The following paper represents results from a research focused on the soil associations and their corresponding vegetation communities (soil-plant catenas), located on the northern slopes (N, NW, NE) of the Rila Mountains. Data from eight key sites located between 815 and 2041 m above sea level is discussed. The slope in each site varies from 2° to 25°, and most often the tests and descriptions were carried out on sites with a slope of 10-15°. Vegetation cover is analyzed with plant community plots which provides data on species composition, abundance and coverage. The size of each plot varies from 16 up to 225 m2 depending on the vegetation type. Topsoil horizons were tested in each site in order to diagnose the subspecies diversity of brown forest soils (Cambisols) using ratio of humic acids to fulvic acids. That ratio varies from 0,69 up to 1,61 in all studied sites. Both acids are associated with the dominance of different vegetation types – deciduous, mixed or coniferous forest or herbaceous canopy. The results are interrupted in terms of the diagnosis and classification of Cambisols and Umbrosols in the area of interest. Differences in soil and vegetation cover of Northwest and Eastern Rila Mountain are highlighted and analyzed.

The present study deals with the investigation of soil organic carbon in two water catchments in Northern Rila, Western Bulgaria. Field research, combined with analysis, provided sufficient data. Six key sites were selected and sampled in order to estimate and compare the amount of organic and inorganic carbon in the topsoil. The applied criteria for the choice of sites included: vegetation cover, predominant soil group, level of anthropogenization and transport accessibility. A total number of 13 samples from both catchments were collected and analyzed in the Central laboratory of the Institute of Soil Science, Agrotechnologies and Plant Protection (ISSAPP) “N. Pushkarov“. The results concern the amount and composition of soil organic matter in different soils – Cambisols (Albic, Humic, Dystric), Fluvisols and Umbrosols. The total carbon content of all samples varies between 1.23 and 9.69%. The amount of organic carbon ranges between 0.45 and 3.73%. The results of the study prove once again that the preservation of natural vegetation and current condition of the soil is of great importance for carbon sequestration and climate change mitigation.

The current study investigates the development of the land cover in the mountainous territory of Mala Planina, located in the western part of Stara Planina. It focuses on cameral and terrain research in which basis is the CORINE Land Cover (CLC), initiated by the European Union. All existing databases for the country were applied (CLC 1990, 2000, 2006 and 2012). Each updated version of the CLC data shows typical transformation in Mala Planina’s land cover. A thorough investigation is made about all parts of the mountain and published within the results. Four GIS derived maps are published. The results show that the most significant dissonance occurs between CLC 1990 and the rest CORINE Land Cover data sets (CLC 2000; 2006; 2012) and the reason for the imparity lies mainly in the extensive timeframe. Almost no distinction is observed, when we compare CLC 2006 and 2012. The most common changes are connected with the transition to land principally occupied by agriculture, with significant areas of natural vegetation, which is explained by the decreasing number of population and abandonment of the agricultural areas.

The current study aims at revealing the forest habitat diversity of Godech Municipality, according to the EUNIS habitat classification. Initial data was collected from the Ministry of Environment and Water and the Forestry Management Plans. Subsequently, 418 vegetation plots (relevés) and 3422 verification points were collected during the fieldwork seasons of 2019 and 2020. The research territory is situated in Western Bulgaria in close proximity to the country’s border with the Republic of Serbia. Forests cover a total of 144.85 km2. Their phytocoenoses are dominated by Fagus sylvatica L. (59.22 km2), Quercus cerris L. (14.85 km2), Carpinus betulus L. (4.94 km2), Quercus dalechampii Ten. (2.39 km2), Q. frainetto Ten. (2.99 km2). There are plantations with Pinus nigra J. F. Arnold (20.87 km2), P. sylvestris L. (16.06 km2) and Picea abies H. Karst (11.65 km2) also. Forests are experiencing some major threats, such as logging, pollution and fires.