# Impact of Climate Change on the Major Eco-Hydrological Parameters in the Dongting Lake Basin
## 3 Results and Discussion
### Contributions of Long-Term Changes to GPP and ET
#### 3.3.1 Relative Contributions of Climate Change to GPP and ET
The role of precipitation was slightly less than that of temperature, with an average contribution of 44.04 \(\pm\) 22.29%, and radiation was the least important climate factor, with an average contribution of 5.37 \(\pm\) 4.46%. An observation can be made that temperature and precipitation played a dominant role in the changes in GPP in the Dongting Lake Basin, and the contributions of precipitation and radiation to GPP were considerably small. Temperature also played a larger role in  
Figure 12: Probability density function plots of temperature, precipitation, and radiation on GPP in Dongting Lake Basin and its different regions. (**a**) Dongting Lake Basin; (**b**) Xiangjiang River Basin; (**c**) Zishui River Basin; (**d**) Yuanjiang River Basin; (**e**) Lishui River Basin; (**f**) Dongting Lake region. each sub-region of the basin, while radiation was the climate factor that played the smallest role in terms of GPP. Among the sub-regions, the temperature played a slightly larger role than precipitation in the Xiangjiang River Basin and Zishui River Basin, while precipitation played a slightly larger role than the temperature in the Yuanjiang River Basin, Lishui River Basin, and Dongting Lake regions. There are more crops and trees in the Xiangjiang Basin and Zishui River Basin than in other sub-regions, indicating that the role of air temperature on GPP is greater in the areas covered by crops and trees in the Dongting Lake Basin. Climate change has an impact on vegetation productivity by affecting the physiological processes and phenology of plants. To be specific, climate warming has a positive effect on the growth of vegetation by prolonging the growing season, leading to an increase in greening [26; 27]. Changes in vegetation productivity in the Dongting Lake Basin were found to be generally influenced by meteorological factors, especially temperature. Spatial characteristics of vegetation productivity, on the other hand, were mainly influenced by land use, followed by precipitation and elevation. For terrestrial ecosystems, processes such as climate change, fertilization effects of CO\({}_{2}\), nitrogen deposition, land use types, and land cover changes are the major influences on vegetation carbon sequestration, in other words, vegetation productivity [28; 29]. Additionally, the interaction between different factors was significant [30]. In the present study, both temperature and precipitation generally contributed more to GPP in the Dongting Lake Basin, while the contribution of radiation was relatively small. The contributions of temperature, precipitation, and radiation to ET are shown in Figure 13 and Table 3. In the entire Dongting Lake Basin, the main climatic factor controlling the trend of ET was the temperature (average relative contribution of 64.60 \(\pm\) 12.89%). Radiation (average contribution of 17.63 \(\pm\) 10.73%) and precipitation (average contribution of 17.77 \(\pm\) 11.76%) had similar contributions, with radiation being slightly smaller. In the Dongting Lake Basin, temperature is the main driver of water evaporation. The climate in the Dongting Lake Basin has fluctuated over the past four decades, but overall temperatures are higher than before. The higher temperature was conducive to the growth of ET. This suggests that the evapotranspiration of water in the Dongting Lake Basin, driven by air temperature, will be more than before. Meanwhile, the precipitation in Dongting Lake Basin has decreased in fluctuation in the last four decades, therefore, Dongting Lake Basin might have a conflict between water demand and water supply in the subsurface in the future. The Xiangjiang River Basin is dominated by crops, trees, and buildings as the main land use types. Among the climate factors, temperature was found to play a dominant role in the variation of ET, with an average contribution of 57.14 \(\pm\) 10.00%. The influence of precipitation on ET was relatively small, with an average contribution of 16.95 \(\pm\) 12.40%.