## 2 Materials and Methods
### Research Methods  
The use of historical GIS allows us to study and analyze the data obtained from different sources, make them available for research, comprehensively examine both mapped forest cover areas and those obtained from other sources, model surfaces based on LIDAR data, and perform complex data analysis; it also allows for the data to be converted into a unified coordinate system. A schematic representation of the methodological approach is illustrated in Figure 5 below. Figure 5: Overall methodology adopted in this study. ArcGIS Desktop software was used for the study. Cartographic and thematic layers installed in ArcMap are as follows: digital copies of old maps, CORINE land covers, forest cadastral databases, and LIDAR data. A problem was encountered after uploading digital technology maps of the 2 nd half of the 19 th century and the 1 st half of the 20 th century--they are not oriented in space. Old, unchanged objects in the area are visually identified for orientation--churches, railway junctions, etc. The history of these objects has been studied. After the spatial constancy of the objects was verified (there were objects burned during the war or moved to other structures; they were eliminated from the list of objects suitable for orientation), their coordinates were determined and the coordination of map sheets was carried out according to these objects in the GIS program. Maps of the 2 nd half of the 20 th century were downloaded and coordinated in the LKS 94 coordinate system. After installing the layers of cartographic material, a geodatabase of forest cover areas was created. The polygon vectorization method was used for this. The maps were vectorized manually due to the poor quality of the cartographic material and to avoid the influence of automatic vectorization errors. This is especially relevant for maps of the 19 th century (Table 1). They are black and white, the image resolution of the available copies is not good, the borders of the objects are partially blurred, and the forests are represented by circles of different sizes filled with conventional signs. The terrain in these maps is represented by a criss-crossed pattern, drawn on the conventional forest marks. The combination of all these factors makes the application of automatic digitization methods very complicated. The cadastral database has been adjusted. Forest cadastral data were uploaded into the GIS program as a layer, and after uploading the orthophoto image layer, a visual analysis of the cadastral plots divided into ranges according to the age of the trees was performed. It was established that a relatively large share of the data does not correspond to the actual situation. In order to conduct a more accurate study (a number of land plots were identified where the forest had already been cut down and the data had not been updated), a visual inspection of all 41,289 land plots was performed to compare them with the image seen in the orthophoto. It was impossible to visually estimate the age of the replanted forest with an accuracy of one year from the orthophoto images, but it can be seen that it consists of seedlings no older than 5 years. The age of the trees indicated in the cadastral database has been adjusted to 1 year for all such land plots. These land plots fall into range I according to the age of the trees (see below) where there is no forest cover or the age of the trees is no older than 5 years. The land plots are divided into 9 groups according to the age of the dominant trees. Parentheses contain the years in which the trees started to grow/were planted:  
1. 0-5 years (2017/2022),
2. 6-9 years (2013/2016),
3. 10-19 years (2003/2012),
4. 20-39 years (1983/2002),
5. 40-59 years (1963/1982),
6. 60-79 years (1943/1962),
7. 80-99 years (1923/1942),
8. 100-120 years (1922/1902),
9. 125 years old and more (1897 and more). All studied groups cover an interval of 20 years. Only groups I, II, III, and IX are distinguished: I and II--6 and 4, III--9-year intervals.