*3.1. Spatio-Temporal Patterns of Forest Change in Guizhou Province*

#### 3.1.1. Forest Transition

Forest transition describes the range of forest change, from shrinking to expansion [62,63]. According to Table 3, forests were the largest land-use type (53%) from 1980 to 2018 and, while their distribution remained relatively stable, some increases over time were evident (Figure 3a: Forest change in Guizhou Province). Notably, the forest cover reached its lowest value in 2000. In terms of the forest subtypes, Table 4 shows that the greatest increase was in the category 'forest land' (i.e., forests with greater biomass and substantial tree-canopy cover).

**Figure 3.** (**a**) Forest changes in Guizhou Province. (**b**) Average forest cover in nine municipalities.


**Table 3.** Guizhou land-use changes from 1980 to 2018.

**Table 4.** Forest subtypes in Guizhou from 1980 to 2018 (km2).


#### 3.1.2. Spatial Changes

The distribution of the forest area in Guizhou is uneven, decreasing from east to west. Figure 3b shows the mean annual proportion of total forest cover in the province's nine major municipalities from 1980 to 2018. Qiandongnan, in the southeast, and Zunyi, in the north, have the greatest forest cover, accounting for 40% of the overall total, followed by Qiannan (south), Bijie (northwest), Tongren (northeast), and Qianxinan (southwest) with 15%, 12%, 11%, and 9%, respectively. Liupanshui (west), Anshun (next to Liupanshui), and Guiyang (central) have the lowest forest cover.

Based on temporal changes over the last 40 years, Figure 4 and Table 5 suggest that the forest cover was either maintained or increased, with the exception of Tongren, Qiannan, Qianxinan, and Anshun, all of which experienced some degree of forest loss. Qiandongnan experienced the greatest degree of forest increase, with 478 km2 (2.6%), followed by Bijie and Guiyang, with increases of 202 km<sup>2</sup> (2.5%) and 138 km<sup>2</sup> (3.6%), respectively. Zunyi and Liupanshui both experienced only very limited increases in forest area (34 km2 and 14 km2, respectively).

**Table 5.** Forest changes from 1980 to 2018 in nine municipalities (km2).


**Figure 4.** Spatial pattern of forest changes in nine municipalities.

*3.2. Possible Drivers of Forest Change*

#### 3.2.1. Land-Use Change

Although the overall forest increase during the study period was relatively small across the province as a whole, in very substantial areas, forests replaced agriculture. Figure 5 demonstrates that forests replacing cropland happened in all nine municipalities in Guizhou Province, which is attributable largely to the implementation of the Grain for Green (GFG) project. Indeed, 36% of the cropland was converted into forests, which is significantly higher than the equivalent values for the grassland and construction land. With respect to individual municipalities, 47% of the farmland was converted into forests in Qiandongnan, followed by Zunyi, Qiannan, and Tongren, where 40%, 39%, and 37% of the land, respectively, was converted from agricultural land. Bijie had the smallest portion of cropland converted into forest land (29%).

The implementation of the Grain for Green program accounts for a considerable, and indeed increasing, proportion of the total forest changes in Guizhou (Figure 6). Prior to the implementation of this policy in Guizhou in 2000, the forest cover was largely unchanged. For instance, the forest area increased by only 109 km2 from 1980 to 1990, which was much less than the change during the periods of 1990–2000, 2000–2010, and 2010–2018 (see Figure 3a) and, indeed, the forest cover actually decreased across the province in 2000. In Figure 6, it can be seen that, in 2018, 17% of the cropland was converted into forests in Guizhou. Given that Guizhou is located in the upper and middle reaches of the Yangtze and Pearl Rivers, the forest-cover change has also been brought about by the implementation of two of China's eight major shelterbelt projects (the Shelterbelt Program for Upper and Middle Reaches of the Yangtze River, 1989 and the Shelterbelt Program for the Pearl River, 1996).

**Figure 5.** Percentages of other land-use types converted into forests in Guizhou and its nine major municipalities 1980–2018. Ei (i = 1, 2, 3, 4) denotes the area of the i category of land in 2018, which transformed from the j category of land in 1980; Vj (j = 1, 2, 3, 4) represents the area of the j class of land in 1980, which converted into the i class of land in 2018; 1 = grassland, 2 = construction land, 3 = cropland, 4 = forest. Red arrows indicate percentages of i-type land in 1980 converted into forests by 2018.

**Figure 6.** Percentages of four major land use types converting into forests in Guizhou: 1980 to 2018.

#### 3.2.2. Population Effects

Figure 7a indicates that the population densities are generally higher in the western part of the province and this, in effect, reflects the forest distribution. At a very basic level, therefore, population density influences forest disturbance or clearance, a relationship that is further illustrated through the correlation analysis in Table 6.

**Figure 7.** Drivers of forest change. (**a**) Population density in 2015 (people per km2). (**b**) Distribution of GDP in 2015 (RMB 10,000/km2). (**c**) Accessibility and forest area. (**d**) Karstification intensity. (**e**) Spatial distribution of drought index. (**f**) Slope in 2009.


**Table 6.** Correlations between and multiple GLM analyses of the relationships between forest areas and factors.

\* *p* < 0.05, \*\* *p* < 0.01; SS, proportion of variances explained by the variable.
