Shelterbelts As a Factor of Soil Formation in Agrolandscapes of the Southern Part of the Central Russian Upland

The impact of forest reclamation on cultivated soils have been studied in automorphic chernozems under wide (30 m) meridionally oriented broadleaf shelterbelts and their arable analogues near the shelterbelts in three key forest-steppe areas of the southern Central Russian Upland. The study sites are located in the area of heavy loamy and clayey typical chernozems. Over 60 years of shelterbelt growth are associated with significant changes in the morphological, physical, and chemical properties of the chernozems. Field soil moisture analysis conducted over two growing seasons (2020–2021) revealed that arable soils are wetter to the west of the shelterbelts than to the east, primarily due to the westerly transport of air masses during the warm seasons. Soils under shelterbelts, which are compared to arable soils, are characterized by an increased thickness of the humus-accumulative horizons (on average, by 13 cm), fragmentary lightening of the middle and lower parts of the humus layer in the form of a weak patchy coating of skeletans and exhibit signs of illuviation process in the B horizons (glossy films and thin cutans). The shelterbelt soils are characterized by a radial outflow of carbonates compared to arable analogs: a 3-m depth of shelterbelt soils contains, on average, 40–50 t/ha less carbon carbonate than the arable soils. These differences indicate an evolutionary transformation of soils under shelterbelts from typical chernozems towards leached chernozems. Also, the 3-m soil depth of shelterbelt soils is characterized by higher stocks of organic carbon (on average, by 27 t/ha compared to arable soils). The composition of humus in chernozems under shelterbelts undergoes significant transformation towards a forest type: the content of fulvic acid increases in the 0- to 20-cm layer, while deeper layers exhibit maximum accumulation of humic acids. Meanwhile, profile distribution of humus acids in arable soils exhibit its characteristic chernozem type. The determined lateral transfer of several substances (particularly phosphorus) from arable soils towards shelterbelt ones is associated with the desuction activity of tree root systems. Thus, shelterbelts activate a complex of autochthonous and allochthonous phenomena in the soil cover, noticeably transforming soils over a 60-year period.