# Evaluation and Prediction of Ecological Benefits in Song-Liao River Basin
## 4 Discussion
### Analysis of Ecosystem Service Assessment  
Ecosystem services are influenced by their components, showing rich spatiotemporal heterogeneity. Figure 5a-d shows the temporal and spatial characteristics of vegetation carbon sequestration capacity in SRB. Time-scale analysis shows that the total amount of carbon sequestration shows an upward trend during the research period from 1990 to 2020, which indicates that the vegetation in SRB is still a carbon sink as a whole. Figure 2m-p depict that carbon fixation keeps similar spatial characteristic with NPP. Comparing with Figure 5c and 5d, it could be found that the carbon sink rate in the northern part of the study area has decreased, and combining with Figure 8d, it could be found that the Woodland area in this area has decreased and the Barren has increased. Planned forest management in this mature forest-rich area will help to improve the carbon sink rate [58]. Figure 5e-h shows the temporal and spatial characteristics of water conservation capacity in SRB. The evaluation results show that the southern and southwestern regions of SRB could not hold water conservation capacity, and the reason for this phenomenon is that the distribution of land use types is related to climate factors (Figure 2). The ESI evaluation research based on ecological protection red line shows that the changes in water yield, soil water capacity, and carbon sequestration are affected by the interaction of climate and land cover, which is consistent with the results of this study [59]. Comparing Figures 5 and 8, it can be seen that most of the areas without water conservation capacity are Cropland and Grassland. Crop planting will lead to soil disturbance and physical properties change, significantly reducing soil's interception ability in its natural state. Compared with the forestry ecosystem, Grassland has reduced its ability to regulate and store rainwater because of the lack of tall trees. The low water conservation capacity in some forest areas in northern China may be due to the strong evapotranspiration capacity of these regional ecosystems, resulting in water loss in the system [60]. On the other hand, the ecosystem structure that has evolved to the top community tends to be stable, and most of the forests widely distributed in SRB are mature natural forests, which limits the ability to intercept precipitation. Figure 5i-l shows the temporal and spatial characteristics of soil conservation capacity in SRB. During the research period from 1990 to 2020, the soil conservation capacity of SRB rose in fluctuation, and the distribution characteristics of areas with soil conservation capacity were similar to those of forests. This phenomenon might be because the forest ecosystem can retain precipitation and increase surface roughness to achieve the effect of soil conservation more effectively [61]. The assessment of regional ecosystem services can contribute to formulating environmental management policies and planning resource development [62]. Figure 5m-p shows the change in the Ecosystem service index in SRB from 1990 to 2020. During the study period, the ecosystem service function generally declined first and then rose, consistent with the conclusion based on the three-dimensional land use multifunctional evaluation framework [63]. Figure 8 shows that the Ecosystem service index of the main distribution areas of forests, such as the Greater Khingan Mountains, Lesser Khingan Mountains, and the northern Changbai Mountains, is higher. In contrast, the Ecosystem service index of cultivated land, Grassland, and human activity gathering areas is lower. This result is consistent with the research results based on ecosystem service clusters [64], which found that soil retention, water yield, and carbon fixation benefits in Northeast China are higher where forest land is widely distributed but lower in the central and southern regions. The policy of returning farmland to forests in the study area has been implemented, but the impact of this policy on ecosystem services is two-sided [65].