Abstract <p>Specially protected natural territories of the forest-steppe zone are designed not only to preserve typical and unique ecosystems but also to monitor the reaction of the biota of this labile ecotone to natural and climatic changes. The parameters of fungal communities in this regard are a very sensitive indicator related, in particular, to the state of woody vegetation. However, in most cases, fungi are studied last; in the forest-steppe south of Tyumen oblast, there are very little data about them. For the first time, materials were obtained on the species composition, distribution, and number of macromycetes of the Lake Solenoye nature monument located in the south of the forest-steppe zone of the region. There are 60 species of fungi: 5 in meadow-steppe areas, 20 in forest plantations, and 42 in a natural birch forest; among them are a number of species scanty for the region. New methodical approaches were used. To assess the structure of mycobiota and the state of the unique landscape and climatic conditions of the lakeside forest area, a matrix analysis of the model community of aphyllophoroid fungi developing on birch wood was conducted. According to the quantitative accounting of fungi, indicator ratios of species are established on the hydrothermal gradient and the gradient of the vital state of the stands. Comparatively, similar materials were used for the <i>Betula-</i>complex of fungi from eight other sites of birch trees of the southern forest steppe and in the forest-steppe zone of the region as a whole. Clustering of the state of birch forests by species lists and matrix groups of fungi was carried out.</p>