Horizons Of Forest Soils Research Articles

Variability of PAH Patterns in Upper Forest Soil (Sub)horizons—A Case Study From South‐Central Poland

ABSTRACTPolycyclic aromatic hydrocarbons (PAHs) are a class of contaminants characterized by their persistent and toxic nature. This study examines the variability in PAH distribution patterns in the upper layers of forest soils, focusing on the influence of different characteristics of individual soil (sub)horizons. A total of 130 samples were collected from five forest areas in south‐central Poland and analyzed for the 16 priority PAHs. Samples were taken from the organic fermentative‐humic (Ofh), humic (A), and humic‐eluvial (AE) (sub)horizons. The highest mean concentrations of total PAHs were found in the subhorizon‐Ofh (Ofh—1547 μg kg−1, A—1103 μg kg−1, AE—109 μg kg−1). The PAH content was significantly correlated with SOM content and pH, but this correlation was only significant in the horizon‐A. The percentage contributions of 3‐, 4‐, 5‐, and 6‐ring compounds to the total PAHs varied among the investigated soil (sub)horizons. The subhorizon‐Ofh had the highest percentage contribution of 6‐ring PAHs, 4‐ and 5‐ring PAHs were most prevalent in the horizon‐A, while 3‐ring compounds in the horizon‐AE. The variability in PAH patterns was also reflected in individual PAH ratios (BaA/BaA+Chr, IcdP/IcdP+BghiP), confirming the different behavior of 4‐, 5‐, and 6‐ring compounds in these (sub)horizons. This suggests that the retention of PAHs in the investigated (sub)horizons is influenced by several factors, including pH, degree of SOM decomposition, and mineral fraction, each to a different extent. Our findings reveal significant knowledge gaps regarding the behavior and accumulation of PAHs in soil (sub)horizons, underscoring the need for further research.

Pokrywa glebowa miasta Lublina (wschodnia Polska)

Lublin is a voivodeship city located in the Lublin Upland (Eastern Poland). The study aimed to present the spatial differentiation of soils of the city of Lublin and some of their properties. The knowledge of soil cover is very important for spatial planning and for protection and proper use of soil resources of each city. The environmental-genetic map of Lublin’s soils included in this work was made on the basis of soil-agricultural map in the scale 1:25 000 of Lublin and the soil-habitat map of the Świdnik Forest District. The soil units distinguished on the map were classified according to the Systematics of Soils of Poland (2019) and the international soil classification (World Reference Base for Soil Resources, WRB). The spatial variability of Lublin’s soils is determined by the occurrence of different parent rocks, relief, water relations, vegetation cover and human activities. The main soil units occurring within the city of Lublin include: brown soils (WRB: Eutric/Dystric Cambisols), rusty soils (Brunic Arenosols), podzolic soils (Albic Podzols), clay-illuvial soils/lessive soils (WRB: Albic/Haplic Luvisols), black earths (WRB: Gleyic Phaeozems), chernozemic rendzinas (WRB: Rendzic Phaeozems) and brown rendzinas (WRB: Calcaric Cambisols), chernozemic/black alluvial soils (WRB: Fluvic Phaeozems) and ordinary alluvial soils (WRB: Dystric/Eutric Fluvisols), peat soils (WRB: Hemic/Sapric Histosols) and murshic soils (WRB: Murshic Histosols), and technogenic soils (WRB: Urbic/Spolic/Ekranic Technosols). The grain size composition of Lublin’s soils is quite diverse, with the most common being silts, loams and sands with varying proportions of skeletal parts. The reaction of the Lublin soils studied also varies. Very acidic and acidic reaction is present mainly in podzolic and rusty soils and typical acid brown soils. In contrast, proper brown soils are slightly acidic to neutral in the upper genetic horizons. Lessive soils also have an acid reaction in the upper genetic horizons. Fluvisols have a slightly acidic to alkaline reaction, and black earths have a neutral to alkaline reaction. The alkaline reaction is found in rendzinas and technogenic soils, in which significant amounts of calcium carbonate are present. Soil organic matter is mainly accumulated in organic soils (peat and muck soils), as well as in the surface organic horizons (O) of forest soils. In the mineral soils of Lublin, the highest content of organic carbon (C-org) was found in such soils as black earths, chernozemic rendzinas, chernozemic alluvial soils and in some technogenic soils. The usable quality of Lublin’s soils is high. There is a phenomenon of management of land with high bonitation classes for non-agricultural purposes, despite the high fees for excluding such land from agricultural production.

Srovnání stavu půd pod porostními skupinami jedle bělokoré a smrku ztepilého – případová studie

The state of upper horizons of forest soils under forest stand groups of silver fir (Abies alba Mill.) and Norway spruce (Picea abies /L./ Karst.) was compared in the same site conditions. The study was performed on the site characterized as oak-fir with Luzula nemorosa, soils were determined as Luvisols, altitude 420–440 m a.s.l. Upper soil horizons (L+F1, F2+H, Ah and B) were sampled in five replications, holorganic horizons quantitatively. The amount of surface humus as well as basic pedochemic characteristics were determined: pH, soil adsorption complex characteristics, exchangeable acidity, the content of total carbon and nitrogen, and content of total and plant available macronutrients. The cellulolytic potential of H and Ah horizons was determined in a laboratory experiment. Results confirmed only mild effects of silver fir on the soil chemistry: soil reaction, base saturation, and especially on nitrogen content and C/N ratio. Basic elements content was slightly affected as well. No visible effects of fir on the cellulolytic activity were detected. Silver fir, compared to Norway spruce, showed only minor soil improving function.

Organic carbon distribution between structural and process pools in the gray forest soil of different land use

The summarized data on the content of organic carbon (Corg) in the subtypes of gray forest soils occurring on the territory of Russia was presented. It was shown that the humus horizons of virgin light-gray, typical-gray, and dark-gray forest soils contain, on average, 2.16 ± 0.67, 2.42 ± 0.61, and 3.58 ± 0.95% Сorg, respectively, while the plowing layers of arable soils contain 1.36 ± 0.40, 1.71 ± 0.40, and 2.84 ± 0.86%, respectively. Structural (particulate organic matter 0.05–2 mm in size, CPOM, and mineral-associated organic matter <0.05 mm in size, CMAOM) and process (potentially mineralizable organic matter, C0, and microbial biomass, Cmic) pools were isolated in the organic matter of samples from different horizons of gray forest soils (Luvic Retic Greyzemic Phaeozems (Loamic)) under small-leaved forest and barley crop. The CPOM/CMAOM ratio in the upper soil horizons under forest and arable land was 0.60 and 0.26, respectively, and this ratio decreased with depth to 0.05 under both land uses. The sizes of the CMAOM, CPOM, C0, and Cmic pools correlated with each other and depended on the depth of the soil horizon, while the effect of land use on the pool ratios was found only for the surface horizons. The contribution of CPOM and CMAOM to the potentially mineralizable pool of organic matter in gray forest soil was 20–41 and 71–87%, respectively. According to the obtained data, the size of the C0 pool was almost equal to the annual amount of the heterotrophic CO2 emission from the soil. It was emphasized that determining of the sizes and ratios of structural and process soil organic matter pools should be important in the programs of carbon monitoring and recarbonization of agroecosystems.

The effect of shrubs admixture in pine forest stands on soil bacterial and fungal communities and accumulation of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent toxic pollutants. The species composition of the stand is important in shaping the quality of soil organic matter and, consequently, the PAH content. The main purpose of the research was to determine the role of shrubs in shaping PAH accumulation in forest soils. The study covered the soils of the pine stands of the Rybnik Forest District, which experiences some of the highest deposition of industrial emissions in Europe. Pine stands with admixture of shrubs (alder buckthorn Frangula alnus and European hazelnut Coryllus avellana) growing in the same soil conditions were selected for the study. Samples for analyses were collected from the organic horizon (O) (from a depth of 0–7 cm) and humus mineral horizon (A) (from a depth of 7–15 cm). The organic C and total N concentrations, pH, alkaline cation content, soil enzyme activity and PAH content were determined. Additionally, the taxonomic composition of soil bacterial and fungal communities was determined. The highest activity of enzymes was noted in soils under influence of shrubs. The enzymatic activity was positively correlated with the content of total N, organic C, pH H2O and KCl and negatively with the C/N ratio. The highest PAH content was recorded in the soils of pine stands without the admixture of shrubs. Our research indicates the importance of shrubs in shaping the properties of surface horizons of forest soil and, consequently on the accumulation of PAHs. Shrubs stimulate biochemical activity of soils which results in lower PAHs accumulation by providing more easily decomposable organic matter.

CARBON AND NITROGEN CONTENT AND RESERVES IN TERRESTRIAL ECOSYSTEMS OF THE MURMANSK REGION

The article provides an overview of own and literature data on phytomass reserves, carbon and nitrogen content, diversity of soil fauna and mycobiota in terrestrial ecosystems of the Murmansk region under conditions of combined action of natural and anthropogenic factors. The environmental factors determining the functioning of ecosystems, including the regulation of carbon cycles, are considered. It is shown that in representative spruce and pine forests, the concentrations and precipitation of carbon compounds from the atmosphere and its removal from soil waters are higher in the subcron spaces than in the intercron spaces. In soil waters, there is a decrease in carbon removal with the depth of the soil profile. The podzols are characterized by a bimodal distribution of humus over the soil profile with maxima in the organogenic and illuvial horizons. The carbon content in the organogenic horizon of the soils of spruce and pine forests varies from 12 to 54%, nitrogen — from 4.7 to 18.7 g/kg. The main carbon reserves in the organogenic horizon of forest soils are concentrated in the sub-crown spaces and reach 27–34 t/ha. Carbon reserves in the meter layer of soil (mineral horizons) are 47–60 t/ha. The phytomass reserves of the North taiga forests are characterized by low values (12–188 t/ha). Significant reserves of plant organic matter of the North Taiga forests are concentrated in the ground cover. The carbon content in the assimilating organs (leaves/needles, shoots) of plants of the North Taiga forests varies from 35 to 73%, nitrogen — from 5.4 to 23.6 g/kg. The rate of decomposition of plant residues and carbon loss during the decomposition of the fall of evergreen plants in spruce forests is higher than in pine forests, as are the indicators of the number of soil macrofauna. The podzols of the North Taiga forests correspond to the predominance of secondary destroyers of plant litter — humifiers of earthworms and mixophages wireworms, litter mollusks) and the absence of calcifilic groups of mineralizers (woodlice, bipedal millipedes). 122 species of microscopic fungi have been isolated from the soils of the Murmansk region. Species of pp. Penicillium and Umbelopsis were dominant in terms of abundance in the background soil, in anthropogenically altered soils — species of pp. Aureobasidium, Penicillium, Trichocladium, Trichoderma and Umbelopsis.

Seasonal controls override forest harvesting effects on the composition of dissolved organic matter mobilized from boreal forest soil organic horizons

Abstract. Dissolved organic matter (DOM) mobilized from the organic (O) horizons of forest soils is a temporally dynamic flux of carbon (C) and nutrients, and the fate of this DOM in downstream pools is dependent on the rate and pathways of water flow as well as its chemical composition. Here, we present observations of the composition of DOM mobilized weekly to monthly from O horizons in mature forest and adjacent harvested treatment plots. The study site was experimentally harvested, without replanting, 10-years prior to this study. Thus, the treatments differ significantly in terms of forest stand and soil properties, and they interact differently with the regional hydrometeorological conditions. This presented an opportunity to investigate the role of forest structure relative to environmental variation on soil DOM mobilization. On an annual basis, fluxes of total dissolved nitrogen (TDN) and dissolved organic nitrogen (DON) were largest from the warmer and thinner O horizons of the harvested (H) treatment compared to the forest (F) treatment; however, neither phosphate nor ammonium fluxes differed by treatment type. On a short-term basis in both H and F treatments, all fluxes were positively correlated to water input, and all concentrations were positively correlated to soil temperature and negatively correlated to water input. Soil moisture was negatively correlated to the C : N of DOM. These results suggest common seasonal controls on DOM mobilization regardless of harvesting treatment. Optical characterization of seasonally representative samples additionally supported a stronger control of season over harvesting. The chemical character of DOM mobilized during winter and snowmelt: lower C : N, higher specific ultraviolet absorbance and lower molecular weight of chromophoric DOM (CDOM; higher spectral slope ratio) were representative of relatively more decomposed DOM compared to that mobilized in summer and autumn. This shows that the decomposition of soil organic matter underneath a consistently deep snowpack is a key determinant of the composition of DOM mobilized from O horizons during winter and the hydrologically significant snowmelt period regardless of harvesting impact. Despite the higher proportion of aromatic DOM in the snowmelt samples, its lower molecular weight and rapid delivery from O to mineral horizons suggests that the snowmelt period is not likely to be a significant period of DOM sequestration by mineral soil. Rather, the higher-molecular-weight, high-C : N DOM mobilized during slow and relatively infrequent delivery during summer and rapid, frequent delivery during autumn are more likely to support periods of mineral soil sequestration and increased export of fresher terrestrial DOM, respectively. These observed seasonal dynamics in O horizon DOM suggest the predicted decreases in winter and spring snowfall and increasing autumn and winter rainfall with climate warming in this region will enhance mobilization of DOM that is more reactive to mineral interactions in deeper soil, but also more biological and photoreactive in the aquatic environment. Understanding the downstream consequences of this mobilized DOM in response to these shifts in precipitation timing and form can improve our ability to predict and manage forest C balance but requires understanding the response of landscape hydrology to these changing precipitation regimes.

Bacterial and fungal community composition and community-level physiological profiles in forest soils.

We characterized the potential functioning and composition of the bacterial and fungal communities in the O and A horizons of forest soils using community-level physiological profile (CLPP) based on BIOLOG analysis, and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis of 16S and 18S rDNA fragments, respectively. In addition, relationships between the potential functioning and the community composition in each horizon, and between the O and A horizons, were assessed using Procrustes analysis. For the bacterial and fungal communities, the CLPP and DGGE profile were clearly separated between the O and A horizons in a principal coordinate analysis except for the fungal CLPP. No significant links for CLPP and DGGE profile between the O and A horizons were observed for either bacterial or fungal communities, suggesting that different factors had considerable influence on the microbial communities between the O and A horizons. Significant couplings between bacterial and fungal DGGE profiles (p <0.05 for O horizon; p <0.01 for A horizon), and between bacterial and fungal CLPPs (p = 0.001 for O horizon; p <0.01 for A horizon), were observed in the O and A horizons, implying that common factors strongly influenced the bacterial and fungal communities in each horizon. Although a significant correlation was observed between bacterial community composition and the potential functioning in the A horizon (p <0.01), such a correlation was not observed for the fungal community in the A horizon, and for the bacterial and fungal communities in the O horizon. This finding suggested that potential functioning, which would reflect only rapidly growing microorganisms, was not strongly associated with the composition of the entire microbial community. Further studies are needed to unravel the factors shaping the composition and functioning of microbial communities in forest soils.

Investigating drivers of active nitrification in organic horizons of tropical forest soils

• Some O horizons showed higher nitrification rate than mineral horizons. • Both total N and pH were positively correlated with nitrification rate in O horizon. • Nutrient richness in litters supported active nitrification in O horizon. • Nitrification rate in O horizon increased along with a pH threshold of 5.5–6.0. High nitrate leaching has been observed from the O horizons of some tropical forests; however, the drivers of high nitrate production (active nitrification) in these O horizons have not yet been identified. This study investigated the drivers of active nitrification in the O horizon of tropical forest soils by focusing on two of the most widely recognized controlling factors of nitrification, total N, and pH. We collected mineral and O horizons from eight tropical forests in Cameroon, Indonesia, and Malaysia and measured gross nitrification rates. Some O horizons showed significantly higher gross nitrification rates than mineral horizons, indicating that these O horizons have a high potential for nitrification. Gross nitrification rates in the O horizons were positively correlated with both total N and pH, and the chemical properties (e.g., total content of N, P, and base cations) were intercorrelated. These correlations suggested that the underlying driver of nitrification in the O horizon was nutrient richness in the litter. Results also indicated a threshold of gross nitrification rates around pH values of 5.5–6.0. We elucidate that active nitrification and subsequent high nitrate leaching from the O horizon could be driven by nutrient-rich litter, possibly derived from soil fertility and tree species.

Post-pyrogenic transformation of biogeochemical properties of grey forest soils under technological load

Purpose. Detection of post-pyrogenic transformation of biogeochemical properties of soils in pine forests of the Kharkiv region under technogenic loading. Methods. Determination of the pH of the water extract by the potentiometric method, the content of humus and gross nitrogen according to the Tyurin method, the granulometric composition according to Kachynskyi, the mobile forms of phosphorus and potassium according to Machigin. The content of mobile forms of heavy metals was determined by the atomic absorption method. Results. There is a certain dependence of the post-pyrogenic transformation on the age of fire impact on the soil. Relatively recent consequences of a fire of medium intensity on the soil were marked by a clear reaction of the complex of their properties. Physical-chemical properties of soils in the post-fire period deteriorate due to a significant decrease in the amount of nutrients in the soil: humus burns, nitrate nitrogen content decreases. The acid-alkaline reaction according to the pH index in the soils affected by fires shifts to neutral, which should be explained by the saturation of the absorbing complex of soils with alkaline earth elements. Forest lowland fires significantly transform the morphological appearance of the upper part of the soil profile. Under the influence of fires, there are changes in pH, the content of exchangeable cations, gross and mobile forms of nitrogen, etc. The behavior and content of heavy metals in the forest floor is determined, in addition to the effect of fire and the geochemical state of the region, the speed of water migration and biological absorption, and the topography of the area. The concentration of heavy metals in the surface horizons of the soils of pine forests increases several times and exceeds the background concentrations as a result of the mineralization of the forest floor and grassy vegetation from combustion and subsequent migration of chemical elements. Conclusions. As a result, the surface horizons of soils change, in particular, a new pyrogenic horizon is formed, which differs in a certain way from natural analogues. Fires, on the one hand, improve the conditions for seed penetration into the soil, but worsen the conditions for the germination, growth and development of coniferous tree species. The concentration of heavy metals in the surface horizons of pine forest soils is an ecological hazard. Further research on the transformation of soil properties under the influence of pyrogenic factors is of significant theoretical and practical importance in the development of scientific approaches to the restoration of ecosystems in the post-fire stage of development.

Modelling the Rhizosphere Priming Effect in Combination with Soil Food Webs to Quantify Interaction between Living Plant, Soil Biota and Soil Organic Matter.

A model of rhizosphere priming effect under impact of root exudate input into rhizosphere soil was developed as an important process of the plant-soil interaction. The model was based on the concept of nitrogen (N) mining, compensating for the N scarcity in exudates for microbial growth by accelerating SOM mineralisation. In the model, N deficiency for microbial growth is covered (“mined”) by the increased SOM mineralisation depending on the C:N ratio of the soil and exudates. The new aspect in the model is a food web procedure, which calculates soil fauna feeding on microorganisms, the return of faunal by-products to SOM and mineral N production for root uptake. The model verification demonstrated similar magnitude of the priming effect in simulations as in the published experimental data. Model testing revealed high sensitivity of the simulation results to N content in exudates. Simulated CO2 emission from the priming can reach 10–40% of CO2 emission from the whole Ah horizon of boreal forest soil depending on root exudation rates. This modeling approach with including food web activity allows quantifying wider aspects of the priming effect functioning including ecologically important available N production.

Watershed-scale liming reveals the short- and long-term effects of pH on the forest soil microbiome and carbon cycling.

Soil microbial community composition routinely correlates with pH, reflecting both direct pH effects on microbial physiology and long-term biogeochemical feedbacks. We used two watershed-scale liming experiments to identify short- (2 years) and long-term (25 years) changes in the structure and function of bacterial and fungal communities in organic horizons (Oe and Oa ) of acid forest soils. Liming increased soil pH, extractable calcium, and soil carbon stocks, reduced biomass-specific respiration, and caused major changes in the soil microbiome in the short and long term. More taxa responded to liming in the short term (70%) than in the long term (30%), with most showing consistent directional responses at both sites. The ratio of change in relative abundance between limed and reference sites was twofold higher at the long than the short-term site, indicating that the effects of liming grew over time. Liming impacts were most pronounced in fungi, as steep declines of dominant ectomycorrhizal fungi (Cenococcum and Russula) occurred at both sites. Liming favoured neutrophilic bacteria over acidophilic populations according to estimated environmental pH optima. Collectively, these results demonstrate that a liming-induced change of one pH unit has an immediate and persistent effect on the structure and function of microbial communities in acid forest soils. The corresponding suppression of respiration indicates that anthropogenic alterations of soil pH, as driven by acid deposition or liming, can affect forest floor C stocks due to pH-driven shifts in community structure.

GIS-BASED MODELING OF CAESIUM-137 CONTENT IN SOIL MATERIAL APPLIED TO COMPUTE PLOWED SOIL LOSSES

Abstract. The paper describes and discusses possibilities for soil loss estimation in the area of an arable slope using the radiocaesium method, GIS-based analysis, and very high resolution satellite imagery. The interdependences between caesium-137 activity, catchment area value, and the (sign of) profile curvature were estimated using GIS facilities. Interdependencies were estimated for four zones of an agricultural field located in the basin of the Sukhaya Orlitsa River in the Oryol district of the Oryol region (central part of European Russia). The zones were delineated according to differences of surface structure. Special attention was paid to the analysis of the caesium-137 and humus lateral and vertical (in the 0–25 cm arable soil layer) distribution in the area of agricultural field located on the slope of southern exposure. Overplowed soils were detected in one of the delineated zones. Overplowed soils are a type of degraded soils. This soil type was formed under conditions of applying a small amount of fertilizers for the period from 1991 to 2017 in agricultural fields remote from the central estates. In the studied area, the humus content in the arable horizon of plowed gray forest soil was reduced to 4%. The specific activity of caesium-137 does not exceed 140.0 Bq/kg (with its value at the reference plot of 174.7 Bq/kg). The radiocaesium method and estimations of morphometric parameters of topographic relief applied to the computation of soil runoff rate, made it possible to formalize the description of soil losses depending on in-the-relief position of the point, and to compile maps of soil runoff for each of the zones in the field. It was found that the area of overplowed soils is characterized by the largest soil losses (reaching 20 t/ha per year or more). Compiled map can allow to undertake a differentiated approach to the reclamation arrangement of the territory in the analyzed area. If enough fertilizers are applied, the productivity of the overplowed soils can be restored in the future.

Microaggregate Composition as a Factor of Variability in the Physical Properties of Gray Forest Soils in Western Siberia

The aim of the study was to study the variability of the microaggregate composition of the soil profile of virgin gray forest soils in the western part of the West Siberian Lowland. 330 soil sections were studied, covering all subtypes of gray forest soils. Empirical data were processed using mathematical methods of variation statistics. The results of the research showed that the humus horizon of light gray forest soils is characterized by good water resistance of microaggregates - the dispersity factor on average for the sample is 14.6%, the variation is small (Cv = 19%). Gray forest soils in the humus horizon have, on average, a dispersity factor of 12.2%. This subtype, in comparison with light gray soils, has a higher variability of the dispersity factor (Cv = 24%), which is due to the variety of combinations of soil formation factors, mainly relief and vegetation. The dispersity factor of the humus horizon of dark gray forest soils averages 7.9% for the sample, which is typical for medium structured soils; the variation is estimated as small (Cv = 18%). The microaggregate composition of gray forest soils is characterized as satisfactory throughout the entire soil profile, which makes it possible to improve structure formation during agricultural development and maintain the optimal structural-aggregate composition for a long time. The results obtained can be used in the development of an adaptive-landscape system of agriculture.

The role of afforestation species as a driver of Hg accumulation in organic horizons of forest soils from a Mediterranean mountain area in SW Europe

Forest areas are a primary sink of atmospheric mercury (Hg) within terrestrial ecosystems, whereas forest vegetation plays a key role in atmospheric Hg transfer to soil horizons. This study assessed variations in total Hg contents (HgT) and accumulation (HgRes) in the soil organic horizons of a forest area in NE Portugal, where post-wildfire afforestation led to the substitution of the native deciduous species (Quercus pyrenaica) by fast-growing coniferous species (Pseudotsuga menziesii and Pinus nigra). The study also evaluated, for each species, the links between Hg contents and other biophilic elements of soil organic matter (C, N, S) present in organic subhorizons (OL, OF, OH). Mean HgT in the organic horizons of the different tree species follow the sequence: P. nigra (88 μg kg−1) < Q.pyrenaica (101 μg kg−1) <P. menziesii (141 μg kg−1). The highest HgRes for the entire organic horizon was found under P. menziesii (471 μg m−2), followed by P. nigra (253 μg m−2) and Q. pyrenaica (189 μg m−2). Among the organic subhorizons, values of HgT and HgRes follow the sequence OL < OF < OH, which is consistent with the degree of organic matter humification. Indeed, HgT and HgRes correlated significantly with the C/N and C/S ratios for all species and organic subhorizons, suggesting that the quality of organic matter may influence strongly the Hg fate in these forest soils. Soils from P. menziesii plots have shown an HgRes 2.5 times higher than in plots dominated by the native Q. pyrenaica. Hg accumulation in the organic horizons, promoted in the coniferous species, may increase the risk of Hg mobilization due to wildfires and forest management practices. Therefore, forest management plans should select cautiously the tree species for afforestation in order to minimize adverse environmental effects caused by changes in the biogeochemical cycle of contaminants such as Hg.

Optimal resolution of soil properties maps varies according to their geographical extent and location

The important development of digital soil mapping (DSM) these last decades has led to a large number of maps of soil properties with increasingly finer raster size. Map resolution is mostly determined by expert knowledge or by matching with the resolution of existing data, while scale is recognized as a major issue. Using the pH and the C/N ratio describing the surface horizon of forest soils and estimated by bioindication, we evaluated the effect of resolution changes on model and map performance for different geographical extents. Using 40,663 plots from the national forest inventory and 25 environmental variables calculated at eight different spatial resolution levels (50, 100, 250, 500, 1000, 8000, 16,000, and 50,000 m), we modeled and mapped pH and C/N over a vast and diversified area of 91,000 km2 in the north-east of France. The models highlighted the importance of geology in pH and C/N spatial variations, and to a lesser extent the importance of stand type, climate and topography, with a slight influence of data resolution on predictor selection. On the contrary, the accuracy of model or map performance decreased significantly above 1000 m resolution. Significant performance differences were observed according to the location and the size of the geographical extent. Globally, the more heterogeneous environmental characteristics and the smaller the geographical extent, the better fine spatial resolution performed. In addition, the aggregation of fine-resolution pH or C/N maps at a coarser cell size improved map performance as compared to the direct use of the coarse-resolution predictors. The impact of resolution changes on map accuracy varies according to the mapping procedure, the local environment, and the geographical extent, and should be evaluated in DSM studies to optimize map accuracy.

Influence of manure application method on gray forest soil fertility, crop yield and quality

The article presents the results of field experiments on deepening the arable horizon of gray forest medium loamy soil to increase its fertility through applying organic fertilizer under PY-3-35 layer plow to a depth of 2527 cm. Low mineralization of organic fertilizer during layer cultivation under oxygen deficiency conditions contributed to accumulation of humus in soil by 6.6 t/ha more than during conventional plowing, and by 7.5 t/ha - than during disking. It also improved water-physical and biological properties of soil: number of water-resistant aggregates increased by 4.6 and 5.3 %, soil density lowered by 0.03 and 0.04 g/cm3, number of earthworms increased by 3...6 individuals, expanded reproduction of fertility was provided, productivity of arable land increased by 7.0 and 6.7 % and crop quality increased compared to conventional plowing and disking, respectively. Deep manure incorporation extended life of organic fertilizer up to 5 years, while after conventional plowing and disking this process lasted only 2...3 years. It is not economically and environmentally beneficial, since frequent application requires a lot of fuel, and a large amount of harmful chemical compounds contained in combustion products is dumped into the environment.

THE CHANGE OF PROPERTIES OF BROWN FOREST SOILS IN 10 YEARS ON THE TRACK “SKOLE − PARASHKA” (NPP “SKOLIVSKI BESKYDY”, UKRAINIAN CARPATHIANS)

Carry out monitoring of the track “Skole−Parashka” by the main five criteria of degradation of the natural environment: 1) width track (І category: to 0,5 m, “Unchanged track”; II category: to 1 m, “Little−changed track”; III category: 2−3 m “Endangered track”; IV category: to 5 m “Devastated track”; V category: over 5 m, “Strongly devastated track”); 2) presence of additional/parallel paths; 3) soil density; 4) quantitative and qualitative changes in vegetation (meadow ecosystems), presence/absence of forest litter (forest ecosystems); 5) the growth of erosion processes and the microrelief of the trail. It was found that for 10 years of exploitation by tourist track “Skole − Parashka” the width of the trail increased by 0,3–1,2 m. Reveal changes in soil over physical, water-physical, physicо-chemical and biotic properties of brown forest soils. The bulk density of soil structure on trails during 2012−2014 increased by approximately 32 % compared to the control, and after 10 years it increased − to 38 %. To reveal within the roadside an increase in soil bulk density from 1,07 to 1,17 g•cm-³ for 2019−2021 years. An increase in the density of the solid phase was recorded. The results of which are characteristic of the Hp horizon of brown forest soils. On the track porosity total to appraise “unsatisfactory”. For 10 years of recreational use of the track, the water permeability on the trails has not changed and was 0,07 and 0,06 mm•min-¹ according to the periods of the study (2012-2014 and 2019-2021). Within the roadside water permeability in 2012−2014 decreased by 60−80%, then in 2019−2021 years water permeability decreased by more than 90%. The actual water permeability of the soil during the downpour rains causes the intensification of surface runoff on the trail. On the track reveal abatement C organic. On the roadside track when lay to plane surface C organic unchanged within a years (2012−2014 and 2019−2021) and even was outstanding within a control. The increase C organic on the roadside is a result of “penetration” of the crushed fractions of forest litter into the H horizon during trampling and is not the result of biochemical processes. On the track increase of soil reaction (pH 5,0) while in the control pH 4,0. As to the biotic activity parameters, among the most significant are the catalase activity indices which are mostly determined by the density of the soil structure and water permeability. Key words: soil bulk density; water permeability; C organic; biotic activity; recreation influence; monitoring; NPP “Skolivski Beskydy”.

Leaching of Phosphomonoesterase Activities in Beech Forest Soils: Consequences for Phosphorus Forms and Mobility

Phosphomonoesterases play an important role in the soil phosphorus (P) cycle since they hydrolyze P monoester to phosphate. Their activity is generally measured in soil extracts, and thus, it remains uncertain how mobile these enzymes are and to which extent they can be translocated within the soil profile. The presence of phosphomonoesterases in soil solutions potentially affects the share of labile dissolved organic P (DOP), which in turn would affect P leaching. Our study aimed at assessing the production and leaching of phosphomonoesterases from organic layers and topsoil horizons in forest soils and its potential effect on dissolved P forms in leachates obtained from zero-tension lysimeters. We measured phosphomonoesterase activities in leached soil solutions and compared it with those in water extracts from litter, Oe/Oa, and A horizons of two beech forests with a contrasting nitrogen (N) and P availability, subjected to experimental N × P fertilization. In addition, we determined phosphate and DOP. In soil solutions leached from litter, Oe/Oa, and A horizons, phosphomonoesterase activities ranged from 2 to 8 μmol L–1 h–1 during summer, but remained below detection limits in winter. The summer values represent 0.1–1% of the phosphomonoesterase activity in soil extracts, indicating that enzymes can be translocated from organic layers and topsoils to greater soil depths. Activities of phosphomonoesterases obtained by water extracts were greater in the organic layer of the P-poor site, while activities of those in soil solutions were similar at the two sites. Nitrogen addition increased phosphomonoesterase activities in leached soil solutions of the organic layer of the N- and P-poor soil. Using a modeling approach, we estimated that approx. 76% of the initial labile DOP was hydrolyzed to dissolved inorganic P within the first 24 h. Back calculations from measured labile DOP revealed an underestimation of approx. 15% of total dissolved P, or 0.03 mg L–1. The observed leaching of phosphomonoesterases implies that labile organic P could be hydrolyzed in deeper soil horizons and that extended sample storage leads to an underestimation of the contribution of DOP to total dissolved P leaching. This has been neglected in the few field studies measuring DOP leaching.

Chemical Speciation and Potential Mobility of Heavy Metals in Forest Soil Near Road Traffic in Hafir, Algeria.

Background.Different fractions of metals, of varying origin and reactivity, are present in sediments of forest soil. Forest ecosystems are privileged sites for the deposition of persistent organic pollutants carried by the atmosphere.Objectives.The present study describes the current state of metallic contamination around the Hafir forest, located southwest of Tlemcen, Algeria, based on analysis of total sediment mineralization and the speciation of each metal to examine the effects of emissions due to road traffic.Methods.The distribution and migration of ten heavy metals were studied, including cadmium (Cd), nickel (Ni), cobalt (Co), chromium (Cr), manganese (Mn), lead (Pb), copper (Cu), zinc (Zn), iron (Fe), and silver (Ag), and four major elements: potassium (K), sodium (Na), magnesium (Mg), and calcium (Ca) in the superficial horizon of forest soil (0–20 cm) at different road distances (0–1700 m), in two sampling campaigns in the dry and wet seasons around the Hafir forest, Algeria.Results.Bioavailability appears to be relatively low due to the small amount of metals present in the carbonate fraction and the alkaline pH. The impact of road traffic was observed in the variability of the concentrations of several trace elements in forest soil, such as Co, Mn, Ni, Zn, Pb, Ag, Cd. They were generally observed at very high levels along the roadside due to dry atmospheric deposition.Conclusions.The high levels of metals in the carbonate, reducible and residual phases indicate a direct influence on the environment stemming from road traffic near the forest as well as contamination from rainfall in the area.Competing Interests.The authors declare no competing financial interests.