2.2.1. Historical Map

The horizontal axis Mercator projection and the U.S. Hayford ellipsoid were applied in 1990 to the military topographic map from China drawn by the Army Map Service of the U.S. Army Corps of Engineers during World War II. The map was drawn based on the supergraph of the topographic map that was investigated and drawn by Japan during the height of its military aggression in 1942. This map reflects the situation in 1944. It was revised in 1945 and published in 1954. This map can be freely obtained from the website of the University of Texas libraries (http://www.lib.utexas.edu/maps/ams/) (accessed on 12 November 2021).

#### 2.2.2. Remote Sensing Images

The period was from 1977 to 2013, with a total of five periods. Data from each period were obtained from the University of Maryland (http://glcf.umiacs.umd.edu/ data/landsat/) (accessed on 18 December 2020), and the data sharing plan for Earth observation was obtained from the website of the Chinese Academy of Sciences (http: //ids.ceode.ac.cn/query.html) (accessed on 18 December 2020). The latter included the following images: Landsat Multispectral Scanner in 1977; Landsat with Thematic Mapper (TM) in 1986, 2000, and 2007; Landsat with Enhanced TM Plus in 2013. To guarantee data accuracy, the seasons of the images that are used are consistent.

#### Other data.

Digital elevation model (DEM) data with a resolution of 90 m were obtained from the International Scientific Data Service platform (http://datamirror.csdb.cn/) (accessed on 18 December 2020). Lithological spatial distribution and soil type data were gathered from the preliminary study materials of the project group [8,28].

#### 2.2.3. For the Historical Military Map

The original historical military map was scanned, the boundaries were cut, and a seamless splice was created using Adobe Photoshop. The resulting map was then combined with a civilian topographic map to conduct overall scanning or accuracy check of the original historical military map (Figure 2). The contents for examination include the karst cave and its size and location, the morphological characteristics of the mountains, the trend of rivers, and the quantity and form of depressions. If the aforementioned features on the historical military map correspond with those on the civilian topographic map, then the historical military map is accurate and the preliminary scanning is acceptable. The location and distribution of the forest were then examined when the preliminary scanning was acceptable. If the preliminary scanning was not acceptable, then the causes of inconsistencies should be examined. If the scanning failed again, then the historical military map might be inaccurate and should thus be abandoned. During the examination of forest location and distribution, local chronicles, local history, agricultural literature, medical materials, military climate graphs, military hydrographs, military environmental diagrams, military installation diagrams, and analysis diagrams of the combat capacity of war zones should be used as references to achieve a comprehensive analysis. If the findings passed the examination, then the historical military map satisfied the research requirements. The historical military map was then cut according to the size of the study area, and digitization and vectorization were implemented to generate a preliminary diagram of forest distribution. In the statistical calculation of the area and sample inspection, an accuracy rate not lower than 95% should be guaranteed. A diagram of forest distribution during wartime could then be generated. A vector diagram of the spatial distribution of forest cover was obtained to establish the spatial and attribute databases of the forest pattern in the study area in 1944 (Figure 3a). The procedure should be repeated if the accuracy rate could not be guaranteed because of problems during digitization and vectorization.

**Figure 2.** The technique flowchart showing the study of spatial patterns of forest landscape based on the military map and remote sensing images. (We constructed this figure using WPS office (https://platform.wps.cn/) (accessed on 29 November 2021)).

**Figure 3.** The military map and remote sensing images in different times. (We constructed this map using ArcGIS9.3 (http://www.esri.com/arcgis/about-arcgis) (accessed on 19 December 2021)).

#### 2.2.4. For the Remote Sensing Images

All Landsat images applied near-infrared, red light, and green light wave bands to perform standard false color composition. Radiation correction was performed to achieve spectrum enhancement, radiation enhancement, and geometric precision correction for fiveperiod images under ERDAS IMAGINE environment. The geometric precision correction was performed to scan and input a 1:50,000 topographic map into the computer to conduct projection disposal. This map was used as the main control data source to correct remote sensing images, and the average position error was controlled within a pixel. Field type samples were selected to perform visual interpretation under man–machine interaction, and then the supervised classification was applied. The obtained data were combined with DEM, weather, hydrological, vegetation, soil, land-use change, forest monitoring, and the corresponding social statistics data of the study area to check and amend the forest distribution diagram, establish the forest spatial and attribute databases in the study area beginning in 1977, and generate a vector diagram of spatial distribution information of the forest cover for the following periods: 1977, 1986, 2000, 2007, and 2013 (Figure 3b–f, respectively).
