In the summer of 2010, about half of the Kerzhensky State Nature Biosphere Reserve territory (total area is 467.9 km 2) suffered from a wildfire. During the seven following years, monitoring of the terrestrial vertebrate populations was conducted there. In total, six amphibian species, six reptile species, 142 bird species, and 20 small mammal species were registered. The particular wildfire impact on different vertebrate species was dissimilar. In the first year after the wildfire impact, bird populations in the habitats affected by different wildfire types were similar according to the Sorensen-Chekanovsky's index. This similarity increased over time. The species richness changed in different directions. At first study years, the abundance of the nesting bird populations increased both in burnt and unburnt sites, while later this parameter decreased a bit and stabilised. The bird populations of the unburnt habitats differ by lower indicators for the last five years. We distinguished the species (e.g. Sylvia communis) recognised as indicators of damaging by fire. These are birds which became abundant in the burnt forest, but were very rarely dominant and less abundant in unburnt forest. Fringilla coelebs was dominant in all habitats studied. For the small mammal communities, the wildfire influence affected a decrease (by 2-3 times) in the abundance and biodiversity indexes, and a change of dominants (from Clethrionomys glareolus to Apodemus flavicollis). ANOVA showed that the fires with a high degree of reliability (0.445; р-level < 1) had a higher impact on the small mammal communities. In amphibians and reptiles, the wildfire caused only a decrease in abundance followed by subsequent recovery without changes in community composition. The most intense postfire changes in terrestrial vertebrate (Tetrapoda) populations were observed within the first five post-fire years. The amphibian and the reptile populations recovered after three post-fire years, while the recovery of bird and small mammal communities noted 4-5 years after the fire.

The purpose of our study is to consider the possibilities of using different approaches to recognize the significance of the territory for the biodiversity conservation. The Ichalkovsky nature reserve (zakaznik) with an area of 1,442 hectares in the Nizhny Novgorod region was selected for analysis as a botanical and geological object unique for the Russian Plain. The criterion of various rare wildlife species records was used as a leading approach. Analysis of published materials and field research in 2020 allowed us to identify in the studied territory the habitat of 88 wildlife species listed in the Red Data Books of Russia and the Nizhny Novgorod Region. They are very different concerning their taxonomy and biology. This criterion use shows the extremely high conservation value of the Ichalkovsky reserve. The territory under consideration is characterized by high biological diversity and a high degree of biota remained, as well as its weak human disturbance. It is shown that, in accordance with the approaches of international nature conservation programs, the Ichalkovsky reserve has the status of a territory of special nature conservation significance within the Emerald Network of Russia, as well as an Important Bird Area. This territory is the core of the environmental framework of European Russia and meets the criteria for identifying several categories of high conservation value forests. The proposed ways have shown high efficiency. Ichalkovsky reserve is very important to conserve the biodiversity, including at the international level. This natural area should have legal protection adequate to its nature conservation value. Such protection can be provided by the status of a cluster of a national park.

In the summer of 2010, about a half of the Kerzhensky State Nature Biosphere Reserve territory suffered from a wildfire. During the 9 following years, monitoring of the bird populations in the breeding season was conducted there. Birds were counted by a route method in 6 main habitats differ in their fire burned types and also in unburned similar habitats. A total of 130 bird species were registered. In the first years after the wildfire impact, bird populations in the habitats affected by different wildfire types were similar according to the Sorensen-Chekanovsky’s index. This similarity increased to 2016. The similarity of the bird populations of burned sites has been decreasing last two years. The species richness changed in different directions. At first study years, the abundance of the breeding bird populations increased both in burnt and unburnt sites, while later this parameter decreased a bit and stabilised. Although interannual changes in indicators are still possible. The bird populations of the unburnt habitats, especially bogs, differ by lower values of indicators for the last five years. The influence of nature-climatic indicators of various months (average the monthly air temperature, the daily amount of precipitation) on the interannual dynamics of the breeding avifauna abundance was noted in only one case, out of 84 indicators. We distinguished the species (e.g. Sylvia communis) recognised as indicators of damaging by fire. Fringilla coelebs was dominant in all habitats studied, but from 2017, Anthus trivialis dominated in the severely burned birch-pine forests and on the raised bogs (burned and unburned). The most intense changes in bird populations were observed within the first five post-fire years.

Рис. 1. Видовое богатство гнездового населения птиц хвойно-широколиственных лесов долины р. Сережа (2017 г.). Рис. 2.Видовое богатство послегнездового населения птиц хвойно-широколиственных лесов долины р. Сережа (2017 г.).We studied changes in the summer population of birds in coniferous-deciduous forests of Seryozha river valley in the period from 2003 to 2017. Surveyed five main areas of habitat -mixed and pine forests, meadowscoppices, long fallow lands and settlements. A marked reduction in the species composition of birds of pine forests in the nesting period was noted, while at the same time, during cluster analysis, their bird communities are combined together with the population of birds of intact mixed forests. The nature of summer dynamics of total abundance and the composition of leaders in most habitats, especially in mosaic meadows and fallow lands, changed. The territorial distribution of birds over the past decade and a half is determined by practically similar factors -the naturalness of the habitat appearance, the build-up and the degree of afforestation of the habitat. The interannual similarity of the appearance of bird communities is most pronounced in mosaic meadows-coppices and minimally in fallow lands.

Based on materials collected during continuous year-round strip censuses, the spatial heterogeneity of bird communities in coniferous and deciduous forests of the Northern Volga region was analyzed for the first time and the key factors determining it were identified. A spatial-temporal classification of bird communities of the study area was made, and a quantitative estimate of the strength and generality of the relationship between the spatial heterogeneity of bird communities and environmental factors is given. The spatial-temporal structure of bird communities is mainly determined by forest cover, seasonal variation in heat supply, tree species composition, build-up area, and relief.