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Topsoil
Terms modified by Topsoil Selected AbstractsAmino acid 15N in long-term bare fallow soils: influence of annual N fertilizer and manure applicationsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2008R. Bol Summary Long-term dynamics of amino acids (AAs), from a bare fallow soil experiment (established in 1928 at INRA-Versailles, France), were examined in unamended control (Con) plots and plots treated with ammonium sulphate (Amsul), ammonium nitrate (Amnit), sodium nitrate (Nanit) or with animal manure (Man). Topsoil (0,25 cm) from 1929, 1963 and 1997 was analysed for C, N and 15N content and distribution of 18 amino acids recovered after acid hydrolysis with 6 m HCl. With time, soil N, C and AA content were reduced in Con, Amsul, Amnit and Nanit, but increased in Man. However, the absolute N loss was 3,11 times larger in Man than Nanit, Amsul, Amnit and Con, due to the much higher N annual inputs applied to Man. From 1929 to 1997 in Con, Amsul, Amnit and Nanit the whole soil and non-hydrolysable-N pool ,15N increased associated with the loss of N (indicative of Rayleigh 15N/14N fractionation). No ,15N change from 1929 to 1997 was found in the hydrolysable AA-N (HAN) pool. Fertilizer N inputs aided stabilization of soil AA-N, as AA half-life in the mineral N fertilizer treatments increased from 34 years in 1963 to 50 years in 1997. The ,15N values of alanine and leucine reflected both source input and 15N/14N fractionation effects in soils. The ,15N increase of ornithine (,6,) was similar to the whole soil. The ,15N change of phenylalanine in Con (decrease of 7,) was related to its proportional loss since 1929, whereas for Amsul, Amnit, Nanit and Man it was associated with isotope effects caused by the fertilizer inputs. However, the soil ,15N value of most individual amino acids (IAAs) did not significantly change over nearly 70 years, even with mineral or organic N inputs. We conclude for these bare fallow systems that: (i) ,15N changes in the whole soil and non-hydrolysable AA pool were solely driven by microbial processes and not by the nature of fertilizer inputs, and (ii) without plant inputs, the ,15N of the HAN pool and (most) IAAs may reflect the influence of plant,soil interactions from the previous (arable cropping) rather than present (fallow) land use on these soil ,15N values. [source] Spatial patterns of desert annuals in relation to shrub effects on soil moistureJOURNAL OF VEGETATION SCIENCE, Issue 2 2010J. Li Abstract Questions: What are the effects of a shrub (Haloxylon ammodendron) on spatial patterns of soil moisture in different seasons? How does productivity of understorey annuals respond to these effects? Are such effects always positive for annuals under shrubs? Location: South Gurbantunggut Desert, northwest China. Methods: Using geostatistics, we explored seasonal patterns of topsoil moisture in a 12 × 9-m plot over the growing season. To determine spatial patterns of understorey annuals in response to H. ammodendron presence, biomass of annuals was recorded in four 0.2 × 5.0-m transects from the centre of a shrub to the space between shrubs (interspace). We also investigated vertical distribution of root biomass for annuals and soil moisture dynamics across soil profiles in shrub-canopied areas and interspaces. Results: Topsoil moisture changed from autocorrelation in the wet spring to random structure in the dry season, while soil moisture below 20 cm was higher in shrub-canopied areas. Across all microhabitats, soil moisture in upper soil layers was higher than in deeper soil layers during the spring wet season, but lower during summer drought. Topsoil was close to air-dry during the dry season and developed a ,dry sand layer' that reduced evaporative loss of soil water from deeper layers recharged by snowmelt in spring. Aboveground biomass of understorey annuals was lowest adjacent to shrub stems and peaked at the shrub margin, forming a ,ring' of high herbaceous productivity surrounding individual shrubs. To acclimate to drier conditions, annuals in interspaces invested more root biomass in deeper soil with a root/shoot ratio (R/S) twice that in canopied areas. Conclusions: Positive and negative effects of shrubs on understorey plants in arid ecosystems are commonly related to nature of the environmental stress and tested species. Our results suggest there is also microhabitat-dependence in the Gurbantunggut Desert. Soil water under H. ammodendron is seasonally enriched in topsoil and deeper layers. Understorey annuals respond to the effect of shrubs on soil water availability with lower R/S and less root biomass in deeper soil layers and develop a ,ring' of high productivity at the shrub patch margin where positive and negative effects of shrubs are balanced. [source] Aerobic Heterotrophic Bacterial and Fungal Communities in the Topsoil of Omo Biosphere Reserve in Southwestern Nigeria,BIOTROPICA, Issue 2 2000A. I. Okoh ABSTRACT As a part of the surveillance effort to monitor the ecological status of Omo Biosphere Reserve in the southwestern region of Nigeria, the aerobic heterotrophic bacterial and fungal communities of the topsoil were investigated in March 1995 and April 1996, before the onset of the rainy season. Four distinct wood-tree plantations, a core strict nature reserve (SNR) area, and a buffer zone were sampled. The topsoil samples (7.5 cm depth), including the litter, were taken with an auger (8 cm diameter) and transported to the laboratory in polyethylene bags. One-gram dry weight equivalent of sample was suspended in 10 ml sterile water, and serial dilutions from it were used for the estimation of bacterial and fungal densities. The bacterial and fungal densities ranged in the order of 106 and 103 cfu/g, respectively. Out of the 18 bacterial and 16 fungal species that were obtained, 13 and 12, respectively, were isolated from the core SNR. About 46 to 69 percent of the bacteria and 50 to 83 percent of the fungi species found in the SNR were absent in different combinations in the plantations and the buffer zone; these variations were significant among the sites monitored. The bacterial and fungal species compositions were significantly different between the SNR and each of the other sites. Proportional distributions within the sites were significant only for the bacterial communities. It would appear that plantation and human activities have caused significant changes in the distribution and species richness of the heterotrophic bacterial and fungal communities relative to the undisturbed SNR area of the Omo Biosphere Reserve. [source] Trace element distributions in soils developed in loess deposits from northern FranceEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2006T. Sterckeman Summary A pedo-geochemical survey was carried out in the Nord-Pas de Calais region (France) on soils developed in loess deposits. Total concentrations of Al, Fe and 18 trace elements, as well as common soil characteristics, were determined in samples from 52 surface and 97 deep horizons developed in these loess deposits. The Pb isotopic composition was determined in two sola. The composition of deep horizons, compared with that of the upper continental crust, with that of horizons developed from 21 other sedimentary rocks from the region and with that of loess from various parts of the world, confirms that loess from the Nord-Pas de Calais region derives from multi-recycled and well-mixed ancient sedimentary rocks. Correlation analysis shows that least mobile (i.e. ionic potential (Z/r) is between 3 and 7) geogenic elements (Bi, Co, Cr, Cu, In, Ni, Pb, Sn, Tl, V, Zn) are associated with the fraction <2 µm (which we define as ,lutum'). More mobile elements (As, Cd, Hg, Mn, Mo, Sb, Se) are less associated with this fraction. Cadmium is particularly linked to Mn. The distribution of [trace element]/([Al] or [Fe]) in the French loess gives the background content for soils developed from most sedimentary materials in northwestern Europe. Topsoils are enriched with all the trace elements examined, except Co, Cr and Ni. Enrichments with Cd, Cu, Mn and Zn are greater in cultivated soils than in forest soils. Enrichments with Pb and with Cu, Hg, Mo, Sb, Se and Sn are mainly due to human contamination through atmospheric fallout. Organic matter seems to act as a sink for all the exogenous trace elements. [source] Modelling increased soil cohesion due to roots with EUROSEMEARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2008S. De Baets Abstract As organic root exudates cause soil particles to adhere firmly to root surfaces, roots significantly increase soil strength and therefore also increase the resistance of the topsoil to erosion by concentrated flow. This paper aims at contributing to a better prediction of the root effects on soil erosion rates in the EUROSEM model, as the input values accounting for roots, presented in the user manual, do not account for differences in root density or root architecture. Recent research indicates that small changes in root density or differences in root architecture considerably influence soil erosion rates during concentrated flow. The approach for incorporating the root effects into this model is based on a comparison of measured soil detachment rates for bare and for root-permeated topsoil samples with predicted erosion rates under the same flow conditions using the erosion equation of EUROSEM. Through backwards calculation, transport capacity efficiencies and corresponding soil cohesion values can be assessed for bare and root-permeated topsoils respectively. The results are promising and present soil cohesion values that are in accordance with reported values in the literature for the same soil type (silt loam). The results show that grass roots provide a larger increase in soil cohesion as compared with tap-rooted species and that the increase in soil cohesion is not significantly different under wet and dry soil conditions, either for fibrous root systems or for tap root systems. Power and exponential relationships are established between measured root density values and the corresponding calculated soil cohesion values, reflecting the effects of roots on the resistance of the topsoil to concentrated flow incision. These relationships enable one to incorporate the root effect into the soil erosion model EUROSEM, through adapting the soil cohesion input value. A scenario analysis shows that the contribution of roots to soil cohesion is very important for preventing soil loss and reducing runoff volume. The increase in soil shear strength due to the binding effect of roots on soil particles is two orders of magnitude lower as compared with soil reinforcement achieved when roots mobilize their tensile strength during soil shearing and root breakage. Copyright © 2008 John Wiley & Sons, Ltd. [source] The importance of plant root characteristics in controlling concentrated flow erosion ratesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2003G. Gyssels Abstract While it has been demonstrated in numerous studies that the aboveground characteristics of the vegetation are of particular importance with respect to soil erosion control, this study argues the importance of separating the influence of vegetation on soil erosion rates into two parts: the impact of leaves and stems (aboveground biomass) and the influence of roots (belowground biomass). Although both plant parameters form inseparable constituents of the total plant organism, most studies attribute the impact of vegetation on soil erosion rates mainly to the characteristics of the aboveground biomass. This triggers the question whether the belowground biomass is of no or negligible importance with respect to soil erosion by concentrated flow. This study tried to answer this question by comparing cross-sectional areas of concentrated flow channels (rills and ephemeral gullies) in the Belgian Loess Belt for different cereal and grass plant densities. The results of these measurements highlighted the fact that both an increase in shoot density as well as an increase in root density resulted in an exponential decrease of concentrated flow erosion rates. Since protection of the soil surface in the early plant growth stages is crucial with respect to the reduction of water erosion rates, increasing the plant root density in the topsoil could be a viable erosion control strategy. Copyright © 2003 John Wiley & Sons, Ltd. [source] The effect of concentrated smoke products on the restoration of highly disturbed mineral sands in southeast VictoriaECOLOGICAL MANAGEMENT & RESTORATION, Issue 2 2003By Terry D. Coates Summary Recent studies have recognized the potential of broad-scale surface application of smoke compounds for enhancing germination from the soil seed-bank in fire-prone vegetation communities. Results suggest that smoke technology may play, in the future, a significant role in the restoration and management of areas supporting indigenous vegetation. An important step in the development of smoke-based restoration tools is the conduct of in situ field trials in a range of geographical locations and environmental conditions. However, most of the published work on the effectiveness of smoke products in promoting seedbank germination has been conducted at sites in southwestern Australia. The present study examines the effect of commercially available smoke-water products on the regeneration of a highly disturbed former mine-site at the Royal Botanic Gardens Cranbourne, in southeastern Victoria. Various combinations of concentrated smoke products and topsoil harvested from a nearby heathy woodland community were applied to exposed, uniform mineral sands to test their effect on seedling density and species richness of regrowth. The trials showed that after 12 months a number of common, herbaceous species including Austrodanthonia setacea, Opercularia varia and Platysace heterophylla were recorded in significantly higher numbers in areas treated with a commercial smoke-water. However, there was no overall improvement in the density of seedlings or the richness of species as a result of the application of the smoke products. Similarly, total seedling density and species richness were not affected by the addition of topsoil, either alone or in combination with smoke products. [source] Below-ground competition between trees and grasses may overwhelm the facilitative effects of hydraulic liftECOLOGY LETTERS, Issue 8 2004F. Ludwig Abstract Under large East African Acacia trees, which were known to show hydraulic lift, we experimentally tested whether tree roots facilitate grass production or compete with grasses for below-ground resources. Prevention of tree,grass interactions through root trenching led to increased soil water content indicating that trees took up more water from the topsoil than they exuded via hydraulic lift. Biomass was higher in trenched plots compared to controls probably because of reduced competition for water. Stable isotope analyses of plant and source water showed that grasses which competed with trees used a greater proportion of deep water compared with grasses in trenched plots. Grasses therefore used hydraulically lifted water provided by trees, or took up deep soil water directly by growing deeper roots when competition with trees occurred. We conclude that any facilitative effect of hydraulic lift for neighbouring species may easily be overwhelmed by water competition in (semi-) arid regions. [source] Bioremediation of 6 % [w/w] Diesel-Contaminated Mainland Soil in Singapore: Comparison of Different Biostimulation and Bioaugmentation TreatmentsENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 1 2006M. Mathew Abstract The efficacy of indigenous microorganisms to degrade diesel oil in contaminated mainland sites in Singapore was investigated. A semi-scale trial was made by spiking topsoil with 6,% [w/w] of diesel oil. The results indicated that in the presence of NPK commercial (Rosasol®) fertilizer a 53,% reduction in contaminant concentration was recorded after 60,days compared to untreated controls while the addition of a mixture of urea and K2HPO4 effected a 48,% reduction in the Total Recoverable Petroleum Hydrocarbons. A commercial culture and an enriched/isolated microbial association proved to be the least effective with 25 and 9,% reductions, respectively. The results confirmed the bioremediation potential of indigenous microorganisms for diesel-oil contaminated mainland soil. Identification of the persistent compounds was done and perceived as a tool in decision-making on strategies for speeding up of the degradation process to achieve clean-up standards in shorter remediation periods. [source] Bioavailability and microbial adaptation to elevated levels of uranium in an acid, organic topsoil forming on an old mine spoilENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2007Erik Jautris Joner Abstract An old mine spoil at a 19th-century mining site with considerable residues of uranium (400,800 mg U/kg) was investigated with respect to U concentrations in soil and plants and tolerance to U in the soil microbial community in order to describe the bioavailability of U. Measurements of soil fractions representing water-soluble U, easily exchangeable U, and U bound to humified organic matter showed that all fractions contained elevated concentrations of U. Plant U concentrations were only 10 times higher at the mine spoil site compared to the reference site (3 mg U/kg vs 0.3 mg U/kg), while the most easily available soil fractions contained 0.18 to 0.86 mg U/kg soil at the mine spoil. An ecotoxicity bioassay using incorporation of [3H]thymidine into the indigenous microbial communities of the two soils in the presence of increasing U concentrations showed that microorganisms at the mining site were sensitive to U but also that they had acquired a substantial tolerance toward U (EC50, the effective concentration reducing activity by 50% of UO2 -citrate was , 120 ,M as compared to 30 ,M in the reference soil). In the assay, more than 40% of the microbial activity was maintained in the presence of 1 ,M UO2-citrate versus 3% in the reference soil. We conclude that U-enriched mining waste can contain sufficiently elevated concentrations of bioavailable U to affect indigenous microorganisms and that bioavailable U imposes a selection pressure that favors the development of a highly uranium-tolerant microbial community, while plant uptake of U remains low. [source] Combined effects of the fungicide propiconazole and agricultural runoff sediments on the aquatic bryophyte Vesicularia dubyanaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2005Qinglan Wu Abstract Pesticides, firmly attached to the topsoil, might enter nearby watercourses at periods with high erosive loss of sediments. Therefore, exposure of aquatic organisms to these low mobility pesticides, in many cases, will coincide with a high sediment concentration. In this study, both individual and combined effects of propiconazole and runoff sediment on the aquatic model bryophyte Vesicularia dubyana are studied. Individual exposure to propiconazole induced responses in V. dubyana at rather low concentration levels (,1 ,g/L), showing that harmful effects of propiconazole potentially may occur in watercourses draining propiconazole-treated fields. Individual exposure to the sediment size fractions S1 (0.16,2 ,m) and S2 (0.03,0.16 ,m) caused plant stress at a concentration of 100 mg/L. The coarser fraction S1 showed strong inhibition effects on photosynthesis, probably due to light attenuation. Compared to S1, the suspension with the finer fraction S2 showed lower turbidity, higher nutrient content, and a higher proportion of sediment-bound propiconazole. The combined effects of propiconazole and suspended sediment are dependent on concentrations of sediment and propiconazole. At low sediment concentration (e.g., 100 mg/L), neither S1 nor S2 reduce the toxicity of propiconazole, as only 2% of propiconazole are bound to particles. An increase in sediment concentration decreases the bioavailable concentration of propiconazole; however, at the same time, this increases the turbidity, thereby inhibiting plant photosynthesis. [source] Sensitivity of multi-coil frequency domain electromagnetic induction sensors to map soil magnetic susceptibilityEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2010D. Simpson Magnetic susceptibility is an important indicator of anthropogenic disturbance in the natural soil. This property is often mapped with magnetic gradiometers in archaeological prospection studies. It is also detected with frequency domain electromagnetic induction (FDEM) sensors, which have the advantage that they can simultaneously measure the electrical conductivity. The detection level of FDEM sensors for magnetic structures is very dependent on the coil configuration. Apart from theoretical modelling studies, a thorough investigation with field models has not been conducted until now. Therefore, the goal of this study was to test multiple coil configurations on a test field with naturally enhanced magnetic susceptibility in the topsoil and with different types of structures mimicking real archaeological features. Two FDEM sensors were used with coil separations between 0.5 and 2 m and with three coil orientations. First, a vertical sounding was conducted over the undisturbed soil to test the validity of a theoretical layered model, which can be used to infer the depth sensitivity of the coil configurations. The modelled sounding values corresponded well with the measured data, which means that the theoretical models are applicable to layered soils. Second, magnetic structures were buried in the site and the resulting anomalies measured to a very high resolution. The results showed remarkable differences in amplitude and complexity between the responses of the coil configurations. The 2-m horizontal coplanar and 1.1-m perpendicular coil configurations produced the clearest anomalies and resembled best a gradiometer measurement. [source] Impact of common European tree species on the chemical and physicochemical properties of fine earth: an unusual patternEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2010L. Mareschal Case studies are necessary to assess the effects of changes to tree species on the physicochemical and chemical properties of soils. To achieve this, the fine earth under five tree species was investigated. This study was performed in the Breuil-Chenue experimental forest site located in the Morvan Mountains (France). This site contains two adjacent blocks with replicated stands. The native forest (old beech and oak coppice with standards) was partially clear-felled and replaced in 1976 with mono-specific plantations of European beech, Norway spruce, Laricio pine and Douglas fir. The same changes in soil properties were revealed in both blocks, thus confirming the tree species effect. The percentage of exchangeable acidity on the cation exchange capacity (CEC) was greater under spruce, Douglas fir and pine than under the other species. Spruce stands, and to a lesser extent those of Douglas fir and pine, had a less acidic soil pH than hardwood stands (which was unusual in view of the data in the literature) and smaller CEC values. The small quantities of carbon added to the soil under these tree species provide an explanation for these effects through a partial control of both CEC and pH. This case study thus demonstrated that the tree species effect was not unequivocal and different criteria are necessary for its interpretation. Tree species significantly influenced certain aspects of the chemical properties of topsoil and have the potential to have an impact on current soil fertility. [source] Percolation characteristics of a water-repellent sandy forest soilEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2008G. Wessolek Summary In a tracer experiment TDR transect measurements were made to study percolation behaviour in a 120-year-old pine stand (Pinus sylvestris) on a water-repellent sandy soil (Haplic Arenosol). The experiment (with potassium iodide) showed an 80% labelling of the total flow in organic layers, whereas the area of transport in the mineral soil was sharply reduced to 12,30%. The average diameters of these preferential flow paths were about 8,15 cm. The TDR measurements indicate a homogeneous flow only for a short period from February until April. At this time of the year preferential flow is insignificant, because the soil is at approximately field capacity and not repellent to water. During summer (May to September) the soil dries out, and most precipitation results in preferential flow during this period. For any daily rainfall exceeding 10 mm, water infiltrates down to 1 m depth in the soil, which nevertheless, is still within the root zone. This kind of deep percolation results in the subsoil's wetting to field capacity (pF 1.8) earlier than the topsoil. A one-dimensional numerical model (SWAP) was used to simulate mean water balance with hydraulic functions with and without a water-repellency term. From the results of our tracer experiment we showed that the de-watering process in spring could be simulated well using the traditional piston flow concept, while the rewetting behaviour could be described more realistically using the mobile,immobile concept for water repellency. [source] Micromorphology of soils derived from volcanic ash in Europe: a review and synthesisEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2007G. Stoops Summary An analysis of the available literature on European volcanic ash soils has been made. Most has been published in Congress proceedings and Journals of national societies, less than half in English. More than half of the papers deal with soils on the Canary Islands. Many papers focus only on one aspect, and complete descriptions are found only in recent publications. Often the use of vague micromorphological terminology and the absence of analytical data make interpretation and comparisons difficult or impossible. Nonetheless, some general features do emerge. In the least-weathered soils, the micromass forms first coatings around the coarse constituents, later granules, finally giving rise to a loose granular microstructure in the topsoil, and a compacted granular one in the Bw horizons of typic andic materials. The b-fabric of the micromass is undifferentiated. With increasing weathering, clay coatings appear, the microstructure becomes more blocky and the b-fabric becomes speckled or even striated. In Vertisols and Aridisols, micromorphological characteristics are not much different from those in the comparable non-volcanic soils, except generally for the tendency to granular (intrapedal) microstructures. In Icelandic soils, microstratification, lenticular microstructure and preservation of plant residues as a result of cryic conditions and permanent volcanic and aeolian activity are observed. Weathering of volcanic glass in well-drained conditions yields allophane alteromorphs similar to palagonite, which are easily subject to fragmentation by pedoturbation. The possible influence of surface transport and burial on the formation of Bw-horizons in andic materials is discussed. [source] Composition of organic matter in a subtropical Acrisol as influenced by land use, cropping and N fertilization, assessed by CPMAS 13C NMR spectroscopyEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2005J. Dieckow Summary We know much about the influence of management on stocks of organic matter in subtropical soils, yet little about the influence on the chemical composition. We therefore studied by CPMAS 13C NMR spectroscopy the composition of the above-ground plant tissue, of the organic matter of the whole soil and of silt- and clay-size fractions of the topsoil and subsoil of a subtropical Acrisol under grass and arable crops. Soil samples were collected from three no-till cropping systems (bare soil; oats,maize; pigeon pea + maize), each receiving 0 and 180 kg N ha,1 year,1, in a long-term field experiment. Soil under the original native grass was also sampled. The kind of arable crops and grass affected the composition of the particulate organic matter. There were no differences in the composition of the organic matter in silt- and clay-size fractions, or of the whole soil, among the arable systems. Changes were observed between land use: the soil of the grassland had larger alkyl and smaller aromatic C contents than did the arable soil. The small size fractions contain microbial products, and we think that the compositional difference in silt- and clay-size fractions between grassland and the arable land was induced by changes in the soil's microbial community and therefore in the quality of its biochemical products. The application of N did not affect the composition of the above-ground plant tissue nor of the particulate organic matter and silt-size fractions, but it did increase the alkyl C content in the clay-size fraction. In the subsoil, the silt-size fraction of all treatments contained large contents of aromatic C. Microscopic investigation confirmed that this derived from particles of charred material. The composition of organic matter in this soil is affected by land use, but not by variations in the arable crops grown. [source] Transformation of haematite and Al-poor goethite to Al-rich goethite and associated yellowing in a ferralitic clay soil profile of the middle Amazon Basin (Manaus, Brazil)EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2005E. Fritsch Summary The red and yellow colours of ferralitic soils in the tropics have for long intrigued pedologists. We have investigated the upward yellowing in a 10-m thick profile representative of the Ferralsols of the plateaux of the Manaus region of Brazil. We determined changes in the nature and crystal chemistry of their Fe oxides by optical and Mössbauer spectroscopy as well as Rietveld refinement of X-ray diffraction patterns. We attribute the upward yellowing of the soil to a progressive transformation of the Fe oxides at nearly invariant iron contents. Aluminium in contrast is strongly mobilized in the uppermost clay-depleted topsoil where there is preferential dissolution of kaolinite and crystallization of gibbsite. Haematite decreases from 35 to 10% of the Fe oxides from the bottom to the top of the profile and the particles become smaller (75,10 nm). Its Al for Fe-substitution remains almost unchanged (10,15 mol %). The average Al-substitution rate of goethite increases from 25 to 33 mol %, and its mean crystal diameter remains in the range 20,40 nm. The proportion of Al-rich goethite (33 mol %) increases at the expense of less Al-substituted Fe oxides (haematite and goethite). This conversion with restricted transfer of iron means that the amount of Al stored in Fe oxides gradually increases. Kaolinite, haematite and Al-poor goethite are thus witnesses of earlier stages of ferralitization of the soil. In contrast, Al-rich goethite and gibbsite initiate the alitization (or bauxitization) of the soil. They correspond to the last generation of soil minerals, which most likely reflects the present-day weathering conditions. The progressive replacement of kaolinite, haematite and Al-poor goethite by new generations of Al-rich goethite and gibbsite attests to greater activities of water and aluminium and smaller activity of aqueous silica in the topsoil than in the subsoil. We interpret this as a consequence of longer periods of wetting in the topsoil that could result from soil aging, more humid climate or both. [source] Characterizing organic matter of soil aggregate coatings and biopores by Fourier transform infrared spectroscopyEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2004R. H. Ellerbrock Summary In some soils, aggregate coatings and walls of biopores differ in the content of clay and organic carbon from that of the aggregate interiors or the soil matrix. The composition of the organic matter on aggregates and on the surfaces of biopores is largely unknown. We have compared the composition of organic matter between inner and outer parts of aggregates and between biopore walls and the soil matrix in a loamy arable soil and a sandy forest one. Hot-water- and sodium-pyrophosphate-extractable organic matter was analysed by Fourier transform infrared (FT-IR) spectroscopy. For the sandy forest soil, the FT-IR spectra showed that organic matter from the walls of root channels contains fewer functional groups with absorption bands at 1740,1710 cm,1 and 1640,1600 cm,1 than that from burrow fillings. For the arable soil, the content of these functional groups in hot-water-soluble organic matter from the coatings is less than in that from the interiors in the topsoil, and the reverse is so in the subsoil, probably because water-soluble organic matter containing these functional groups has moved from topsoil to subsoil. The results indicate that root channels in the forest soil have more reactive zones in an otherwise relatively inert sandy matrix, whereas aggregate coatings in the arable subsoil have a greater cation exchange capacity and a greater sorption potential for hydrophobic substances than the aggregate interiors. [source] Cadmium leaching from some New Zealand pasture soilsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2003C. W. Gray Summary Cadmium (Cd) inputs and losses from agricultural soils are of great importance because of the potential adverse effects Cd can pose to food quality, soil health and the environment in general. One important pathway for Cd losses from soil systems is by leaching. We investigated loss of Cd from a range of contrasting New Zealand pasture soils that had received Cd predominantly from repeated applications of phosphate fertilizer. Annual leaching losses of Cd ranged between 0.27 and 0.86 g ha,l, which are less than most losses recorded elsewhere. These losses equate to between 5 and 15% of the Cd added to soil through a typical annual application of single superphosphate, which in New Zealand contains on average 280 mg Cd kg,1 P. It appears that Cd added to soil from phosphate fertilizer is fairly immobile and Cd tends to accumulate in the topsoil. The pH of the leachate and the total volume of drainage to some extent control the amount of Cd leached. Additional factors, such as the soil sorption capacity, are also important in controlling Cd movement in these pasture soils. The prediction of the amount of Cd leached using the measured concentrations of Cd in the soil solution and rainfall data resulted in an overestimation of Cd losses. Cadmium concentrations in drainage water are substantially less than the current maximum acceptable value of 3 µg l,1 for drinking water in New Zealand set by the Ministry of Health. [source] Changes in variance and correlation of soil properties with scale and location: analysis using an adapted maximal overlap discrete wavelet transformEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2001R. M. Lark Summary The magnitude of variation in soil properties can change from place to place, and this lack of stationarity can preclude conventional geostatistical and spectral analysis. In contrast, wavelets and their scaling functions, which take non-zero values only over short intervals and are therefore local, enable us to handle such variation. Wavelets can be used to analyse scale-dependence and spatial changes in the correlation of two variables where the linear model of coregionalization is inadmissible. We have adapted wavelet methods to analyse soil properties with non-stationary variation and covariation in fairly small sets of data, such as we can expect in soil survey, and we have applied them to measurements of pH and the contents of clay and calcium carbonate on a 3-km transect in Central England. Places on the transect where significant changes in the variance of the soil properties occur were identified. The scale-dependence of the correlations of soil properties was investigated by calculating wavelet correlations for each spatial scale. We identified where the covariance of the properties appeared to change and then computed the wavelet correlations on each side of the change point and compared them. The correlation of topsoil and subsoil clay content was found to be uniform along the transect at one important scale, although there were significant changes in the variance. In contrast, carbonate content and pH of the topsoil were correlated only in parts of the transect. [source] Geostatistical Simulation for the Assessment of Regional Soil PollutionGEOGRAPHICAL ANALYSIS, Issue 2 2010Marc Van Meirvenne Regional scale inventories of heavy metal concentrations in soil increasingly are being done to evaluate their global patterns of variation. Sometimes these global pattern evaluations reveal information that is not identified by more detailed studies. Geostatistical methods, such as stochastic simulation, have not yet been used routinely for this purpose in spite of their potential. To investigate such a use of geostatistical methods, we analyzed a data set of 14,674 copper and 12,441 cadmium observations in the topsoil of Flanders, Belgium, covering 13,522 km2. Outliers were identified and removed, and the distributions were spatially declustered. Copper was analyzed using sequential Gaussian simulation, whereas for cadmium we used sequential indicator simulation because of the large proportion (43%) of censored data. We complemented maps of the estimated values with maps of the probability of exceeding a critical sanitation threshold for agricultural land use. These sets of maps allowed the identification of regional patterns of increased metal concentrations and provided insight into their potential causes. Mostly areas with known industrial activities (such as lead and zinc smelters) could be delineated, but the effects of shells fired during the First World War were also identified. En los estudios de contaminación de suelos as escala regional, es práctica común la implementación de inventarios de concentraciones de metales pesados en el suelo con el fin de evaluar sus patrones globales de variación espacial. A veces dichas evaluaciones de patrones globales proporcionan información que no son aparentes en estudios realizados a escalas más detalladas. En este contexto, a pesar del potencial analítico que poseen, los métodos geostadísticos como la simulación estocástica han recibido poca atención. Los autores del presente artículo proponen llenar este vacío aplicando métodos geostadísticos para el análisis de dos bases de datos: 14,674 observaciones de cobre (Cu) y 12,441 observaciones de cadmio (Cd). Los datos corresponden a la capa superior de suelo en un área de 13,522 km2 en Flandes, Belgica. Tras la remoción de los valores extremos (outliers) y la desaglomeración de las distribuciones, los autores analizan los datos vía dos procedimientos: a) una Simulación Secuencial Gausiana (SGS) para los datos de cobre, y b) una Simulación Secuencial Indicador (SIS). La diferencia en el tratamiento analítico para ambos metales obedece a la considerable proporción (43%) de datos censurados de cadmio. Los mapas resultantes de valores estimados fueron complementados con mapas que ilustran la probabilidad de exceder los umbrales críticos para uso agrícola de la tierra. Esta serie de mapas permitió la identificación de patrones regionales de concentraciones crecientes de metales y proporciono claves importantes acerca de sus posibles causas. Los patrones hallados coinciden con áreas donde se realizan actividades industriales (como fundiciones de plomo y zinc), pero también con la distribución espacial de casquillos de balas disparadas durante la Primera Guerra Mundial. [source] Experimental evidence for the attenuating effect of SOM protection on temperature sensitivity of SOM decompositionGLOBAL CHANGE BIOLOGY, Issue 10 2010JEROEN GILLABEL Abstract The ability to predict C cycle responses to temperature changes depends on the accurate representation of temperature sensitivity (Q10) of soil organic matter (SOM) decomposition in C models for different C pools and soil depths. Theoretically, Q10 of SOM decomposition is determined by SOM quality and availability (referred to here as SOM protection). Here, we focus on the role of SOM protection in attenuating the intrinsic, SOM quality dependent Q10. To assess the separate effects of SOM quality and protection, we incubated topsoil and subsoil samples characterized by differences in SOM protection under optimum moisture conditions at 25 °C and 35 °C. Although lower SOM quality in the subsoil should lead to a higher Q10 according to kinetic theory, we observed a much lower overall temperature response in subsoil compared with the topsoil. Q10 values determined for respired SOM fractions of decreasing lability within the topsoil increased from 1.9 for the most labile to 3.8 for the least labile respired SOM, whereas corresponding Q10 values for the subsoil did not show this trend (Q10 between 1.4 and 0.9). These results indicate the existence of a limiting factor that attenuates the intrinsic effect of SOM quality on Q10 in the subsoil. A parallel incubation experiment of 13C-labeled plant material added to top- and subsoil showed that decomposition of an unprotected C substrate of equal quality responds similarly to temperature changes in top- and subsoil. This further confirms that the attenuating effect on Q10 in the subsoil originates from SOM protection rather than from microbial properties or other nutrient limitations. In conclusion, we found experimental evidence that SOM protection can attenuate the intrinsic Q10 of SOM decomposition. [source] Loss of forb diversity in relation to nitrogen deposition in the UK: regional trends and potential controlsGLOBAL CHANGE BIOLOGY, Issue 10 2006CARLY J. STEVENS Abstract In this study we investigate the impact of nitrogen (N) deposition on the diversity of three different vegetation functional groups , forbs, grasses and mosses , using a field survey of acid grasslands across Great Britain. Our aim is to identify the vegetation types that are most vulnerable to enhanced N deposition, and to shed light on the mechanisms that may be driving N-initiated species changes in the UK. Sixty-eight randomly selected grasslands belonging to the UK National Vegetation Classification group U4 (Festuca ovina,Agrostis capillaris,Galium saxatile grassland) were studied along a gradient of atmospheric N deposition ranging from 6 to 36 kg N ha,1 yr,1. At each site, vegetation was surveyed and samples were taken from the topsoil and subsoil. Aboveground plant material was collected from three species: a forb, grass and moss. Both the species richness and cover of forbs declined strongly with increasing N deposition, from greater than eight species/20% cover per m2 quadrat at low levels of N to fewer than two species/5% cover at the highest N deposition levels. Grasses showed a weak but significant decline in species richness, and a trend toward increasing cover with increasing N input. Mosses showed no trends in either species richness or cover. Most of the decline in plant species richness could be accounted for by the level of ammonium deposition. Soil KCl-extractable ammonium concentration showed a significant positive correlation with N input, but there was no relationship between N deposition and extractable nitrate. In the soil O/A horizon, there was no relationship between N deposition and %N, and only a very weak positive relationship between the level of N deposition and the C : N ratio. Finally, in the vegetation, there was no relationship between N deposition and either shoot tissue N concentration or N : P ratio for any of the three reference species. Combining our regional survey with the results of published N-addition experiments provides compelling evidence that there has been a significant decline in the species richness and cover of forbs across Great Britain, and that the primary cause is competition due to an increase in the cover of grasses in response to enhanced deposition of reactive N, primarily NH4+. [source] Impact of land use on the hydraulic properties of the topsoil in a small French catchmentHYDROLOGICAL PROCESSES, Issue 17 2010E. Gonzalez-Sosa Abstract The hydraulic properties of the topsoil control the partition of rainfall into infiltration and runoff at the soil surface. They must be characterized for distributed hydrological modelling. This study presents the results of a field campaign documenting topsoil hydraulic properties in a small French suburban catchment (7 km2) located near Lyon, France. Two types of infiltration tests were performed: single ring infiltration tests under positive head and tension-disk infiltration using a mini-disk. Both categories were processed using the BEST,Beerkan Estimation of Soil Transfer parameters,method to derive parameters describing the retention and hydraulic conductivity curves. Dry bulk density and particle size data were also sampled. Almost all the topsoils were found to belong to the sandy loam soil class. No significant differences in hydraulic properties were found in terms of pedologic units, but the results showed a high impact of land use on these properties. The lowest dry bulk density values were obtained in forested soils with the highest organic matter content. Permanent pasture soils showed intermediate values, whereas the highest values were encountered in cultivated lands. For saturated hydraulic conductivity, the highest values were found in broad-leaved forests and small woods. The complementary use of tension-disk and positive head infiltration tests highlighted a sharp increase of hydraulic conductivity between near saturation and saturated conditions, attributed to macroporosity effect. The ratio of median saturated hydraulic conductivity to median hydraulic conductivity at a pressure of , 20 mm of water was about 50. The study suggests that soil texture, such as used in most pedo-transfer functions, might not be sufficient to properly map the variability of soil hydraulic properties. Land use information should be considered in the parameterizations of topsoil within hydrological models to better represent in situ conditions, as illustrated in the paper. Copyright © 2010 John Wiley & Sons, Ltd. [source] Retention of chloride in soil and cycling of organic matter-bound chlorineHYDROLOGICAL PROCESSES, Issue 11 2005G. Öberg Abstract Chloride (Clinorg) is generally considered to be a hydrologically and chemically inert substance. Past research suggests that Clinorg participates in a complex biogeochemical cycle involving the formation of organically bound chlorine (Clorg). The present study examines whether Clorg cycling is sufficiently extensive as to influence the geochemical cycling of Clinorg. Undisturbed soil cores were collected in a coniferous forest soil in SE Sweden. The cores were stored in climate chambers for three months, irrigated with artificial rain, and the leachate was collected and analysed. The water balance of the lysimeters could be well described, and we found that 20,50% of the chlorine leached from the lysimeters was organically bound and that the amounts lost did not decrease with time. This strongly suggests that a substantial amount of Clorg forms in topsoil, and that subsequent leaching to deeper layers causes a considerable withdrawal of Clinorg. The concentration of both organic carbon and Clorg in the leachate was considerably higher than concentrations observed in the runoff in the actual catchment, suggesting that organic matter precipitates or is mineralized on its way through the soil. Copyright © 2005 John Wiley & Sons, Ltd. [source] Runoff generation and routing on artificial slopes in a Mediterranean,continental environment: the Teruel coalfield, SpainHYDROLOGICAL PROCESSES, Issue 3 2002José-Manuel Nicolau Abstract The aim of this study was to identify the mechanisms of runoff generation and routing and their controlling factors at the hillslope scale, on artificial slopes derived from surface coal mining reclamation in a Mediterranean,continental area. Rainfall and runoff at interrill and microcatchment scales were recorded for a year on two slopes with different substrata: topsoil cover and overburden cover. Runoff coefficient and runoff routing from interrill areas to microcatchment outlets were higher in the overburden substratum than in topsoil, and greater in the most developed rill network. Rainfall volume is the major parameter responsible for runoff response on overburden, suggesting that this substratum is very impermeable,at least during the main rainfall periods of the year (late spring and autumn) when the soil surface is sealed. In such conditions, most rainfall input is converted into runoff, regardless of its intensity. Results from artificial rainfall experiments, conducted 3 and 7 years after seeding, confirm the low infiltration capacity of overburden when sealed. The hydrological response shows great seasonal variability on the overburden slope in accordance with soil surface changes over the year. Rainfall volume and intensities (I30, I60) explain runoff at the interrill scale on the topsoil slope, where rainfall experiments demonstrated a typical Hortonian infiltration curve. However, no correlation was found at the microcatchment level, probably because of the loss of functionality of the only rill as ecological succession proceeded. The runoff generation mechanism on the topsoil slope is more homogeneous throughout the year. Runoff connectivity, defined as the ratio between runoff rates recorded at the rill network scale and those recorded at the interrill area scale in every rainfall event, was also greater on the rilled overburden slope, and in the most developed rill network. The dense rill networks of the overburden slope guarantee very effective runoff drainage, regardless of rainfall magnitude. Rills drain overland flow from interrill-sealed areas, reducing the opportunity of reinfiltration in areas not affected by siltation. Runoff generation and routing on topsoil slopes are controlled by grass cover and soil moisture content, whereas on overburden slopes rill network density and soil moisture content are the main controlling factors. Copyright © 2002 John Wiley & Sons, Ltd. [source] Spontaneous succession in limestone quarries as an effective restoration tool for endangered arthropods and plantsJOURNAL OF APPLIED ECOLOGY, Issue 1 2010Robert Tropek Summary 1. The view of post-mining sites is rapidly changing among ecologists and conservationists, as sensitive restoration using spontaneous succession may turn such sites into biodiversity refuges in human-exploited regions. However, technical reclamation, consisting of covering the sites by topsoil, sowing fast-growing herb mixtures and planting trees, is still commonly adopted. Until now, no multi-taxa study has compared technically reclaimed sites and sites left with spontaneous succession. 2. We sampled communities of vascular plants and 10 arthropod groups in technically reclaimed and spontaneously restored plots in limestone quarries in the Bohemian Karst, Czech Republic. For comparison, we used paired t -tests and multivariate methods, emphasizing red-list status and habitat specialization of individual species. 3. We recorded 692 species of target taxa, with a high proportion of red-listed (10%) and xeric specialist (14%) species, corroborating the great conservation potential of the quarries. 4. Spontaneously restored post-mining sites did not differ in species richness from the technical reclaimed sites but they supported more rare species. The microhabitat cover of leaf litter, herbs and moss, were all directly influenced by the addition of topsoil during reclamation. 5.Synthesis and applications. Our results show that the high conservation potential of limestone quarries could be realized by allowing succession to progress spontaneously with minimal intervention. Given the threat to semi-natural sparsely vegetated habitats in many regions, active restoration measures at post-mining sites should be limited to maintenance of early successional stages, instead of acceleration of succession. [source] Vertical distribution of soil properties under short-rotation forestry in Northern GermanyJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2010Petra Kahle Abstract Short-rotation forestry (SRF) on arable soils has high potentials for biomass production and leads to long-term no-tillage management. In the present study, the vertical distributions of soil chemical and microbial properties after 15 y of SRF with willows and poplar (Salix and Populus spp.) in 3- and 6-year rotations on an arable soil were measured and compared to a pertinent tilled arable site. Two transects at different positions in the relief (upper and lower slope; transect 1 and 2) were investigated. Short-rotation forestry caused significant changes in the vertical distribution of all investigated soil properties (organic and microbial C, total and microbial N, soil enzyme activities), however, the dimension and location (horizons) of significant effects varied. The rotation periods affected the vertical distribution of the soil properties within the SRF significantly. In transect 1, SRF had higher organic-C concentrations in the subsoil (Bv horizon), whereas in transect 2, the organic-C concentrations were increased predominantly in the topsoil (Ah horizon). Sufficient plant supply of P and K in combination with decreased concentrations of these elements in the subsoil under SRF pointed to an effective nutrient mobilization and transfer from the deeper soil horizons even in the long term. In transect 1, the microbial-C concentrations were higher in the B and C horizons and in transect 2 in the A horizons under SRF than under arable use. The activities of ,-glucosidases and acid phosphatases in the soil were predominantly lower under SRF than under arable use in the topsoil and subsoil. We conclude, that long-term SRF on arable sites can contribute to increased C sequestration and changes in the vertical distribution of soil microbial biomass and soil enzyme activities in the topsoil and also in the subsoil. [source] Spatial patterns of desert annuals in relation to shrub effects on soil moistureJOURNAL OF VEGETATION SCIENCE, Issue 2 2010J. Li Abstract Questions: What are the effects of a shrub (Haloxylon ammodendron) on spatial patterns of soil moisture in different seasons? How does productivity of understorey annuals respond to these effects? Are such effects always positive for annuals under shrubs? Location: South Gurbantunggut Desert, northwest China. Methods: Using geostatistics, we explored seasonal patterns of topsoil moisture in a 12 × 9-m plot over the growing season. To determine spatial patterns of understorey annuals in response to H. ammodendron presence, biomass of annuals was recorded in four 0.2 × 5.0-m transects from the centre of a shrub to the space between shrubs (interspace). We also investigated vertical distribution of root biomass for annuals and soil moisture dynamics across soil profiles in shrub-canopied areas and interspaces. Results: Topsoil moisture changed from autocorrelation in the wet spring to random structure in the dry season, while soil moisture below 20 cm was higher in shrub-canopied areas. Across all microhabitats, soil moisture in upper soil layers was higher than in deeper soil layers during the spring wet season, but lower during summer drought. Topsoil was close to air-dry during the dry season and developed a ,dry sand layer' that reduced evaporative loss of soil water from deeper layers recharged by snowmelt in spring. Aboveground biomass of understorey annuals was lowest adjacent to shrub stems and peaked at the shrub margin, forming a ,ring' of high herbaceous productivity surrounding individual shrubs. To acclimate to drier conditions, annuals in interspaces invested more root biomass in deeper soil with a root/shoot ratio (R/S) twice that in canopied areas. Conclusions: Positive and negative effects of shrubs on understorey plants in arid ecosystems are commonly related to nature of the environmental stress and tested species. Our results suggest there is also microhabitat-dependence in the Gurbantunggut Desert. Soil water under H. ammodendron is seasonally enriched in topsoil and deeper layers. Understorey annuals respond to the effect of shrubs on soil water availability with lower R/S and less root biomass in deeper soil layers and develop a ,ring' of high productivity at the shrub patch margin where positive and negative effects of shrubs are balanced. [source] Effects of field reorganisation on the spatial variability of runoff and erosion rates in vineyards of Northeastern SpainLAND DEGRADATION AND DEVELOPMENT, Issue 1 2010M. C. Ramos Abstract This study analyses the spatial variability of runoff and erosion rates in vineyards due to mechanisation works. Runoff samples were collected at three positions in two plots after 33 erosive events in three years (2001, 2003, 2004) with different rainfall patterns. Three replications were considered at each position. Soil properties were evaluated in order to analyse its relationship with runoff and erosion rates. Runoff and erosion rates were, on average, higher in the levelled plot (HD), ranging between 8·4 and 34·3 per cent, than in the non-levelled plot (LD) ranging between 8·2 and 24·1 per cent. Mean sediment concentration in runoff ranged between 6 and 8,g,L,1 in the HD plot and about 4·6,g,L,1 in the LD plot, but with high differences within the plot. In the HD plot, runoff-rainfall rates were significantly higher (at 95 per cent level) in the upper part of the slope and decreased along the slope, while in the LD plot, differences in runoff rates were not significant and similar to those observed in the less disturbed areas of the HD plot. The higher susceptibility to soil sealing in areas where the original topsoil was removed conditioned runoff rates. In the lower part of the HD plot runoff rates were, on average, 20 per cent lower than in the upper part of the slope. In those positions runoff rates up to 79 per cent were recorded. Organic matter content and water retention capacity at different potentials are the soil characteristics related to the differences on runoff and erosion rates in the resulting soils. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||