Assessment of the Vegetation Cover State in a Northern Fennoscandia Transboundary Watercourse (Russian Part of the Paz River)

An assessment of the vegetation cover of the transboundary Paz River based on the materials of 2019 demonstrated a high diversity of flora that is uncharacteristic of other rivers in northern Fennoscandia. The core of the vegetation cover consists of Sparganium angustifolium , Myriophyllum alterniflorum , Ranunculus schmalhausenii , Potamogeton gramineus , and P . perfoliatus in the river channel; Subularia aquatica , Isoëtes echinospora , and I . lacustris in the shallow waters; and Equisetum fluviatile , Carex rostrata , and Comarum palustre along the bank, which are mainly species of oligo- and oligomesotrophic waters. The macrophyte composition have almost not changed in the >25 years since the first study. The overgrowing of the river is increased when compared with the watercourses of the region. Potamogeton perfoliatus and P . gramineus , which are the dominant species in the river channel, make the greatest contribution to the production of organic matter. The main reason for this is the hydrological regime formed by a cascade of hydroelectric power plants on the river, which is favorable for the development of plants. According to the characteristics of the vegetation cover, the state of the studied part of the watercourse can be considered stable and safe.