Yu. G. Chendev

Spatial and temporal features of soil erosion in the forest-steppe zone of the East-European Plain

Data on the rate of the erosion-accumulation processes within the sloped junctions of soils studied on key plots in Tula, Kursk, and Belgorod oblasts were analyzed. Using the method of different-age tracers characterizing the erosion-aggradation of the soils during the last 140–150 years (the magnetic tracer) and during the last 20–25 years (the radiocesium tracer), the spatial and temporal features of the redistribution of the drifts on typical slopes in different parts of the forest-steppe zone of the East-European Plain were established. A clear trend of an increase in the soil erosion rate in this zone during the last 20–25 years was revealed compared to the average rate for the last 140- to 150-year-long plowing period, which was related to the climate warming, an abrupt reduction of the surface runoff during the spring snowmelt period, and the increasing soil-protecting role of the agricultural plants in the crop rotations because of the decrease in the proportion of row crops. The obtained results confirmed the continuous nature of the soil erosion and accumulation during the transport of the sediments, which was manifested in the alternation of the erosion zones and deposition zones on the slopes.

Anthropogenic evolution of dark gray forest-steppe soils in the southern part of the Central Russian Upland

A sequence of dark gray forest soils developing under a virgin broadleaved forest and under croplands used for 100 and 150 years was studied in the southern part of the forest-steppe zone on the Central Russian Upland. The application of multiple study methods for these objects made it possible to trace the evolutionary changes in the soil properties during the 150-year-long period of regular plowing. Several important trends in the soil development under the impact of the cultivation were revealed: (a) an increase in the thickness of the humus layer (according to the measurements at 20 points for each of the objects), (b) an increase in the amount of mole tunnels, (c) a decrease in the coefficient of the textural differentiation of the soil profile (with respect to the clay content), (d) an increase in the contents and reserves of the major nutrients upon a stable pool of humus in the upper meter, and (e) some alkalization and carbonization of the profile. Powdery accumulations of carbonates and whitish calcareous coatings on the faces of prismatic peds appeared at a depth of more than 130 cm. The plowed soils contained thin deep fissures, the surface of which was covered by dark-colored clayey-humus coatings at the depth of 50–110 cm. The radiocarbon age of the humus in these coatings was 500–1000 years younger than the age of the humus in the soil mass between the fissures. This set of features attests to the evolution of the plowed dark gray forest soils into chernozems under the impact of plowing.

Trends of the natural evolution of chernozems on the East European Plain

A generalized chronosequence of changes in the morphometric parameters of chernozems in the past 5100 years is analyzed. It is shown that the development of chernozems in the center of the East European Plain is characterized by both long-term (interglacial, encompassing the entire Holocene) and short-term (within separate climatic periods of the Holocene) trends. The long-term trend of the evolution of ordinary chernozems developed from the loess-like calcareous loam consists of a continuous increase in the thickness of the soil humus profile and an oscillating increase in the depth of the carbonate accumulations. The Late-Holocene short-term trends of the natural evolution of chernozems are characterized by the high spatial heterogeneity related to the patterns of climatic fluctuations and to the lithological composition of parent materials. In that period, the thickness of genetic horizons in the forest-steppe chernozems was increasing faster than that in the steppe chernozems.

Accumulation of Organic Carbon in Chernozems (Mollisols) under Shelterbelts in Russia and the United States

Shelterbelts that were created in place of meadow and meadow-steppe landscapes of the forest-steppe zone of northern continents serve as areas of carbon accumulation and participate in the formation of soil organic matter. In the Great Plains of the United States (in North Dakota, South Dakota, and Nebraska) and on the Central Russian Upland (Belgorod, Voronezh, and Kursk oblasts), a general tendency toward an increase in the Corg pool in the topsoil (0–30 cm) from the marginal parts of the shelterbelts toward their central parts by about 3.5–10.0 t per each 10 m has been identified. In 55 years of the existence of shelterbelts on chernozems in the European part of Russia, the mean annual rate of the organic carbon accumulation in the upper meter has been varying within 0.7–1.5 t/ha. In 19 years of the existence of a shelterbelt in the area of Huron (South Dakota), the mean annual rate of the organic carbon accumulation in the 1-m-thick layer of the Bonilla soil series (Haplustolls) has reached 1.9 t/ha.

Climatic Changes in the East-European Forest-Steppe and Effects on Scots Pine Productivity

Climate change during the 20th and early 21st centuries in the transitional zone between forests and grasslands at the center of the East-European Plain (Voronezh oblast) was determined by examining climate trends and variability using tree ring radial increment data as representative of productivity. An increase in atmospheric moisture for the warm period of the year (May–September) since 1890s, and mean annual temperatures since the 1950s was identified. During the same time period, there was a marked increase in amplitude of the annual variations for temperature and precipitation. Study results revealed trends, variability in the climatic indices, and corresponding radial wood increment for the regional stands of Pinus sylvestris L. These fluctuations are consistent with 10–12-years Schwabe–Wolf, 22-years Hale, and the 32–36-years Bruckner Solar Cycles. There was an additional relationship found between high-frequency (short-period) climate fluctuations, lasting for about three years, and 70–90-years fluctuations of the moisture regime in the study region corresponding to longer cycles. The results of this study can help guide management decisions in the study region and elsewhere, especially where climate change induced alterations to the state and productivity of forest ecosystems and associated natural resource commodities are of growing concern.

Transformation of forest soils in Iowa (United States) under the impact of long-term agricultural development

The evolution of automorphic cultivated soils of the Fayette series (the order of Alfisols)—close analogues of gray forest soils in the European part of Russia—was studied by the method of agrosoil chronosequences in the lower reaches of the Iowa River. It was found that the old-arable soils are characterized by an increase in the thickness of humus horizons and better aggregation; they are subjected to active biogenic turbation by rodents; some alkalization of the soil reaction and an increase in the sum of exchangeable bases also take place. These features are developed against the background of active eluvial-illuvial differentiation and gleyzation of the soil profiles under conditions of a relatively wet climate typical of the ecotone between the zones of prairies and broadleaved forests in the northeast Central Plains of the United States.

Evolution of the carbonate state of agrogenically transformed dark gray forest soils in the central forest-steppe

The integrated study of the carbonate state of soils, which involves all the forms of soil carbonates at different levels of the soil organization, allows exactly assessing the degree and the rate of the soil transformation due to agricultural development. The evolution of the carbonate state in agrogenically transformed soils was assessed on a site with a known land-use history and with remaining natural soils. The direction, rate, and stages of the carbonate state transformation upon the agrogenic use of dark gray forest soils were determined on the basis of the morphogenetic analysis. Agricultural development entails a significant reorganization of the carbonate profile: a dark gray forest soil evolves into a medium-thick slightly podzolic chernozem with a greater pool of carbonates. The calcareous pedofeatures and horizons evolve stepwise: in the soil of a 100-year-old plowland, the transition to another organization of the carbonate state is observed: carbonates migrate more actively, and the dissolution-precipitation conditions are most dynamic. In the upper calcareous horizons, the structure of the calcitic pedofeatures becomes more collomorphic, and this mass fills almost all the voids; in the lower calcareous horizons, calcite is predominantly segregated into calcareous pedofeatures.

Dynamics of the Soil Cover in the Southeast of Europe and in the Southern Trans-Ural Region during the Subboreal Period

An inventory of published data on the natural evolution of forest-steppe, steppe, and semidesert soils in the southern part of the East European Plain and in the southern Trans-Ural region during the Subboreal period of the Holocene has been performed. Schematic maps of the thickness of soil humus profiles and the depth of soil carbonates have been developed for the chronosections of 5000–4200, 4100–3900, and 3800–3200 years ago. On this basis, the areas with specific patterns of natural evolution of soils in the Subboreal period are delineated.

The pool of pedogenic carbon in the soils of different types and durations of use as croplands in the forest-steppe of the Central Russian Upland

Based on studying five agrochronoseries, including recent forest (dark) gray soils and soils plowed for 100, 150, and 200–240 and more years in the forest-steppe zone of the Central Russian Upland, the dynamics of the pedogenic carbon pool, including the Corg and Ccarb, are considered. In the 2-m-thick layer of the agrogenic soils studied, the pedogenic carbon pool was shown to increase by 15–30% (up to 50%) mainly due to the changes in the Ccarb content. The insignificant (by ∼10%) growth of the Corg content was found in the soils that were plowed for more than 200–250 years. As the hydrothermal regime changed when passing from the forest to croplands, the Ccarb reserves increased due to the ascending of carbonates from the parent rock through the capillary pores, probably, in colloid solution-suspensions. This process proceeded without exchange with the soil CO2, since the 14C age and the content of the newly formed carbonates became higher. These carbonates may be called pedogenic-lithogenic agrocarbonates, since they appear in soils as a result of the (agro-) pedogenesis. In this case, their additional source is the lithogenic carbonates, which bring in the “old” carbon. The process of carbonates ascending could be referred to the rapid soil-forming ones with their implementation time being close to ≤50 years.

Evolution of forest pedogenesis in the south of the forest-steppe of the Central Russian Upland in the Late Holocene

The Late Holocene stage of forest pedogenesis has been studied on the interfluves along river valleys in the forest-steppe zone of the Central Russian Upland. The development of gray forest soils from the former chernozems as a result of the Late Holocene advance of forest vegetation over steppes is discussed. It is argued that the climatic conditions of the Subatlantic period were unstable, so that multiple alternation of forest and steppe vegetation communities took place. This specified a complex character of soil evolution upon contrasting substitution of forest pedogenesis for steppe pedogenesis. On the interfluves near the natural drainage network (balkas, ravines, and steep slopes of river valleys), the climate-driven dynamics of forest and steppe vegetation with corresponding changes in the character of pedogenesis could take place during the entire Holocene, which is reflected in a lower thickness of humus profiles and deeper leaching of carbonates from chernozems of the Early Iron Age in comparison with their analogues formed under steppe cenoses in central parts of the interfluves. Two variants of the evolution of gray forest soils can be suggested: the pulsating evolution typical of balkas and interfluves near river valleys and the continuous progressive evolution typical of automorphic (plakor) positions in central parts of the interfluves.