## 3 Results
### Accuracy of the PL-Based and the Other Five Forest Maps
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Forest Maps** & **Type** & **UA (\%)** & **PA (\%)** & **OA (\%)** & **Kappa** \\ \hline \multirow{2}{*}{FROM-GLC} & Forest & 81.26 & 71.52 & \multirow{2}{*}{87.96} & \multirow{2}{*}{0.68} \\  & Non-Forest & 90.02 & 93.40 & & \\ \multirow{2}{*}{GlobeLand30} & Forest & 78.62 & 71.22 & \multirow{2}{*}{87.47} & \multirow{2}{*}{0.66} \\  & Non-Forest & 90.20 & 93.19 & & \\ \multirow{2}{*}{GLCF-VCF} & Forest & 72.33 & 67.30 & & \\ \multirow{2}{*}{JAXA} & Non-Forest & 89.16 & 91.27 & \multirow{2}{*}{85.20} & \multirow{2}{*}{0.60} \\  & Forest & 59.01 & 67.28 & & \\ \multirow{2}{*}{OU-FDL} & Non-Forest & 91.15 & 87.82 & \multirow{2}{*}{83.57} & \multirow{2}{*}{0.52} \\  & Forest & 65.30 & 67.47 & & \\ \multirow{2}{*}{OU-FDL} & Non-Forest & 90.29 & 89.41 & & \\ \multirow{2}{*}{PALSAR/Landsat} & Forest & 91.07 & 76.41 & \multirow{2}{*}{91.27} & \multirow{2}{*}{0.77} \\  & Non-Forest & 91.33 & 97.07 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Accuracy comparison between PL-based forest map and existing five forest maps with 30–50 m resolutions. Figure 7: The spatial distribution map of the forest frequency in the Loess Plateau in 2010. The input forest maps were from the PALSAR/Landsat forest map, JAXA forest map, FROM-GLC forest map, and OU-FDL forest map, respectively. Specifically, the consistent forest between PALSAR/Landsat forest map and FROM-GLC forest map, JAXA forest map and OU-FDL forest map accounted for 10.48%, 7.33%, and 9.22% of the total pixels respectively, as well as 80.87%, 84.90%, and 84.37% of the consistent non-forest pixels (Figure 8). Compared to the PALSAR/Landsat forest map, JAXA forest map clearly underestimated forests in the Loess Plateau and overestimated the non-forest areas while the FROM-GLC forest map underestimated the forest areas in the Loess Plateau. Compared with the PALSAR/Landsat forest map, the JAXA forest map obviously underestimated the fragile forests in the Loess Plateau, and there were obvious omission errors in the forest areas  
Figure 8: Spatial comparison between the PALSAR/Landsat forest map and (**a**) FORM-GLC forest map, (**b**) JAXA forest map, and (**c**) OU-FDL forest map. (Figure 9a,d,g,j). The OU-FDL forest map improved the accuracy of forest area on the basis of JAXA forest map, but the accuracy of non-forest area decreased (Figure 9b,e,h,k). The FROM-GLC forest map underestimated the non-forest areas, resulting in high commission errors (Figure 9c,f,i,l). By comparing the accuracy of PL forest map with that of the other five forest maps, the PL forest map has a higher accuracy and consistency which lay a good foundation for the analysis of forest dynamic change monitoring in the Loess Plateau. Figure 10 showcases the forest changes on the Loess Plateau between 2007 and 2017. First, the grey part is the unchanged non-forest areas (Figure 10a), specifically, the non-forest areas in 2007 (Figure 10b) are still in the non-forest areas in 2017 (Figure 10c). Second, the green part means unchanged forest areas (Figure 10d) from 2007 (Figure 10e) to 2017 (Figure 10f). Third, the blue part means the conversion from the non-forest areas to the forest areas where the main change areas are in the black and red circles (Figure 10g), the two major areas have changed from forests in 2007 (Figure 10h) to urban lands in 2017 (Figure 10i). Fourth, the red parts are related to the conversion from the non-forest areas to the forest areas where the main change areas are concentrated in yellow, red, and black circles (Figure 10j), these three major areas have changed from desert areas in 2007 (Figure 10k) to the forests (Figure 10l) in 2017. Figure 9: Zoom-in windows of the spatial comparison between the PALSAR/Landsat forest map and FROM-GLC forest map (**a**,**d**,**g**,**i**); OU-FDL forest map (**b**,**e**,**h**,**k**); and JAXA forest map (**c**,**f**,**i**,l**) in 2010.