# Evaluation and Prediction of Ecological Benefits in Song-Liao River Basin
## 3 Results
### System of Ecosystem Service Assessment  
This study evaluates the temporal and spatial aspects of ecosystem services in the Song-Liao River Basin from 1990 to 2020 based on carbon fixation, water yield, and soil retention (Figure 3b step 2). The Weight of each indicator for the Ecosystem service index is shown in Table 1.  
The temporal and spatial characteristics of carbon fixation are depicted in Figure 5a-d. The primary forest distribution areas, including the northern Changbai Mountains, the Greater Khingan Mountains, and the Lesser Khingan Mountains, demonstrated a steady spatial pattern of carbon fixation during the research period spanning from 1990 to 2020. The principal regions of carbon fixation are also Songnen Plain and Sanjiang Plain; in contrast, the Hulunbeier Plateau and the southern human settlements have comparatively low levels of carbon fixation. The ecosystem's capacity for carbon fixation tended initially to increase and then decrease between 1990 and 2020. While the ecosystem's rate of carbon fixation in the Song-Liao River Basin stayed at roughly 4%, it had a growth rate of \(-\)16.3% between 2010 and 2020. This could be attributed to the substantial increase in Barren and the decline in Woodland in the SRB's northern region in 2020.  
Figure 5e-h illustrates the water yield in SRB. The Song-Liao River Basin had a low water yield level, and some regions did not successfully retain precipitation during the research period from 1990 to 2020. However, considering spatial characteristics, the water yield is larger in important forest distribution areas like the northern Changbai Mountains, the Greater Khingan Mountains, and the Lesser Khingan Mountains. This phenomenon might be explained by the forest ecosystem's complicated spatial organization, allowing it to retain more precipitation. The Song-Liao River Basin's soil retention is depicted in Figure 5i-l. With an average growth rate of 11.34%, the soil retention in SRB exhibited a varying rising trend between 1990 and 2020. From the geographical perspective, the major Woodland distribution areas, the northern Changbai Mountains, the Greater Khingan Mountains, and the Lesser Khingan Mountains, are where soil retention is concentrated. This distribution pattern may be caused by widely dispersed plants in forested areas that slow downwind and block runoff, preventing soil erosion and loss.  
According to the weight in Table 1 and Figure 3 (Step 2b), the calculation of carbon fixation, water yield, and soil retention are used to form the Ecosystem Services Index (ESI) in each period. The ESI's temporal and spatial distribution features in the Song-Liao River Basin are displayed in Figure 5m-p. The average Ecosystem service index for the Song-Liao River Basin tends to drop first and then improve between 1990 and 2020. During the studying period, the average Ecosystem service index reached its maximum value in 1990 and its lowest value in 2000. The average Ecosystem service index showed a positive trend  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Year**} & \multicolumn{3}{c}{**Weight**} \\ \cline{2-4}  & **Carbon Fixation** & **Water Yield** & **Soil Retention** \\ \hline
1990 & 24.36\% & 3.79\% & 71.86\% \\
2000 & 22.90\% & 0.28\% & 76.82\% \\
2010 & 14.56\% & 1.81\% & 83.63\% \\
2020 & 20.76\% & 0.49\% & 78.74\% \\ \hline \hline \end{tabular}
\end{table}
Table 1: Weight of each indicator for Ecosystem service index.  
between 2000 and 2020. According to the results of the analysis of spatial characteristics, the Ecosystem service index is higher in the northern Changbai Mountains, the Lesser Khingan Mountains, and the Greater Khingan Mountains than it is in the central and southern regions, which are the areas with the highest concentration of human activity.