Ecological condition of natural forests located within the territory of a large industrial center, Eastern Siberia, Russia

Forest surveys were conducted in 2015–2018 on 12 sample plots (SPs), located in different districts of the city of Bratsk, a large industrial center of Eastern Siberia. The ecological state of natural forests preserved within the city’s territory was estimated by a set parameters of pine ( Pinus sylvestris L.) trees, understory vegetation, moss-and-lichen cover, and soil. Significant changes in the parameters caused by technogenic pollution and a high recreational load on the soil cover have been revealed. The high level of technogenic pollution of urban forests is evidenced by the accumulation of pollutants (sulfur, heavy metals, PAH) in the needles of pine trees and soil horizons, changes in the ratios of elements-pollutants and elements-nutrients in plants and soils, shift in the acid-base balance of the soil solution to alkalinity. A high recreational load on urban forest soils is indicated by many negative changes: a decrease in the thickness of the forest litter or its complete destruction; violation of the natural structure of the upper horizons due to increase in physical clay content, stony content, and anthropogenic inclusions; significant increase in soil density, and decrease in humidity, porosity, and aeration. The impact of a complex of negative factors also leads to a decrease in the species diversity of the understory vegetation, mosses, lichens, and an increase in the number of ruderal species in the herbaceous vegetation. The biggest negative changes in the parameters of forest ecosystems have been found in Tsentralny district of the city, located in close proximity (from 2 to 8 km) to a large aluminum smelter and timber industry complex. Less-pronounced negative changes in parameters were found in samples taken in the Padunsky district, located 25 km from the emission source, and the smallest changes in the parameters were found in Pravoberezhny district, 45 km away from the emission sources. The main recommendations for improving the condition of forests in all areas of the city are as follows: planning a road-path network, restoring the fertile soil layer, sodding open areas of soil with herbaceous vegetation, and selecting an assortment of trees and shrub plants that are resistant to industrial pollution and recreational stress.