The Influence of Eurasian Beaver (Castor fiber L.) Activity on the Transformation and Functioning of Riparian Phytocoenoses in the Southern Boreal Zone (European Russia)

The reintroduction of Eurasian beaver (Castor fiber L.) results in significant changes in ecosystems. The purpose of this study is to assess the impact of the environment-forming activity of C. fiber on the riparian phytocoenoses of the Raifa forest sector of the Volga-Kama State Nature Biosphere Reserve (Middle Volga region, European Russia) after the reintroduction. Phytoindication methods of ecological–coenotic groups and indicator values were used to assess changes in environmental conditions under the influence of beaver activity. The influence of the beaver reintroduction factor on the increase in the moisture regime (by three points according to the Tsyganov indicator values) and the illumination of habitats, the richness of soils in nitrogen, and the acidity and salt regime of soils (by one point) was revealed. Under the conditions of fodder and construction activities of the beaver, an increase in the proportion of aquatic and wetland groups from 10.2% to 28.2% and boreal plant species from 15.0% to 27.6% was detected. An expansive nature of the change in the degree of landscape occupancy with wetland plants was noted. A decrease in the degree of landscape occupancy (3 to 2 points) of the distribution of ruderal species in the riparian zones of the waterbodies of the reserve due to the activity of the beaver was revealed. Based on phytoindication and ecological–coenotic analyses, it was shown that the reintroduction of C. fiber into the waterbodies of the Raifa forest sector of the reserve is responsible for maintaining the necessary microclimatic conditions for the preservation of natural southern boreal communities. The results obtained can be used for predictive assessment of the influence of the beaver on riparian (small rivers and lakes) plant communities of forest ecosystems in the Middle Volga region of European Russia and other regions of the planet with similar environmental conditions.