## 4 Discussion
### Relationship between Land Cover Changes and Vegetation Leaf Area and Carbon Sequestration  
Since 1850, LUCC's carbon emissions have accounted for one-third of global greenhouse gas emissions [41]. Improving land management can improve the carbon sequestration capacity of ecosystems and increase China's contribution to greening the Earth. We digitized the contributions of the different vegetation changes in the different regions to the LAI and GPP. The results show that land management played an important role in greening and terrestrial carbon sequestration in China, and the self-rehabilitation of forest-grassland vegetation has the greatest potential for greening and terrestrial carbon sequestration. The principle may be to close the mountains for afforestation and transform the low-efficiency forest into a forest ecosystem. In the cropland ecosystem, the carbon in the biomass can be increased through rational fertilization, artificial grass planting, rotational grazing, and reducing grazing pressure. Through artificial management, the carbon input of the ecosystem can be increased, and the carbon output caused by ecological disturbances can be decreased. Each land cover type has different water conservation characteristics, which determine differences in the plant species, growth characteristics, and spacing. Specific management measures can have a significant impact on species richness and ecological composition [42]. For example, in a given external environment, the same crop species in different types of land causes differences due to variations in the soil characteristics [43], and often does notproduce the species richness and composition associated with the original communities [44]. In China, the public green spaces in parks, streets, communities, and other urban areas have a higher canopy closure and density, which provides more favorable environmental conditions for increasing the vegetation greening rate and carbon storage. However, vegetation intensification in these areas affects species performance and reduces species abundance. Change in the vegetation abundance in surface areas is an important factor leading to the distribution of solar radiation, and changes in the nature of the surface lead to redistribution of the energy [45]. In the process of LUCC, in recent years, almost all of the surface atmospheric conditions have changed, including solar radiation, precipitation, temperature, and humidity [46]. Urban expansion is the best example of the ecological and climatic impacts caused by the increase in population. The significant increase in the artificial surface area reduces evapotranspiration and base flow. In addition, due to the changes in the properties of the underlying surface, such as the surface reflectance, roughness, vegetation coverage, temperature, humidity, and wind speed, the regional climate changes [47; 48]. [PERSON] et al. [49] found that in recent decades, the ground carbon storage capacity in China's urbanized regions decreased briefly and then increased. Urbanization generally promotes ecosystem carbon sequestration, and the conclusions of this study are consistent with this assessment. Since 2013, China has started incorporating ecological civilization construction into the national plan and constitution, all residential areas need a certain proportion of green space [50], most of which are trees and shrubs, and high biomass is an important reason for this phenomenon. We also found that the GPP in the SW urbanization area decreased by 0.69 TgC, and the LAI in the EC urbanization area decreased by 2783.14 km\({}^{2}\) from 2000 to 2018. Figure 13 shows the proportions of the other land types occupied by the urbanization process in these two regions. The common feature of these two regions is that the proportion of urbanization construction through the occupation of cropland was the largest. The cropland area occupied in SW was 1.06 \(\times\) 10\({}^{4}\) km\({}^{2}\), accounting for 74.7%.