Mineralization of sulphur in sulphoquinovose by forest soils

Surface soils from four watersheds located in the Coweeta Basin near Franklin, North Carolina were assayed for their capacity to mineralize sulphur in 6-sulphoquinovose. All soils rapidly converted S in this component of the plant sulpholipid to inorganic sulphate, a soluble (salt extractable) ester sulphate and an insoluble ester sulphate. Sulphur in this latter fraction was released by acidhydrolysis of soil residues at 121°C. Although maximum concentrations of S in each fraction varied with duration of incubation, rates of conversion of S into all fractions were highest during the first hour. Mineralization rates based upon sulphate release and total S released from sulphoquinovose are reported.     

A scheme for sampling inorganic nitrogen in forest soils

Abstract

An efficient sampling scheme for evaluating seasonal changes of inorganic nitrogen in a forest soil was designed. It was based on variances of ammonium‐ and nitrate‐nitrogen estimated from core samples from each of three horizons (A1, A2, B1) taken from 8 randomly selected sites in a three‐hectare study area. The scheme adopted was: At each sampling time a single composite sample for each horizon was made using 15 cores from randomly‐selected locations; duplicate subsamples from each composite were analyzed for ammonium‐ and nitrate‐nitrogen.     

Mineralization of methionine sulphur in soils and forest floor layers

A1-horizon soils and 01, 02 forest floor layers from a mixed mature hardwood forest rapidly converted methionine-S to readily-available (salt-extractable) and less readily-available (acid- and base-extractable) inorganic sulphate (SO^?2₄). It is suggested that this latter conversion represents the incorporation into organic matter of a portion of the (SO^?2₄) released by mineralization. On a dry weight basis, the 02 layer of the forest floor was the most active with respect to both conversions. Moreover, capacities for mineralization and (SO^?2₄) incorporation decreased with increasing sample depth within the mineral horizon. Both conversions were dependent upon temperature and duration of incubation and were absent from samples which had been autoclaved. Sodium azide and the broad-spectrum antibiotic, tetracycline also inhibited each conversion to varying extents depending upon the type of sample incubated with methionine.     

Aluminium sulphate solubility in acid forest soils in Denmark

Ion leaching in 3 sandy spruce forest soils of different origin and pH was investigated in the laboratory. Zero-tension lysimeters containing undisturbed soil columns of varying soil depth were subjected to H₂SO₄ loadings for a period of 9 weeks. The analysis of the resulting leachate supports the hypothesis that Al-sulphate minerals may form in acidic soils when exposed to acid (H₂SO₄) deposition. In the B horizon of a glaciofluvial sandy soil (pH 4.2), both H⁺ and sulphate ions were retained to maintain 2pH + PSO₄ = 11.9 in the leachate solutions. This relation between H⁺ and sulphate activity may be due to an adsorption mechanism or a precipitation mechanism. The precipitation mechanism is favored by the good fit of leachate composition to the conditions for jurbanite [AlOHSO₄] formation from gibbsite [Al(OH)₃]. In the B horizon of a sandy till at pH 3.7, the Al in soil solution (0.5 mmol L^?1) was leached with sulphate. As the sulphate load was increased, some sulphate was retained. This may also be due to the dissolution and precipitation of an Al-sulphate mineral. The ion activity products of leachate solutions from the B horizon of this soil were close to the pK_s reported for jurbanite. The conditions for the possible existence and/or formation of Al-sulphate minerals in acidic soils are discussed.     

Improved SMP buffer method for determining lime requirements of acid soils

Abstract

Single buffer‐two pH and two‐buffer adaptations were compared as double buffer features of the SMP method using a group of 54 soils of wide range in lime requirement (LR). Data from both methods were highly correlated both with each other and with Ca(OH)₂‐titrated acidity.

Formulas for LR based on the schematics of similar triangles relating differences in measured pH vs corresponding acidities for the double buffer system were developed. A regression equation relating buffer‐indicated LR and Ca(OH)₂ titrated acidity was used to adjust the quick‐test double buffer‐indicated values to levels nearer the actual ones. A recommended SMP double buffer procedure, and a formula for computing LR from soil‐buffer pH's measured by the double buffer, quick‐test method are presented.     

Fate of inorganic 15N in the profile of different coniferous forest soils

The fate of inorganic ¹⁵N added to different coniferous forest soils was traced throughout the soil profile (0–25 cm) in a laboratory experiment under controlled conditions of temperature and water content. Six soils with different chemical climates were compared. The sequestration of labelled N was significantly explained by the clay content but the correlation was improved when C and N content were included. The level of acidification, even in soil with a fine texture, reduced the immobilization. For a similar N input, sandy soils with low C content or high acidification showed a reduced N storage capacity, so that N excess would be able to pollute the ground-water.     

酸性土壤水溶性氟浸提方法的研究

本文比较研究了振荡、超声、沸水浴和烘箱4种浸提酸性土壤水溶性氟的方法,然后采用离子色谱法对浸提液进行测定,并通过对测定数据进行统计与方差分析来确定最佳浸提方式。结果显示,水土比5:1,浸提时间20 min、温度60℃是振荡法与超声法浸提酸性土壤水溶性氟含量的最佳条件。在此条件下,振荡法与超声法浸提的土壤水溶性氟含量无显著差异,标准偏差均小于0.3%。超声法浸提的酸性土壤水溶性氟含量显著高于各自最佳处理条件下的沸水浴法与烘箱法浸提的水溶性氟含量。在离子色谱测定水溶性氟过程中,质量控制样品均在1倍标准偏差范围内。因此,采用离子色谱法测定超声法或振荡法浸提的酸性土壤水溶性氟是一种可行的、准确的试验方法,特别对于批量土壤样品的测定具有重要意义。     

Molybdenum fractions and mobilization kinetics in acid forest soils

We extracted molybdenum (Mo) from eight acid forest soils (19 A, E, and B horizons) in NE-Bavaria and from one site in the Ore Mountains, using (1) anion exchange-resin, (2) 0.2 M ammonium oxalate, and (3) ascorbic acid/ammonium oxalate. The Mo concentrations in the anion exchange-resin fraction varied between 5 and 28 μg kg^-1. Oxalate-extractable Mo ranged from 44 to 407 μg kg^-1 and after reduction of iron (Fe) with ascorbic acid, 135 to 1071 μg Mo kg^-1 were extracted. The lowest concentrations of Mo were measured in acid and sesquioxide impoverished E horizons. The total concentrations of Mo in spruce needles correlated with ion exchange resin extractable Mo, indicating that this fraction represents Mo readily available to plants. The Mo and Fe dissolution kinetics during oxalate extraction were studied on 8 of the soil samples to obtain further information on Mo mobilization. Oxalate extractable iron (Fe_o) was mobilized within a few hours. A first order equation was applicable to the Fe dissolution kinetics with the rate constants ranging between 0.9 and 9.0 h^-1. The mobilization of Mo occurred in two distinct stages. An initially rapid dissolution was followed by a further increase in extractable Mo but with slower kinetics. A combined first order-diffusion equation was found to be appropriate for modelling the results. The first order rate constants for Mo mobilization ranged from 0.6 to 11.4 h^-1. However, correlations between the rates of reaction of Mo and Fe could not be established, indicating that Mo is either not distributed equally along Fe minerals or that there is another pool, possibly the organic substance of the soil, from which Mo is extractable by oxalate.     

A carbon balance model for organic layers of acid forest soils

Organic layers of acid forest soils are highly dynamic carbon reservoirs. During forest succession the stored amount of organic carbon (OC) changes drastically. Because of feedback between OC storage in organic layers and in mineral soils and other compartments of the environment (plant, atmosphere, and groundwater), there is a strong need for applicable carbon balance models, particularly for organic layers. In this paper a simplified model for the carbon balance of organic layers (CABOLA model) of acid forest soils is presented. The model considers two horizons, the L and O horizon. Decomposition and transport processes are described by first order differential equations. C input into the organic layer is due to litter fall onto the L horizon. The governing equations are solved by integration. To demonstrate the model's capability of simulating the OC dynamics of organic layers, data on OC storage in organic layers of acid sandy forest soils with deep groundwater tables (Podzols) under pine stands were used. Together with literature data and some assumptions, these data were used for a first, rough estimation of the model parameters. Model calculations confirm that the CABOLA model is in principle able to simulate the dynamics of OC storage in organic layers during forest succession. Nevertheless, intensive research efforts will be necessary to independently parameterize the model for broad applications.     

Modelling low molecular weight organic acid dynamics in forest soils

Low molecular weight organic acids such as citrate and oxalate have been hypothesized to play a key role in rhizosphere ecology and pedogenesis. A mathematical site-specific model, DYNLOW, was constructed to describe the temporal and spatial dynamics of these organic acids in coniferous forest soils using the modelling software STELLA^®. Experimentally derived values for biodegradation, adsorption, and daily values of soil temperature, moisture and hydrological flow were used to parameterize the model. The model describes the dynamics and downward movement of oxalate and citrate through the horizons (O, AE, E, Bhs, Bs) of three podzolic soil profiles in Sweden. After calibration, the model predicted average soil solution organic acid concentrations ranging from <1 to 90 μM, which was in agreement with experimental measurements (<1 to 116 μM). The model results indicated that microbial degradation of organic acids was in quantitative terms the biggest process regulating soil solution concentrations. Primary production rates of organic acid in the soil were predicted to be high (<1 to 1250 nmol g⁻¹ soil d⁻¹) in comparison to the amount present at steady state in the soil solution pool (<0.1 to 240 nmol g⁻¹ soil). The downward transfer of organic acids between soil horizons due to mass flow was predicted to be a small flux (<0.1 to 3% of the total loss) compared to that lost by microbial biodegradation. The model predicted that the amount of basal soil respiration that could be attributable to the microbial turnover of organic acids was on average 19±22% of the basal CO₂ production across all sites and horizons for citrate and 7±7% for oxalate. The model results are discussed in the context of pedogenesis, forest soil respiration and organic matter production.     

Quantitative determination of minerals in acid forest soils of granite

A procedure for quantifying minerals in particle size fractions of fine earth (< 2 mm) is presented. Mineral fractions of the acid forest soils are characterised by various transition products. Transitional minerals between illite and vermiculite or smectite, polyhydroxy-Al polymers interlayered in smectite and vermiculite, as well as poorly crystalline compounds are present. Normative calculations with standard minerals, generally applied to rocks, cannot be used to quantify precisely minerals of these soil samples. Conventional qualitative and quantitative chemical analyses are therefore completed by microanalyses of well-identifiable minerals. The calculation procedure is based mainly on a system of simultaneous linear equations. These are set up from the chemical contents of a particle size fraction on the one hand and from the corresponding element contents of single minerals on the other hand. The contribution of single minerals to overall parameters can be calculated by programmed algorithms. The methodology was adjusted to different particle size fractions.     

Buried organic horizons represent amino acid reservoirs in boreal forest soils

We examined the composition and concentration of amino acids by soil horizon and depth on the Tanana River floodplain in interior Alaska. Soils from mid-successional stages of balsam poplar and white spruce were separated into successive forest floor (Oe/Oa), buried organic horizons (BOHs), and mineral horizons; and water-extractable amino acid composition and concentration were determined by HPLC. The number, depth, and thickness of BOHs were highly variable across the landscape and among replicates of the same stand type, reflecting differences in terrace age, flood frequency, flood intensity, river channel position, vegetation inputs, and decomposition. BOHs generally had lower pH and bulk density, higher moisture content, and greater concentrations of carbon, nitrogen, and roots than the surrounding mineral horizons. In each horizon of both successional stages, the soil amino acid pool was dominated by glutamic acid, glutamine, alanine, asparagine, aspartic acid, and histidine, which together accounted for approximately 80% of the total amino acids found. Despite the similar overall amino acid composition among the horizons, proportions of glutamine generally increased with depth and were generally greater in the mineral horizons than in the BOHs, suggesting root exudation or fine root turnover as an amino acid source. In both successional stages, amino acid concentrations were nearly always highest in the Oe/Oa horizon and rapidly decreased with depth. BOHs generally had greater amino acid concentrations than the surrounding mineral horizons in both successional stages, but amino acid concentrations in successive BOHs declined with depth in the soil profile, suggesting that although BOHs do remain as biological hot spots and potential nutrient reservoirs as far down as 60 cm depth, their importance declines over time.     

Changes in chemistry and mineralogy of forest soils by acid rain

The goal of the present study was a qualitative and quantitative determination of chemical and mineralogical changes in forest soils due to acid atmospheric depositions. In the NE/SE Vienna Woods soil samples were taken at 4 depths (0 to 5 cm, 5 to 10 cm, 10 to 20 cm, 20 to 30 cm) in the contaminated infiltration zone of stemflow (S) of 8 beech trees (Fagus sylvatica), strongly influenced by acid atmospheric depositions (soil-pH 2.8 to 3.0) and in their non contaminated reference areas (R) between trees, where acid imput is much smaller (soil-pH 5.0 to 6.0). The results show that intensive weathering processes took place in the contaminated soil areas, which show higher clay and silt contents and smaller aggregates, as well as clay illuviation. Moreover, in the top of the contaminated soil areas higher contents of C_t and S_t and of the heavy metals Pb, Zn and Cu could be observed, accompanied by extreme low base saturation (expecially of Ca and Mg) and high Al-saturation (50 to 80% of the CEC). These data were confirmed by analysis of the water saturation extract. Moreover, in the contaminated top soils high amounts of Fe-oxides were found, whereas no “secondary” Al-chlorite (due to its instability at pH-values <4.0) could be traced. The desilification process which took place at the same time could be shown through total element analysis. In the clay-fraction strong weathering led to a loss of layer charge and to the genesis of highly expandable three-layer-silicates which could be determined by X-ray diffraction using n-alkylammonium-chloride technics and other chemical treatments.     

Determination of suitable chemical extraction methods for the available iron content of brown forest soils in Turkey

The aim of this research was to determine the available iron (Fe) content of brown forest soils of Edirne Province and the most suitable chemical extraction method. Eight chemical extraction methods (the 0.005 M DTPA + 0.01 M CaCl2 + 0.1 MTEA, 0.05 M HCl + 0.012 M H2SO4, 1 M NH4OAc (pH: 4.8), 0.01 M EDTA + 1 M NH4OAc, 1 M MgCl2, 0.01 M EDTA + 1 M (NH4)2CO3, 0.005 M DTPA + 1 M NH4HCO3, and 0.001 M EDDHA methods) and six biological indices (the dry matter yield, Fe concentration, Fe uptake, relative dry matter yield, relative Fe concentration, and relative Fe uptake) were compared. The biological indices were determined with barley (Hordeum vulgare L.) grown under greenhouse conditions. At the end of the experiment, the highest correlation coefficients (r) were determined to be between the 0.005 M DTPA + 0.01 M CaCl2 + 0.1 M TEA method and the biological indices and between the 0.005 M DTPA + 1 M NH4HCO3 method and the biological indices. The corresponding correlation coefficients (r) for the 0.005 M DTPA + 0.01 M CaCl2 + 0.1 M TEA method and the six biological indices were 0.621**, 0.823**, 0.810** 0.433**, 0.558**, and 0.640**, respectively. For the 0.005 M DTPA + 1 M NH4HCO3 method, these coefficients were equal to 0.618**, 0.520**, 0.679**, 0.521**, 0.492**, and 0.641**, respectively (** indicate the validity of the relationships at p < 0.01) These extraction methods, out of all the methods tested, were suggested for the determination of the available Fe content of the brown forest soils. Published in Russian in Pochvovedenie, 2006, No. 9, pp. 1068–1074. The text was submitted by the author in English.     

磷矿粉在酸性土壤中的施用: 比较磷酸盐提取方法测定磷矿粉溶解程度

Three phosphate extraction methods were used to investigate the dissolution,availability and transfo-mation of Kunyang phosphate rock(KPR) in two surface acid soils.Dissolution was determined by measuring the increase in the amounts of soluble and adsorbed inorganic phosphate fractions,and did not differ signifi-cantly among the three methods.Significant correlations were obtained among P fractions got by the three extraction methods.Dissolution continued until the end of the 90-day incubation period.At the end of the period,much of the applied phosphate recovered in both soils were in the Al- and Fe-P or in the hydroxide-and bicarbonate-extractable inorganic P fractions.The dissolution of KPR in the two soils was also similar: increased addition of phosphate rock resulted in decreased dissolution.The similarity in the order and extent of dissolution in the two soils was probably due to the similarity in each soil of several factors that are known to influence phosphate rock dissolution,namely low CEC,pH,P level,and base status;and high clay and free iron and aluminum oxide contents.The results suggested that KPR could be an aternative P source in the soils are not limiting.     

Modified method for measuring acid phosphatase activities in forest soils with high organic matter content

Abstract

The acid phosphatase activity (APA) is a key factor in phosphorus (P), mineralization, P nutrition of plants, and P cycling. However, the widely used method of Tabatabai and Bremner for APA determinations is seriously restricted in soils with high organic matter contents, owing to interference in photometric detection by dissolved organic matter. The objectives of this study were: A) to modify the procedure of Tabatabai and Bremner with a view to its application to forest soils rich in organic carbon, b) to determine APA contents in forest soils of the Sierra de Gata mountains, and c) to establish relationships between the APA with different soil parameters. The modified procedure was well adapted to forest soils with high organic matter contents and had good reproducibility, while maintaining the relative simplicity and accuracy of the original Tabatabai and Bremner procedure. APA in the forest soils studied was high but did not correlate with labile P. The APA in the soils studied depended principally on availability of readily degradable energy sources and soil nitrogen (N).     

Phosphomonoesterase activity in forest soils

Phosphatases are important in the mineralization of organically-bound phosphorous. Although phosphatases have been studied extensively in agricultural soils, there are few reports on phosphatase activity in forest soils, and no information on the effect of forest management practices, such as thinning and N-fertilization, on phosphomonoesterase (PME) activities. In the present study, the (PME) activity of forest soils from Shawnigan Lake and Jordan River (mg p-nitrophenol released g⁻¹ dry soil h⁻¹ was highest in the forest floor horizon (L-H) and decreased with depth to 60 cm in mineral soil horizons. Addition of orthophosphate and urea during the assay of PME demonstrated these chemicals competitively depressed PME activity. With Shawnigan Lake soil (L-H), the minimum rate (V_max) of PME activity was 5.71 mg p-nitrophenol released g⁻¹ dry soil h⁻¹. For Jordan River, V_max was 3.33 mg p-nitrophenol released g⁻¹h⁻¹. Incubation of L-H horizon of both soils, fumigated or non-fumigated, at 30°C for up to 40 days after rewetting resulted in an initial reduction in PME activity. Comparatively, the PME activity of Jordan River soil recovered faster than that of the Shawnigan Lake soil whose activity remained very low at the end of the incubation. In field plots where trees were thinned and urea and ammonium nitrate fertilizers had been applied 2 yr previously, assays for PME demonstrated that urea fertilization and thinning depressed PME activity while ammonium nitrate did not. This study demonstrated (1) PME activity depended on soil geographic location and depth, and (2) fertilization of forests with phosphates and urea appeared to reduce PME activity and thus may have the potential to depress the mineralization of organic-P.     

土壤中有效结合态氨的一种测定方法

Dynamics of fixed NH₄⁺ in NH₄⁺-treated soils incubated with glucose at 37±2 ℃ during the course of incubation and factors affecting it were studied. Results showed that content of fixed NH₄⁺ in soil reached a minimum on day 7 after incubation and then increased gradually regardless of the amount of glucose added and the kind of soil tested. However, the amount of fixed NH₄⁺ released from the soil at the given time varied with both the amount of glucose added and the kind of soil examined. In cases glucose was added at a rate of 10.0g C/kg soil, the amount of fixed NH₄⁺ retained in soil after 7 days of incubation was almost identical to that found by Neubauer test. Addition of K⁺ depressed the release of fixed NH₄⁺ significantly. Based on the results obtained a method for determining the content of available fixed NH₄⁺ in soils was proposed and the amount of N as available fixed NH₄⁺ in two soils measured by this method on an area profile-depth basis was presented.