Variations of plant communities in diversity and composition along the western coast of Lake Khanka caused by high water level

Lake Khanka is the largest freshwater body of water in northeast Asia, with a basin of about 25 000 km2. The hydrological regime of the lake is cyclical in nature due to various factors affecting water inflow and outflow. The last increase of water level in the lake began in the 2000s and by 2015 reached the maximum value of 416 cm (with the average annual level of 293 cm). A steady decline in water level has been observed since 2021. To assess the diversity and structure of coastal plant communities on the sandy-pebbly substrate along the western shore of Lake Khanka and their dynamics under the influence of flooding, we laid 20 transects and performed descriptions at seven sites, including two sites in the protected area of the Cluster Sosnovy of the Khanka Nature Reserve. Using the diversity and similarity/difference indices, plant communities were compared across the sites. It was shown that their heterogeneity is due to the diversity of both aboriginal and adventive species. In protected areas, the role of adventive species is significantly lower than in recreational areas. The five dominant species in the communities account for 50 % or more of the total abundance. Vegetation groupings in the three identified zones, which have been inundated for different periods of time, have a similar diversity, with differences due only to the native fraction of species. The second zone, characterized by the greatest influx of species of different ecological and cenotic groups during water recession, differs in species richness. The obtained data show for the first time the diversity and structure of coastal plant communities of the sandy-pebble beech of the western coast of Lake Khanka and reflect some processes of its dynamics in connection with the long-term standing water. For more successful coverage of the issues raised, long-term monitoring on the laid transects, at least covering one 20–30-year cycle of the dynamics of the hydrological regime of Lake Khanka, is necessary.