Medium-scale historical maps are often the only cartographic source of former forest area distribution on a regional level. In conjunction with a database of the current distribution of species or functional traits, maps may be valuable tool for studying the impact of previous land use on ecosystems. In this study a heterogeneous set of historical maps was used to reconstruct the multi-temporal pattern of the forest area in a moderately forested region (5,180 km²) of southern Latvia during the last 220 years. Changes in the total forest cover were assessed in four time slices and compared with available historical statistical data. To validate the obtained multi-temporal data for ecological studies, the impact of continuous forest cover on the present-day mean stand area and tree species richness derived from the present-day forest inventory database of 94,886 stands was quantified by bivariate and regression analyses. We found no significant impact of inaccuracy of the historical maps on the entire forest continuity pattern of the study area. In particular, the diversity metrics dependencies on the forest continuity can be described by quadratic regression models with coefficients of determination close to one. We also found that the mean stand area is for about 18% larger in woodlands with longer forest continuity irrespective of the forest type. The older woodland the less difference was found between boreal deciduous and nemoral deciduous forests in terms of tree species richness.

Keywords: forest continuity, historical maps, mean stand area, nemoral deciduous forests, tree species richness, Zemgale.