## 4 Results Analysis  
### Temporal Change Characteristics of Land-Use Changes (LUCs)  
From Figure 2 and Table 4, forest land areas made up the majority of the land, accounting for more than half of the total land area at each of the three time points analyzed. Cultivated land (CL) followed as the second-largest type, covering an area exceeding 1000 km\({}^{2}\). The average proportion of CL to the total area across the three-time nodes reached 28.80%. This indicates that the land-use structure of Putian City over the past two decades has primarily centered on agricultural and forestry production. Nevertheless, the areas of CL, forest land (FL), and grassland (GL) experienced declines during this period, while orchard land (OL), water bodies (WB), built-up land (BL), and unused land (UL) witnessed increases. Notably, CL experienced the most substantial decline among all land types, exhibiting a continuous downward trajectory from 1261.15 km\({}^{2}\) in 2000 to 1003.29 km\({}^{2}\) in 2020, representing a decrease of 20.45%. Among all land types, FL exhibited the smallest area reduction over the past 20 years, with a decrease of 24.79 km\({}^{2}\). The GL area experienced a notable decline from 2000 to 2010, with a reduction area of 45.44 km\({}^{2}\) and an average annual reduction rate of 0.09%; however, from 2010 to 2020, there was a minor expansion of 2.67 km\({}^{2}\). As for OL, its area started at 12.76 km\({}^{2}\) in 2000 and saw a growth of 50.86% over twenty years, culminating in an area of 19.25 km\({}^{2}\). This increase is largely due to the favorable climate of Putian City, situated in the mid-subtropics, which supports the cultivation of local fruit species like longan, lychee, loquat, graprefruit, and olive. The local government has been proactively encouraging the development of this category of agriculture. The area of BL has seen a substantial expansion, from 109.15 km\({}^{2}\) in 2000, which constituted 2.78% of the total area, to 335.65 km\({}^{2}\) in 2020. This represents a more than twofold increase and is the most significant growth among all land-use types. Additionally, the area of WB has shown a steady increase, which can be credited to Putian City's initiatives in advancing river ecological management and the ecological restoration and management project of the Mulan River, both of which have led to notable achievements. Figure 2: Land-use structure in Putian City during 2000–2020. Sources: Drawings from this study. The variation in the land-use dynamic degree can also be utilized as an indicator to assess changes in the land-use structure within a defined timeframe from an alternative perspective. As shown in Table 4, the average land-use dynamic degree values for the intervals between 2000 and 2010, and between 2010 and 2020, were 21.96% and 8.17%, respectively. This indicates ongoing LUCs in Pution City for the past two decades. The rate of LUCs from 2000 to 2020 reached 19.09%, reflecting a substantial human impact on the city's LUCs. From 2000 to 2020, the dynamic degrees of cultivated land, forest land, and grassland were \(-\)1.02%, \(-\)0.06%, and \(-\)0.69%, respectively, indicating a downward trend in the area of these land types. In contrast, the WB's change rate was 0.49%, indicating a gradual expansion. OL showed a more rapid increase, with a change rate of 2.55%. The BL had the highest change rate at 10.37%, while the UL had the second-highest rate at 7.44%, both indicating a quickened pace of expansion. From the distribution results of land use (Figure 2), distinct patterns of LUCs were observed across the city's spatial distribution. Starting from the urban core and extending to the outskirts, the primary types of land shifted from urban areas to agricultural and forested regions, among others. CL was notably dense in the southeastern Xiuyu District and the southwestern Xianyou County of Potian City. Conversely, FL was mainly distributed in Hanjiang District in the northeast and Xianyou County in the northwest.