Development of a Diagnostic Scale for Assessing the Vital State of Pine Stands under Conditions of Technogenic Pollution by Emissions from a Large Aluminum Smelter

Abstract

Over many years of research into assessing the condition of pine forests polluted by emissions from the Bratsk Aluminum Smelter (BAS), a large array of data of different sizes has been accumulated; when generalizing and structuring it, two groups of representative indicators are identified. The first group includes indicators characterizing with a high degree of reliability the state of assimilated phytomass and growth processes of polluted trees: the percentage of green needles in the tree crown, the mass of needles on the shoots, the total content of chlorophyll in the shoot needles, the ratio of protein and nonprotein nitrogen in the needles, and the value of the F_v/F_m ratio. The second group includes indicators reflecting the efficiency of the antioxidant system: the content of low molecular weight metabolites (proline, catechin, and total glutathione diketogulonic acid (DKGA)), as well as the activity of the peroxidase enzyme. Integral indices are calculated based on these parameters. Regression dependencies between indices and the level of accumulation of elements–pollutants in needles are used to develop scales for assessing the vital state (VS) of forest stands under conditions of technogenic pollution by emissions from a large aluminum smelter. Using this scale, it is possible to identify changes at the earliest stages, when external signs of tree weakening do not yet appear or are minimally expressed. A schematic map is made showing the distribution of pine forests of varying degrees of oppression. It has been established that the maximum deterioration in the condition of tree stands (more than 70%) is observed in local areas in the industrial zone of the BAS, strong deterioration (within 50–69%) is found in different directions from the plant at a distance of up to 10 km away, average (31–49%) is typical for tree stands at a distance of up to 40 km, and weak (11–30%) can be found at a distance of 40–60 (less often 80 km) from the BAS. In the rest of the surveyed territory, changes in the VS of pine stands are minimal, which allows the stands to be characterized as healthy (background).