Features of overgrowing the urbanized segment of the Vorskla River

Abstract

We investigated the indices of overgrowing by higher aquatic vegetation (coenotic diversity, ecological structure, the degree of overgrowing, the type of overgrowing, belt structure) at five sites of the river Vorskla, located near the city of Poltava, which are subject to varying degrees of human impact. The formation of the plant cover is provided by 15 dominant species, based on which we allocated 3 associations of submerged vegetation, 5 associations of vegetation with floating leaves (including 4 – free-floating), 7 associations of air-aquatic vegetation. In part of the thicket zone the communities of different ecological groups spatially prevail: the submerged vegetation is on the middle urban site, the air-water vegetation is at the peri-urban sites and the floating-leaf vegetation is on the extra-urban sites. Limit values of the index of the aquatorium overgrowing registered on the most transformed urban sites with a high degree of urbanization of the landscape. The aquatorium overgrowing type changes from the curb to the dispersed-spotty confined to sites with the most significant violation of the hydrological regime. The deviations in the belt structure of vegetation are the most typical for urban sites, where due to anthropogenic impact was an increase in structure heterogeneity of low air-water grasses belt and simplification (and in some places – the complete reduction) of high air-water grasses belt as well as belts of truly aquatic vegetation. The factors of urbanized landscape, which have a leading influence on the development of higher aquatic vegetation, include violation of hydrological regime, change of morphometric parameters of riverbed, water pollution, recreation. The middle urban and lower urban sites of the Vorskla River are the most heavily transformed as a result of the combined effect of urbanized landscape.