Fine Earth Fraction Research Articles

Adsorção de fósforo, superfície específica e atributos mineralógicos em solos desenvolvidos de rochas vulcânicas do Alto Paranaíba (MG)

Muitos solos tropicais com grau avançado de intemperismo, apesar de apresentarem teores totais de P relativamente elevados, mostram-se deficientes em P disponível, pela baixa solubilidade das principais formas de P encontradas. Neste trabalho, estudou-se o processo de adsorção de P em solos desenvolvidos de rochas vulcânicas básicas e ultrabásicas do Alto Paranaíba em Minas Gerais, algumas das quais ricas em apatita, estabelecendo-se relações com atributos de solo, como superfície específica (SE) e mineralogia. Foram estudados onze horizontes B diagnósticos de perfis de solos da região, por meio de análises químicas, físicas e mineralógicas; foram determinadas as capacidades máximas de adsorção do fósforo (CMAF), SE pelo método direto BET-N2 e indiretamente por cálculos, bem como foi feita a quantificação dos minerais de argila pelo método de alocação. Os valores da SE obtidos indiretamente de cada mineral, foram superestimados em relação à SE determinada pelo método BET-N2 na fração argila total. Nos Latossolos estudados, com texturas e materiais de origem variáveis, desde rochas básico-alcalinas até ultrabásicas, a proporção e a área superficial da gibbsita e goethita têm participação destacada na adsorção de P. A faixa de valores de CMAF TFSA encontrada está consistente com os valores na literatura reportados para Latossolos, embora os valores de CMAF TFSA e CMAF ARG corrigida, de 2,98 e 4,38 mg g-1, respectivamente, do Latossolo Vermelho-Amarelo de rocha ultrabásica (P6), sejam comparáveis àqueles de solos subtropicais alofânicos derivados de cinzas vulcânicas. A CMAF ARG corrigida para percentagem de argila evidenciou expressivos valores nos Cambissolos de rochas vulcânicas ultrabásicas (4,32 e 5,52), com valor menor naquele derivado do tufito (3,16 mg g-1). Os valores de substituição isomórfica de Al na goethita são mais elevados que nas hematitas. Em contraste com os Latossolos, os Cambissolos mostraram variações grandes nos atributos químicos, mineralógicos e na CMAF, em virtude da natureza diversificada de materiais de origem e do menor grau de intemperismo.

Effect of particle-size distribution, soil organic carbon content and organo-mineral aluminium complexes on acid phosphatases of seasonally flooded forest soils

We studied the acid phosphatase activity (APA) and its relationships with some soil physico-chemical properties along a seasonally flooded forest gradient. The soil samples were collected during the non-flooded period in three zones subjected to different flooding periods: a zone inundated 8 months per year (MAX), a zone inundated 5 months per year (MED), and a zone inundated 2 months per year (MIN). In the MAX zone APA was low and negatively correlated with the fine earth fraction of soil. In this zone, clay minerals appeared to reduce the enzymatic activity. In the MIN zone acid phosphatase had a relatively higher activity, which was positively correlated with the soil organic C content and with Al associated with the organic matter. The highest value of APA was obtained in the MED zone, and no correlation was found between edaphic factors and the enzymatic activity in this zone. However our results are restricted to a single sampling date and, therefore, they do not take into account the seasonal dynamics of acid phosphatase in relation to other soil factors over time.

Rock fragments in soil support a different microbial community from the fine earth

Two sandstone-derived soils under pure stands of silver fir ( Abies alba Mill.) and European beech ( Fagus sylvatica L.) were studied to determine if the fine earth (<2 mm material) and two size-classes of porous rock fragments (>2 mm material) supported different microbial communities. Samples from three soil horizons (A, Bw, and BC) were analysed under both optical and scanning electron microscopes. Small stones (2–10 mm in average diameter) appeared more altered than larger ones (40–60 mm) and the effects of weathering became more obvious with shallower depth. In both soils, numerous hyphae and other living forms were observed on the surface of the stones from the A and Bw horizons; this contrasted with the stones from the BC horizon, which showed little or no colonisation. The microbial community of each fraction was characterised using Biolog-Community Level Physiological Profiles (CLPP) and phospholipid fatty acid analyses (PLFA) for samples in the A and B horizons. Significant potential microbial activity (C source utilisation) was associated with rock fragments, from the A horizon and, to a lesser extent, the B, although this was lower than for the equivalent fine earth fraction. The microbial colonisation of the stones appeared inversely related with their size and sampling depth. The PLFA analysis showed not only quantitative differences in the microbial biomass between horizons and size-fractions but also highlighted that the communities differed between soils, horizons (for the sole beech soil) and fractions. These findings demonstrate that by considering rock fragments as a microbiologically inert fraction and discarding them before analysis, as usually is done, can lead to an incomplete picture of both the total amount and, perhaps more importantly, the structure of soil microbial community.

Genesis of the terrae rossae of the Sierra Gádor (Andalusia, Spain)

SummarySome aspects of the genesis of terrae rossae are still subject to controversy while others related to the genesis of the mineral fraction have been studied very little. We have studied four terrae rossae over limestone (two Chromic‐Leptic Luvisols, a Rhodi‐Leptic Luvisol and a Chromi‐Leptic Cambisol) in Sierra Gádor (Almería, southern Spain), in particular the various formation processes by (i) examination of their morphological, analytical and mineralogical characteristics (including crystallochemical parameters of the mica), (ii) examination of the insoluble residue of the gravel and rock, (iii) scanning electron microscopy (SEM) of sand and silt grains, and (iv) examination of the geochemistry of the soil solution. We have investigated the autochthonous or allochthonous nature of the soil material (fine earth and gravel) in relation to the rocky substrate, concluding that both origins are possible. Our SEM study of the morphology of the quartz grains shows that some are insoluble residue and some are probably wind blown from desert and coastal sources. The micas in the fine earth fractions are inherited from the insoluble residue. Comparison of the crystallochemical parameters of micas in the insoluble residue and the soil clay shows that the clay has more SiIV and (Fe, Mg)VI, and less AlIV, AlVI and x (layer charge) than the insoluble residue. It also has fewer polytypes 2M1 and more 1M and has a smaller crystal size, especially in B horizons. The kaolinite is of varied origins including neoformation and inheritance from underlying rock. Some of the kaolinite and some mica has been blown in from elsewhere, probably from desert and coastal sources. The soils have undergone other typical processes of terrae rossae including dissolution of carbonate, illuviation of clay and iron oxides, and rubifaction.

THE CHANGES WITH DEPTH OF HUMIC AND FULVIC ACIDS EXTRACTED FROM THE FINE EARTH AND ROCK FRAGMENTS OF A FOREST SOIL

Although much is known about the transformation of humic substances in the fine earth fraction of surface horizons, little is known about these processes in the coarse fragments (>2 mm) or about the changes with depth of humic and fulvic acids extracted from an entire soil profile. For each horizon of a forest soil developed on sandstone, the humic acids (HAs) and fulvic acids (FAs) were extracted from four fractions: fine earth, washing (i.e. fine material adhering to the clasts) and highly altered and slightly altered rock fragments. The HAs and FAs were also extracted from samples of the parent rock. The humic substances were then analyzed for their elemental composition and chemical structure by FT-IR and 13 C NMR spectroscopy. In the A horizons (upper 20 cm of the profile), the HAs from all the fractions appeared highly aromatic, with a high degree of C substitution and an abundance of carboxyl groups; however, the HAs of the rock fragments were more aromatic and richer in carbohydrate and proteinaceous residues than those of the fine earth. The HAs showed a more condensed and unsubstituted aromatic pattern at depth than in surface horizons. In the Bw and BCb horizons the contribution of biological residues to the humic substances seems to be progressively replaced by the contribution of organic materials derived from the sedimentary parent rock. The presence of features ascribable to the HAs and FAs of the parent rock decreased following the order: slightly altered clasts > highly altered clasts > washing > fine earth. Conversely, FAs showed a high homogeneity throughout the profile and are considered mostly of pedogenic origin. The chemical characteristics of both HAs and FAs showed a break in the trend with depth between Bw and BCb horizons, confirming the presence of a pedogenic discontinuity between the upper modern soil (A-Bw2 horizons) and the buried paleosol (BCb horizons).

The dynamics of organic matter in rock fragments in soil investigated by 14C dating and measurements of 13C

SummaryRock fragments in soil can contain significant amounts of organic carbon. We investigated the nature and dynamics of organic matter in rock fragments in the upper horizons of a forest soil derived from sandstone and compared them with the fine earth fraction (&lt;2 mm). The organic C content and its distribution among humic, humin and non‐humic fractions, as well as the isotopic signatures (Δ14C and δ13C) of organic carbon and of CO2 produced during incubation of samples, all show that altered rock fragments contain a dynamic component of the carbon cycle. Rock fragments, especially the highly altered ones, contributed 4.5% to the total organic C content in the soil. The bulk organic matter in both fine earth and highly altered rock fragments in the A1 horizon contained significant amounts of recent C (bomb 14C), indicating that most of this C is cycled quickly in both fractions. In the A horizons, the mean residence times of humic substances from highly altered rock fragments were shorter than those of the humic substances isolated in the fine earth. Values of Δ14C of the CO2 produced during basal respiration confirmed the heterogeneity, complexity and dynamic nature of the organic matter of these rock fragments. The weak 14C signatures of humic substances from the slightly altered rock fragments confirmed the importance of weathering in establishing and improving the interactions between rock fragments and surrounding soil. The progressive enrichment in 13C from components with high‐14C (more recent) to low‐14C (older) indicated that biological activity occurred in both the fine and the coarse fractions. Hence the microflora utilizes energy sources contained in all the soil compartments, and rock fragments are chemically and biologically active in soil, where they form a continuum with the fine earth.

Water Holding Capacity of Ironstone Gravel in a Typic Plinthoxeralf in Southeast Australia

Water retention by coarse fragments in the soil is often ignored in agronomic and water balance studies. Following the calculation of inexplicably high water retention by the fine earth fraction, water contents at −20 and −1500 kPa and apparent bulk density were determined for remnant pisolithic ironstone gravel samples isolated from soils on the Dundas Tableland in southeast Australia. The volumetric water content of the ironstone gravel at −1500 kPa was found to vary between 0.12 and 0.24 m3 m−3, while at −20 kPa it varied between 0.16 and 0.36 m3 m−3 Available water holding capacity (AWHC) of the ironstone gravel varied between 0.03 and 0.15 m3 m−3 Both the AWHC and the water content at −1500 kPa of the ironstone gravel showed significant increases with depth. Magnetic ironstone gravel, found almost exclusively in the A and E horizons, was much denser than nonmagnetic ironstone gravel (average 3.38 vs. 2.64 Mg m−3), but had similar water retention characteristics. Ignoring the water retention characteristics of the ironstone gravel would have led to overestimation of the AWHC of the bulk soil by a factor 1.08 to 1.67 for various horizons. For the combined top 1.0 m of the soil, ignoring the water held by the ironstone gravel would have led to an estimated AWHC of 162 mm, while in fact it was only 129 mm. Water balance studies of soils with ironstone gravel clearly need to take into account the water holding characteristics of that gravel.

Factors affecting establishment of a gypsophyte: the case of Lepidium subulatum (Brassicaceae)

The restriction of vascular plants to gypsum-rich soils under arid or semiarid climates has been reported by many authors in different parts of the world. However, factors controlling the presence of gypsophytes on these soils are far from understood. We investigated the establishment of Lepidium subulatum, a gypsophyte, in a nondisturbed semiarid gypsum-soil landscape in central Spain, both from spatial and temporal perspectives. Over 1400 seedlings were tagged, and their growth and survival were monitored for a 2-yr period. Several biotic and abiotic variables were measured to determine the factors controlling the emergence and early survival. These variables included the cover of annual plants, bryophytes, lichens, litter, gypsum crystals, bare fraction and cover of each perennial plant, and several soil properties (gravel, fine gravel, and fine-earth fraction, conductivity, pH, gypsum content, organic matter and penetrometer soil resistance). Our results support the linkage of gypsophily with some physical properties of the surface crust. Seedlings tended to establish on the gypsum surface crust, and their survival was size dependent, probably as a consequence of the necessity of rooting below the surface crust before summer drought arrives. However, once seedlings emerged, a higher survival rate occurred on the alluvial soils of the piedmont-slope boundary where soil crusts are absent or thinner. We conclude that Lepidium subulatum may be considered a refuge model endemic with a distribution range that occupies a reduced fraction of a wider habitat from which it is probably excluded by competition.

Acidification of Solid and Solution Phases at Greater Depths (> 150 cm) at Solling Spruce Site

The acidification of the soil and percolation water at soildepths from 150 to 500 cm was studied at the Solling spruce sitefrom 1991 to 1996. NH4Cl exchangeable cations of the fineearth and bedrock fractions were obtained from different depthsand the soil solution composition was monitored at 150, 200,300, 400 and 500 cm depths using seven suction lysimeters at each depth.In the seepage water collected from 150 and 200 cm depth, pHvalues decreased in the period 1991 to 1996, but no significantchanges were observed in solutions collected below 200 cm depth.Element budgets of Al and Mb (Na, K, Mg, Ca) cationsindicated that buffering by exchange of Al with Mb cationsoccurred mainly in surface 200 cm soil depth. High variabilities in concentrations of SO4 (at 150 cm) andMa (Al, Mn, H, Fe) cations (at 300 and 500 cm) wereobserved. High variabilities in Ma cations could beassigned to one of the lysimeters at each depththat extracted low pH solutions. The amount of exchangeablecations in the fine earth and the bedrock fractions indicatedthat the acidification front (exchangeable Mb cations < 80equivalent percent) had occurred to soil depth of more than 360cm, but the extent of acidification that might have occurred inthe preindustrial period is not known. In both fine earth andbedrock fractions, depthwise changes of exchangeable Ma andMb cations were quite similar, suggesting that rockfractions have contributed to proton buffering not only bysilicate weathering but also by cation exchange.

Quantification of weathering processes in an acid brown soil developed from tuff (Beaujolais, France): Part II. Soil formation

Mineralogy and chemical properties of the fine earth and particle size fractions were examined with total chemical analysis, selective chemical analyses and X-ray diffraction. Clay minerals were investigated using microprobe and transmission electron microscopy. The chemical changes during soil formation were calculated from results of the chemical weathering mass balance. The study soil is of the brown acid type, unsaturated and poor in short-range ordered products. All soil fractions sized between 0 and 1 cm originate from transformation of the weathered rind developed around tuff stones, where chemical weathering is intense. The same weathering reactions which were initiated in the early stages of tuff weathered rind were continued in the soil with strong dissolution of plagioclases and transformation of biotite. Two chemical weathering reactions led to the formation of clay minerals in the soil: the precipitation of kaolinite into biotite pseudomorphs and into the small white mica and the transformation of the biotite (BI) into hydroxy-interlayered vermiculite (HIV) with intermediary stages shown in HIV-BI interstratified minerals, which were defined (95–75% of biotite layers). Pure vermiculite or V-BI interstratified minerals were hydoxy-interlayered, even in the weathered rind of the tuff. The chemical and mineralogical mass balance between the weathered rind and the soil shows a heavy dissolution of andesine (90%) and to a lesser extent of albite (55%) and of apatite (60%), a precipitation of kaolinite and a transformation of biotite into HIV. The plagioclase dissolution in weathered tuff was almost complete, while there were only traces remaining in silt. The biotite has almost disappeared in the fine earth fractions due to dissolution and transformation into HIV.

Water‐retention capacity in fine earth and gravel fractions of semiarid Mediterranean Montane soils

Water retention capacity was studied in fine earth and gravel from loamy‐textured soils with medium‐low carbon content in a semiarid Mediterranean montane location. Sierra Gador, southeastern Spain. In fine earth, typical water retention curves were established at six soil water potentials (‐10, ‐33, ‐100, ‐500, ‐1000, and ‐1500 kPa), and the water retention was compared against different physical, chemical, and miner‐alogical properties. Percent total sand and organic carbon content were the variables that gave the best fit in the pedotransfer functions for the calculation of water retention at ‐33 and ‐1500 kPa. Results for water retention in gravel at ‐33 and ‐1500 kPa show that gravel can make a significant contribution to the available water in the soil. Bulk density of gravel was the property most closely related to water content at both soil water potentials, and was the variable that gave the best fit in the pedotransfer functions. Other properties that were useful with this function were citrate‐ditionite extractable Fe content, quartz, feldspathic, and phillosilicates content. In semiarid environments, the greatest differences in water retention are found between soils derived from different parent materials, regardless of their taxonomic relation.

Hydric properties of some Spanish soils in relation to their rock fragment content: implications for runoff and vegetation

Physical and hydric characteristics of the upper three horizons (average depth of sampling: 0–0.25; 0.25–0.60 and 0.60–1.20 m) of 92 soil profiles of Spain, grouped according to the geological nature of the rock fragments on the soil surface, or in the soil profile, were studied. Mathematical relations were developed to separate the contributions of the fine earth fraction and of the fraction above 2 mm. Indexes were obtained that relate gravitational water and available water in the fine earth fraction with the values from total soil. A multiple comparison statistical study was performed for the mean values of: (1) Rock fragment content; (2) Organic matter content; (3) Silt plus clay content; (4) Gravimetric water content at different suction values. The linear correlations of the gravitational and available water indexes, with the rock fragment content by volume as independent variable were studied. They showed positive or negative effects of the increase of rock fragment content on both indexes depending on their petrographical composition. Finally, conclusions related tothe development of vegetation and to the production of runoff have been drawn. When rock fragment content increases the results show positive effects for the development of vegetation and for the production of saturation overland flow.

Soils on igneous and metavolcanic rocks in the Sonoran Desert of Baja California, Mexico

Soils were examined on the widespread volcanic, plutonic and metavolcanic rocks within the Sonoran Desert of Baja California. In order to focus on in situ weathering and pedogenesis, most of the soils studied were on stable, nearly level summits. The combination of summit landscape positions and the aridic moisture regime tended to yield shallow soils, yet these soils display features of strong morphologic development, including eluvial horizons, subsoil clay increases, strong blocky and prismatic structure, reddish hues, and illuviation and stress argillans. Soils derived from volcanic materials are Paleargids with clayey natric horizons, saline subsoils, and petrocalcic horizons. Soils on granodiorite and metavolcanic rocks are loamy Haplargids that are neither saline nor sodic and are entirely noncalcareous. The granodiorite-derived soils had pH values as low as 4.0, apparently the result of metal sulfide weathering in the hydrothermally altered, ore-bearing rock. Torripsamments have formed in the reworked mantle of grus on an extensive tonalite pediment. Despite the variety of parent materials, smectite and kaolin are ubiquitous in the clay fraction of the soils. The smectites are dioctahedral and are neoformed and/or transformed from biotite or chlorite, depending on the parent material. The kaolin is l largely the result of feldspar weathering. A Paleargid on rhyolite contained abundant palygorskite in the clay and silt fractions, particularly in association with the petrocalcic horizon. In all of the soils, oxalate-extractable Si plus Al was <1% of the fine earth fraction. Most of the soils contained 2–3% dithionite-extractable Fe, but Fe d values were as high as 11% in the soil on metavolcanic rock. Goethite and hematite are the dominant Fe oxides, judging from low Fe o/Fe d ratios and 1OYR-2.5YR soil hues. Only the soils on basalt and rhyolite were calcareous, but the amount of CaCO 3 in the soils was unrelated to the Ca content of the rock, since these two rocks contained the most and the least amounts of Ca, respectively, of the five rock types represented in the study. Apparently, CaC0 3 accumulation in the soils is more dependent on dust contributions, possibly from nearby calcareous plays and fluvial sediments, than on in situ mineral weathering.

Physical and Chemical Properties of Potential Topsoil Substitutes in Kentucky Oil Shale Mining Reclamation

AbstractBecause the soils that frequently overlie eastern U.S. oil shale outcrops and near‐surface deposits are relatively shallow, acidic, and infertile, use of topsoil substitutes and supplemental materials are anticipated to achieve satisfactory reclamation during surface mining. This study was conducted to determine the effects of weathering on selected overburden strata (the Borden and Bedford Shales) in terms of particle‐size distribution, moisture retention character, reactivity, and macronutrient availability. Shale samples were subjected to 40 freeze/thaw cycles in the laboratory to simulate field conditions. Laboratory analyses of “weathered” shales indicate these materials could be used as effective topsoil substitutes in mine reclamation. Shale weathering produced a material in the fine earth fraction that approached residual soils in ability to retain moisture and have low lime requirements. Suggested P amendment of weathered overburden was 75 to 150 kg P ha−1. Availability of K in weathered overburden exceeded levels in native soils and because these values were generally very high, K amendment of overburden materials would not be needed. To confirm these findings in terms of vegetative cover and growth response, the establishment of field test plots is necessary.

Comparison of Morphological, Physical, and Chemical Properties of a Minesoil and a Natural Soil of Southeast Kansas

Morphological, physical and chemical properties of minesoil were determined and compared to natural soil in southeast Kansas. The morphological and physical properties of the minesoil were less favorable for plant growth than those of the natural soil and probably would be major limiting factors in the establishment and growth of plants on minesoil. The minesoil lacked well-developed and contrasting horizons and contained shale fragments ranging in amounts from less than 5 to 25 percent. The structure of the minesoil was mostly clods, varying in shape and size, with many open voids in the subsoil. The average coarse-fragment (> 2 mm) content of the minesoil was 15 percent compared to less than 2 percent for the natural soil. The minesoil contained more material in the sand-size ranges of the fine-earth (<2 mm) fraction. Averaged over depth, the amount of silt-size material in the minesoil was less than that of the natural soil, and the amount of claysize material was nearly equal. The surface 12 inches of the minesoil contained from 35.3 to 61.8 percent less plant-available water than the natural soil. The major differences between the chemical properties of the minesoil and the natural soil were essentially in their distributions with depth. In the natural soil elemental concentrations increased with depth, and in the minesoil they were more uniformly distributed. Averaged over depth the chemical properties of the two soils were quite similar indicating that from a chemical perspective the minesoil was adequate and maybe more favorable for plant growth than the natural soil. The slight differences that existed were attributed to different fertilizer management histories and weathering of primary minerals in freshly exposed shale fragments in the minesoil. Surface coal mining disturbs large areas of land and alters the natural soil in a mined area. Soil is a natural resource and over the long term its value This content downloaded from 157.55.39.118 on Mon, 06 Mar 2017 18:36:51 UTC All use subject to http://about.jstor.org/terms VOLUME 91, NUMBERS 3-4 109 may be greater than that of coal. Natural processes of soil formation are slow and can take decades to form new soil. To hasten soil formation processes and to achieve a soil productivity level equal to or greater than the premined condition, man implements land reclamation procedures and constructs a new soil. The characteristics of this new soil or minesoil depend on the kinds and sequences of reclamation procedures employed. Few data exist on properties of Kansas minesoils (Brady and Livingston, 1979). Comparisons of properties of minesoils and natural soils to assess the effects of mining and reclamation procedures on the properties of minesoil are limited. This study was initiated to provide some basic data on soil properties of minesoil on surface-mined land in southeast Kansas. The specific objectives were to determine the morphological, physical, and chemical properties of minesoils and compare these to the same properties of the predominant natural soil in the area to assess the potential of the minesoil for sustaining plants.

Determining the Saturated Hydraulic Conductivity of a Soil Containing Rock Fragments

AbstractMany rangeland soils contain various amounts of rock fragments (&gt;2 mm and &lt;75 mm), which influence soil hydraulic and water storage properties. Most published data on these properties are only for the fine earth fraction (&lt;2 mm). Determining properties for soils containing rock fragments requires either in situ measurements or procedures that adjust fine earth fabric properties for the coarse fraction content. The hydraulic conductivity is a major determinant of the infiltration and water movement properties of soils. Additionally, the saturated conductivity is used as a scaling parameter in modeling partially saturated flow in porous media. In this Note, literature is reviewed on calculating the saturated hydraulic conductivity for soils containing rock fragments. The two most widely used methodologies are based on knowing either the volume fraction of the rock fragments or the void ratio of the field soil and the fine earth fabric. Both of these soil properties require somewhat laborious laboratory procedures. We show that a calculation of the saturated conductivity of the bulk soil can be accomplished by using only the rock fragment fraction on a weight basis. For many soils the rock fragment fraction on a weight basis is routinely determined and published. For example, the Soil Conservation Service pedon data files list the rock fraction on a weight basis. We test our calculation of the saturated hydraulic conductivity with published data on the saturated conductivity of a stony soil. We show that our simple formulation using the rock fraction on a weight basis duplicates the observed data. Furthermore, it is as accurate as the more complicated procedure requiring void ratio information.

Movement of aluminium as an inorganic complex in some podzolised soils, New Zealand

Chemical and mineralogical data are presented for three Spodosols (podzols) and a related Inceptisol (yellow-brown loam). Allophane with an Al/Si atomic ratio close to two is identified in the B horizons of all four soils, and minor amounts of imogolite are present in association with allophane in all but one soil where small-particle gibbsite occurs. Parent materials for these soils are essentially non-vitric. Allophane (Al/Si = 2) has been estimated quantitatively in all soils using oxalate-extractable Si (Si 0) and is selected clay fractions using both Si 0 and infrared spectroscopy. Maximum concentrations of allophane (Al/Si = 2) range from 5% to 18% of fine earth (< 2 mm) fractions and all occur in B horizons. Fe 0 values are low relative to Al 0 values except for the upper horizons of the Inceptisol. Al 0 values peak in B horizons and the ratio pyrophosphate-extractable Al to Al 0 decreases from about 1 in A and upper B horizons to 0.1–0.4 in lower B horizons. An interpretation of the data is consistent with recent proposals that the movement of Al in podzolisation is due primarily to the formation of inorganic complexes with Si. Chemical criteria for spodic horizons should be consistent with the total illuviation of Al and Fe (and perhaps Si), rather than just the organic-bound fraction of Al and Fe in these horizons as indicated by amounts in extractants such as pyrophosphate.

Application of Autocorrelation Analysis to Transect Data from a Drainage Basin in Eastern Ohio

Soil morphological, physical, and chemical properties from a transect across a drainage basin in eastern Ohio were evaluated by autocorrelation analysis to test the performance and value of this statistical technique. Autocorrelation analysis may be used to estimate the average magnitude of intervals of mutual dependence of observations within a continuous series of observations. Intervals of mutual dependence were determined from observations made every 20 m along a transect for solum thickness, fine-earth fraction of the A, B, and C horizons, and for soil pH, percent base saturation, and exchangeable cations from the deepest horizon. Using statistical criteria to estimate the magnitude of the intervals, the range was from 20 m for solum thickness and exchangeable K to 60 m for pH and exchangeable Mg. A difference in the event of mutual dependence among various properties, among similar properties in different horizons, and among similar properties within the same horizon was noted. Although interpretation of the results of autocorrelation analysis in pedological studies needs further development, the technique emphasizes the continuous, orderly nature of soils and the fact that spatially related observations may be mutually dependent.

Some New Zealand and New Caledonian Plant Accumulators of Nickel

Although plant indicators or accumulators of copper are well represented in the literature (Duvigneaud 1958; Duvigneaud & Denaeyer de Smet 1963; Cole, Provan & Tooms 1968; Howard-Williams 1970), the list of nickel indicators or accumulators is considerably smaller. The term 'accumulator' is here defined as a plant whose mean content of a particular element (expressed on an ash-weight basis) is greater than the content of the same element in the fine earth fraction of the substrate. Table 1 lists all the known nickel

The Morphology and Genesis of Some Alpine Soils in British Columbia, Canada: II. Physical, Chemical, and Mineralogical Determinations and Genesis

AbstractThe results of selected physical, chemical, and mineralogical analyses, carried out on five soils occurring in three alpine regions in British Columbia, Canada, are presented and discussed. An evaluation of the genesis of these soils is made in relation to the analytical results and to the literature.The soils have developed on relatively young post‐Pleistocene parent materials and are gravelly and have loamy sand to silt loam textures, in the fine earth fractions, the slight accumulations of silt and clay at the surface, are due primarily to more intense physical weathering and partly to surface additions of eolian material. Volcanic ash was found in the surface horizons at three of the sites.Physical weathering is significant in these soils and chemical weathering is taking place as evidenced by the presence of spodic horizons, abundant amorphous iron and aluminum in all horizons, and the content of secondary minerals.Several properties of these soils were correlated with total carbon contents and hence organic matter contents. Volcanic ash was believed to have had an influence, to a minor degree, on the soil properties where it occurred.With sufficient leaching, soils with spodic characteristics develop. Under a coniferous or ericaceous vegetative cover Spodosols occur; however, under a cover of grasses, sedges, and forbs the spodic characteristics may be masked by organic matter accumulations in the surface mineral horizons.