Ecological and agricultural assessment of the state of forage lands of boreal river floodplains in the oil-producing region (case study in the floodplain of the Kolva River, Usinsky district, Komi Republic)

Floodplain forage lands of the Pechora basin (Usinsky district of the Komi Republic) are experiencing a complex anthropogenic impact associated with both agricultural activity and pollution with petroleum products coming with flood waters. An ecological and agricultural assessment of the soil-vegetation cover of the Kolva floodplain used as hayfield (right-bank part) and pasture (left-bank part) was carried out. Soil combinations of the main part of the surveyed floodplain include alluvial sod, sod-meadow and meadow soils. Morphological signs of gley formation in meadow soils are observed in the lower part of the soil profile and are expressed moderately. Soils are characterized generally by favorable agrochemical and morphological properties, with the exception of areas subjected to pasture digression. The vegetation cover of the central and near-river part of the floodplain massif of the right bank is mainly represented by legume-cereal-grass communities formed both in inter-ridge depressions and on flat ridges. On the high floodplain of the left bank, legume-cereal-grass meadows, grass-clover and tufted hairgrass meadows are common, horsetail–butterbur, clover-cereal and cereal communities are common in the near-river part of the left bank. Despite the relatively high productivity and the presence of valuable forage species of cereals and legumes, the qualitative characteristics of hay deviate from optimal ones due to the participation of low-nutritious, unattractive, weedy and poisonous species in the herbage. On the pasture, as a result of pasture digression, there is a decrease in species diversity with the dominance of tufted hairgrass and low-value species of various grasses. In the most disturbed areas, the total projective vegetation coverage is reduced to 50%. The soil cover of the studied territory of the Kolva floodplain is currently not contaminated with hydrocarbons, with the exception of a few spots of petroleum products with a total area of 6 m2. The effect of oil pollution on the vegetation cover of the Kolva floodplain is not manifested. Background values of the content of petroleum products in soils are slightly higher in the left-bank part compared to the right-bank part.