## 3 Results Analysis
### Tupu Analysis of Land-Use Transitions (LUTs)  
#### 3.2.1 Tupu Analysis of LUTs from 2000 to 2010  
In the analysis of LUTs using the Tupu method in Ningde City from 2000 to 2010, a total of 49 types of Tupu units were identified, with 27 undergoing changes, encompassing a combined area of 318.73 km\({}^{2}\) (Table 4). The spatial distribution of Tupu units exhibited notable disparities during the aforementioned period (Figure 4a).  
As can be seen from Table 4 and Figure 4a, the conversion area of cultivated land was 210.42 km\({}^{2}\), of which 37.61% was converted to forest land (79.15 km\({}^{2}\), code 12), 28.97% to water bodies (60.97 km\({}^{2}\), code 15), 21.6% to grassland (45.45 km\({}^{2}\), code 14), and 8.81% to  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Code** & **Number of Tupu Units** & **Area/km\({}^{2}\)** & **Change Ratio/\%** \\ \hline
12 & 87,939 & 79.15 & 24.83 \\
15 & 67,744 & 60.97 & 19.13 \\
14 & 50,503 & 45.45 & 14.26 \\
21 & 46,397 & 41.76 & 13.10 \\
24 & 32,700 & 29.43 & 9.23 \\
16 & 20,603 & 18.54 & 5.82 \\
23 & 13,541 & 12.19 & 3.82 \\
26 & 9939 & 8.95 & 2.81 \\
17 & 4865 & 4.38 & 1.37 \\
27 & 3005 & 2.70 & 0.85 \\ \hline \hline \end{tabular} Note: Code 1–7 represent cultivated land, forest land, orchard land, grassland, water bodies, built-up land, and unutilized land, respectively. For example, Code 12 means the transition of cultivated land to forest land. Code 26 signifies the transition of forest land to built-up land. The rest of the code follows the same rules.  
\end{table}
Table 4: Tupu units of LUTs during 2000–2010 in Ningde City (Top 10).  
Figure 4: Tupu patterns of LUTs in Ningde City during 2000–2020.  
built-up land (9.22 km\({}^{2}\), code 16); the transferred area of cultivated land was 43.59 km\({}^{2}\), of which 95.79% came from forest land (41.76 km\({}^{2}\), code 21) and 3.33% from grassland (1.45 km\({}^{2}\), code 41). Moreover, the area of forest land transfer was 96.98 km\({}^{2}\), of which 43.06% was converted to cultivated land (41.76 km\({}^{2}\), code 21) and 30.35% was converted to grassland (29.43 km\({}^{2}\), code 24); the area of forest land transferred was 81.60 km\({}^{2}\), mainly from cultivated land (code 12) and orchard land (code 32). Furthermore, the most obvious changes in Tupu units were \"cultivated land \(\rightarrow\) forest land\" (code 21), \"cultivated land \(\rightarrow\) water bodies\" (code 15), \"cultivated land \(\rightarrow\) grassland\" (code 14), and \"forest land \(\rightarrow\) cultivated land\" (code 21), accounting for 24.83%, 19.13%, 14.26%, and 13.10% of the total land-use types that were converted, respectively. In addition, the Tupu units \"forest land \(\rightarrow\) grassland\" (code 24) and \"cultivated land \(\rightarrow\) built-up land\" (code 16) were noteworthy, accounting for 9.23% and 5.82%, respectively. In short, the amount of cultivated land transfer was the largest type of all types of land, the cultivated land that has changed is scattered throughout Ningde City, mainly converted to built-up land in the main urban area, and converted to forest land and grassland in areas such as Fuding and Gutian Counties.