Epiphytic Lichenosynusia under Conditions of Chemical Pollution: Dose-Effect Dependencies

Abstract

Abstract -The dose-effect dependencies, which characterize response of the epiphytic lichenosynusia of southern taiga in the Middle Urals to pollution by discharges of a copper-smelting plant, are substantially nonlinear and, in most cases, have an S-shaped form. A transition from background to impact state is very sharp and begins when the background level of pollution is exceeded by 1.5 -2.3 times .. Epiphytic lichens are traditionally used as a subject for ecological monitoring and bioindicators of chemical pollution of the environment Most studies on using lichens as bioindicators were performed on the territory of cities and large industrial agglomerations. Natural habitats were much rarer. In the former case, the works include sufficiently big samples, making it possible to map the territory in detail. In the latter case, insufficient segmentation along the gradient of pollution (only "experiment," "control," and several intermediate sample areas) is a common defect. Such a scheme allows us to determine only general trends of changes and their range. Moreover, many important problems have not been considered. One of these problems is construction of the dose-effect dependencies, in which the amount of toxicants penetrating into an ecosystem is regarded as a dose, and parameters of condition of the lichenosynusia is an effect. These dependencies are necessary to understand how the lichen cover behaves under the stress of unfavorable factors and to determine the limits of stability of the lichens. In addition, the anthropogenic maximum tolerance load can be estimated by means of these dependencies. Many years ago, ecologists realized the importance of the dose-effect dependencies, which might be analogous with the dose curves (a basic element of classical toxicology) at the level of community and ecosystem THE REGION UNDER STUDY Our study was performed on the western slope of the Middle Urals in the southern taiga subzone. The discharges of a copper-smelting plant affected the studied area. By the time of our investigation, the plant had been functioning for 50 years. The following substances are the main pollutants: S0 2 and heavy metals (Cu, Pb, Cd, Zn, As, etc.). In previous work