Indication of the State of Natural Forests Preserved within a Large City
摘要
The state of urban forests of natural origin, which is the most important component when improving the ecological environment of a large city (Irkutsk, Eastern Siberia), has been studied. The condition of forests was assessed based on a set of parameters of trees, soil, and herbaceous cover. The impact of aerotechnogenic pollution on forests is shown; it is determined by the accumulation of heavy metals (HMs) in the assimilation organs of forest-forming species (Pinus sylvestris, Larix sibirica, Betula pendula) and horizons of soil profiles, as well as by the quantity of suspended particles of solid aerosol (Particulate Matter, PMx) adsorbed by needles and leaves. The degree of recreational load in urban forests is judged by the violation of the morphological, physical, and pedochemical properties of the forest litter and upper soil horizons. A number of negative changes in the parameters of trees have been identified—the defoliation level of crowns can reach 50–65%; the photosynthetic volume of the crowns decreases more than 2 times; photosynthesis productivity decreases (maximum) by 35–48% compared to the background; and other physiological and biochemical parameters of pine, larch, and birch also change. The herbaceous cover in the forests is sparse, the projective cover averages 60%, and the share of ruderal species averages 44%. Negative processes were also found in the soil—the destruction of forest litter, decrease in aeration and moisture content, violation of acid-base, cation exchange, and humification properties. The results indicate that most of the surveyed urban forests are polluted and subjected to recreational pressure. When summarizing the data obtained from field and laboratory studies, a complex of correlating highly sensitive indicators characterizing the state of urban forest biogeocenoses is identified.