# Temporal Changes in Land Use, Vegetation, and Productivity in Southwest China
## 3 Results
### The Characteristics of Inter-Annual Variation in NDVI  
From 2000 to 2019, the average NDVI of vegetation in the growing season in the whole study area showed an overall upward trend with fluctuations (slope = 0.0023 year\({}^{-1}\), \(p<0.01\)). The growing season average NDVI values of different land cover types all showed an increasing trend, but there were some differences. Among them, forest had the highest NDVI value, ranging from 0.79 to 0.84; cropland NDVI value ranged from 0.74 to 0.79; grassland vegetation NDVI varied from 0.70 to 0.73 (Figure 3b). The increase in the NDVI of forest was 0.0025 year\({}^{-1}\), and the trend of NDVI of cropland was 0.0023 year\({}^{-1}\), which was twice the increase in grassland (0.0011 year\({}^{-1}\)). \begin{table}
\begin{tabular}{c c c c} \hline
**2000–2019** & **Cropland** & **Forest** & **Grassland** \\ \hline Cropland & 264,799.33 & 61,318.48 & 3956.10 \\ Forest & 55,715.85 & 719,978.95 & 4073.26 \\ Grassland & 4231.28 & 10,948.30 & 166,551.06 \\ \hline \end{tabular}
\end{table} 
Table 1: Transformation matrix of land cover types from 2000 to 2019 (km\({}^{2}\)). Figure 2: Changes in area of different LULC types: (**a**) cropland, (**b**) forest, (**c**) grassland. (Note: the black solid line represents the trend line, and the formula of cropland is y = \(-0.707\)x + \(1759.78\); the formula of forest is y = \(1.04\)x \(-\) \(1294.51\); the formula of grassland is y = \(-0.64\)x + \(1469.68\)). The vegetation coverage in southwest China in 2000 was dominated by medium and high coverage, accounting for 87.05% of the regional area. In 2019, the vegetation coverage was dominated by highest and high coverage, accounting for 83.66% of the regional area. In terms of spatial distribution, there was a large heterogeneity in the level of surface cover (Figure 3a). The coverage situation in the southwest region showed that the area of lowest coverage, low coverage, medium coverage, and high coverage decreased, but the area of highest coverage increased. Overall, the degree of the greening of vegetation was strengthened. From 2000 to 2019, the area of highest coverage (0.85\(\sim\)1.0) increased from 10.52% to 34.37%, and the main change region was concentrated on the edge of the Sichuan Basin and the three provinces of Yunnan, Guizhou, and Guangxi, with the land cover being forest. The area of high coverage (0.75\(\sim\)0.85) decreased from 54.73% to 49.30%, mainly concentrated in the Sichuan Basin, the eastern Yunnan-Guizhou Plateau, and the northern hills of Guangxi, with the land cover being mainly cropland and forest. The area of medium coverage (0.55\(\sim\)0.75) decreased the most from 32.32% to 14.12%. The main change region was distributed in the Yunnan-Guizhou Plateau, with the cover area being mainly grassland and cropland. There was little change in the low coverage (0.35\(\sim\)0.55) and lowest coverage (0\(\sim\)0.35), which decreased from 2.70% to 2.21%, with the main type of cover being grassland, distributed in the northwest of Sichuan. The vegetation cover types remained unchanged at 48.66% of the total area, while vegetation cover improved to 45.60%. Figure 3: (**a**) Spatial distribution of NDVI in southwest China and (**b**) Changing trends in NDVI values from 2000 to 2019 for different land use types. From 2000 to 2019, the vegetation cover in southwest China mainly shifted from \"high coverage to highest coverage\" and \"medium coverage to high coverage and highest coverage\" (Table A1). The specific transfer amount was as follows: the area from high coverage to highest coverage was 311,870.61 km\({}^{2}\), accounting for 44.17% of the total change, and the area from medium coverage to high coverage was 259,673.48 km\({}^{2}\), accounting for 36.77% of the total change.