Horizon Thickness Research Articles

Опыт изучения трансформации подзолистых почв в условиях городской среды Севера

The results of soil studies of one of the medium-sized cities of the Russian European Northeast – Syktyvkar (Russia, Komi Republic, middle taiga subzone) are presented in the article. The series from a podzolic soil with a microprofile of podzol (Albic Retisol (Loamic, Protospodic)) typical for the region to various variants of its human transformation in urban conditions – cultivated agrodernovo-podzolic soil (Eutric Albic Retisol (Loamic, Aric, Humic)), represented on the site of the Botanical Garden, to urbodernovo-podzolic soil (Eutric Albic Retisol (Loamic, Humic, Transporti-Novic, Thaptoaric)) and urbostratozem (Urbic Technosol (Loamic, Eutric, Humic Transport)) described in the central part of the city, included in the urban development in the first half of the XX century is considered. In urbo-soil and urbanostratozem the thickness of urbogenic horizons is approximately 40 and 70 cm. It is shown the first stages of the development of the territory of Syktyvkar city are associated with the agricultural impact. Subsequently, the arable horizons overlap with the horizons of the urban cultural layer. In the considered series of soils, weak alkalinization, an increase in the absorbed bases and the total mineralization of the soil solution were found. A noticeable increase in the concentration of organic carbon in modern arable and urban horizons, as well as the thickness of horizons with the organic carbon content of more than 0.6% was revealed. An indirect evidences of changes in the composition of iron and manganese minerals (due to an increase in the pH) with partial preservation of zonal soil formation trends has been found. The revealed direction of soil evolution is consistent with the one previously described in the cities of the European part of Russia.

Analysis of organic matter stock dynamics in arable soils of Yamal: simulation experiments with the ROMUL model

The goal of this work is to analyze the dynamics of soil organic matter (SOM) in arable soils of Yamal using computational experiments with the ROMUL model. Soil temperature and moisture dynamics were simulated using the SCLISS model. The Yamal experimental station was organized in 1932. The soil is Plaggic Podzol. The thickness of humus horizon (PY) is 30 cm. Pools, kg/m2: SOM – 9.32 and 13.75; N – 0.46 and 0.66 for 0–20 and 0–30 cm respectively. Background: soddy-green-moss tundra near Salekhard. Soil: Folic Podzol: litter (O, 2 cm) and humus-accumulative (AY, 4 cm) and illuvial ferruginous (BF, 6 cm) horizons. Pools, kg/m2: SOM – 1.38 and 2.69, N – 0.03 and 0.18 for 0–2 and 2–6 cm respectively. The quantity and quality of background fall was estimated according to literature data. Clarification of the amount of fall was carried out by the method of inverse problem solving (spin-up). Peat application was simulated: starting application in the dose of 12 kg/m2 and maintenance (every 6 years) in doses 4, 8 and 12 kg/m2, N 1%. Application of mineral fertilizers, 2 variants: a) N 4 g/m2 (40 kg/ha) in peatting years and b) application of the same dose of nitrogen every year. The duration of computational experiments is 30 and 90 years. Computational experiments showed that after the starting peatting of Folic Podzol at the rate of 12 kg/m2 after 30 years, only 15% of the applied detritus remained. Maintenance peatting of 8–12 kg/m2 leads to an increase in SOM pool to 20–30 kg/m2 and excessive accumulation of detritus. Application of 4 kg/m2 of peat once every 6 years for 90 years shows the dynamics of SOM pools from Folic Podzol to Plaggic Podzol which is confirmed by field survey data. Application of mineral nitrogen (4 g/m2) once every 6 years does not affect SOM pools. Annual application of mineral N (4 g/m2) increases SOM pools due to intensified humification. This fact requires experimental verification.

Study on the Factors Affecting the Humus Horizon Thickness in the Black Soil Region of Liaoning Province, China

Understanding the spatial variability and driving mechanisms of humus horizon thickness (HHT) degradation is crucial for effective soil degradation prevention in black soil regions. The study compared ordinary kriging interpolation (OK), inverse distance weighted interpolation (IDW), and regression kriging interpolation (RK) using mean error (ME), mean absolute error (MAE), root mean square error (RMSE), and relative RMSE to select the most accurate model. Environmental variables were then integrated to predict HHT characteristics. Results indicate that: (1) RK was superior to OK and IDW in characterizing HHT with the smallest ME (11.45), RMSE (14.98), MAE (11.45), and RRMSE (0.44). (2) The average annual temperature (0.29), precipitation (0.27), and digital elevation model (DEM) (0.21) were the primary factors influencing the spatial variability of HHT. (3) The HHT exhibited notable variability, with an increasing trend from the southeast towards the central and northern directions, being the thinnest in the southeast. It was thicker in the northeast and southwest regions, thicker but less dense along the southern Bohai coast, thicker yet sporadically distributed in the northwest (especially Chaoyang and Fuxin), and thick with aggregated distribution over a smaller area in the northeastern direction (e.g., Tieling). These findings provide a scientific basis for accurate soil management in Liaoning Province.

Interpreting the spatial distribution of soil properties with a physically-based distributed hydrological model

Digital soil maps are commonly data-driven as the development of physically-based models for soil mapping is difficult due to the complexity of soils. However, physically-based hydrologic models have been successful in simulating water dynamics. Since water movement is a major driver of pedogenesis, the physical rules that govern water movement might help explain and predict the spatial variation of soil properties. Here, we demonstrate the novel use of a physically-based, distributed hydrologic model to inform the spatial distribution of soil properties. The Distributed Hydrology Soil Vegetation Model (DHSVM) was utilized to simulate soil moisture content (SM) and water table depth (WTD) in two hillslope catchments under pasture and forest management wherein hydrologic model outputs were then compared with soil properties measured in situ. SM sensors and wells were installed in both catchments to validate simulations of soil water movement via Nash-Sutcliffe Efficiency (E). In-situ observations were made at 87 sites within both catchments to study the connection between simulated water movement (SM and WTD) and observed soil properties, namely the depth and thickness of the argillic (Bt), fragic (Btx), and C horizons, and the depth of redoximorphic features. The simulated time series of SM and WTD were also clustered per season using Dynamic Time Warping (DTW), which identified similarity among time series at varying timescales. Model validation suggested that simulations of surficial SM (0–20 cm) were reasonable (E = 0.45), however, simulated subsurface SM (45–60 cm) and WTD were not sufficiently accurate. The thickness of Btx horizons were spatially grouped into different populations by SM clusters from every season except spring. For the other properties, only SM dynamics of specific seasons grouped into significantly different populations, suggesting that the explanatory power of simulated water movement varies seasonally and was greater during winter. Here, we show clusters of simulated SM separated soil properties into statistically different populations, showing that hydrologic models could inform areas that followed different water dynamics related to pedogenic trajectories and related biogeochemical processes not necessarily simulated by the model. As such, physically-based modeling of water dynamics can, therefore, inform and advance digital soil mapping by linking water movement patterns stemming from hydrologic model outputs to spatial patterns of soil properties and pedogenesis.

Spatial distribution of soil depth in relation to slope as a consequence of erosion-accumulation processes in loess lowland hills of Slovakia

Abstract In our study, we examined the influence of slope gradient on erosion processes and present soil formation and change on loess hills. We analysed data from the two study areas and found that slope gradient is a significant factor influencing soil depth as well as humus horizon thickness. At the Báb locality, we observed a negative correlation between slope gradient and soil depth (r = –0.206, p < 0.05) and a negative correlation between slope gradient and humus horizon thickness (r = –0.227, p < 0.01). At the Nová Vieska locality, there was a negative correlation between slope gradient and soil depth (r = –0.334, p < 0.02), as well as between slope gradient and humus horizon thickness (r = –0.356, p < 0.01). These findings confirm that slope gradient is a key factor influencing soil formation in loess hills, and has a significant impact on its depth and soil profile. The analysis revealed that a critical slope of 3° significantly influences soil formation, with shallower soils and a thinner humus horizon occurring on steeper slopes. Our findings have important implications for planning erosion control measures and soil management depending on the location and slope gradient. Overall, our work provides insights into soil formation processes in loess hills and contributes to a better understanding of the interactions between slope gradient and erosive processes.

Organic carbon in Mollisols of the world − A review

Mollisols represent 29 % of agricultural land and they are considered to be one of the most fertile soils in the world. Here, we compare soil organic carbon (SOC) concentrations and pools of Mollisols for the globe, the USA and Poland, and review how differences are caused by climate, land use, and key environmental factors. Globally, the mean thickness of the A horizon in Mollisols is 50 cm. At 0–30 cm the mean SOC concentration is 2.3 %, SOC pool is 84 t ha−1, and clay content calculated at 0–50 cm soil depth is 21 %. Mollisols in the USA have an A horizon thickness of 36 cm and have a mean clay content of 27 % (0–50 cm). SOC concentrations are 2.0 and 1.7 % and SOC pools are 85 and 116 t ha−1 at 0–30 and 0–50 cm soil depth, respectively. Mollisols in Poland have SOC concentrations of 1.8 and 1.5 % at 0–30 and 0–50 cm soil depth, respectively, and lower clay content (17 %) at 0–50 cm depth. The SOC pool at 0–30 cm depth is 74 t ha−1 whereas it is 106 t ha−1 at 0–50 cm. At the global scale, the highest SOC concentrations and pools are in Mollisols from Eastern Europe (including Ukraine and Western Russia) and Asia, while the lowest SOC pools are found in Mollisols from South America. The Mollisols in Western and Central Europe and North America have similar SOC pools, although Mollisols in North America have higher SOC concentrations and lower A horizon thickness. Globally, the mean pH value of Mollisols is 7.1, and the pH is slightly lower in Mollisols of the USA (6.9 ± 0.9). The SOC concentrations and pools are strongly and positively correlated with clay content. Soil moisture and temperature regimes determine SOC concentration and pools in Mollisols, and higher SOC concentrations and pools are in Mollisols with frigid and frigid-cryic soil temperature regimes as well as aquic, xeric, and aridic soil moisture regimes. Mollisols under grassland have the largest SOC pools compared to those cultivated or under forest. The important environmental factors on SOC concentrations and pools in Mollisols worldwide are soil texture, land use, and soil temperature regime.

Influence of Morphometric Relief Parameters on Soil Depth Changes and Humus Horizon Thickness in Relation to Erosion-Accumulation Processes: A Study in the Ipeľská Pahorkatina Hills, Slovakia

Abstract This study examines the spatial distribution of soil types and their susceptibility to erosion and accumulation processes in a study area in Slovakia. Field research involving 71 probes identified various soil types, with Regosols and Cutanic Luvisols being predominant. The study found that erosion-accumulation processes were detected in 69.97% of the probes, with changes observed in soil horizons. Soil analysis revealed different relations between soil depth, humus thickness, and terrain characteristics such as slope, slope length, and slope length and steepness factor (LS factor). Specifically, we confirmed a moderately strong positive correlation between soil depth and humus thickness (r = 0.597, n = 71, p < 0.001). Shallow soils (0–30 cm) exhibited a very strong positive correlation between soil depth and humus horizon thickness (r = 0.978, n = 33, p < 0.001). Conversely, no relationship was found in moderately deep soils (30–60 cm) (r = 0.018, n = 14, p < 0.948). For deep soils, we identified a moderately strong positive correlation (r = 0.345, n = 24, p = 0.098). While slope and slope length showed relationships with soil depth and humus thickness, the LS factor did not exhibit a clear correlation. These findings underscore the importance of understanding soil dynamics in informing land management practices, especially in areas susceptible to erosion. Recommendations include continued monitoring of eroded soils and implementing erosion control measures to maintain soil health and sustainability in agricultural production amidst climate change challenges.

ВЛИЯНИЕ АБИОТИЧЕСКИХ ФАКТОРОВ СЕВЕРО-ЗАПАДНОГО РЕГИОНА НА УРОВЕНЬ СОДЕРЖАНИЯ БЕЛКА И АДАПТИВНУЮ ИЗМЕНЧИВОСТЬ ДИПЛОИДНЫХ СОРТОВ ОЗИМОЙ РЖИ

The aim of the study is a comprehensive analysis of winter rye varieties for environmental sustainability and identification of the most promising ones. The object of the study is 9 varieties of diploid winter rye (Grafinya, Kiprez, Flora (Kirov Region), Moskovskaya 18 (Moscow Region), Talovskaya 45 (Voronezh Region), Saratovskaya 10 (Saratov Region), Novosibirskaya 17 (Novosibirsk Region), Sudarushka (Tomsk Region)), which have been added to the VIR collection in recent years. The Era variety (Leningrad Region) served as a standard. The study was carried out on the experimental fields of the Pushkin and Pavlovsk Laboratories of VIR National Research Scientific and Practical Institute in 2019–2022. The soils of the experimental field are sod-weakly podzolic, sandy loam in mechanical composition, with neutral acidity (pH = 7.1–7.6). The thickness of the humus horizon is 23–47 cm, the humus content is 2.1–3.0 %. The supply of mobile forms of potassium is average, phosphorus is high, the predecessor is pure fallow. For an accurate and reliable assessment, the following indicators were used: environmental variation (Si2), variation coefficient (CV), measure of superiority (Pi), indicator of agroecological superiority (Jsp), stress susceptibility index (SSPi), stability indicator (YSi), ecological valence (Wi), degree of adaptation (DAA), reaction effect (Er), intensity indicator (I), stress resistance (Ymin – Ymax), compensatory capacity (Ymin + Ymax)/2, stability (Ymin/Ymax), responsiveness coefficient (Kr). Significant variability of protein content in grain was determined from 11 % in 2020 to 13 % in 2022. The varieties Talovskaya 45, Moskovskaya 18, Novosibirskaya 17, Sudarushka exceeded the standard variety Era by 1–0.4 %. Of the 14 indicators used, the following should be used for a more reliable assessment: the coefficient of variation (CV), the measure of superiority (Pi), the index of susceptibility to stress (SSPi), the ecological valence (Wi), the degree of adaptation (DAA), the effect of reaction (Er), the intensity index (I). The varieties Moskovskaya 18, Novosibirskaya 17, Sudarushka, Talovskaya 45 have a high degree of adaptability.

Influence of Forest Strips on Changes in Soil Properties in the Agrolandscape

Background: In Russia 5.2 million hectares of protective forest plantations were created on agricultural land. Forest strips optimize moisture turnover, heat and gas exchange of the territory and transform agrarian landscapes into more sustainable forest-agrarian ecosystems (agroforest landscapes). Studying the impact of shelterbelt forests on the transformation of soil properties in the context of climate change (organic carbon storage) is an important problem. The aim of our research was to study the effect of shelterbelt forests on soil indicators and to digitally map the contours of forest-meliorated soils on the test site using GIS-technology and field studies. Methods: In the present study, the methodology of soil studies in agroforested soils (1978) and the methodology of assessing the accumulation of substances in plants and soils in agroforested landscapes were used to study forest-meliorated soils. We proceeded from the position that the reclamation effect of forest belts occurs at a distance of 30 heights. The research was conducted from 2016 to 2022. Result: Research has established, that the soil profile under the forest belt has an organogenic horizon A0 (forest floor); the thickness of the humus horizon (A+B1) under the forest belt is 8-10 cm higher compared to other zones. Spatial distribution of humus content in the A+B1 horizon from the forest belt to the centers of inter-belt squares (zone 20H) is not characterized by great variability and clear patterns and on average makes 1.15-1.2%. The increase in calcium carbonate (CaCO3) content in the soil occurs in the direction from the forest belt to the 20H zone. The indicator of dense residue in terms of the content of readily soluble salts is not relevant in estimating the forest belt’s influence on transformation of soil properties. A preliminary digital map of the contours of forest-reclaimed soils has been compiled. The obtained materials will serve as a basis for modeling the spatial and temporal dynamics of soils under forest belts in the zonal section and improving soil fertility in the interstrip space.

Grey alder at the regeneration stage: Long-term effects on soil nitrogen and carbon pools and Norway spruce growth

Increasing soil N availability is an effective way to enhance soil organic carbon (SOC) sequestration and biomass production in N-limited ecosystems such as boreal Norway spruce forests. Alder has a root nodule symbiosis with Frankia, an N2-fixing bacterium, and can thus add considerable amounts of N to soil mainly through its N-rich leaf litter. The objective of this study was to determine whether the presence of grey alder at the regeneration stage had any long-term effects on soil C and N cycling and stocks and spruce growth. The study sites were two relatively fertile 40-year-old Norway spruce stands (Luhdansuo and Porkkola) in Southern Finland. At both study sites, half the spruce stand had an admixture of grey alders for approximately 10–15 years after regeneration (alder treatment), but no alder had been present in the other half (control treatment). Alders were cut from the alder treatment 25 (Luhdansuo) or 30 (Porkkola) years before the measurements. At Porkkola, alder treatment received ash fertilisation 13 years ago. We observed no significant differences in the plant-available N fluxes, measured with a microdialysis technique, or SOC stocks between treatments. The total N stock (organic horizon + 0–30 cm mineral soil) and organic horizon thickness were larger, while the microbial biomass C:N and C mineralisation rate were lower in the alder versus the control treatment at Luhdansuo. The annual ring widths of spruces were larger in the alder versus the control treatment for up to six years after alder removal at both sites, but no differences were observed in the current tree diameters or diameter increments. In conclusion, most of the current soil or tree properties did not differ significantly between treatments, possibly because the effect of alder had faded out over the 25–30 years since its removal, and because the sites were initially relatively fertile.

Wildfires’ Effect on Soil Properties and Bacterial Biodiversity of Postpyrogenic Histic Podzols (Middle Taiga, Komi Republic)

Data on the main properties of Histic Podzols in the pine forests of semi-hydromorphic landscapes in the middle taiga of the Komi Republic after forest fires are presented. A decrease in topsoil horizon thickness by more than 7.6 times, an increase in litter density by 6 times, and a decrease in litter stock by 4 times were observed in postfire soil. There was an increase in carbon content in the pyrogenic horizon (48%) and in the upper part of the podzolic horizon—from 0.49 at the control plot to 1.16% after the fire. The accumulation of all studied trace metals (Cu—from 2.5 to 6.8 mg × kg−1; Zn—from 35.7 to 127.4 mg × kg−1; Ni—from 2.2 to 8.1 mg × kg−1; Pb—from 1.4 to 28.3 mg × kg−1; Cd—from 0.3 to 1.1 mg × kg−1) in soils after wildfires was recorded. The effect of the fire can be traced to a depth of approximately 20–30 cm. A significant influence of the pyrogenic factor on the alpha and beta bacterial diversity was noted. The bacterial response to a forest fire can be divided into an increased proportion of spore-forming and Gram-negative species with complex metabolism as well.

Productivity of vegetation and carbon stock in meadow steppe on fallow areas in the Bashkir Cis‐Urals (Southern Urals region), Russia

Aim. Data collection and analysis of the composition and productivity of vegetation and assessment of carbon sequestration by vegetation and soil in meadow steppe at a fallow site in the Bashkir Cis‐Urals, Russia. Material and Methods. The work is based on a survey of vegetation and soils of meadow steppe located in fallow areas, where post‐agrogenic restoration succession has been going on for more than 20 years. Results. The plant cover of the area studied is close to natural rich‐forb meadow steppes but differs in lower indicators of species richness and saturation, as well as the presence of weedy segetal species. The total plant biomass on the plot studied was estimated at 11.35 t/ha (including live aboveground biomass 2.98 t/ha, mortmass 3.11 t/ha, root weight 5.25 t/ha). The average stock of carbon in the plant biomass is 427.6 g/m2, and the total carbon stock in plant matter within the site is 36.88 tons. The soil cover of the area studied is Chernozem Calcic. The average levels of carbon stocks in short‐thickness soil at the 0–90 cm layer is 308 t/ha, while in medium‐thick soil it is 378 t/ha. Conclusions. A feature of the communities surveyed is a poor floristic composition, low productivity and low proportion of roots (47 % of the total plant biomass), which is caused by incomplete recovering of steppe vegetation and low thickness of the humus horizon. The soils of the site are close to virgin steppe lands in terms of carbon content and reserves.

THE DETERMINATION OF THE MOST OPTIMAL METHODS FOR THE IRRIGATION OF CROPS ON DIFFERENT SOIL TYPES

Climate change due to multiple pollution problems (forest clearing, overgrazing, motor vehicle emissions, construction expansion, etc.), has led to increased global average temperature and reduced rainfall. Under these conditions, the mineralization of organic matter is intensified, the activity of soil microorganisms is reduced and implicitly decreases soil trophicity. These aspects further show the need to apply irrigation in the agricultural sector, rationalysing water, managing it and recommending the best methods of water distribution, on soils with different textural classes. In this regard, research was carried out on water permeability, on soils formed in different pedo-climatic conditions. Thus, three soil profiles were opened, in the Tecuci Plain, on a typical arenosoil, in the Dobrogea Plateau, on a calcaric chernozem and in the Gavanu-Burdea Plain on a chromic luvisol. Soil profiles were characterized morphologically and physico-chemically, soil samples were collected both in natural and modified settlement (metal cylinders). The physico-chemical analyses for the three soil types were determined within INCDPA laboratories Bucharest. Based on soil samples collected in metal cylinders, water permeability was determined using the ratio between the thickness of the soil horizon and the time of water infiltration. Depending on the permeability of the soil on the three different soil types, the most suitable and economical watering methods for the current climatic conditions have been established and recommended.

MODERN ASSESSMENT OF FERTILITY OF DARK CHESTNUT SOILS OF KAMYSTINSKY DISTRICT OF KOSTANAY REGION

The article presents the results of a study on the morphological, nutritional characteristics of arable dark chestnut soils in the Kamystinsky district of the Kostanay region. According to the structure of the morphological profile, dark chestnut soils belonged to medium and low thickness types, where the thickness of the humus horizon A + B1 is noted within the range of 29 - 45 cm in depth. The accumulation of carbonates and ready soluble salts depends on the parent rocks and the grain-size distribution of dark chestnut soils. In dark chestnut immature soil, there are no carbonates along the soil profile, but gypsum is found at a depth of 36 cm. The line of bubbling from hydrochloric acid is different in ordinary and carbonate genus of dark chestnut soil. The humus content is low, in the plough-layer of soils it ranges 1.10 - 3.05%, the supply of nitrate nitrogen is very low, moving forms of phosphorus are medium and low, while potassium content is very high and elevated.

Оценка биологического ресурса базовых компонентов агроценоза с бинарными посевами подсолнечника и галеги восточной

The article provides an analysis of binary sunflower crops with eastern galega and typical chernozems as basic components of the agrocenosis from the point of view of soil conservation as a natural resource, as well as increasing the biological productivity of cultivated agricultural plants in the Buturlinovsky district of the Voronezh region. The sunflower yield is significantly influenced by the sowing of a perennial legume crop – eastern galega. Perennial leguminous grasses have an impact on the economic value of the soil cover, which is expressed in such indicators as the thickness of the humus horizon, the percentage of humus, the amount of alkaline hydrolyzable nitrogen. There was no significant effect of eastern galega on the amount of exchangeable potassium and phosphorus. Binary crops contribute to the preservation of soil moisture, due to a denser covering of the soil cover, which prevents the physical evaporation of moisture from the surface. Therefore, the introduction of binary crops leads not only to the stabilization of the soil component, the integrity of the agroecosystem is preserved, the productivity of the agrocenosis increases. Keywords: AGROECOSYSTEMS, BINARY CROPS, EASTERN GALEGA, SUNFLOWER, ALKALINE HYDROLYZABLE NITROGEN, EXCHANGEABLE PHOSPHORUS, EXCHANGEABLE POTASSIUM, HUMUS

Whoa on the wobble! Stem sinuosity in juvenile Douglas-fir across levels of genetic gain, silvicultural treatments, site conditions, and climatic variables in the Pacific Northwest

Managed forests serve as a natural climate change solution through sequestration of C and long-term storage in harvested wood products, in addition to providing ecosystem services and wildlife habitat. Specifically, commodity products such as dimensional lumber and building materials, utilized from high-quality, defect free trees, provide greatest economic return and long-term C reservoir. Stem sinuosity is a noted deformity in juvenile coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) and can result in loss of value and degraded economic end-product. While the causal mechanisms have been of interest for decades, relatively little is known regarding the influence of tree improvement, silviculture, and local growing conditions. A network of experimental plots (n = 132) across six installations in the Pacific Northwest (PNW) were assessed to determine the effects of tree spacing, vegetation control, genetic gain, soil, site, and climate variables on stem sinuosity 10 years since planting. Sinuosity presence was greatest in wild genetic sources and on sites with low soil C and A horizon thickness. Severity increased with stem size and declined with concomitant gains in stand density and local windspeed. Findings suggest that site-specific deployment of genetic resources and silvicultural treatments may enhance Douglas-fir stem form in the PNW.

Rates of soil organic carbon change in cultivated and afforested sandy soils

Considerable advances have been made in the assessment and mapping of soil organic carbon stocks, but rates of change in carbon stocks remain to be quantified for many soils and ecosystems. We sampled 145 sandy soils (mostly Psamments) under permanent cultivation and forest. We used aerial imagery to determine the period of cultivation and to calculate changes in soil organic carbon stocks. Topsoil organic carbon stocks, including the A and O horizons, were highest in soils under forest which were never cultivated (36 Mg C ha−1) and lowest in soils under red pine with prior cultivation (31 Mg C ha−1). Average soil organic carbon stocks of the A horizons of cultivated soils were 33 Mg C ha−1. To meet the 4 per 1000 international initiative, these soils need to achieve a soil organic carbon sequestration rate of 0.1 Mg C ha−1 yr−1. A mean rate of change of −0.16 Mg C ha−1 year−1 was found. The A horizon thickness increased under cultivation, but soil organic carbon concentrations decreased leading to reduced soil organic carbon stocks. The decline in soil organic carbon stock could be explained by an increased rate of organic matter decomposition due to tillage, irrigation, nitrogen applications, and lower clay and silt contents. After about 70 years of afforestation with red pine, soil organic carbon stocks increased. The O horizon accrued organic carbon at a rate of +0.19 Mg ha−1 yr−1, but soil organic carbon stocks were lower in the A horizon compared to cultivated soils. Afforestation of abandoned cultivated fields maintained soil organic carbon in the A horizon and gained organic carbon in the O horizon, but the soil organic carbon stocks were below soils under forest which were never cultivated.

Updating of the Archival Large-Scale Soil Map Based on the Multitemporal Spectral Characteristics of the Bare Soil Surface Landsat Scenes

For most of the arable land in Russia (132–137 million ha), the dominant and accurate soil information is stored in the form of map archives on paper without coordinate reference. The last traditional soil map(s) (TSM, TSMs) were created over 30 years ago. Traditional and/or archival soil map(s) (ASM, ASMs) are outdated in terms of storage formats, dates, and methods of production. The technology of constructing a multitemporal soil line (MSL) makes it possible to update ASMs and TSMs based on the processing of big remote-sensing data (RSD). To construct an MSL, the spectral characteristics of the bare soil surface (BSS) are used. The BSS on RSD is distinguished within the framework of the conceptual apparatus of the spectral neighborhood of the soil line. The filtering of big RSD is based on deep machine learning. In the course of the work, a vector georeferenced version of the ASM and an updated soil map were created based on the coefficient “C” of the MSL. The maps were verified based on field surveys (76 soil pits). The updated map is called the map of soil interpretation of the coefficient “C” (SIC “C”). The SIC “C” map has a more detailed legend compared to the ASM (7 sections/chapters instead of 5), greater accuracy (smaller errors of the first and second kind), and potential suitability for calculating soil organic matter/carbon (SOM/SOC) reserves (soil types/areals in the SIC “C” map are statistically significant are divided according to the thickness of the organomineral horizon and the content of SOM in the plowed layer). When updating, a systematic underestimation of the numbers of contours and areas of soils with manifestations of negative/degradation soil processes (slitization and erosion) on the TSM was established. In the process of updating, all three shortcomings of the ASMs/TSMs (archaic storage, dates, and methods of creation) were eliminated. The SIC “C” map is digital (thematic raster), modern, and created based on big data processing methods. For the first time, the actualization of the soil map was carried out based on the MSL characteristics (coefficient “C”).

Combining ground penetrating radar methodologies enables large‐scale mapping of soil horizon thickness and bulk density in boreal forests

AbstractForest soil properties must be observed with the appropriate resolution by depth and landscape area to understand biogeomorphological controls on soil carbon (C). These observations, particularly in boreal forests, have been limited because of the poor resolution and unavailability of physical soil sampling results, especially for soil bulk density measurements. Ground penetrating radar (GPR) has been demonstrated to non‐destructively and continuously estimate forest soil properties required in Cstock estimates, such as soil horizon thickness and soil bulk density, across small spatial scales and shallow depths. Yet, successful small‐scale forest GPR approaches represent a potential opportunity to obtain soil property estimates at relevant resolution and depth across forest landscapes, enabling improvement to much needed soil mapping and stock estimates. This review discusses the existing soil property studies that utilize ground penetrating radar (GPR) and explores how the adaptation of GPR methodology can contribute to investigating soils in forest landscapes. We have identified common GPR surveying practices, data processing steps and interpretation methods employed in multiple studies. These approaches have proven effective in obtaining higher‐resolution estimates of important soil properties, such as bulk density and horizon thickness, within small‐scale forest plots. By applying relevant findings in this review to our own boreal forest investigation across an 80 m hillslope transect, we provide recommendations on how to tailor GPR methodology for landscape‐scale estimates of soil horizon thickness and bulk density to examine forest soil property distribution. These findings should enable the future collection of soil datasets informing the distribution of soil C stocks and their relationship to landscape features, and thus their controls and responses to climate and environmental change.

Mapping of peatlands in the forested landscape of Sweden using lidar-based terrain indices

Abstract. Globally, northern peatlands are major carbon deposits with important implications for the climate system. It is therefore crucial to understand their spatial occurrence, especially in the context of peatland degradation by land cover change and climate change. This study was aimed at mapping peatlands in the forested landscape of Sweden by modelling soil data against lidar-based terrain indices. Machine learning methods were used to produce nationwide raster maps at 10 m spatial resolution indicating the presence or not of peatlands. Four different definitions of peatlands were examined: 30, 40, 50 and 100 cm thickness of the organic horizon. Depending on peatland definition, testing with a hold-out dataset indicated an accuracy of 0.89–0.91 and Matthew's correlation coefficient of 0.79–0.81. The final maps showed a national forest peatland extent of 60 292–71 996 km2, estimates which are in the range of previous studies employing traditional soil maps. In conclusion, these results emphasize the possibilities of mapping boreal peatlands with lidar-based terrain indices. The final peatland maps are publicly available at https://doi.org/10.17043/rimondini-2023-peatlands-2 (Rimondini et al., 2023) and may be employed for spatial planning, estimating carbon stocks and evaluating climate change mitigation strategies.