At present 19 subtypes of 8 types of floodplain soils are within the limits of nature protected areas in the territory of the Komi Republic in the status of a reserved regime. Floodplain soils are not the direct objects of special protection within the existing network of nature protected areas of the Komi Republic, however, being represented within the limits of many reserves (taiga and mountain river valleys), they are automatically included in the special protection system. The preservation regime includes both standards of alluvial soils represented by alluvial sodic acidic, alluvial meadow acidic and alluvial bog soils, which are widespread in the taiga river valleys, and rare soils – saturated and carbonate alluvial, occupying small areas in the sites of limestone outcrops. The significant influence of bioclimatic factors on the morphological and physico-chemical properties of river valley soils is confirmed. The significance of the lithological composition of soil-forming deposits in the formation of the acid-base properties of alluvial saturated and alluvial carbonate soils and their humus state is noted. The high content of calcium exchange cations and the presence of carbonates in the soil profile determines a weakly acidic or neutral reaction of the medium, a high degree of saturation with bases (> 80 %), and the formation of a relatively thick (30–40 cm) humus-accumulating horizon. The zonality of alluvial saturated and carbonate soils was reflected in the fulvate nature of humus and the low values of HA-2 fraction in the humic acid group (up to 23 % of the total amount of HA) probably associated with calcium. Floodplain soils formed in the extreme climatic conditions of the tundra are characterized by a specific profile with a thin fine-earth stratum, cryoturbations, graveliness and peaty upper part of the soddy horizon. During developing the projects on including the new reserves in the system of nature protected areas of the Komi Republic, special attention should be paid to the creation of nature reserves and natural monuments in areas that are included in the Arctic sector of the Russian Federation.