Eurasian Soil Science

A study was conducted to examine the influence of ancient anthropogenic activity on the properties of modern virgin soils in northwestern Crimea. Soils were studied along a transect passing through a Bronze Age settlement and including lithozems (Petrocalcic Leptosols) and migratory-segregational chernozems (Luvic Chernozems). The contents of particle-size fractions, organic carbon, total nitrogen, its mobile mineral forms, various forms of phosphates, macro- and microelements, as well as microbial biomass and phosphatase activity were determined. It was shown that residential land-use and livestock keeping during the Bronze Age (12^th–9^th centuries BC) resulted in increased of contents of phosphates, zinc, manganese, and other elements associated with economic use of soils in ancient times. Soils in the zone of active modern erosion processes were characterized by increased contents of physical sand, carbonates, and sulfur, as well as organic carbon, microbial biomass, and phosphatase activity. Soils in the accumulation zone outside the settlement showed increased contents of chemical elements associated with clay minerals and silt particles, namely iron, aluminum, titanium, magnesium, and sodium.

The dynamics of major and trace elements during the formation, fermentation, and humification of forest litter, as well as the analysis of its spatial variability in relation to landscape conditions, contribute to a better understanding of the forest ecosystem biogeochemistry. The study focused on the dynamics of 17 elements (Ca, K, Fe, Mn, Mg, P, S, Ti, Zn, Sr, Rb, Cr, Cu, Pb, Ni, Co, Cd) by determining their concentrations using ICP-MS/OES methods in the organic and mineral horizons of Retisols and Stagnosols, as well as in the green phytomass of tree species within the background catena located in the southern taiga zone. Along the catena, with an increase in soil hydromorphism and the transition from mixed (coniferous and broad-leaved) to coniferous forest communities, a significant decrease in the ash content in organic horizons and a drop in the concentrations of Mn, Cr > Fe, Ti, Sr > Ca, K, Mg, Zn, Ni, Rb, Co were observed. A comparison of the elemental concentrations in freshly fallen leaves and living green parts of woody plants revealed significant disparities. Specifically, fallen leaves and needles exhibited higher concentrations of Cu, Co, Cr, Fe, Ni, Sr, Ti, Zn, Mn, and Cd, but lower levels of K, P, and Rb. This discrepancy can be attributed to the retranslocation of these elements within the living organs of plants. The transformation of fresh litter (Oi horizon) into fermented litter (Oe) in the summit and slope landscapes was accompanied by a loss of alkaline and alkaline earth elements – K, Mg, Rb, – and an accumulation of Mn, Pb, Zn, Cd, and Co. The further humification of plant residues and the transformation of the Oe horizon into the Oa horizon led to the accumulation of Ti, as well as Fe, Pb, K > Co, Cr, Rb > Cd, Ni > Mg, Mn, Zn > Cu. In waterlogged footslope and toeslope positions of the catena, where coniferous litter predominates, the fermentation of organic residues in the Oe horizon resulted in the accumulation of Mn, Pb, Zn, and Cd. The development of oxidation-reduction processes in waterlogged footslope and toeslope contributed to the removal of alkaline elements from acidic organic horizons, as well as Fe and Mn and associated elements such as Cr, Co, Ni, and Zn.

The present article is devoted to the studies of the biological activity of eutrophic peat soils in the floodplain of the Poros River, located in the basin of the ancient Tom River (Western Siberia, Tomsk Region, Tomsk District). Microbial biomass, respiration intensity, methanogenesis, nitrogen fixation, and denitrification were determined in soils of native and long-drained areas of the left- and right-bank floodplains. Microbial biomass reserves in the 1-meter layer of the studied soils ranged from 240 to 1068 g/m², and basal respiration rates ranged from 87 to 351 µg CO₂/(g per day). Nitrogen cycle activity indicators were characterized by low values: 3–12 ng C₂H₄/(g per day) for nitrogen fixation, estimated by the acetylene reduction method, and 0.1 to 8 µg N₂O/(g per day) for denitrification. It was found that drainage of the floodplain 27 years after land reclamation contributed to the increase of total microbial biomass in the soil (due to the fungal component in the eutrophic-peat horizon and the bacterial component in the peat layer), respiratory and nitrogenase activity, and led to a decrease in methanogenesis and denitrification. The negative effect of prolonged drainage (loss of up to 45% of carbon reserves and 50% of nitrogen) was only evident in the subsurface layer of the eutrophic peat horizon (TE, 0–25 cm).

This study analyzes the influence of the spatial and species structure of plant communities formed during post-agrogenic transformation of agricultural lands to forests on changes in soil organic matter (C_org) stocks. The distribution and dynamics of C_org were estimated with application of the EFIMOD3 simulation modeling system using fallow areas of agro-gray (Luvisols) soil in the broadleaf forest zone (54.833770 N, 37.568915 E) as an example. We simulated typical for European Russia the reforestation on the abandoned soils with pine (Pinus sylvestris L.) or birch (Betula spp.) trees, with random, clustered, or gradient tree placement within the fallow area, at the same initial density (5,000 trees/ha). According to the estimates, over 50 years, a forest litter pool corresponding to an average of 1.5–2.5 kg C/m² is formed under birch stands, with spatial variation from 0.5–1.0 to 3.0–3.5 kg C/m² depending on the tree placement. For pine stands, litter accumulation is lower—an average of 1.0–1.5 kg C/m², but with higher variation—from 0.5 to 4.0 kg C/m². In the former arable horizon of fallow lands overgrown with birch, calculations show an increase in the carbon pool by an average of 1.0–2.0 kg C/m² from the initial value; the greatest increase is observed in the random placement option. For pine, the estimates obtained correspond to a decrease in soil C_org stocks in the first 25–30 years, with subsequent recovery and a slight increase in average storage for the site by 0.5–1.0 kg C/m² only for the clustered placement. An about twofold difference was obtained between the maximum and minimum estimates of the total (in the litter and former arable horizon) accumulation of C_org over 50 years in the soils of the simulated area, corresponding to the random placement of birch (73.6 t/ha) and pine (38.4 t/ha), whereas for the clustered placement of trees, the model, on the contrary, shows the small differences between birch and pine stands – 59.2 and 60.8 t/ha, respectively. Numerical experiments have shown that to obtain correct territorial estimates of carbon storage, it is necessary to take into account not only the species composition, but also the spatial structure of forests formed on abandoned lands.