: Boxplot of AGPP, PRE, and LST distribution. (**a**) shows the boxplot of AGPP distribution in Beijing, (**b**) shows the boxplot of PRE distribution in Beijing, and (**c**) shows the boxplot of LST distribution in Beijing.  
Therefore, in the context of environmental considerations, the utilization of appropriate water resource management strategies to align the water-heat relationship, enhance urban water resource regulation capabilities, and mitigate extreme events such as floods and droughts can significantly enhance vegetation productivity in Beijing and contribute to the advancement of sustainable urban development.