Uppermost Soil Horizons Research Articles

Enhancing Soil Mapping with Hyperspectral Subsurface Images generated from soil lab Vis-SWIR spectra tested in southern Brazil

The Remote Sensing (RS) products involving the visible, near-infrared and short-wave infrared (Vis–NIR-SWIR, simply Vis-SWIR) wavelengths are applicable for spatial prediction of soil properties, usually in the process called Digital Soil Mapping (DSM). The multispectral optical orbital sensors lack spectral resolution, while the Proximal Soil Sensing (PSS) offers many application possibilities. The limited spectral resolution and soil cover are the main challenging aspects for DSM. The objective of the study was to combine the soil lab Vis-SWIR spectra within DSM technique to create new hyperspectral images to use as covariates in a novel method of soil mapping. The advantages of the method were demonstrated throughout the spatial prediction of the Total Carbon (TC) content on soils of the upper part of Itatiaia National Park (INP), (Rio de Janeiro and Minas Gerais States, southeastern Brazil). The covariates applied were multispectral orbital bands from Sentinel 2, relief with its terrain derivations, geology and geomorphology. Using uppermost soil horizon lab Vis-SWIR spectra information from 72 points in the upper part of INP, 130 hyperspectral images were generated, in other words, Hyperspectral Subsurface Image. The validation methods were 8-fold cross-validation (CV) and External Validation (EV) running alongside within Random Forest algorithm, where randomness was locked. The DSM reaches an average CV coefficient of determination (R2) of 0.39 and Root Mean Square Error (RMSE) of 4.6, while creating a new model with a set of hyperspectral images gave a CV R2 of 0.60 and RMSE of 4.06. The EV also presented an advantage for the second approach. The results support the method as the first strong integration between PSS and DSM, named by the authors as Hyperspectral Soil Mapping (HSM), which proved to be more efficient for mapping TC due to the pure soil lab Vis-SWIR spectra signal (free of atmospheric influence and vegetation cover). The method can be applied in dense or sparsely vegetated areas, for agricultural or conservation purposes, for various soil properties, with each and every wavelength.

Influence of tree species on carbon, nitrogen, and phosphorus stocks and stoichiometry under different soil regeneration scenarios on reclaimed and afforested mine and post-fire forest sites

In this work, we present the effects of Scots pine (Pinus sylvestris L.), common birch (Betula pendula Roth), and black alder (Alnus glutinosa Gaertn.) on the carbon (Cstock), nitrogen (Nstock), and phosphorus (Pstock) stocks and stoichiometry in the uppermost soil horizons (Oi + Oe, 0–5 cm) on afforested post-mining sand-pit and post-fire forest sites. These results were compared to those for undisturbed forest sites under the same tree species. The Cstock and Nstock of the post-fire soils were similar to those of the undisturbed soils, but lower for the reclaimed mine site. Notably, tree species affected the distribution of Cstock between the organic and mineral horizons. Compared to the other tree species, pine was characterized by a higher Cstock in the Oi + Oe horizons of the post-mining and undisturbed soils. In the 0–5-cm soil horizons, the highest Cstock values were detected under alder at the post-mining site and under birch and alder at the undisturbed site. For all of the studied sites, the C:N ratios in the litter horizons occurred in the following order: alder < birch < pine. This trend was only reflected in the mineral horizons of the undisturbed sites, which indicates the very temporary impact of organic matter on the disturbed sites. The C:P and N:P ratios in the mineral soil horizons were higher for the post-fire site than the post-mining and undisturbed sites, which may indicate a P limitation for the given content of C and N. Black alder, as a N-fixer, can increase the C:P and N:P ratios in nutrient-poor, sandy soils after disturbance in comparison with the other studied tree species, especially in post-fire soils. The uppermost mineral soil horizons under alder were characterized by higher C:P and N:P ratios than the soils under pine on the post-mining site and under the other tree species on the post-fire site. The N:P ratios in the litter horizons under alder on the disturbed sites were higher than for the other tree species, while this was not true for the undisturbed soils where alder grew under nutrient-optimal conditions. This suggests that the phytomelioration influence of N-fixers on degraded and nutrient-poor soils, may be inhibited by P limitation.

Soil Organic Carbon Pools and Associated Soil Chemical Properties under Two Pine Species (Pinus sylvestris L. and Pinus nigra Arn.) Introduced on Reclaimed Sandy Soils

The roles of different tree species and their impacts are key in assessing the dynamics of soil restoration in afforested post-mining sites. The objective of this study was to compare the effect of Scots pine (Pinus sylvestris L.), which is native to Central Europe and commonly used in afforestation, to that of the non-native black pine (Pinus nigra Arn.) on the development of carbon pools and the chemical properties of reclaimed soils after sand exploitation. The study was carried out in 20- and 35-year-old stands, and the results were compared to undisturbed forest sites. Samples of the litter horizon and mineral soils (0–5 and 5–20 cm) were analyzed for pH, soil organic carbon (SOC), and total nitrogen (Nt). In addition, electrical conductivity (EC), sorption complex properties, water-soluble carbon, and hot-water-extractable carbon were determined from the mineral soil samples. Scots and black pine had a similar effect on the properties of the reclaimed soils. However, the soils under Scots pine were characterized by lower pH values in the litter and 0–5 cm horizons, higher EC in the 0–5 cm horizon, and higher C stocks in the litter horizon. Changes in the C stocks and chemical properties with afforestation years were limited to the uppermost soil horizons (litter and 0–5 cm). For both pine species, soils under the older stands were characterized by lower pH, higher EC, higher exchangeable acidity, higher cation-exchange capacity, lower base saturation, higher SOC and Nt contents, and more stable soil organic matter than soil under younger stands. After 35 years, about 20% and 27% of the C stocks in the reclaimed mine soils had been restored under black pine and Scots pine, respectively (compared to undisturbed soils). This difference between the pine species resulted from the higher C stocks in the litter horizons under Scots pine. Pedogenesis in post-mining sites after sand exploitation under pine species tended to result in more acidic and oligotrophic soils in relation to the undisturbed soils in adjacent forest ecosystems with pine.

Hydrological soil properties control tree regrowth after forest disturbance in the forest steppe of central Mongolia

Abstract. The central Mongolian forest steppe forms a transition between different ecozones and is as such particularly sensitive to environmental changes. It is commonly affected by disturbances such as logging and forest fires. Intensified drought events aggravate stress on the trees that are anyway at their drier limit in the forest steppe. Climate change increases evapotranspiration and reduces the distribution of discontinuous permafrost, which leads to drier soil conditions. The motivation for this study came about through our previous observation that forest stands show great differences with respect to their recovery after disturbance by fire or logging. Sometimes, no regrowth of trees takes place at all. As water availability is the main limiting factor of forest growth in this region, we hypothesised that differences in soil hydrology control the forest recovery pattern. To test this hypothesis, we analysed soil properties under forests, predominantly consisting of Siberian larch (Larix sibirica Ledeb.), in the forest steppe of the northern Khangai Mountains, central Mongolia. We distinguished the following four vegetation categories: (1) near-natural forest (FOR), (2) steppe close to the forest (STE), (3) disturbed forest with regrowth of trees (DWIR), and (4) disturbed forest showing no regrowth of trees (DNOR). A total of 54 soil profiles were described in the field and sampled for soil chemical, physical, and hydrological analysis. We found a significant difference in soil texture between soils under DWIR and DNOR. Sand generally dominated the soil texture, but soils under DWIR had more silt and clay compared to soils under DNOR. Soil pF curves showed that soils under DWIR had higher plant-available field capacity in their uppermost parts than soils under DNOR. In addition, hydraulic conductivity tended to be higher in the uppermost horizons of soils under DWIR compared to their counterparts under DNOR. Chemical properties of the soils under DWIR and DNOR showed no significant differences. We conclude that the differences in post-disturbance tree regrowth are mainly caused by different soil hydrology. High plant-available field capacity is the key factor for forest recovery under semi-arid conditions. High hydraulic conductivity in the uppermost soil horizons can further support tree regrowth because it reduces the evaporation loss and the competition of larch saplings with grasses and herbs for water. Another important factor is human impact, particularly grazing livestock on cleared forest sites, which often keeps seedlings from growing and, thus, inhibits forest recovery. None of the disturbed sites (DWIR and DNOR) had permafrost. We, thus, conclude that permafrost is no major factor for the post-disturbance tree regrowth pattern, although it generally supports tree growth in the forest steppe by preventing meltwater from seasonal ice from seeping below the root zone, thus increasing the water supply in summer.

The Conversion of Abandoned Chestnut Forests to Managed Ones Does Not Affect the Soil Chemical Properties and Improves the Soil Microbial Biomass Activity

Recently, several hectares of abandoned chestnut forests (ACF) were recovered into chestnut stands for nut or timber production; however, the effects of such practice on soil mineral horizon properties are unknown. This work aimed to (1) identify the better chestnut forest management to maintain or to improve the soil properties during the ACF recovery, and (2) give an insight into the effect of unmanaged to managed forest conversion on soil properties, taking in consideration sweet chestnut (Castanea sativa Mill.) forest ecosystems. The investigation was conducted in an experimental chestnut (Castanea sativa Mill.) forest located in the northern part of the Apennine chain (Italy). We identified an ACF, a chestnut forest for wood production (WCF), and chestnut forests for nut production with a tree density of 98 and 120 plants ha−1 (NCFL and NCFH, respectively). WCF, NCFL and NCFH stands are the result of the ACF recovery carried out in 2004. After 15 years since the ACF recovery, generally, the effects on the main soil chemical properties were negligible. Some differences occurred for the water-soluble organic carbon (WSOC) and microbial biomass and its activity. NCFL showed the highest WSOC content in the uppermost soil horizon likely due to higher amount of roots which are source of labile organic compounds. The higher WSOC amount might explain the greatest amount of microbial biomass in the A horizon of NCFL. Furthermore, the microbial biomass harboring in the A horizon of NCFL has also shown both a better C use efficiency and a larger soil organic carbon immobilization in the microbial biomass itself. Our data would indicate that the ACF recovery into pure chestnut forests did not have negative impacts on soil chemical and biochemical properties, though chestnut stands for nut production with a low plant density are the most suitable ones.

Use of bathymetry and clay mineralogy of reservoir sediment to reconstruct the recent changes in sediment yields from a mountain catchment in the Western High Atlas region, Morocco

The dam of Takerkoust, located at the outlet side of N'fis Basin (Western High Atlas of Morocco), is one of the strategic reservoirs in Morocco facing a serious problem of siltation due to soil erosion. A paleo-hydrology approach combining chronological and sedimentological analyses is conducted to understand the evolution of the depositional sediment history of the Takerkoust reservoir between 1988 and 2016. First, a series of 8 bathymetric surveys in the Takerkoust reservoir was used to determine the chronology of flood event deposits. Second, grain size distribution, clay mineralogy (XRD) and organic matter content were analyzed in 2 cores drilled in the Takerkoust reservoir and the newly build Ouirgane reservoir in upstream (from which 46 samples were taken). Third, Soils samples collected from the uppermost soil horizons (First 5 cm) of different localities of the N’fis watershed were also analyzed to identify sediments origins. Eleven couplets with different textures and thickness are identified in the Takerkoust reservoir corresponding to the period 1988–2016. The highest correlation is observed between instantaneous maximum flow and thickness of the sandy component of the couplets. The variation of the siltation rate allows highlighting two distinct periods: the oldest period (1988–1999) characterized by a high sediment yield SY (908.6 t·km−2·yr−1) and a youngest one (1999–2016) characterized by a low SY (203.9 t·km−2·yr−1). The newly built Ouirgane dam, seems to be responsible for the decreasing siltation rate and change of the clay assemblages of the sedimentary series in Takerkoust reservoir.

Mobility of Pb, Zn, Cu and As in disturbed forest soils affected by acid rain

Early efforts at remediation of contaminated soils involve overturn or removal of the uppermost soil horizons. We find that such disruption is counterproductive, as it actually increases the mobility of the heavy metals involved. In our study, we sought to replicate in a controlled manner this commonly used remediation strategy and measure Pb, Zn, Cu and As concentrations in all soil horizons-both prior to and 1year after disruption by trenching. BCR analyses (sequential leaching) indicate that Pb is affected to the greatest degree and is most highly mobile; however, Zn and As remain insoluble, thus partially ameliorating the detrimental effect. Differences in vegetation cover (i.e. spruce vs. beech forest) have little influence on overall element mobility patterns. The Krušné hory (Ore Mts., Czech Republic) study area is one of the more heavily contaminated areas in Central Europe, and thus the results reported here are applicable to areas affected by brown-coal-burning power plants.

Retention of 137Cs in forest floor at three temperate coniferous forest stands in the Czech Republic diversely affected by fallout after the Chernobyl disaster in 1986

Distribution of the 137Cs activity concentrations, soil pH, content of organic matter and composition of mineral portion in humus were investigated in forest soils variably loaded by Chernobyl-derived fallout. Maximum in the 137Cs activity concentrations were found in the uppermost organic soil horizons. In forest humus the 137Cs activity concentrations was negatively related to pH and the content of organic matter. No significant content of clay minerals was detected in humus. Slow vertical migration (0.04–0.06 cm year−1) and effective half-life of 137Cs in humus about 20 years was found. The initial surface 137Cs activities in 1986 were estimated.

A comparative study on carbon stock in Sal (Shorea robusta) forest in two different ecological regions of Nepal

Estimation of total biomass and carbon sequestration in any forest is crucial as it gives ecological and economic benefits through various environmental services. With an aim to quantify the carbon stock densities in the two different ecological regions–the Hills and the Terai, two Community Forests (CFs) having the dominance of Shorea robusta were selected from Gorkha (in the Hills) and Chitwan (in the Terai) districts for the purpose of the study. Systematic random sampling with 1% sampling intensity was used to collect necessary data. The total carbon stock in the CFs of the Hills and the Terai were found to be 234.54 t ha-1 and 479.29 t ha-1, respectively. The biomass carbon stock density in the CF of the Terai was found to be higher (384.20 t ha-1) than the one in the Hills (123.15 t ha-1). Carbon densities of different carbon pools such as tree; sapling; leaf litter, grass and herbs were significantly higher (P&lt;0.05) in the Terai than in the Hill forest whereas dead wood and stumps and the soil organic carbon density were found to be not significantly different in these regions. Similarly, the highest amount of soil organic carbon (SOC) was found in the uppermost soil horizon in the forests of both the regions. These results revealed that the biomass carbon stock density was higher in the Terai S. robusta forest than in the Hill S. robusta forest. However, the SOC obtained was in inverse relation to that of the biomass carbon stock in both the ecological regions. It would not be biased if different ecological regions with similar forest types are intervened with different management strategies for having more carbon stocks and for the conservation of biodiversity in the days to come.Banko JanakariA Journal of Forestry Information for NepalVol. 26, No. 1, Page: 24-31, 2016

Particulate matter pollution from a small coke-burning factory: soil magnetic screening and its relation with a simple atmospheric dispersion model

Coal combustion processes lead to release of gases and particulate matter (PM) into the atmosphere that are often harmful to human health. These airborne pollutants seem to be dispersed and deposited in soils mainly according to the prevailing atmospheric conditions. Several trace elements can be found attached to PM as well as Fe-rich magnetic particles that can produce magnetic enhancement in the uppermost soil horizons. In the present work, we use a simple Gaussian Dispersion Model (GDM) for modelling the distribution of fine PM emission coming from a small coal (coke) burning factory in order to evaluate the relationship between such modelled data (PM distribution) and measured data (soil magnetic properties and trace metal contents). Our results show a strong spatial variation of concentration-dependent magnetic parameters based on a uniform magnetomineralogy in the overall study area. In addition, these results were analysed using multivariate statistics for 13 magnetic and chemical variables and the GDM results for two different atmospheric stability classes, and hence the in-situ magnetic susceptibility, anhysteretic and saturation remanent magnetization showed positive and statistically significant correlation with the GDM results (R = 0.70). Therefore, these results demonstrate the usefulness of magnetic properties in monitoring the PM distribution in soils or other environmental PM collectors.

Use of a flux‐based field capacity criterion to identify effective hydraulic parameters of layered soil profiles subjected to synthetic drainage experiments

AbstractThis study explores the feasibility of identifying the effective soil hydraulic parameterization of a layered soil profile by using a conventional unsteady drainage experiment leading to field capacity. The flux‐based field capacity criterion is attained by subjecting the soil profile to a synthetic drainage process implemented numerically in the Soil‐Water‐Atmosphere‐Plant (SWAP) model. The effective hydraulic parameterization is associated to either aggregated or equivalent parameters, the former being determined by the geometrical scaling theory while the latter is obtained through the inverse modeling approach. Outcomes from both these methods depend on information that is sometimes difficult to retrieve at local scale and rather challenging or virtually impossible at larger scales. The only knowledge of topsoil hydraulic properties, for example, as retrieved by a near‐surface field campaign or a data assimilation technique, is often exploited as a proxy to determine effective soil hydraulic parameterization at the largest spatial scales. Comparisons of the effective soil hydraulic characterization provided by these three methods are conducted by discussing the implications for their use and accounting for the trade‐offs between required input information and model output reliability. To better highlight the epistemic errors associated to the different effective soil hydraulic properties and to provide some more practical guidance, the layered soil profiles are then grouped by using the FAO textural classes. For the moderately heterogeneous soil profiles available, all three approaches guarantee a general good predictability of the actual field capacity values and provide adequate identification of the effective hydraulic parameters. Conversely, worse performances are encountered for the highly variable vertical heterogeneity, especially when resorting to the “topsoil‐only” information. In general, the best performances are guaranteed by the equivalent parameters, which might be considered a reference for comparisons with other techniques. As might be expected, the information content of the soil hydraulic properties pertaining only to the uppermost soil horizon is rather inefficient and also not capable to map out the hydrologic behavior of the real vertical soil heterogeneity since the drainage process is significantly affected by profile layering in almost all cases.

Excess of Organic Carbon in Mountain Spruce Forest Soils after Bark Beetle Outbreak Altered Microbial N Transformations and Mitigated N-Saturation.

Mountain forests in National park Bohemian Forest (Czech Republic) were affected by bark beetle attack and windthrows in 2004–2008, followed by an extensive tree dieback. We evaluated changes in the biochemistry of the uppermost soil horizons with the emphasis on carbon (C) and nitrogen (N) cycling in a near-natural spruce (Picea abies) mountain forest after the forest dieback, and compared it with an undisturbed control plot of similar age, climate, elevation, deposition, N-saturation level, and land use history. We hypothesised that the high litter input after forest dieback at the disturbed plot and its consequent decomposition might influence the availability of C for microorganisms, and consequently, N transformations in the soil. The concentrations of dissolved organic C (DOC) and N (DON) in soil water extracts rapidly increased at the disturbed plot for 3 yeas and then continually decreased. Net ammonification exhibited a similar trend as DOC and DON, indicating elevated mineralization. Despite the high ammonium concentrations found after the forest dieback (an increase from 0.5 mmol kg-1 to 2–3 mmol kg-1), net nitrification was stable and low during these 3 years. After the DOC depletion and decrease in microbial biomass 5 years after the forest dieback, net nitrification started to rise, and nitrate concentrations increased from 0.2–1 mmol kg-1 to 2–3 mmol kg-1. Our results emphasize the key role of the availability of organic C in microbial N transformations, which probably promoted microbial heterotrophic activity at the expense of slow-growing nitrifiers.

Physical and microbiological properties of alluvial calcareous Çumra province soils (Central Anatolia, Turkey)

Alluvial calcareous soils in Central Anatolia (Konya province, Cumra district) has a heavy granulometric composition (average clay), low organic carbon content (less than 1%), but stable pore space structure and favorable agrophysical properties. Studies of the water regime in drip irrigation confirm favorable hydrological properties of these soils. It is assumed that the favorable structure of the pore space due to vigorous activity a large and diverse soil biota. Four phyla dominate in soil biota, among which predominate Actinobacteria. The higher (Streptomyces), and lower (three species Rhodococcus) actinobacteria are predominant in large amounts as a part of this phyla. Large biodiversity at a sufficiently high bacteria richness formed the structure of the microbial community that contribute to the balanced production of specific metabolites, including gases (CO2, N2), which allows the soil to function actively, preventing compaction of the pore space and maintaining optimal density, porosity, hydrologic properties of the studied silty clay soils. m the uppermost soil horizons. Analyses of heavy mineral fraction show presence of metamorphic and igneous minerals which indicate participation of weathering products from other rock types in the nearby area. The types of heavy minerals in soils depend more on composition of parent rocks and geomorphic position than on climate type. Soils from Nova Lovcha show similar composition, but the quantity of goethite and hematite significantly increase in soil from plain. Typical high-metamorphic minerals as andalusite, kyanite and sillimanite present only in Nova Lovcha, while garnet dominates in Petrovo and opaque minerals - in Dobrostan. Red soils, formed on slopes, where erosion prevails over accumulation, contain more illite, smectite and vermiculite-smectite, and very few or no kaolinite, whereas the kaolinite is dominant in soils formed on plain. The mineralogical composition of clays in different polygons depends on geomorphic position (altitude, slope or plain), and less on climate type. The weathering processes in the highest polygon Dobrostan (more than 1200 m) are in early stage (illite, vermiculite-smectite, and smectite), whereas in Nova Lovcha (above 700-900 m) and Petrovo (1000 m) the domination of kaolinite suggests an advanced weathering processes.

Comparative mineralogical characteristics of red soils from South Bulgaria

The present study aims to compare mineralogical composition of red soils, formed on marbles in South Bulgaria. We used mineralogical analysis of heavy and light mineral fraction in immersion under polarizing microscope and X-ray diffraction analysis of bulk sample and clay fraction. Three test polygons, located in South Bulgaria were examined: Petrovo, Nova Lovcha and Dobrostan, which are characterized with different latitude, altitude, and exposition. Three or more sites from each polygon were sampled and analyzed. The red soils are formed on white and gray calcite and calcite-dolomite marbles, impure silicate-rich marbles and only in one site – on marble breccias. We determined the following mineral phases in red soils: calcite, dolomite, quarts, and feldspars, mica, illite-type mica, illite, smectite, vermiculite-smectite, and kaolinite. Heavy minerals are represented by amphibole, titanite and epidote, and minor amounts of zircon, garnet, tourmaline, rutile, pyroxene, andalusite, kyanite, sillimanite and apatite. Opaque minerals are predominantly goethite and hematite. Plant tissue is abundant in light fraction from the uppermost soil horizons. Analyses of heavy mineral fraction show presence of metamorphic and igneous minerals which indicate participation of weathering products from other rock types in the nearby area. The types of heavy minerals in soils depend more on composition of parent rocks and geomorphic position than on climate type. Soils from Nova Lovcha show similar composition, but the quantity of goethite and hematite significantly increase in soil from plain. Typical high-metamorphic minerals as andalusite, kyanite and sillimanite present only in Nova Lovcha, while garnet dominates in Petrovo and opaque minerals - in Dobrostan. Red soils, formed on slopes, where erosion prevails over accumulation, contain more illite, smectite and vermiculite-smectite, and very few or no kaolinite, whereas the kaolinite is dominant in soils formed on plain. The mineralogical composition of clays in different polygons depends on geomorphic position (altitude, slope or plain), and less on climate type. The weathering processes in the highest polygon Dobrostan (more than 1200 m) are in early stage (illite, vermiculite-smectite, and smectite), whereas in Nova Lovcha (above 700-900 m) and Petrovo (1000 m) the domination of kaolinite suggests an advanced weathering processes.

Functional diversity of soil microbial communities under Scots pine, Norway spruce, silver birch and mixed boreal forests

Functional structure and diversity of forest soil microbial communities may depend on plant diversity. The objective of our study was to compare community level physiological profiles (CLPPs) of microbial communities from uppermost soil horizons under Scots pine (Pinus sylvestris), Norway spruce (Picea abies), silver birch (Betula pendula) and mixed pine–birch–spruce stands representing boreal forests differing in the identity of the dominant tree species and diversity of overstory and understory plant species in the system. The samples of O and A soil horizons were measured for pH, organic carbon, and total nitrogen. Microbial analyses included determination of microbial biomass (Cmic) and measurement of CLPPs with the MicroResp™ system. The studied forest types differed significantly in plant species diversity with birch and mixed forests being the most and the pine forest the least diverse. Functional microbial diversity only slightly differed between the studied forest types and was not related to plant diversity. Despite similar functional diversity of soil microbial communities there were significant differences in CLPPs in the O horizons under the pine, spruce and birch forests indicating that plant cover affects the rate at which particular organic compounds are degraded. Differences in physiological profiles between the birch, pine and spruce forest soils were mainly due to variable decomposition of readily decomposable organic compounds represented mainly by carboxylic acids.

Short-term impact of de-vegetation on organic/inorganic interactions and cation transfers in uppermost soil horizons

The soil solutions of a natural soil covered by grass and of the same soil after grass removal were collected and analyzed after each rainfall and percolation through the two soils during a fifteen-month experiment. To identify and quantify the water–mineral–plant interactions during this period of time, plastic tubes containing calcite and smectite particles were inserted into the two soils, some powder of both being recovered after three and fifteen months, water leached and the leachates analyzed. The contents of various elements including the rare-earth elements were measured in the soil solutions and the water leachates, to identify the extent of the interactions and evaluate the contribution of the plants. The immediate impact of de-vegetation was recorded in the soil solutions that exported systematically more Si and Ca, and often more Mg from de-vegetated soil. The supplement of exported Si was probably released by altering microorganisms as a response to de-vegetation, whereas that of Mg resulted probably from dissolution of oxy-hydroxides and that of Ca from partial dissolution of the calcite reference mineral. The removed elements were about 50 times higher in the soil solutions than in the plain rainwater before percolation through the soils. The contents of the dissolved organic carbon and ammonia of the soil solutions from de-vegetated soil were about one third higher than in those of the vegetated soil.On the basis of the elemental contents of the soil solutions that percolated through the two soils, removal of plants did not significantly affect adsorption of the nutrient K on the inserted smectite and calcite during the initial three months. However, less K was adsorbed on smectite and calcite of the de-vegetated soil than on the same minerals of the same soil covered with grass during the following twelve months, indicating in turn that more K was removed from de-vegetated soil within a one-year time.

Elucidating the formation of terra fuscas using Sr–Nd–Pb isotopes and rare earth elements

Carbonate weathering mantles, like terra fusca, are common in Europe but their formation and evolution is still badly understood. We propose to combine geological, mineralogical and pedological knowledge with trace element and isotope data of a weathering mantle as a novel approach to understand the evolution of terra fuscas. Sr–Nd–Pb isotopes and rare earth element (REE) contents were analyzed in a cambisol developing on a typical terra fusca on top of a condensed Bajocian limestone-marl succession from the eastern side of the Paris Basin. The isotope data, REE distribution patterns and mass balance calculations suggest that the cambisol mirrors the trace element enrichments present in this carbonate lithology, which are exceptionally high compared to global average carbonate. The deeper soil horizons are strongly enriched not only in REE (ΣREE: 2640ppm) but also in redox-sensitive elements such as Fe (44wt.%), V (1000ppm), Cr (700ppm), Zn (550ppm), As (260ppm), Co (45ppm) and Cd (2.4ppm). The trace element distribution patterns of the carbonate bedrock are similar to those of the soil suggesting their close genetic relationships. Sr–Nd–Pb isotope data allow to identify four principal components in the soil: a silicate-rich pool close to the surface, a leachable REE enriched pool at the bottom of the soil profile, the limestone on which the weathering profile developed and an anthropogenic, atmosphere-derived component detected in the soil leachates of the uppermost soil horizon. The leachable phases are mainly secondary carbonate-bearing REE phases such as bastnaesite ((X) Ca(CO3)2F) (for X: Ce, La and Nd). The isotope data and trace element distribution patterns indicate that at least four geological and environmental events impacted the chemical and isotopical compositions of the soil system: 1. An oxygen-deficient diagenetic or hydrothermal event caused trace metal enrichments in the Bajocian limestone-marls. 2. Carbonate dissolution caused the enrichment of detrital silicate phases and authigenic REE-bearing residual phases – e.g. marine authigenic fluorapatites and bastnaesite – in the newly formed condensed horizons. 3. Dissolution/precipitation of metastable bastnaesite phases and downward migration of the REE during soil formation. 4. Overprinting of the chemical and isotopical compositions of the uppermost soil horizon by recent atmospheric depositions.

Stoichiometric analysis of nutrient availability (N, P, K) within soils of polygonal tundra

Plant growth in arctic tundra is known to be commonly limited by nitrogen. However, biogeochemical interactions between soil, vegetation and microbial biomass in arctic ecosystems are still insufficiently understood. In this study, we investigated different compartments of the soil-vegetation system of polygonal lowland tundra: bulk soil, inorganic nutrients, microbial biomass and vegetation biomass were analyzed for their contents of carbon, nitrogen, phosphorus and potassium. Samples were taken in August 2011 in the Indigirka lowlands (NE Siberia, Russia) in a detailed grid (4 m × 5 m) in one single ice-wedge polygon. We used a stoichiometric approach, based on the N/P ratios in the vegetation biomass and the investigated soil fractions, to analyze limitation relations in the soil-vegetation system. Plant growth in the investigated polygonal tundra appears to be co-limited by nitrogen and phosphorus or in some cases only limited by nitrogen whereas potassium is not limiting plant growth. However, as the N/P ratios of the microbial biomass in the uppermost soil horizons were more than twice as high as previously reported for arctic ecosystems, nitrogen mineralization and fixation may be limited at present by phosphorus. We found that only 5 % of the total nitrogen is already cycling in the biologically active fractions. On the other hand, up to 40 % of the total phosphorus was found in the biologically active fractions. Thus, there is less potential for increased phosphorus mineralization than for increased nitrogen mineralization in response to climate warming, and strict phosphorus limitation might be possible in the long-term.

Acidification processes in soils with different acid buffering capacity in Cryptomeria japonica and Chamaecyparis obtusa forests over two decades

Although plant–soil interactions play important roles in regulating soil acidity, it remains unclear whether the species influence is changeable across soil acidity gradients. We resampled soils in eight stands of Cryptomeria japonica and seven stands of Chamaecyparis obtusa in which soil chemical properties were documented in the 1990s. Half of the sites for each species had soils with a high acid buffering capacity (ABC), and the remaining sites had soils with a low ABC. ABC was defined by two criteria: the concentration of exchangeable base cations and the concentration of exchangeable Al. The aims of this study were (i) to characterize the accumulation of base cations and exchangeable Al by both tree species in high- or low-ABC soil profiles down to a depth of 40cm and (ii) to clarify the changes of soil ABC in stands of C. japonica or C. obtusa grown in high- or low-ABC soil over the past two decades. In the low-ABC group, Ca depletion and Al accumulation were observed in both species. Potassium depletion also occurred in C. obtusa stands. In contrast, high-ABC soils showed different trends. In C. japonica soils, Ca accumulated during this period and sharp distinctions in exchangeable Ca concentrations were observed between the uppermost soil horizons and deeper horizons; however, in C. obtusa soils such distinctions were not evident and depletions both Ca and K occurred. These results suggest that plant–soil interactions differed in the two soils. We speculate that C. japonica accumulates Ca in soils with high ABC but loses this trait in low-ABC soils, meaning that C. japonica responds to an acidic environment with a positive feedback of soil acid buffering capacity, such that ABC becomes greater in a high-ABC soil and smaller in a low-ABC soil. It appears that C. obtusa promotes depletion of cations such as Ca and K and accumulation of exchangeable Al in soils regardless of ABC. Neither C. japonica nor C. obtusa is suitable for planting in nutrient-poor soils as they promote a shortage of base cations and an increase in Al toxicity.

Impact of artifacts on topsoil magnetic susceptibility enhancement in urban parks of the Upper Silesian conurbation datasets

Urban and industrial dusts of various origins contain technogenic magnetic particles (TMPs) that exhibit ferro- or ferrimagnetic properties. Their deposition leads to topsoil magnetic susceptibility enhancement. TMPs are commonly known as carriers of many trace elements, including heavy metals, which have accumulated in the uppermost horizons of the soil profile. Soils of urban parks display a different stage of anthropogenic transformation of the soil profile as well as physical and chemical degradation. Besides TMPs deposited on the uppermost soil horizon, artifacts play a significant role in the magnetic properties of soil. Analysis of the vertical distribution of volume magnetic susceptibility (κ) values were conducted in 106 topsoil cores taken in areas of four urban parks of the Upper Silesian Conurbation. In order to examine the relationship between heavy metal concentrations and mass-specific magnetic susceptibility (χ) values, 57 soil samples from A horizons were taken for detailed analysis. Additionally, the κ and χ values of artifacts, sampled from the topsoil of the studied urban parks, were measured. Results pointed out that magnetic susceptibility enhancement in topsoil cores was significantly influenced by artifacts and translocations of topsoil horizons. In order to assess the level of anthropogenic transformation on topsoil horizons, we introduced the Topsoil Transformation Factor (TTF) on the basis of soil core magnetic susceptibility measurements. Low TTF corresponds to high positive Pearson correlation coefficients (r) between magnetic susceptibility and heavy metal contents in analyzed soil samples. TTF seems to be a promising indicator to improve soil magnetic susceptibility screening in urban and industrial areas where topsoil transformations and the presence of artifacts are common. In areas where natural sequences of the uppermost soil horizons were observed, the vertical distribution of κ value exhibits a one-peak curve, which is characteristic of TMP accumulation. In human modified soils, containing artifacts, a multipeak curve of the vertical distribution of κ value is commonly observed. Magnetic susceptibility measurements of individual artifacts display a wide range of κ and χ values.