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We analyzed the spatial distribution and temporal dynamics of 1083 forest fires within the Ilmensky Reserve (Southern Urals, Russia) over 1948–2014. We observed a significant increase in the number of forest fires over the studied period, with the locations of the most frequently burned sections of the reserve changing over time. The average number of fires over the whole period increased by a factor of 1.9; there were 0.41 fires per compartment per 10 years in 1948–1970, there were 0.58 fires per compartment per 10 years in 1971–1990, and there were 0.77 fires per compartment per 10 years in 1991–2014. In parallel, the spatial pattern of ignitions became more aggregated. The fire frequency increased across the reserve, with the most pronounced change being observed along the reserve borders. Human-related fires dominate the modern fire activity within the Ilmensky Reserve, which is modulated by the local conditions.

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Variations of stable carbon (13С and 12С) and nitrogen (15N and 14N) isotopic composition are analyzed in forest plants subjected to the emissions of large copper smelting plant. The studies were carried out in pine forests at ten test plots near the Karabash copper smelting plant and in the Ilmen State Reserve at South Urals. The 13С/12С and 15N/14N isotopic ratios were analyzed in leaves of plants of different functional groups (with ecto-, ericoid, or arbuscular mycorrhiza; with nitrogen-fixing symbiosis, and non-mycorrhizal). The 13С/12С ratio did not change under technogenic pollution. The low isotopic 15N/14N ratio was established in ectomycorrhizal trees, while the high ratio was found in herbs with arbuscular mycorrhiza, nitrogenfixing symbiosis, and non-mycorrhizal groups. As compared to nonpolluted habitats, the 15N content in leaves near the copper smelting plant increases by 2.7‰ in the ectomycorrhizal trees and by 3.4‰ in undershrubs with ericoid mycorrhiza, and by 2.2‰ in herbs with arbuscular mycorrhiza. This indicates a significant change in conditions of mineral feeding of plants under heavy metal pollution of natural ecosystems.