The seasonal dynamics of the species structure of epiphytic yeasts on the leaves and in the flowers of 25 plant species was studied throughout the period of their vegetation. It was shown that, on average for the vegetation period, the composition of epiphytic yeast communities was nonspecific. The same species of epiphytic yeasts dominated on different plant species, irrespective of their taxonomic identity and ecological peculiarities. However, different species of yeasts exhibited different types of seasonal dynamics of relative abundance. Therefore, a combination of the dynamics of yeast species and the ontogenetic cycles of plants creates a pattern of the dynamics of the epiphytic yeast population, which is unique for each plant species. The species diversity of yeasts on the leaves of a plant is determined by the duration of its ontogenetic cycle: the longer the vegetation of a plant, the higher the diversity of the epiphytic yeasts population. The greatest diversity of epiphytic yeasts was revealed on the leaves of perennial hygrophytes and mesophytes; the minimal diversity, on ephemeroids and annuals with a short ontogenetic cycle.

Significant differences were revealed in the taxonomic structure of the epiphytic yeast communities formed on Sphagnum mosses and on the leaves of vascular plants. On mosses, low abundance of red yeasts was found (the most typical epiphytes on vascular plant leaves), along with a relatively high content and diversity of nonpigmented dimorphic basidiomycetes related to the order Leucosporidiales. The species composition of epiphytic yeasts from mosses is different from that of both forest and meadow grasses and of the parts of vascular plants submerged in the turf. The specific composition of the Sphagnum mosses yeast community is probably determined by the biochemical characteristics of this environment, rather than by the hydrothermal regime in the turf.

The cotyledons of whole intact acorns were shown to contain yeasts; their number increased sharply before acorn germination. The yeasts in the cotyledons are mainly represented by one species, Candida railenensis, with the number in the germinating cotyledons reaching 10⁷ CFU/g. After germination or exocarp destruction, the cotyledons were colonized by the usual epiphytic and litter yeasts Cryptococcus albidus, Rhodotorula glutinis, and Cystofilobasidium capitatum.

The year-round dynamics of the number and taxonomic composition of yeast communities in the soddy-podzolic soils under invasive thickets of Heracleum sosnowskyi were investigated. The yeast groups that are formed in the soil under the continuous Sosnowsky’s hogweed thickets significantly differ from the indigenous yeast communities under the adjacent meadows. In the soils of both biotopes, typical eurybiotic yeast species predominate. In the soil under Heracleum sosnowskyi, the share of the ascomycetes Candida vartiovaarae and Wickerhamomyces anomalus is much lower, and the portion of yeast-like fungi with high hydrolytic activity such as Trichosporon moniliforme and Trichosporon porosum is greater. A possible explanation for this phenomenon is that Sosnowsky’s hogweed, unlike most aboriginal meadow grasses, does not hibernate with green leaves that do not gradually die out with the formation of semidecomposed plant residues—the main source of nutrients for the soil-litter microbial complex. In addition, grasses of the lower layer do not develop under Sosnowsky’s hogweed due to the strong shading and allelopathic impact preventing the development of typical epiphytic copiotrophic species of yeasts.