Landscape position and soil redistribution under three soil types and land use practices in Prince Edward Island

Soil redistribution by erosive processes is a serious problem for the potato growing areas of Prince Edward Island. Studies were conducted to evaluate soil loss for three major soil types under two different cropping systems, at catenary sequences with five slope positions, using the ¹³⁷Cs tracer method. Adjacent forest catenas were sampled to provide baseline ¹³⁷Cs levels. Soil loss over time (1960–1990) on a specific mass (kg m⁻² yr⁻¹) basis was calculated by comparing the ¹³⁷Cs at the same slope positions for the cropping system and adjacent forest site. The effects of land clearing and long-term cultivation were to increase both the depth and density of the Ap horizon, and decrease the total ¹³⁷Cs on an area basis, in comparison to the forested sites. The average ¹³⁷Cs in the forested sites for all three soil types was 3133 Bq m⁻². Catena average soil loss across all soil types and slopes, for the 1960–1990 time period, was 21 and 38 Mg ha⁻¹ yr⁻¹ for the pasture and crop rotation (potato) rotations, respectively. Shoulder slope positions tended to have the highest ¹³⁷Cs loss, which was suggestive of tillage erosion.     

Bodenentwicklung am Rande oligotropher Moore im Raum Berlin

Soil development in the surrounding of oligotrophic mires in the Berlin region Polygenetic soils, surrounding oligotrophic kettle hole mires in the valley and aeolian sand areas of the Berlin region, were investigated. The typical soil catena is formed by the sequence of Ombric Histosol (Niedermoor), Ombric Histosol/Albi‐gleyic Podzol (Moor‐Podsol‐Gley), Albi‐gleyic Podzol (Nasspodsol‐Gley), Gleyic Podzol (Podsol‐Gley), and Dystri‐gleyic Arenosol (Gley‐Podsol‐Braunerde) (German soil classifications in parenthesis). Field and laboratory work showed, that the investigated soils were strongly related to each other and that their development depends on the trophy of the mire and groundwater fluctuations during the Holocene. Compared with the Bh‐horizon of terrestrial soils the Gh‐horizon is nearly free of Fe and Mn, but very rich in pedogenic Al‐oxides and rich in organic matter. The genesis of the soils is explained as follows: 1. The development of different Gleyic Podzols was due to rise of groundwater. Consequently the Bh and Bs horizons of Podzols surrounding the mire were converted to Gh and Gr horizons. 2. Humic substances and Al in the Gh and Gr horizons were not re‐mobilized due to the rise of groundwater, whereas Fe and Mn were reduced and removed by groundwater. 3. At the periphery of the mire Fe was enriched in the Go horizon of the Gley‐Podzols but not Mn. 4. The fact that the mire is completely surrounded by Podzol‐Gleys, indicates, that movement of the groundwater from the central parts of mires towards the periphery is an essential pedogenetic factor.     

Selective depletion of organic matter in mottled podzol horizons

Some well-drained podzols on quartz sands in the Netherlands and neighbouring Belgium and Germany show mottling in all horizons due to selective removal of organic matter. Phospholipid analysis and morphology of the mottles suggests that this removal is due to a combination of bacteria, fungi, and actinomycetes. Investigation by pyrolysis-GC/MS of organic matter in the depleted zones as compared to their surroundings indicates (1) selective decay of relatively palatable components, (2) residual accumulation of aliphatic biopolymers such as cutan and suberan that produce alkanes, alkenes and methylketones upon pyrolysis, and (3) accumulation of microbial polysaccharides and N-containing compounds. Although the selective organic matter decay in the depleted mottles is similar to the process that causes degradation of organic matter at the top of the B-horizon and its conversion to an E-horizon, the essential difference is that, while decay at the E-B-horizon transition in podzols is governed by the presence or absence of aluminium and iron, the micro flora that is responsible for the decay mottles acts independently from metal concentrations.     

Podzol development with time in sandy beach deposits in southern Norway

The coastal areas of SE Norway provide suitable conditions for studying soil development with time, because unweathered land surfaces have continuously been raised above sea level by glacio‐isostatic uplift since the termination of the last ice age. We investigated Podzol development in a chronosequence of six soils on sandy beach deposits with ages ranging from 2,300 to 9,650 y at the W coast of the Oslofjord. The climate in this area is rather mild with a mean annual temperature of 6°C and an annual precipitation of 975 mm (Sandefjord). The youngest soil showed no evidence of podzolization, while slight lightening of the A horizon of the second soil (3,800 years) indicated initial leaching of organic matter (OM). In the 4,300 y–old soil also Fe and humus accumulation in the B horizon were perceptible, but only the 6,600 y–old and older soils exhibited spodic horizons. Accumulation of OM in the A horizons reached a steady state in <2,300 y, while in the B horizons OM accumulated at increasing rates. pH dropped from 6.6 (H₂O)/5.9 (KCl) in the recent beach sand to 4.5 (H₂O)/3.8 (KCl) within approx. 4,500 y (pH_H2O)/2,500 y (pH_KCl) and stayed constant thereafter, which was attributed to sesquioxide buffering. Base saturation showed an exponential decrease with time. Progressive weathering was reflected by increasing Fe_d and Al_d contents, and proceeding podzolization by increasing amounts of pyrophophate‐ and oxalate‐soluble Fe and Al with soil age. These increases could be best described for most Fe and Al fractions by exponential models. Only the increasing amounts of Fe_p could be better described by a power function and those of Fe_o by a linear model.     

Organic C and N storage, and organic C fractions, in adjacent cultivated and forested soils of eastern Canada

As a major attribute of soil quality, organic matter is responsive to agricultural land use practices including tillage. A study was initiated in eastern Canada to characterize changes in the masses of organic C and total N, and organic matter fractions in forested and adjacent cultivated or forage sites. Generally, the cultivated and forage sites had denser soil profiles than the forest sites. Based on an equivalent soil mass, to accommodate differences in soil bulk density, the paired forest and cultivated sites showed that cultivation decreased the mass of organic C (35%) and total N (10%) in the soil profile of the Podzolic soils, but increased organic C (25%) and total N (37%) in the Brunisolic (Cambisol) and Gleysolic soils. For the Podzolic soils, use of forages increased soil stored organic C and N by 55% and 35%, respectively. Organic C fractions were mainly of significance in the A horizon. Soil microbial biomass C was greater in the forested, compared to the cultivated soil, but the proportion of soil organic C as microbial biomass C (1.3% to 1.6%) was similar. The proportion, however, was greater (2.1%) for the forage soil, compared to the corresponding cultivated (1.3%) soil, suggesting that organic C was continuing to increase under the former. The relatively large proportion (19%) of organic C found in the light fraction of forest soils in the A horizon was decreased (up to 70%) by cultivation. In contrast, the proportion of macro-organic C present in the soil sand fraction was not greatly influenced by cultivation. Overall, soils in eastern Canada have a relatively large potential to store organic matter. The study illustrates the importance of soil type and cultivation interactions for maintenance of soil organic matter storage, and the positive influence of forages in this regard in agroecosystems.     

Biological influences on the morphology and micromorphology of selected Podzols (Spodosols) and Cambisols (Inceptisols) from the eastern United States and north-east Scotland

Biological activities greatly influence the formation of many soils, especially forest soils under cool humid climates. The objective of this study was to investigate the effects of vegetation and soil biota on the formation of selected soils. Field morphology, micromorphology, and carbon and organic matter analysis were determined on six Podzols (Spodosols) and two Cambisols (Inceptisols) from the eastern United States and north-east Scotland. Humification of plant material by soil fauna and fungi occurs in all organic horizons. Thick organic coatings are observed on soil peds and rock fragments from the E1 to the Bs horizon in a Haplic Podzol from Clingmans Dome Mt., TN. Thin sections reveal large accumulations of root material in different stages of decomposition in the spodic horizons of a Haplic Podzol from Whiteface Mt., NY. Organic carbon ranges from 5.4 to 8.5% in the spodic B horizons of the Whiteface Mt. Podzol. Earthworms and enchytraeids have a great effect on the structure of the surface and subsurface horizons in the Dystric Cambisols from Huntly and Clashindarroch Forests, Scotland and a Cambic Podzol from the Corrie Burn Basin, Scotland. Podzols from Speymouth Forest, Scotland (Gleyic Podzol), Clingmans Dome Mt., and Whiteface Mt. have thick organic horizons. The Podzols from the Flatwoods in Georgia, the Pine Barrens in New Jersey, the Corrie Burn Basin, and the Cambisol from Huntly Forest have only A horizons at the surface. The Clashindarroch Forest soil has a very thin organic horizon. Warm and humid climates and sandy parent material are responsible for thick E horizons and lack of thick organic horizons in the Flatwoods (Carbic Podzol) and Pine Barrens (Ferric Podzol) soils. Earthworms and enchytraeids thrive in the Corrie Burn Basin and Huntly Forest soils due to the vegetation and the highly weathered basic parent material. The site at Clashindarroch once carried oak, and then birch forest, both of which produce a mild litter and also encourage earthworm and enchytraeids. This fauna is responsible for much mixing of the topsoil. The present conifer vegetation will eventually produce a deep litter and cause podzolization.     

Andic properties in soils developed from nonvolcanic materials in Central Bhutan

A number of soils are described in the literature as having andic and spodic soil properties, but have developed in nonvolcanic and nonallophanic materials and lack typical Podzol eluvial and illuvial horizons. They cover a wide range of parent materials and different types of climate. They have always been regarded as restricted to small areas. They were assigned to Andisols/Andosols, Podzols/Spodosols, or andic Inceptisols in the WRB and Soil Taxonomy and sometimes also named Cryptopodzols or Lockerbraunerden. Recent soil surveys in Bhutan, E Himalayas, show these soils are widespread at altitudes between 2200–3500 m asl and are spanning several bioclimatic zones. The aim of this study is the detailed characterization of specific properties and processes of formation by physical and chemical analyses, NMR spectroscopy, column experiments, SEM, XRD, and ¹⁴C dating in one of these soils in E central Bhutan. The results indicate advanced soil development with high amounts of oxidic Fe and Al compounds, low bulk densities (partly <0.5 g cm^–3), P retention >85%, and a dominance of Al‐hydroxy‐interlayered phyllosilicates. Scanning electron microscopy of sand fractions indicate microaggregates highly resistant to dispersion. Column experiments show podzolization with mobilization and translocation of DOM, Fe, and Al. Nuclear‐magnetic resonance spectroscopy and ¹⁴C ages of 16,000 BP indicate stabilization of DOM. Applying classification criteria, these soils appear to have andic and spodic features, but are neither Andosols nor Podzols senso strictu. Especially the role of Fe seems to be underestimated with regard to the specific soil‐forming processes. Because of their widespread occurrence and distinct properties, we suggest either a simplification of the criteria for existing soil types or a clearly defined separation of volcanic and nonvolcanic/nonallophanic Andosols.     

Low molecular weight organic acid adsorption in forest soils: effects on soil solution concentrations and biodegradation rates

Low molecular weight (LMW) organic acids are believed to play a key role in many rhizosphere and pedogenic processes; However, their efficiency is likely to depend on their susceptibility to sorption and biodegradation. The sorption characteristics of three organic acids (citrate, oxalate and acetate) and phosphate were examined over the concentration range 0-1000 μM in three coniferous forest soil profiles. Sorption to the soil's solid phase could be adequately described by the Langmuir equation with sorption capacity following the horizon series: B>C>E>O. The strength of anion sorption followed the series: phosphate>oxalate≥citrate?acetate. Calculations indicated that between 50 and 95% (O and E horizons) and >93% (B horizons) of these LMW organic acids entering the soil will become sorbed to the solid phase. The amount of organic acids predicted to be present on the solid phase at typical soil solution concentrations ranged from <1 to 1100 nmol g⁻¹ yielding adsorbed-to-solution ratios (adsorption coefficients) of between <0.1 and 3100. In the case of citrate, sorption to the solid phase significantly reduced its biodegradation potential by 35-99% depending upon the degree and type of sorption surface. The findings of this work are discussed in the context of the quantitative effects of adsorption on organic acids, their ecological functions and role in soil forming processes.     

Soil altitudinal sequence on base-poor parent material in a montane cloud forest in Sierra Juárez, Southern Mexico

The soils of montane cloud forests (MCF) are still insufficiently studied. A number of researchers report Podzols to be the main soil group for MCF ecosystems; however, a great deal of contradictory data exists. We studied an altitudinal sequence of soils formed on ferrous chlorite shale under natural MCF vegetation in Sierra Juárez, Southern Mexico, from 1500 to 2500 m asl. The soils of the upper part of the toposequence were Folic Stagnic Podzols, with inclusions of Folic Stagnosols in local depressions, while the soils of the lower part of the toposequence were Folic Cambisols (Humic, Hyperdystric). All the soils in the toposequence were extremely acid, and had thick organic surface horizon. Mineral horizons of all soils were poor both in exchangeable and total reserves of bases; the bases were concentrated mainly in organic topsoil. With decreasing altitude both the thickness of albic horizons, the depth of the maximum acid oxalate-extractable Fe and Al concentrations, and the difference in clay content between the eluvial and illuvial horizons decreased. In the upper part of the toposequence the composition of soil clays was similar to that of parent material (chlorite and mica), with some mixed-layered 2:1 minerals. However, gibbsite and kaolinite were also present in the soils of the other site within the same upper MCF belt. The phenomenon was ascribed to parent material heterogenity. In the medium and lower parts of the toposequence gibbsite and kaolinite were the dominant minerals. We consider that the main pedogenic processes in the study area are raw humus accumulation, weathering in situ, podzolization, and iron reduction due to water stagnation in mineral topsoil. The intensity of weathering decreases, while the extent of water stagnation increases with altitude. To a great extent the genesis and altitudinal distribution of the soils in the MCF depends on parent material.