## 3 Results and Analysis  
### Evaluation Results of Cultivated Land Quality Based on Cultivated Land Function  
The evaluation results of cultivated land quality based on the cultivated land function in the BSNC demonstrate excellence across multiple dimensions, with the incorporation of specific area data providing additional clarity. From the northwest to the southeast, the primary productivity (PP) function of cultivated land exhibits an increasing trend (Figure 3a), with over 97.40% of the land classified as Grade 3 or higher, indicating significant agricultural production potential. Specifically, the area classified as Grade 3 is 131,200 m\({}^{2}\), Grade 2 is 231,401 m\({}^{2}\), and Grade 1 is 7838 m\({}^{2}\), reflecting regional variations in PP (Table 3), such as the predominance of Grade 1 and Grade 2 land in the LHP and CBMEL, where they account for 99.6% and 93.8% of the total area, respectively. The soil nutrients and maintenance (SNM) function gradually weakens from northeast to southwest (Figure 3b), with 372,259 m\({}^{2}\) of land rated as Grade 3, 339,022 m\({}^{2}\) as Grade 2, and 3104 m \begin{table}
\begin{tabular}{c c c} \hline \hline
**Cultivated Land Function** & **Indicator** & **Weight** \\ \hline \multirow{3}{*}{Primary productivity} & Accumulated temperature & 0.1098 \\ \cline{2-3}  & Average annual & \\  & precipitation & 0.1258 \\ \cline{2-3}  & Altitude & 0.0867 \\ \hline Soil nutrients and & Soil texture & 0.1621 \\ maintenance & Soil organic matter & 0.0706 \\ \hline \multirow{6}{*}{Infrastructure Regulation} & Effective soil depth & 0.1086 \\ \cline{2-3}  & Irrigation capacity & 0.0489 \\ \cline{2-3}  & Drainage capacity & 0.0768 \\ \cline{2-3}  & Field shelterbelt ratio & 0.0789 \\ \hline Biodiversity supply & Soil biodiversity level & 0.0630 \\ \hline Resource utilization & Per-acre production cost & 0.0688 \\ efficiency & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Weights of cultivated land function indicators. as Grade 1, demonstrating overall good soil quality, particularly in regions such as the SJP, where all cultivated land is classified as high grade. The infrastructure regulation (IR) function is most pronounced in CBMEL (Figure 3c), where 181,925 m\({}^{2}\) of land is categorized as Grade 3, 184,377 m\({}^{2}\) as Grade 2, and 12,321 m\({}^{2}\) as Grade 1. The biodiversity supply (BS) function, however, is the weakest among all, with 41,649 m\({}^{2}\) and 153,280 m\({}^{2}\) of land classified as Grades 5 and 4, respectively, while only 13,488 m\({}^{2}\) falls into Grade 1, highlighting significant constraints in biodiversity support. Resource utilization efficiency (RUE) also shows considerable variation (Figure 3e), with 32,868 m\({}^{2}\) and 15,586 m\({}^{2}\) of land categorized as Grades 5 and 4, respectively, while land classified as Grades 1 and 2, comprising 157,301 m\({}^{2}\) and 123,630 m\({}^{2}\), respectively, is concentrated in regions such as DXXXL and SJP, demonstrating advantages in cost-effectiveness and resource use efficiency. Overall, the cultivated land function in the BSNC performs well, with Grade 2 and Grade 3 land accounting for 59.27% and 40.73% of the total area, respectively, reflecting a balanced approach to agricultural productivity and land use efficiency within the study region (Figure 3f). Figure 3: Spatial distribution and area proportion of cultivated land function in the BSNC. (**a**) For primary productivity function; (**b**) for soil nutrients and maintenance function; (**c**) for infrastructure regulation function; (**d**) for biodiversity supply function; (**e**) for resource utilization efficiency function; and (**f**) for cultivated land function. As shown in Figure 4, the scores for comprehensive cultivated land function and SNM function in most areas range from 0.6 to 0.8. In contrast, the BS function is generally weaker. The cultivated land function of the LHP is the most balanced, with most function indices ranging from 0.6 to 0.8.