Ecological and Agrochemical Assessment of the Kamennaya Steppe Soils under Forest Cenosis

A set of parameters of soils under forest belts was studied. The objects of research were old-growth (65–68 yrs) ravine and shelterbelt forest plantations of the Kamennaya Steppe. The results allow assessing the trends of changes in soil characteristics over a long period of time. Key plots of 100×100 m were laid out using a regular sampling grid. The sampling interval is 15–25 m. A positive effect of forest shelterbelts on the properties of chernozems was found. There is an increase in thickness of the humus horizon from 42.3 cm (arable land on the slope) to 72.6±5.1 cm (under forest). The maximum values are typical for chernozems of watershed areas: 59.6±2.4 cm (arable land) and 85.6±3.9 cm (forest belt). Chernozems leached due to the activation of migration processes of carbonates into the underlying soil horizons have the maximum depth of soil effervescence. Chernozems zooturbated due to mechanical transport and mixing of accumulative-carbonate horizon have the lowest depth of soil effervescence. A general trend to decrease the depth of soil effervescence under the forest cenosis was found. The highest humus content is observed in watershed areas: 7.14±0.24 % (arable land) and 8.56±0.18 % (forest belt). A ravine forest belt reduces the risk of erosion processes. A fairly strong humus profile with a high content of organic matter: 7.03±0.27% (under forest) and 6.10±0.10% (on arable land), was possible to preserve on arable lands in the zone of the belt’s influence. The planting of forest belts causes a change in the nature of vegetation. The influence of acidic products of litter decomposition formed soil horizons with a moderately acidic reaction of the environment in the humus layer. Despite the leading position of calcium, an increased content of magnesium was found in the composition of exchange-absorbed cations. Forest belts have become especially important in recent decades due to changing climatic conditions. In the steppe regions of Russia, such plantations are a powerful soil conservation factor that helps stabilize and increase soil fertility. It is necessary to intensify the planting of artificial forest stands in the steppe regions of Russia. For citation: Cheverdin Yu.I., Bespalov V.A., Sautkina M.Yu., Titova T.V. Ecological and Agrochemical Assessment of the Kamennaya Steppe Soils under Forest Cenosis. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 5, pp. 76–91. DOI: 10.37482/0536-1036-2021-5-76-91

Growth and State of Mixed Stands of Forest Plantations of the Kamennaya Steppe

By now, a vast amount of experimental material has been accumulated in the field of protective afforestation of the Central Chernozem Region of Russia, which allows estimating the stability and longevity of various trees and shrubs in different environmental conditions. Good growth and high vitality of woody vegetation largely depend on growing conditions and are determined primarily by the relationship between species (individuals within a species) when they are placed in the forest area and the type of terrain. The researchdifferent combinations in tree and shrub mixing schemes and unequal location by types of terrain. The study was carried out in mature (115–118-year-old) forest strips laid out by the staff of the Kamennaya Steppe experimental forestry G.F. Morozov and N.A. Mikhailov on the territory of the Kamennaya Steppe (Voronezh region, Talovsky district) using archival materials, scientific works of the authors of this article and the employees of the Department of Agroforestry. A comparative analysis of the materials of forest survey work carried out in protective forest plantations created according to the tree-shrub type of mixing on different types of terrain revealed an excess of biometric indicators of tree species growing on the upland type of terrain over those on the slope. It is shown that the initial percentage of participation of English oak is a significant, but not always decisive factor in the creation of oak plantations. They can also be grown with a smaller proportion of this species in the culture, but in this case, timely thinning will be of paramount importance. Over time, there have been significant changes in the composition of plantations, the number of trees and their valuation indicators. There are no viable ash and elm specimens left in the upper tier of the stands. They are severely damaged by stem pests. Certain tree species are damaged by the following pests: common ash by large ash bark beetle (Hylesinus crenatus) and ash bark beetle (Hylesinus fraxini); elm species by cambium-feeding beetles (large elm bark beetle (Scolytus scolytus), European elm bark beetle (Scolytus multistriatus), and pygmy elm bark beetle (Scolytus pygmaeus); English oak by gold pit oak splendour beetle (Chrysobothris affinis), oak borer (Agrilus angustulus), longhorn beetle (Plagionotus detritus), and European oak bark beetle (Scolytus intricatus). The predominant number of trees of all tree species belongs to the categories of limited viable and inviable.

Changes in the hydrophobic-hydrophilic properties of the organic matter of the chernozems of the Kamennaya Steppe

Soil samples and physical size-density fractions isolated from them (silt particle size less than 1 µm, light fraction (LF) with a density of less than 2 g/cm3 and a fraction of the residue) of ordinary chernozem were studied in three contrasting variants of the experimental fields of the Kamennaya Steppe agrolandscape of the Voronezh region: mowed steppe, long-term permanent bare fallow and permanent corn – the main differences of which are in tillage (cultivated and not cultivated lands) and in the supply/absence of plant residues and root secretions. The LF content changes in the series: “mowed steppe” > “permanent corn” > “permanent bare fallow”, which corresponds to the direction of changes in the total carbon content of the soil and a decrease in the value of the contact angle of wetting (CA) of the surface of the solid phase of the studied chernozems. The determination of the total C and N content revealed the change in the qualitative and quantitative composition of the size-density fractions for different land use cases. Chromatographic fractionation of alkaline extractions of humus substances (HS) of chernozem samples and size-density fractions revealed an increase in the degree of hydrophilicity of HS while simultaneously increasing the hydrophobicity of the solid phase surface and the carbon content in the soil. HS of LF of the “mowed steppe” turned out to be by 63% more hydrophilic than HS of LF of “permanent bare fallow” and by 47% more hydrophilic than HS of LF of “permanent corn”. While the hydrophilicity of the HS silt differed by 16 and 27%, respectively. The hydrophilicity of the HS of the original soil in the plot of the “mowed steppe” was by 41% higher than the hydrophilicity of the HS in the soil in the plot of “permanent bare fallow” and by 24% higher than in the soil of the plot of “permanent corn”. In addition, changes in the hydrophilicity of HS of size-density fractions are more intense than the HS of the soil, so the change in the degree of hydrophilicity of HS of size-density fractions is an indicator of soil degradation under different agrogenic pressue.

Dynamics of soil formation factors and their influence on agricultural technology in the Kamennaya Steppe

The analysis of long-term observations in the Kamennaya Steppe (over 125 years) for climatic parameters (air temperature and precipitation), ground water level, vegetation species composition revealed the main trends in their variability. Since 1969 there has been an increase in temperature and a reduction in temperature fluctuation during the year. Over the last 30 years, the difference has reached 1.90, and over the last decade it has grown by 0.40 due to the cold season. The amount of precipitation over the same 50-year period has not changed much. In total, an increase of 45 mm was observed over the decade (1999-2008). In the XXI century, there has been registered an increase in the amount of precipitation in the cold season by 12.7% and a decrease in the warm season, which creates certain prerequisites for climate continentality mitigation during the annual cycle. During the first 70 years of observations, the groundwater level in the well No. 1 was on average at the depth of 6.5 m (5.7-7.3 m). At the end of the XX century and at the beginning of the XXI century, there was marked a pronounced rise in the ground water level, the average depth was 3.8 m, which coincided with the growth of average annual temperature and an increase in total rainfall. In this period changes in the long-term regime of ground and surface soil moisture resultedin expanding the area of wetlands and hydromorphic soils on the territory of the steppe. The period of 2009-2018 is characterized by a continued increase in average annual temperatures and a decrease in precipitation, which may lead to a seasonal change in temperature and precipitation to milder and wetter winters and warmer and drier summers. Transformation of vegetation for 100 years of observations had several stages with a general trend to change the steppe grasslands to meadow-steppe, shrubs and woody species.