## 3 Results and Analysis
### Evaluation Results of Cultivated Land Quality Based on Degradation Risk  
This study conducted a comprehensive assessment of the cultivated land degradation risk in different types of regions within the BSNC. The results indicate that in the SNP, low-to-moderate-risk land accounts for 96.30% of the total area (Figure 5). In the SJP, 87.80% of the cultivated land faced moderate or lower risk. In the LHP, 98.32% of the cultivated  
Figure 4: Cultivated land function index in different regions. Different colors represent different types of regions. The outermost part represents the six cultivated land functions, and the inner number represents the cultivated land function index.  
\begin{table}
\begin{tabular}{c c c c c c} \hline  & **Grade 5** & **Grade 4** & **Grade 3** & **Grade 2** & **Grade 1** \\  & **(m\({}^{2}\))** & **(m\({}^{2}\))** & **(m\({}^{2}\))** & **(m\({}^{2}\))** & **(m\({}^{2}\))** \\ \hline Primary & 287 & 9675 & 131,200 & 231,401 & 7838 \\ productivity & & & & & \\ Soil nutrients and & & & & & \\ maintenance & 0 & 0 & 37,259 & 339,022 & 3104 \\ Infrastructure & & & & & \\ regulation & 0 & 954 & 181,925 & 184,377 & 12,321 \\ Biodiversity supply & 41,649 & 153,280 & 99,451 & 73,693 & 13,488 \\ Resource utilization & & & & & \\ efficiency & 32,868 & 15,586 & 51,882 & 123,630 & 157,301 \\ \hline \end{tabular}
\end{table}
Table 3: The area proportion of each grade of the six major cultivated land functions.  
land was at moderate or lower risk. In DXXXL and WS, the distribution of degradation risk was not significant, while in CBMEL, the degradation risk showed a trend of being lower in the north and higher in the south. Based on Table 4, it can be observed that low-risk and very-low-risk cultivated land accounts for the majority of the region. However, the Liaohe Plain and Sanjiang Plain exhibit relatively higher degradation risks, making them key areas for future land protection and management efforts. These findings provide a clear basis for the regionalized and refined management of degradation risks in the black soil region, while also laying a foundation for the development of differentiated protection strategies.  
Overall, low-risk cultivated land is mainly concentrated in the SNP and WS, accounting for 38.55% of the total area. Lower-risk cultivated land is widely distributed, accounting for 40.64%. Moderate-risk cultivated land accounts for 17.14%, primarily located in the SNP, LHP, and SJP. Higher- and high-risk cultivated land makes up only 3.67%, primarily concentrated in the southern parts of the SJP and the SNP. The western regions, due to their arid climate and minimal human activity, exhibited lower degradation risks for cultivated land. In contrast, the eastern regions faced greater risks of soil erosion and nutrient loss due to higher precipitation and intensive agricultural activities.  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline  & **Very High (m2)** & **High (m2)** & **Moderate (m2)** & **Low (m2)** & **Very Low (m2)** \\ \hline Songnen Plain & 19 & 4467 & 14,844 & 35,982 & 64,812 \\ Sanjiang Plain & 0 & 7057 & 16,218 & 30,827 & 3321 \\ Changbai & & & & & \\ Mountain and & 0 & 1209 & 14,515 & 36,398 & 18,058 \\ Eastern Liaoning & & & & & \\ Liaohe Plain & 2 & 1283 & 18,548 & 15,507 & 6506 \\ Western Sandy & 2 & 35 & 752 & 30,302 & 31,875 \\ Daxing’an and & 0 & 5 & 610 & 6741 & 20,767 \\ Xiaoxing’anling & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 4: Proportion of degradation risk areas in the six types of areas.  
Figure 5: Spatial distribution and risk grade area proportion of cultivated land degradation risk in the BSNC. The location map represents the risk level faced by different regions, and the pie chart represents the proportion of areas with different risk levels. (**a**) represents the Songnen Plain, (**b**) represents the Sanjiang Plain, (**c**) represents the Changbai Mountain and Eastern Liaoning, (**d**) represents the Liaohe Plain, (**e**) represents Western Sandy, and (**f**) represents Daxing’an and Xiaoxing’anling.