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Abstract Pedogenic iron rich soils are prevalent worldwide covering approximately 1000 million hectares. These soils are fragile and prone to severe degradation, in many cases resulting in high erosion rates and formation of gullies. Restoration and revegetation practices face many barriers in degraded Acrisols, including low nutrient availability exacerbated by high iron concentrations. The objective of this work was to evaluate the performance of two tree species, Pinus pseudotrobus , and Fraxinus uhdei , growing in Acrisol soils in the presence of endo, ecto or both types of mycorrhizic fungi, in order to assess the effect of the interaction for management of degraded lands. The largest Fraxinus plants, those inoculated with both types of mycorrhizic fungi, accumulated three times more biomass than the smallest, and for Pinus the largest plants, those growing in soil with both types of fungi, had 1.5 times more biomass. Iron content in tissues of the Fraxinua uhdei plants was within that reported for plants in general (0.014%), and for Pinus pseudostrobus our values were higher for all treatments but within the same order of magnitude. For ecological restoration and other management purposes these results strongly suggest that dual inoculation or planting species that allow for both types of mycorrhizic fungi to be present in the soil can improve tree species performance and therefore facilitate the recovery process of heavily degraded sites. Highlights • Fraxinus in Acrisols inoculated with endo- and ectomycorrhiza, had the best growth. • Pinus growing in soil with both types of mycorrhizic fungi, grew the tallest. • Acrisol revegetation benefits from the presence of both endo- and ectomycorrhiza. [ABSTRACT FROM AUTHOR]

Biochar is a carbon-rich porous material intensively studied for its agronomic benefits, such as decrease of greenhouse gases emission and nutrient losses via leaching, increased crop production and improved soil physical and chemical properties. We investigated the effect of holm oak biochar produced at 600 °C on mineral nitrogen (N) leaching from two contrasting soils (Acrisol and Calcisol). Biochar was applied at three rates (0%, 1% and 2% w/w) with (B0-F, B1-F and B2-F, respectively) and without (B0, B1 and B2, respectively) ammonium-based fertilizer. Soil columns were leached with deionized water and mineral N in leachate was monitored during ten weeks after each fertilization. Sorption behavior of biochar-amended soils was assessed in batch experiments before and after leaching. Biochar increased ammonium (NH 4 + -N) sorption in sandy Acrisol but had no effect on nitrate (NO 3 − -N) sorption. Furthermore, sorption properties of soil decreased by up to 25% during the study. In Acrisol, biochar affected NH 4 + -N leaching, which was increased by both doses of biochar without fertilization, but decreased by the lower biochar application rate when fertilizer was added. The leaching of NO 3 − -N was not affected by biochar in Acrisol. The ability of Calcisol to adsorb NH 4 + -N was high and was not further increased by biochar, which corresponds to no NH 4 + -N leaching from Calcisol regardless the biochar application rate. Moreover, biochar had no effect on NO 3 − -N leaching from Calcisol. Our results demonstrate that biochar effect on leaching of inorganic N forms is inconsistent, evolves in time and is highly dependent on soil properties. Alleviation of soil acidity by biochar application to Acrisol resulted in short-term stimulation organic N mineralization, which resulted in enhanced amount of NH 4 + -N being leached. Furthermore, the fact that biochar lost its effect on N leaching already after the second fertilizer application could cast a doubt on the efficiency of biochar application to soil in order to increase N retention and decrease N leaching. [ABSTRACT FROM AUTHOR]

The Armed Forces Medical Examiner System – Armed Forces DNA Identification Laboratory (AFMES-AFDIL) and the Defense POW/MIA Accounting Agency (DPAA) are partners in the identification of missing United States service members. Skeletal materials are recovered world-wide from past military conflicts; however, this project examines the relative success of skeletal materials recovered from Southeast Asia. The soils in Southeast Asia are known to be largely acidic, with the majority being classified as acrisol or gleysol (pH4.4–7.2). Acidic soils are thought to compromise the structural integrity of buried skeletal materials leading to a degradation of the DNA found within. This study evaluates whether this idea is apocryphal or if acidic soils truly have an impact. [ABSTRACT FROM AUTHOR]

Erosion is a major cause of soil degradation. Understanding the sources of sediment and the processes that exacerbate this problem is crucial for soil conservation. Remote and proximal sensing technologies have contributed to advance our understanding of soil erosion processes and support soil conservation research. The objective of this study is to use two proximal sensors, a portable X-ray fluorescence spectrometer (pXRF) and a magnetic susceptibilimeter, to identify the origin of sediments deposited in the lower portion of a drainage subbasin by using a fingerprinting approach. Five sediment tracing elements were selected: Fe, Si, Al, Ti, and Zr. The sediment source area is composed of gabbro, granite, and felsic orthogneiss, upon which two soil classes were formed: Rhodic Ferralsol (Dystric) (Latossolo Vermelho Distroférrico típico, LV) and Haplic Acrisol (Argissolo Vermelho-Amarelo Distrófico típico, PVA). In the source area, 35 samples were collected from the topsoil layer (0–2 cm of depth) using a regular grid of 50 × 50 m2. In the deposition area, 24 samples were collected in a regular grid of 7 × 7 m2. The source of the sediments was determined using cluster analysis with data provided by the proximal sensors and topographic attributes. Results indicated that the Haplic Acrisol, which is more susceptible to erosion, contributed most to sediment deposition. Analysis of pXRF data showed its potential to identify and differentiate sediments and their sources. Cluster models based on the abundance of Fe, Si and Al, as well as the Ti/Zr ratio, demonstrated the best results with a global accuracy of 88% and a Kappa coefficient of 0.74. The use of the susceptibilimeter data alone did not yield satisfactory results. Results indicate the usefulness of pXRF in identifying the source of sediments in drainage basins, making it a valuable tool in soil conservation and erosion assessments. • pXRF was capable of identifying the origin of sediments. • Fe, Si, Al and the Ti/Zr ratio were efficient in identifying sediment sources. • The Chromic Acrisol contributed most with sediment deposition. • Magnetic susceptibility contributed little to identify sediment sources. [ABSTRACT FROM AUTHOR]

An inventory of soil organic carbon (SOC) stocks to 100-cm depth was carried out at four pedologically comparable forest sites in the Amani Nature Reserve (Eastern Usambara Mountains, NE Tanzania). Three plots at primary tropical submontane forests and one plot at a secondary forest derived from selective cutting were sampled. The aim was to quantify the SOC stocks including the spatial variation, and to put the findings into a pedological context. At each site, a combined approach was applied with auger samples taken to 40-cm depth (topsoil) at eight points (10 cm depth intervals) surrounding a central soil pit. The subsoil was sampled at 40–100 cm depth in the soil pit, accompanied by a detailed soil description and classification according to FAO and WRB. In addition, soil analysis comprised a set of chemical and physical parameters. According to WRB, the soils belonged to the reference groups Acrisols and Alisols, depending on the method used for estimating clay-related potential cation exchange capacity. The SOC stocks to 100-cm depth ranged between 16.9 and 22.4 kg C m − 2 (mean 19.7 kg C m − 2 ). The SOC stock at the secondary forest (20.2 kg C m − 2 ) did not differ from those of the primary forest plots. In all profiles the subsoil contributed to the SOC stocks to 100-cm depth, whereas the contribution of the forest floor was small. The variation of SOC stocks between the forest sites may be explained by ‘old’ land-use and/or differences in soil chemical parameters controlling SOC stabilization. The SOC stocks appear to be related to the amounts of poorly crystallized Fe- and Al-oxides. The mechanisms and potentials for SOC sequestration are, however, unclear and merit further detailed study. Our inventory of SOC under forest represents a suitable baseline for the assessment of SOC stock changes after land-use conversion to agriculture on typical soils of the humid tropics. [ABSTRACT FROM AUTHOR]

The application of electron donor and electron shuttle substances has a vital influence on electron transfer, thus may affect the reductive dechlorination of 1,1,1-trichoro-2,2-bis(p-chlorophenyl)ethane (DDT) in anaerobic reaction systems. To evaluate the roles of citric acid and anthraquinone-2,6-disulfonate (AQDS) in accelerating the reductive dechlorination of DDT in Hydragric Acrisols that contain abundant iron oxide, a batch anaerobic incubation experiment was conducted in a slurry system with four treatments of (1) control, (2) citric acid, (3) AQDS, and (4) citric acid + AQDS. Results showed that DDT residues decreased by 78.93%–92.11% of the initial quantities after 20 days of incubation, and 1,1-dichloro-2,2-bis(4-chlorophenyl)-ethane (DDD) was the dominant metabolite. The application of citric acid accelerated DDT dechlorination slightly in the first 8 days, while the methanogenesis rate increased quickly, and then the acceleration effect improved after the 8th day while the methanogenesis rate decreased. The amendment by AQDS decreased the Eh value of the reaction system and accelerated microbial reduction of Fe(III) oxides to generate Fe(II), which was an efficient electron donor, thus enhancing the reductive dechlorination rate of DDT. The addition of citric acid + AQDS was most efficient in stimulating DDT dechlorination, but no significant interaction between citric acid and AQDS on DDT dechlorination was observed. The results will be of great significance for developing an efficient in situ remediation strategy for DDT-contaminated sites. [ABSTRACT FROM AUTHOR]

Loss of soils and the consequent damage at local and regional scales is one of the most severe and extensive environmental problems. When the soil structure, and even the soil itself, is lost, revegetation faces difficult obstacles, not least the availability of nutrients for plants. As part of a project to develop revegetation strategies in the gullies formed in acrisols, a revegetation assay was established with Pinus pseudostrobus , in which the effect of inoculation with the ectomycorrhizal fungus Pisolithus tinctorius and the addition of phosphorous (KH 2 PO 4 ) was tested. Five years after initial plantation, the inoculated and non-inoculated trees presented 86% and 65% survival, respectively, representing a difference of 21% between both groups ( X 2 = 10.17 ; P = 0.001 ) . Differences in growth were also correlated with inoculation; inoculated trees reached 158 ± 5.4 cm in height and 4.8 ± 0.16 cm in diameter, while non-inoculated trees reached 134 ± 6.1 cm in height and 3.8 ± 0.14 cm in diameter ( P < 0.05 for both variables). These results indicate that inoculation allows this sensitive species to prosper in severely degraded soils and that phosphorus fertilization is not an effective measure. [ABSTRACT FROM AUTHOR]

Abstract: 137Cs tracing technique combined with soil composition characterization was used to investigate the mechanism and effectiveness of conservation measures for cultivated hill slopes of strongly weathered acidic Acrisol. The results of analysis of 66 soil samples taken across six plots showed much lower losses of 137Cs, soil organic carbon (SOC), and nutrients in the four treatments of alley cropping with hedgerows compared to the two control treatments of bare land and without conservation measures. No-tillage cultivation combined with vetiver grass hedgerows was most effective in securing high levels of 137Cs, SOC, N, P, K, and CEC while reducing considerably the contents of dissolved cations and anions. Within the plots of alley cropping, 137Cs, SOC, nutrients, dissolved ions, and sand were accumulated in the areas immediately upslope of the hedgerows, whereas the clay content and bulk density were highest downslope of the hedgerows. SOC inversely correlates with clay in concurrence with observations for the soils derived from basaltic parent materials, in which clay minerals are predominated by kaolinite. The correlations of 137Cs with dissolved Ca, Mg, and P indicate that in the highly leaching Acrisol 137Cs may partly occur in the soil solution that is susceptible to leaching and loss. The interrelationships among soil components were interpreted as being driven by the redistribution of soil aggregates which were fractionated in situ according to their sizes and specific densities by erosion forces combined with tillage and conservation measures (hedgerows). [Copyright &y& Elsevier]

Abstract: The transformation of inorganic iodine (I− and IO3 −) incubated in soils with varying amounts of organic matter (Andosols from the surface layer of an upland field and forest, as well as Acrisols from surface and subsurface layers of an upland field) was investigated by using the iodine K-edge X-ray absorption near-edge structure (XANES). After 60d of reaction, both I− and IO3 − were transformed into organoiodine in surface soils containing sufficient amounts of organic matter, whereas IO3 − remained unchanged in the subsurface soil of Acrisols with low organic matter contents. Transformation of IO3 − into organoiodine was not retarded when the microbial activity in soil was reduced by γ-ray irradiation, suggesting that microbial activity was not essential for the transformation of inorganic iodine into organoiodine. Soil organic matter has the ability to transform inorganic iodine into organoiodine. [Copyright &y& Elsevier]

Abstract: Prediction of soil changes that occurs as a result of agronomic management practices is very useful, particularly when restoration of degraded soils wants to be implemented. The aim of this work was to study the short-term effect (4 years) of different agricultural practices on biochemical and microbial indicators related to soil organic matter (SOM) and to validate the sensibility of a set of biological indicators expressing C dynamic in a representative Mexican volcanic soil. Four soil management systems (2002–2005): traditional (Tt), improved (Ti), organic (To), and fallow (Tf) were assayed in experimental plots (Acrisol) located at the Mexican Trans-volcanic Belt. An uncultivated soil under grass cover (Sg) was used as reference. The Acrisol came from weathered volcanic materials and had severe problems of erosion. Soil samples (0–10cm depth) were analyzed for soil organic C (SOC), total N (Nt), water-soluble C (WSC), and humic C (Hm-C); and for microbial biomass (MB), soil respiration (SRv), net N mineralization (Nm), dehydrogenase activity (DHa), arginine ammonification (ARa), and extra-cellular enzyme activities (urease, protease, β-glucosidase, and acid phosphatase). Higher values of SOC, Nt, WSC, Hm-C, MB, SRv, Nm, DHa and ARa were found under To and Ti as compared to Tt and Tf managements. A similar response pattern was observed in the case of extra-cellular enzyme activities. These results suggested an interaction between the available energy-rich compounds and the biochemical energy preserved in humus–enzyme complexes. Higher levels of the biological parameters measured in To and Ti treatments were associated to a higher SOC content. These two treatments contributed to the regeneration of these degraded Acrisols, while no soil quality improvements were registered under Tt and Tf managements in the short-term. The selected biological indicators were useful to evaluate the soil quality changes of degraded Mexican cultivated Acrisols. [Copyright &y& Elsevier]

• Water erosion mechanisms on sloping cropland in central Vietnam were investigated. • Using the short-term water budget could successfully analyze water erosion processes. • Tropical storms strongly affect the rainfall regime of the research site. • Crop cover showed a substantial influence on soil loss and runoff generation. • The seasonal changes in water erosion mechanisms were significant. Water erosion has created severe degradation problems in Vietnam and its Thua Thien Hue Province because it lies on the tropical typhoon belt and frequently experiences typhoons and floods. To clarify which environmental factors affect runoff generation and soil loss under specific climatic and soil conditions in the study area, we analyzed the short-term water budget for almost two consecutive years, using small-scale runoff plots developed on a slope of the highland region. Four treatments were established: February cassava (Manihot esculenta) plot, bare land plot, April cassava (Manihot esculenta) plot, and April cassava (Manihot esculenta) + September acacia (Acacia hybrid) intercropping plot. Our results showed that the early planting of cassava (February cassava) was advantageous for decreasing soil loss by the early development of soil surface coverage and decreasing surface runoff. On the other hand, acacia intercropping did not seem as effective in suppressing surface runoff and soil loss, relative to cassava monocropping. Runoff generation was determined by rainfall volume and maximum rainfall intensity (at 10 min intervals). In addition, initial volumetric water content was an important driving factor of outcome variables in the plots cultivated during the minor rainy seasons. The mechanisms of water erosion were different in the minor and major rainy seasons: in the minor rainy seasons, the runoff volume generated during rainfall events was the decisive factor that triggered soil loss; whereas in the major rainy seasons, a threshold of 10 min of continuous rainfall was the driving force of soil loss. [ABSTRACT FROM AUTHOR]

Soil organic C (SOC) and total soil N (TSN) sequestration estimates are needed to improve our understanding of management influences on soil fertility and terrestrial C cycling related to greenhouse gas emission. We evaluated the factorial combination of nutrient source (inorganic, mixed inorganic and organic, and organic as broiler litter) and forage utilization (unharvested, low and high cattle grazing pressure, and hayed monthly) on soil-profile distribution (0–150cm) of SOC and TSN during 12 years of pasture management on a Typic Kanhapludult (Acrisol) in Georgia, USA. Nutrient source rarely affected SOC and TSN in the soil profile, despite addition of 73.6Mgha−1 (dry weight) of broiler litter during 12 years of treatment. At the end of 12 years, contents of SOC and TSN at a depth of 0–90cm under haying were only 82±5% (mean±S.D. among treatments) of those under grazed management. Within grazed pastures, contents of SOC and TSN at a depth of 0–90cm were greatest within 5m of shade and water sources and only 83±7% of maximum at a distance of 30m and 92±14% of maximum at a distance of 80m, suggesting a zone of enrichment within pastures due to animal behavior. During 12 years, the annual rate of change in SOC (0–90cm) followed the order: low grazing pressure (1.17MgCha−1 year−1)>unharvested (0.64MgCha−1 year−1)=high grazing pressure (0.51MgCha−1 year−1)>hayed (−0.22MgCha−1 year−1). This study demonstrated that surface accumulation of SOC and TSN occurred, but that increased variability and loss of SOC with depth reduced the significance of surface effects. [Copyright &y& Elsevier]

Timber extraction with crawler tractors in humid tropical forests causes degradation of soil physical properties and decreases plant growth. We tested rehabilitation of tracks in a second rotation Acacia mangium plantation in Sabah, Malaysia, by tilling with additions of NPK-fertilizer, ash and organic material to a depth of 15–20 cm. Two years after planting total basal area of A. mangium seedlings was 62% higher outside tracks compared to unimproved tracks, while on NPK-fertilized tracks performance was 700% higher compared to unimproved tracks. Corresponding figures for average height were 40 and 80%. After 8 days with little rain track topsoil experienced water shortage with all studied soil improvements. For ‘non-tracked’ areas wilting-point (-1500 kPa) was not reached during 17 days of dry weather, and more meso-pores were present. Consequently, depending on rainfall after planting the effect of soil rehabilitation on tree performance may be less positive than shown here, because dry periods of 2 weeks length are common in the humid tropics. Bulk density on plots outside tracks in this second-generation plantation was 60% higher than have been reported in similar first-generation plantations. It is discussed that this might be a warning that repeated logging and fire may have a detrimental effect on soil physical properties. [Copyright &y& Elsevier]

Shifting cultivation is a globally important form of agriculture covering over 280 million hectares in the tropics, but it has often been blamed for deforestation and forest degradation. In North East India (NEI) it has been practiced for millennia and it is an important element of the cultural identity of indigenous communities. It is often practiced on slopping lands with fragile soils (mostly Acrisols), which are prone to rapid degradation with cultivation. The shortened fallow cycle as practised currently is ecologically unsustainable and economically not viable. This study aimed to quantify (i) changes in soil bulk density, aggregate stability and compaction in relation to chronosequence and soil depth, (ii) changes in the proportion of macro, meso, and micro aggregates and associated soil organic carbon (SOC) content in relation to soil depth and fallow chronosequence, and (iii) determine the minimum fallow length that achieves SOC stocks comparable with adjacent intact forest land. The proportion of soil macro-aggregates and meso-aggregates significantly varied with land-use and soil depth as well as their interactive effects. Across all soil depths, forest land had the highest proportion of macro-aggregates (75.6%), while the currently cultivated land had the least proportion (51.1%). The SOC contents in macro-aggregates increased with fallow age and decreased with soil depth; the highest (1.95%) being in the top 10 cm soil of 20 years old fallows and the lowest (0.39%) in 21–30 cm depth of 5 years old fallows. Multivariate analysis identified bulk density and porosity as the most important variables to discriminate between land use practices. The analysis provided evidence for significant changes in soil compaction, aggregate stability and SOC content with the transition from undisturbed forest to slash-and-burn cultivation and fallow phases. It is concluded that a minimum of 20 years of fallow period is required to achieve SOC content and C stocks comparable with intact forest land. Unlabelled Image • SOC content was positively correlated with MWD, GMD, and negatively with BD. • Soil macro- and meso-aggregates significantly varied with land-use and soil depth. • Macro-aggregates increased from cultivated land through the different fallow ages. • Macro-aggregates had higher SOC content than meso- and micro-aggregates. [ABSTRACT FROM AUTHOR]