Role of Environmental Heterogeneity in the Species Distribution of Vascular Plants in Periods of High and Low Emissions from a Copper Smelter

Environmental heterogeneity can significantly modify the rate of species extinction with an increase in anthropogenic load and the rate of recolonization of disturbed territories after a decrease in load, but this issue is poorly understood. The distribution of 14 species of the herb–dwarf shrub layer of forests on an area of 1734 km² in two natural regions of the eastern and western macroslope of the Urals during periods of high (1995–1998) and low (2014–2016) emissions from the Middle Ural Copper Smelter has been analyzed. With an increase or decrease in load, the pattern of dynamics and the magnitude responses are species-specific and significantly depend on habitat conditions, but the main contribution to the spaciotemporal dynamics of species affects the load level. During the period of high emissions, the environmental heterogeneity slows down the decrease in area of species distribution along a load gradient, but the distribution decreases under very heavy pollution, regardless of habitats or species. After the reduction of emissions, the distribution of most species in the heavily polluted areas has changed little for 19 years; the elimination and reduction in the distribution of the most sensitive species continues. Positive shifts have been revealed mainly in less polluted areas; the rates of recolonization vary in different habitats. Depending on habitat conditions, the species response to an increase or decrease in pressure can be “fast” (relatively high rates of change) or “slow” (lower rates of change and even a continued decline in distribution, despite reductions in pressure).