Heterogeneity of soil conditions and biodiversity of plant communities of floodplain forests is a result of site conditions and long-term anthropogenic impacts. The aim of the paper was to assess the heterogeneity and properties of organic and organomineral soil horizons and main components of phytocoenoses. The accumulation of organic residues in forest floor shows important heterogeneity in mixed stands of pedunculate oak and ash and also in ash and oak monocultures. The floodplain forest regeneration using a clear-felling system and soil/site preparation by ploughing and accumulation of decaying wood in nature reserves are the most important effects. The chemistry of leaf litter and temperature and moisture conditions of the soil surface condition also the rate of decomposition of organic residues within a year. The litter decomposition proceeds fastest at ash and hornbeam and the largest decrease of organic matter at all kinds of litter occurs in winter. In addition to forest floor, heterogeneity was also assessed of organomineral soil horizons A and the concentrations of C and N and pH values were monitored in the horizons. Although this soil layer was affected by the plant cover and various methods of land use from about the beginning of the 13th century, there are differences conditioned by the present effects of forest management. To assess the plant component of phytocoenoses two series of plant relevés were monitored, namely in the course of time and in area, which made possible to assess the diversity of vegetation from the aspect of changes in the hydric regime of soils and from the aspect of changes in the response to forest management. By means of the analysis of the vegetation composition at the level of species, ecological and other properties of the phytocoenose components relationships were demonstrated between the effect of man and the quantitative and qualitative vegetation heterogeneity.