Responses of co-occurring populations of Dendrobaena octaedra (Lumbricidae) and Cognettia sphagnetorum (Enchytraeidae) to soil pH, moisture and resource addition

Dendrobaena octaedra (Lumbricidae) and Cognettia sphagnetorum (Enchytraeidae) are the two most dominating soil invertebrates in terms of biomass in boreal coniferous forest soils. A microcosm experiment was set up in order to study the influence of pH, moisture and resource addition on D. octaedra and C. sphagnetorum when both species are simultaneously present. Two kinds of coniferous forest humus were used as substrate, pine stand humus (pH 4.2), and spruce stand humus (pH 4.6); in the third treatment the pine stand humus was adjusted with slaked lime (CaOH₂) to the same initial pH as the spruce stand humus. Each substrate was adjusted to water contents of 25%, 42.5% and 60% of WHC (referred to as ‘dry’, ‘moist’ and ‘wet’). In the second part of the experiment, spruce needle litter and birch leaf litter were separately added into the pine stand humus (‘moist’, unlimed) and compared with a control without litter. The microcosms were plastic jars with 75 g (d.m.) of humus, into which 4 specimens of D. octaedra and 70 specimens of C. sphagnetorum were added. D. octaedra showed the highest biomass and C. sphagnetorum the lowest biomass in the spruce stand humus with higher pH. Moisture did not affect earthworms, while C. sphagnetorum thrived best at the highest moisture. Addition of both kinds of litter increased the numbers and biomass of D. octaedra, while on C. sphagnetorum resource addition had little effect. The results help to explain the abundance of these two species in coniferous forests differing in soil acidity, moisture and fertility.     

Natural and Anthropogenic Changes in the Soils and Environment of the Moskva River Floodplain in the Holocene: Pedogenic,Palynological, and Anthracological Evidences

Several series of well-developed paleosols of different ages have been examined on the Moskva River floodplain. In the beginning of the Holocene, forest-steppe biomes were widespread in this area, and dark-humus (Black) soils with stable humate humus and without features of textural differentiation predominated on the floodplain. The presence of meadow-steppe vegetation communities during this period is confirmed by the results of palynological and anthracological analyses. The lower paleosol in section RANIS 2 is represented by the deep humus horizon with ¹⁴C dates from 5500 to 8400 BP and the carbonate-accumulative horizon; it also contains large and deep tunnels of burrowing animals typical of chernozems. Wood charcoal is absent, and pollen of Artemisia and Chenopodium species predominates. Paleosols of the second half of the Holocene are represented by gray-humus and soddy-podzolic soils (Luvisols). In these soils and in the alluvial sediments, beginning from the Subboreal period, pollen of trees predominates; there are abundant charcoal of spruce and burnt spruce needles. In that time, forest-steppe and broadleaved forest biomes on the floodplain were replaced by southern taiga biomes. The second half of the Holocene is also specified by the human impacts on the local landscapes. Palynological and anthracological data attest to the large-scale burning of forests for pastures in the Bronze Age and, later, for cropland. The paleosol of the Iron Age is enriched in humus. It contains tunnels of burrowing animals related to the stage of anthropogenic meadows. It also contains pyrogenic calcite. The recent centuries have been characterized by extremely high floods triggered by the human activity; they have been accompanied by the fast accumulation of coarse-textured alluvial sediments and the formation of weakly developed alluvial soils.     

Morphological characterisation of humus forms in recent coastal dune ecosystems in Belgium and northern France

The morphology of humus profiles, developed on recent sandy coastal dune ecosystems, is studied on macro- and microscale. Humus and soil profiles were described, sampled and analysed. Undisturbed, oriented samples were taken from the surface horizons for micromorphological study. The soils are situated in the National Biological Reserve of the Opal Coast, Merlimont, France and near De Haan, Belgium. On both sites, the parent material consists of aeolian calcareous sand. Surface horizons, however, are decarbonated due to leaching processes.In Merlimont, the sequence consists of two profiles, one under Pinus nigra ssp. laricio and one under Populus nigra ssp. nigra, characterised by a Resimor¹/Dysmoder^{, 2} and Rhizomull^{, 1}/Mesomull ^{, 2} humus type, respectively. At the De Haan site, three profiles under Quercus robur, Populus ssp. and P. nigra var. austriaca are investigated. The humus types are respectively Mullmoder^{, 1} to Mull/Dysmull ^{, 2}, Mull ^{, 1}/ Oligomull ^{, 2}, Mormoder ^{, 1}/Dysmoder ^{, 2}.Differences among the humus profiles are related to presence/absence among the L-, F-, H- and A-horizons, structure, rooting, presence of hyphae, sclerotia and excrements.Macromorphologically, the difference between humus profiles under coniferous and deciduous forest/grassland is evident by thicker L-, F and/or H-horizons under coniferous trees. The microstructure of the L- and F-horizons shows a loose packing of subhorizontally oriented needles. The microstructure of the H-horizons varies from intergrain microaggregate to locally weak crumb. The microstructure of the surface mineral horizon of all profiles is mainly intergrain microaggregate, sometimes single grain and exceptionally bridged grain. Intimate mixing and complexation of organic matter to the mineral fraction into aggregates is very limited in the A-horizons. All A-horizons, irrespective of the humus type, are to some degree characterised by a “pepper and salt” appearance. The horizon symbol “H+E” is introduced to label this morphology.The Mull humus forms under deciduous trees are indicative of rather intense mesofauna activities. The absence of a crumb structure in the A-horizon of these soils could be due to the fast disintegration of earthworm casts in these sandy soils with no clay or silt fraction.     

Spatial and temporal variation in podzol organic matter studied by pyrolysis-gas chromatography/mass spectrometry and micromorphology

A well‐developed podzol hydrosequence that has been partially covered with drift sand, and partially subjected to improved drainage, provides new insights into the causes of variation in soil organic matter chemistry in such soils. While E horizons invariably move towards a dominance of aliphatic components reflecting residual accumulation, the chemistry of organic matter in well‐drained B horizons is determined mainly by decaying roots, which are transformed by microorganisms to humus aggregates. In poorly drained, stratified B horizons, humus coatings dominate and the chemistry is very close to that of dissolved organic carbon. When a sand cover inhibits the supply of fresh litter, microbial decomposition in the A horizon causes a shift in chemistry towards that of the E horizon. Similarly, upon improved drainage and removal of complexed metals from the top of the B horizon, microbial decomposition of all palatable organic matter in the top of the B horizon causes a shift towards E‐horizon chemistry. This is probably the mechanism by which most E horizons in podzols are formed, and not by re‐solution. Marked chemical changes upon improved drainage may take only decades. During microbial decay, small polysaccharide‐derived pyrolysis products (mainly furans, furaldehydes and acetic acid) remain abundant due to the contribution of microbial sugars. Both micromorphology and factor analysis on quantified results of pyrolysis‐gas chromatography/mass spectrometry contribute significantly to the interpretation of the humus chemistry of these profiles and thus to our understanding of soil genesis. Organic chemistry of the investigated podzols can be understood only in the context of their genesis.     

Soil formation in Greyzems in Moscow district: micromorphology, chemistry, clay mineralogy and particle size distribution

Greyzems (Grey Forest Soils) are zonal soils of the forest–steppe, in Russia geographically situated between the (Podzo) Luvisols of the southern taiga forest and the (Luvic) Chernozems of the steppe. Greyzems are characterized by a dark mollic horizon, with uncoated (bleached) silt and sand grains on pedfaces, and an argic horizon as diagnostic horizons. The FAO–Unesco soil map of the world shows Greyzems and Luvisols in Russia at this transition (the Russian soil map shows only Greyzems), while in similar geographic position in the USA and Canada the proportion of Greyzems is very small and Luvic Phaeozems/Chernozems and Albic Luvisols occupy those transitional zones of the grassland–forest interface. Three Greyzem profiles, presently under forest, and developed on loess-like mantle loams of Late Weichselian (Valday) age in the northern forest–steppe zone of the East European plain (Middle Russian Upland) were described and sampled near Pushchino, some 100 km south of Moscow. Micromorphology, particle size data, chemical data and clay mineralogy were studied. Based on the particle size distribution and the occurrence of fragments of a second humus horizon (SHH) the presence of two, rather similar, deposits in the solum is advocated. The following processes have been deduced from the study: (i) decalcification and secondary accumulation of carbonates; (ii) humus accumulation, including the significance of the SHH; (iii) clay illuviation, presumably two main phases; (iv) biological activity; (v) degradation of the mollic A: occurrence of bleached grains; (vi) downward migration of textural components and organic matter, in the Bt horizon along major pedfaces: occurrence of black organo-clay coatings and uncoated silt/sand grains; (vii) gleying. The tentative sequence of these processes during Late Weichselian and Holocene times leads us to conclude that Greyzems are polygenetic. They formed as Podzo(Luvisols) under forest, with fine clay coatings in the fine pores inside the blocky and prismatic peds, in the Late Glacial and Early Holocene. The change to tall grass steppe in the Atlanticum created a mollic horizon, that degrades when forest re-invades during the Subatlanticum. Fine clay, combined with organic matter forms black coatings on the major pedfaces. Uncoated silt and sand particles also migrate downward along those major pedfaces. Biological activity is involved in the very complex pattern of the transitional AhE and EBt horizons. Active gleying only occurs in the profile on the lowest topographic position. These latter processes are still active today. Similar soils do occur in the grassland–forest interface in North America, except where the younger age of the landscape and high CaCO3 content at shallow depth prevented their full development.     

免耕和秸秆还田对东北黑土区土壤团聚体组成及有机碳含量的影响

为解决东北黑土区因不合理耕作导致的土壤结构性状变差及有机碳含量下降的问题，该研究于2015年开始，在黑龙江省哈尔滨市东北农业大学向阳试验基地开展。设置免耕+秸秆还田（NTS）、免耕（NT）、翻耕+秸秆还田（CTS）、翻耕（CT）4种处理，于2018、2019年采集土样，研究免耕措施及秸秆还田对东北薄层黑土区0～10、>10～20 cm土壤团聚体稳定性、土壤有机碳含量、各粒径团聚体内有机碳含量影响。结果表明：2018和2019年0～10、>10～20 cm土层NTS处理>5 mm水稳性团聚体百分比含量及平均重量直径（MWD）显著高于其他3种处理，NTS及NT处理土壤有机碳含量显著高于CTS及CT处理（P?<0.05），4种处理各粒径水稳性团聚体有机碳含量峰值总体出现在1～2 mm处，NTS及NT处理>5、2～5、1～2 mm有机碳贡献率整体高于CTS及CT处理。研究表明，免耕与秸秆还田有利于薄层黑土坡耕地耕层土壤团聚体稳定性的提高和各粒级下团聚体有机碳的积累，与其他3种处理相比，免耕+秸秆还田效果更佳。     

Changes in humus properties and collembolan communities following the replanting of beech forests with spruce

Differences of collembolan communities within the organo-mineral A layer were studied in relation to physico-chemical changes in humus at nine sites of beech forests (Fagus sylvatica L.) and first generation spruce stands (Picea abies (L.) Karst.), planted on former beech forest 30 years ago (Central Pyrenees, France). Changes in humus form were caused by the spruce plantation and occurred mainly within the fermentation horizon where acidifying litter accumulation increased the horizon depth. The recent replacement of beech by spruce induced a shift from mull towards moder humus forms, which is explained by the decreasing organic matter turnover rate. A significant decrease in the three exchangeable cations and pH under spruce was also observed. Collembolan species diversity within the A horizon was significantly lower under spruce at this early stage of the silvogenetic cycle. Differences between species composition of Collembola between the two forest stands is related to changes in environmental conditions (e.g. nutrient availability, soil porosity, soil moisture). This study shows how forest management practices are susceptible to modify biological activity within the A horizon under exotic conifer plantations.     

The impact of earthworms on the abundance of Collembola: improvement of food resources or of habitat?

I assessed the direct influence of earthworm excretions, and the impact of earthworms through their action on the soil structure (increased macroporosity), on the population dynamics of the collembolan species Heteromurus nitidus. The intestinal content of Collembola arising from cultures on different soil types was observed, and two experimental cultures of H. nitidus were run: (1) a culture performed on an inert substrate supplied either with earthworm casts or with soil as food resource, (2) an experiment using microcosms with cores of two humus forms (moder and calcic mull), in the presence or absence of earthworms. The observation of gut contents revealed that H. nitidus feeds on excrements, the composition of which (ratio organic matter/mineral matter) varies according to the humus form where it lived. Slightly aged (10–15 days) organo-mineral casts of earthworms appeared to be a better food than calcic mull aggregates or organic material from moder. Densities of H. nitidus cultured in cores of calcic mull were higher than in moder, except when cores of moder were inhabited by an anecic earthworm for 2 months. The humus form strongly influenced populations of H. nitidus, firstly because densities of predators were higher in moder than in calcic mull, and probably also because of soil macroporosity. It was concluded that earthworms would affect predation on H. nitidus by creating a network of interconnected macropores in which Collembola can move and find shelter.     

Distribution of transformed organic matter in structural units of loamy sandy soddy-podzolic soil

The effect of land use types and fertilizing systems on the structural and aggregate composition of loamy sandy soddy-podzolic soil and the quantitative parameters of soil organic matter has been studied. The contribution of soil aggregates 2–1 mm in size to the total C_org reserve in the humus horizon is higher than the contributions of other aggregates by 1.3–4.2 times. Reliable correlations have been revealed between the contents of total (C_org), labile (C_lab), and active (C₀) organic matter in the soil. The proportion of C₀ is 44–70% of C_lab extractable by neutral sodium pyrophosphate solution. The contributions of each of the 2–1, 0.5–0.25, and <0.25 mm fractions to the total C₀ reserve are 14–21%; the contributions of each of the other fractions are 4–12%. The chemically labile and biologically active components of humic substances reflect the quality changes of soil organic matter under agrogenic impacts. A conceptual scheme has been proposed for the subdivision of soil organic matter into the active, slow (intermediate), and passive pools. In the humus horizon of loamy sandy soddy-podzolic soil, the active, slow, and passive pools contain 6–11, 34–65, and 26–94% of the total C_org, respectively.     

Acidity of podzolic soils subjected to sulphur pollution near a Cu-Ni smelter at the Kola Peninsula

The acidity of the podzolic soils in coniferous forests on the northern tree line (Kola Peninsula) subjected to severe sulphur pollution is considered. The pH values of precipitation were positively correlated with the distance from the pollution point source. There was also a correlation between base saturation of the organic horizon and distance. The long-term SO₂-emissions have resulted in the higher leachability of base cations and dissolution of fulvic acids in the humus horizon. In polluted areas the flux of H⁺ from the organic layer could be stronger owing to higher proportion of hydrolysable humus compounds. Inputs of H⁺ from the atmosphere and humus horizon have resulted in the higher concentrations of the exchangeable aluminium in the illuvial horizon.     

Chronology of plaggic deposits; palynology,radiocarbon and optically stimulated luminescence dating of the Posteles (NE-Netherlands)

Plaggic agriculture was the dominant land use system on Pleistocene sandy soils in Northwest Europe before the introduction of chemical fertilizers. In the today's landscape plaggic deposits are still recognizable as characteristic soils and landforms, related to this historical land use system. They are also important constituents of the soil archives in Northwest Europe. In preliminary studies of plaggic anthrosols, the reconstruction of the development of the plaggic deposits was based on palynological and historical data and radiocarbon dates. Disagreement appeared between palaeopedological and historical explanation of the evolution of plaggic anthrosols. Application of OSL dating improves the knowledge of chronology of plaggic deposits. The soil organic matrix, including pollen grains, consists of a complex mix of compounds of different ages and sources. Pollen diagrams of plaggic anthrosols show a palynological registration of the Late Holocene landscape evolution, but the palynological signal is not consequently correlated with the age of the plaggic sediments. An older soil organic matrix is suspended in the voids of a younger mineral soil skeleton.     

Variation in soil macro-fauna diversity in seven humus orders of a Parrotio-Carpinetum forest association on Chromic Cambisols of Shast-klateh area in Iran

Soil biodiversity includes organisms which spend a part or all of their life cycle on or in the soil. Among soil-dwelling animals, macro-fauna as an important group of animals have important effects on the dynamics of soil organic matter and litter decomposition process. The humus forms interact with the climatic conditions, flora, as well as soil fauna, and microbial activity. In new humus form classifications, soil organisms play an important role in separation of humus horizons from one another. The subject of this study was to determine the diversity of macro fauna for different humus forms. We determined humus forms using morphological classification, and then 69 random samples were taken from plots of 100 cm² in area, and soil macro-fauna species were collected by hand sorting method. Two classes of humus forms, including Mull (with three humus orders, namely Dysmull, Oligomull, and Mesomull,) and Amphi (with four humus orders, namely Leptoamphi, Eumacroamphi, Eumesoamphi, and Pachyamphi) were identified. A number of 13 macro-fauna orders were identified using identification key. Among the humus orders, Shannon diversity, Simpson evenness and Margalef richness indices were the highest in Pachyamphi order. Arthropod diversity in Pachyamphi humus order was higher than those of Mull. These results showed that diversity of soil macrofauna increase by increasing the thickness of the organic horizons (OL, OF, OH), especially OH horizon.     

Soil formation in the technogenic forest-steppe landscapes of the Nazarovskaya Depression in western Siberia

The soil formation was studied in the 21- to 35-year-old pine plantations created on the overburden dumps of the Nazarovskaya Depression without applying the material of the humus horizon. The surface technogenic formations under the pine plantations belong to the group of naturfabricats (surface formations devoid of the humus horizon and composed of natural substrate). The morphological characteristics, bulk chemical and particle-size compositions, and labile properties of the soils indicate that the accumulation and transformation of organic matter are dominant processes in the artificially planted forests. The accumulation of organic residues and destruction and humification are tightly related to the environmental conditions transformed by the technogenesis and conceal other processes forming the soil profiles. Quasizems created for agricultural production purposes were the objects of the study. They were formed by covering the technically planned overburden rocks with the material of humus layers. The thickness of the humus horizons of the quasizems varies greatly (25–64%); the variation of the humus reserves in them is 34–122%. Middle-profile horizons have not been formed by the present time.     

Forest humus forms as potential indicators of soil carbon storage in Mediterranean environments

The aim of this work was to investigate the potential of forest humus forms as indicators of soil C storage. To this purpose, Mediterranean forest soils in Southern and Central Italy were examined. Sites differed for elevation, climate, parent material and vegetation conditions, while summer drought was the common ecological factor. A morpho-functional criterion, based on holorganic layers thickness and A horizon properties, was used to classify humus forms, which ranged from Dysmoder to Eumull. Such variability allowed understanding of factors influencing organic matter storage. The relations between carbon stock and humus form were investigated for the topsoil layer (0–20 cm), which was supposed to contain the soil C pools most sensitive to climate change. We found that humus forms can be grouped in statistically different populations, with respect to topsoil C stocks. The use of A horizon structure was the main diagnostic criterion and represented the most effective approach to humus classification in Mediterranean conditions. It appears that humus forms have a clear potential as indicators of organic carbon status in Mediterranean forest soils.     

The use of micromorphology in soil pollen analysis: The interpretation of the pollen content of slope deposits in Galicia, Spain

Humic horizons of soil profiles often contain pollen and spores. Comparison of the sequence of pollen associations of soil profiles with pollen zones of reference diagrams offers palyno-ecological information, relevant for reconstruction of landscape ecological development. In palynological studies of semiterrestrial and aquatic deposits, pollen is considered to be part of the sediment and anaerobic conditions in water-saturated deposits promote its conservation. This is not true for pollen in soils. Aerobic conditions in drained soils result in bio-oxidation of unprotected pollen grains. Interpretation of soil pollen associations requires knowledge of the processes of infiltration and conservation of pollen grains in the soil material. Micromorphology is an important technique to investigate these processes. This is demonstrated in a case study of polycyclic slope deposits in Galicia (Spain). The buried cambisols, in pleistocene solifluction deposits, contain post-sedimentary infiltrated pollen. The pollen associations reflect successive phases in soil ecological development. The holocene colluvial deposits contain syn-sedimentary incorporated pollen. The pollen associations reflect environmental conditions during the deposition of colluvial layers.     

Characterization of the soil organic matter and plant tissues in an initial stage of the plant succession and soil development by means of curie-point pyrolysis coupled with GC-MS

The composition of the soil organic matter in soil developing under the influence of vegetation during the primary succession in the poor sandy area was investigated. The Curie-point pyrolysis method coupled with gas chromatographic separation and mass spectrometric identification of pyrolysates was applied during the investigation. A comparison of occurrence and diversity in composition of organic compounds in plant tissues and humus horizon of soils under the communities of coniferous forest series in the initial stages and phases was carried out. A large diversity of organic compounds under Algae-Cyanophyta communities, biological soil crusts and Polytrichum piliferum was noticed. A clear differentiation in the composition of the soil organic matter at different phases of succession under predominating communities with cryptogamous and vascular plants was observed. The analysis of organic compounds in plant tissues was found to facilitate the determination of origin of various groups of organic compounds in the soil. The results obtained from the Curie point pyrograms in the humus horizon (A) under grasses (Corynephorus canescens, Koeleria glauca) differed from the pyrolysates obtained under Algae-Cyanophyta communities. The polysaccharide derivates are more frequent in the pyrolysis products under algae, grasses (Corynephorus canescens, Koeleria glauca) and mosses than under Pinus sylvestris. In the beginning of the terminal stage of succession, lignin, phenols and aliphatic substances, prevailed over the polysaccharide derivates in the humus horizon.     

Does moder development along a pure beech (Fagus sylvatica L.) chronosequence result from changes in litter production or in decomposition rates?

The development of temperate deciduous and conifers forests stands usually results in accumulation of forest floor organic matter and a shift from mull to moder humus forms. It has been suggested that an increase in nutrient uptake by trees during their rapid growth phase leads to topsoil acidification, decrease in earthworm density and thereby a decrease in litter turnover. The focus of this paper was to examine if the mull-moder shift with forest ageing results from higher leaf litter production and/or lower litter decay rates. The objectives of this research were to determine (1) changes in macro-morphological properties of humus forms, leaf litter production, litter decay rates, soil nutrients content and pH along a 130-year pure beech (Fagus sylvatica L.) chronosequence in Normandy (Northwest France), (2) if humus form varied from mull to moder with increasing stand age, and (3) if a shift from mull to moder resulted from increased litter production, decreased litter decay rates, or both. Annual litter production did not change significantly along the chronosequence (mean 2.41 t ha⁻¹). In contrast, litter decay rates decreased significantly during the rapid growth phase of trees. In consequence, the litter turnover time (1/k) was lower in the youngest stands (20 months) compared to the oldest ones (31 months). Even in the absence of a significant pattern of variation, litter production was positively correlated with the thickness of the OF (Oi) horizon. In contrast, litter decay was strongly negatively correlated with maximum thickness of the OH (Oa) horizon, suggesting that the appearance of the humification layer was mainly due to a decrease in litter decay rate. We did not find significant changes in the main properties of the organo-mineral horizon, suggesting that soil nutrient availability may not directly affect litter dynamics. We concluded that moder development along the chronosequence resulted in decreasing litter decay rates during the aggradation phase while litter production was stable. Further studies are required to identify the ecological factors responsible for moder development along forest ageing.     

Humus structure during a spruce forest rotation: quantitative changes and relationship to soil biota

Temporal dynamics of edaphic communities affect numerous processes in forests and also strongly influence the soil's organic matter status. We have linked long-term changes in the formation of organic matter (using humus micromorphological analyses) to changes in the soil's community structure during a spruce forest cycle on acid soil. The study was carried out at four sites of different age-classes in the Tharandter forest, Germany. The composition of the deeper humus layers (OH, A) was stable. Herbaceous litter, recent spruce litter, fragmented spruce litter, decomposed litter and faeces and fungi, which contributed to the organic layer (OL and OH horizon), significantly changed during the forestry cycle, especially with the shift from the early stage to intermediate stages. Parallel changes of the faunal assemblage of the soil showed quantitative relations between major stages of the forest development, humus dynamics and soil community composition. The herbaceous litter was correlated with surface-dwelling Collembola and microbial properties with faeces and fungi. Our results suggest that the long-term stability of deep organic layers provides a refuge for decomposers and detritivores that allows a rapid response to both adverse and favourable conditions, taking place in OL and OF layers. Furthermore, the opening of the canopy in mature stands allows the decomposers to adapt to changes in resource input long before the collapse of the forest.     

Micromorphological and analytical studies of the fine matrix of an Australian humus iron podzol

Detailed micromorphological observations and associated electron probe microanalyses are used to examine the proposition that kaolinite and gibbsite in the B horizon of a humus iron podzol could arise by transformation of allophanic deposits. The B horizon of this podzol is highly complex. In the upper B horizon, this complexity is due to alternating episodes of the influx of organic matter and the deposition of allophanic material; evidence for the separate deposition of allophane and organic matter is presented. Material within the B horizon that has gibbsiporphyric fabric appears to have arisen by crystallization of gibbsite from aluminium-rich gels deposited before the main influx of allophanic material; there is no convincing evidence that allophanic material has transformed to kaolinite or gibbsite.     

Heavy metals (copper,lead, nickel,and cadmium) in the organic part of gray forest soils in the Buryat Republic

The levels of the accumulation of copper, lead, nickel, and cadmium in the parent material-soil-plants-soil organic matter system are given for gray forest soils in the Buryat Republic. The concentrations of copper, lead, and nickel in the parent materials do not exceed the corresponding clarkes, and cadmium is present in trace amounts. The concentrations of copper and nickel in the humus horizon are lower than those in the parent material; an opposite situation is observed for lead. The concentrations of copper, lead, and nickel in the soil organic matter and in the herbaceous plants correspond to their contents in the soil and do not exceed the background (clarke) values. Cadmium was not detected in the aboveground part of the plants, though it was found in the root mass and in the organic soil horizon. In the humus of gray forest soils, these heavy metals are mainly present in the acid filtrate remaining after the precipitation of humic acids.