Wirkung des Mikroreliefs auf die räumliche Variabilität des Kohlenstoffgehaltes eines Podzoluvisols in einem Dauerdüngungsversuch

Effect of microrelief on the spatial variability of carbon content of a Podzoluvisol in a long term field trial The relationship between microrelief and spatial distribution and variability of the soil C_t-content was investigated in a long term field experiment with different fertilizer and herbicide treatments near Moscow. Only 20% of the C_t-variability were related to agricultural factors. In order to analyse the influence of the microrelief on soil C_t-content the relief was formalized. This formalization included the calculation of the local inclination, local water gathering area and local relative intensity of the temporary water streams, while distinguishing between convex and concave relief forms. Relief forms of different order were identified by kriging with different distances between the block centers. The parameters of the formalized relief were compared with the C_t-content of the soil by means of semivariograms and correlations. Through combination of relief parameters, it was possible to divide the field into different elements characterized by different correlations and effect types. The water gathering relief forms with maximal values of the relative intensity of the water streams and the arched forms with increasing intensity reduced soil C_t-content. C_t-accumulation occurred at transit positions between the convex and concave relief forms with medium intensity.     

Maßstabsabhängige räumliche Variabilität mikrobieller Bodenkenngrößen in einem Buchenwald

Scale-dependent spatial variability of microbiological characteristics in soil of a beech forest The spatial variability of the microbial biomass content (C_mic), the microbial respiration rate (basal respiration) and the metabolic quotient (qCO₂) was analyzed in sandy Cambisols and Luvisols in a beech forest in Northern Germany. Highest variability of microbiological features and, thus, the distance of independent samples was around 10 m that is discussed with reference to spatial hierarchy. Structural changes between the 10 m and 50 m grid were suggested for the Ah horizon due to the break of correlations of C_mic content and the contents of C_org and plant-available Ca, Mg, K and N_t. The C_mic content correlated with the C_org content close to tree trunks and ecotones like borders of the forest and clearings. The qCO₂ did not generally increase with declining pH value. High H⁺ concentrations and C_org content in the litter layer near to the tree trunk indicated retarded microbial mineralization rates. High proportion of microorganisms that are resistant to low pH value and adjusted ro readily-degradable substrates seems to dominate in the soil close to the tree.     

Räumliche Variabilität der Phosphorgehalte im Oberboden landwirtschaftlich genutzter Flächen in kleinen Einzugsgebieten

Spatial variability of Phosphorus contents in topsoils of two small catchments under agricultural use The spatial variability of total phosphorus (P_t) contents was investigated in two small agriculturally used catchments in Saxony/Germany. The mean P_t concentration was 982 mg kg^–1, with 80 % of values between 560 and 1530 mg kg^–1. The largest P_t contents were found at the tops and foots of slope, and the smallest at the middle slope positions. At the scale of slopes (microscale) the spatial variability was caused by the relief and soil properties, whereas at the scale of catchments, agricultural management had the largest influence. These differences must be considered for the modeling of diffuse P inputs to surface waters.     

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.     

Depth distribution of humic substances in Andosols in relation to land management and soil erosion

Although Andosols are relatively resistant to water erosion, they can be severely affected by changes in land use, resulting in accelerated erosion and loss of soil organic matter (SOM). We hypothesized that if the contents of specific components of SOM and organo–metallic complexes (humic acids –HAs–, fulvic acids –FAs–, sodium pyrophosphate extractable carbon –C_p–, aluminium –Al_p–, and iron –Fe_p–) consistently tend towards certain ratios in A and B horizons, they could be used to identify soils denuded by erosion. To test this hypothesis, we investigated the vertical distribution of humus components and certain ratios, namely C‐HA/C‐FA, C‐FA/total organic C (TOC), C_p/TOC and (Fe_p + Al_p)/C‐FA, in representative profiles of andic soils located in natural ecosystems with different degrees of human disturbance. Furthermore, we analysed these parameters in the topsoil of a natural protected area and in adjacent soils under different land use scenarios (natural reserve vs. traditional exploitation). We found that the ratios of C‐HA/C‐FA and, to a lesser extent, of C‐FA/TOC and C_p/TOC changed with depth in the selected soil profiles, but the values were characteristic of each type of soil horizon. The values of these ratios in the topsoils of the disturbed areas were closer to a B horizon than an A horizon. This pattern may be superimposed on pre‐existing gradients, such as those related to the type of natural vegetation. The use of these indices emerges as a possible land use and erosion indicator.     

Effects of biosolids from tomato processing on soil fertility and wheat growth in a Greek alfisol

The effects of biosolids from tomato processing on soil properties and wheat growth were investigated in an Alfisol from central Greece. Biosolids were mixed with soil from the surface (Ap) or subsurface (Bt) horizon in plastic containers at rates of 1%, 5%, and 10% by dry weight (d.w.; equivalent to 10, 50, and 100 Mg ha^–1). Biosolid treatments were compared to an NH₄Cl application (50 mg N kg^–1) and an untreated control in (1) a 102 d incubation experiment at 28°C to determine biosolid nitrification potential and (2) a 45 d outdoor experiment to evaluate effects on soil fertility and wheat growth. Mineralization of biosolids in the incubation experiment resulted in accumulation of nitrate‐N and indicated that biosolids were able to supply N that was in excess of crop needs in treatments of 5% and 10%. After 45 d of wheat growth, available soil nutrients (N, P) and P uptake by wheat were distinctly lower in the Bt than in the Ap horizon. However, soil pH, electrical conductivity, organic matter, total N, nitrate‐N, extractable P, and exchangeable K increased with increasing rate of biosolid application in both soils. These were followed by corresponding increases in wheat nutrient uptake and biomass production, thus demonstrating the importance of this organic material for sustaining production in soils of low immediate fertility. Compared to the NH₄Cl treatment (50 kg N ha^–1 equivalent), biosolid application rates of 5% and 10% had higher available soil nutrients, similar or higher nutrient uptake and higher wheat biomass. But only an application of 10% biosolids provided sufficient N levels for wheat in the surface soil, and even higher applications were required for providing sufficient N and P in the Bt horizon.     

Biological activity and organic matter mineralization of soils amended with biowaste composts

This study aims to elucidate the significance of compost and soil characteristics for the biological activity of compost‐amended soils. Two agricultural soils (Ap horizon, loamy arable Orthic Luvisol and Ah horizon, sandy meadow Dystric Cambisol) and a humus‐free sandy mineral substrate were amended with two biowaste composts of different maturity in a controlled microcosm system for 18 months at 5 °C and 14 °C, respectively. Compost application increased the organic matter mineralization, the C_mic : C_org ratio, and the metabolic quotients significantly in all treatments. The total amount of C_org mineralized ranged from < 1 % (control plots) to 20 % (compost amended Dystric Cambisol). Incubation at 14 °C resulted in 2.7‐ to 4‐fold higher cumulative C_org mineralization compared to 5 °C. The C_mic : C_org ratios of the compost‐amended plots declined rapidly during the first 6 months and reached a similar range as the control plots at the end of the experiment. This effect may identify the compost‐derived microbial biomass as an easily degradable C source. Decreasing mineralization rates and metabolic quotients indicated a shift from a compost‐derived to a soil‐adapted microbial community. The C_org mineralization of the compost amended soils was mainly regulated by the compost maturity and the soil texture (higher activity in the sandy textured soils). The pattern of biological activity in the compost‐amended mineral substrate did not differ markedly from that of the compost‐amended agricultural soils, showing that the turnover of compost‐derived organic matter dominated the overall decay process in each soil. However, a priming effect occurring for the Dystric Cambisol indicated, that the effect of compost application may be soil specific.     

Veränderungen physikalischer Bodenmerkmale im „Statischen Düngungsversuch”︁ während einer Vegetationsperiode

Temporal variations of physical soil properties in the “Static Fertilization Experiment” The objective of the present paper was to observe short-term changes in physical soil properties of a differently fertilized loess-Chernozem. Samples were taken weekly from the plots with 17.2 g C_org kg^?1 (unfertilized) and 25.0 g C_org kg^?1 (NPK + farmyard manure) of the “Static Fertilization Experiment”, Bad Lauchstädt, and their moisture contents (θ), bulk densities (?_d) and particle densities (?_s) were determined. The soil moisture contents showed very similar variations in the two treatments. Clear differences between the unfertilized (≈ 16 Vol.-%) and the NPK + farmyard manure treatment (≈ 10 Vol.-%) only occurred during summer (means 25th–29th week). The values for ?_d were lower in the NPK + farmyard manure plot (mean: –0.10 g cm^?3). Similar short-term changes in ?_d were found in both treatments and correlated to both, organic matter contents and composition (C_org, N_t, C/N). These data, however, gave no indication of reasons for the short-term changes in particle densities up to 0.09 g cm^?3.     

Einfluss eisenhaltiger Klärschlämme auf Kenngrößen der P‐Verfügbarkeit in Ackerböden

Influence of iron content in sewage sludges on parameters of phosphate availability in arable soils The use of iron salts for the P elimination in sewage plants is widely used. But it is not clear whether the P availability in arable soils is negatively influenced by iron compounds or not. The aim of the investigations was, therefore, to study the influence of two sewage sludges with a high and a low Fe content respectively on P sorption and phosphate concentration (P_i) in the soil solution after application of CaHPO₄ or sewage sludge to 5 loamy and 4 sandy soils (pot experiments and 1 silty loam (field experiment)). Soils were analyzed 1, 6, and 13 months after P application. Sludge Gö contained 12 kg P and 65 kg Fe (t DM)^—1 (P : Fe = 1 : 5.4) and sludge Sh 25 kg P and 39 kg Fe (t DM)^—1 (P : Fe = 1 : 1.5). The basic P application was 60 kg P ha^—1 (= 30 mg P (kg soil)^—1 in the pot experiment, as sludge or as CaHPO₄). P uptake by maize was determined in a separate pot experiment with a loamy soil and the same P application rate. The P sorption capacity remained similar in all soils after application of sludge Sh (P : Fe = 1:1.5) compared with soils without sludge, however, after application of sludge Gö the P sorption increased by 16% (0—59%). After application of sludge Sh the mean P_i concentration increased in loamy soils by 34% and in sandy soils by 15%. On the other hand the P_i concentration decreased after applying sludge Gö by 13% and 36% as compared to the controls of the respective soils. In the field experiment the P_i concentration of plots with a high P level (50 mg lactate soluble P (kg soil)^—1) was also significantly decreased after application of 10 t sludge Gö (126 kg P ha^—1) in comparison with triple phosphate. One month after the application of increasing amounts of sludge Gö (5, 10, 15 t DM ha^—1) both the concentration of oxalate‐soluble Fe in the soil and the P sorption were increased. The elevated relationship between these two parameters was highly significant (r² = 0.6 — 0.97). Plant uptake of P was less after application of sludge Gö than after application of sludge Sh and much less than P uptake from CaHPO₄. Sewage sludges with a P : Fe ratio of 1 : 5 should not be recommended for agricultural use, as the P availability is significantly reduced. Iron salts should not be used for conditioning of sludges.     

Microbial C,N, and P relationships in moisture‐stressed soils of Potohar,Pakistan

In 11 rain‐fed arable soils of the Potohar plateau, Pakistan, the amounts of microbial‐biomass C (C_mic), biomass N (N_mic), and biomass P (P_mic) were analyzed in relation to the element‐specific total storage compartment, i.e., soil C_org, N_t, and P_t. The effects of climatic conditions and soil physico‐chemical properties on these relationships were highlighted with special respect to crop yield levels. Average contents of soil C_org, N_t, and P_t were 3.9, 0.32, and 0.61 mg (g soil)^–1, respectively. Less than 1% of P_t was extractable with 0.5 M NaHCO₃. Mean contents of C_mic, N_mic, and P_mic were 118.4, 12.0, and 3.9 µg (g soil)^–1. Values of C_mic, N_mic, P_mic, soil C_org, and N_t were all highly significantly interrelated. The mean crop yield level was closely connected with all soil organic matter– and microbial biomass–related properties, but showed also some influence by the amount of precipitation from September to June. Also the fraction of NaHCO₃‐extractable P was closely related to soil organic matter, soil microbial biomass, and crop yield level. This reveals the overwhelming importance of biological processes for P turnover in alkaline soils.     

Einfluß chemischer Bodeneigenschaften auf Ausmaß und Zusammensetzung der Denitrifikationsverluste drei verschiedener Bakterien

Effect of soil properties on the quantity and quality of denitrification with different bacteria The influence of 4 different soils on the intensity and quality of gaseous denitrification losses from 3 bacteria (Aeromonas “denitrificans” S224, Azospirillum lipoferum DSM 1843 and Bacillus licheniformis ATCC 14580) was examined in model experiments at complete anaerobic conditions at the expense of a relatively high nitrate concentration (300 μg NO₃^? N/g dry soil) at standard conditions (30°C, 80% WHC). The soils (Ah-material) were obtained from gleyo-eutric Fluvisol (A), orthic Luvisol (L), calcaric Fluvisol (AR) and eutric Cambisol (KB) and represented different chemical properties. Gas production (CO₂, NO, N₂O, N₂ and CH₄) was analyzed by gaschromatography in regular intervals, whereas changes in N_t, C_t, water extractable organic carbon (C), nitrate, nitrite, ammonium, pH (H₂O) were determined at the end of each experiment. The intensity and composition of denitrification (NO, N₂O, N₂) differed considerably from organism to organism and from soil to soil. With A. “denitrificans” NO was released from the calcaric Fluvisol and orthic Luvisol, whereas B. licheniformis produced this gas only from the Cambisol. A. lipoferum did not produce NO in any of the soils tested. N₂O was liberated by A. “denitrificans” in all soils, but A. lipoferum produced it only in the Fluvisol and B. licheniformis exclusively in the Cambisol. Apparently, the production of NO and N₂O as products of incomplete denitrification at relatively high nitrate concentration is determined primarily by the organism in question and in the second place by the chemical properties of the soil. The main properties that govern the quality of denitrification in soils are discussed.     

Der Einfluß des Wassergehaltes auf den Atrazin-Abbau im Boden

The influence of water-content on atrazine degradation in soil In samples of the standard soil 2.2 (loamy sand, 3 % C, pH 7,0) and of a Luvisol (Ap-horizon, loam 1,4 % C, pH 5,2), the degradation of [ethyl-1-¹⁴C]atrazine was investigated in dependence of the soil water content. The experimental conditions were choosen in accordance with the methods proposed by the Biologische Bundesanstalt to study the degradation of pesticides in the soil. The soil water content was varied to simulate the moisture conditions observed in a soil during plant growth. Therefore, besides a steady water content of 20, 40, 60, and 80 % of the maximum water holding capacity of the soils, the soil water contents were fluctuated by 20 to 60 % of the maximum water holding capacity by passing dry air through the soil. At a concentration of 10mg atrazin/kg of soil between 4 and 6 % of the ethyl-1-carbonatom of the atrazine molecule was mineralized to CO₂ within 71 days at a constant soil temperature of 22°C. In the standard soil 2.2 the mineralization in total was reduced to 2/3 compared to the degradation in the Luvisol. With decreasing water content increasing hydroxilated metabolites were formed. About 30–40 % of the applied radioactivity was determined as non-extractable residue in the soil. In general the degradation processes were more enhanced and more intense in the Luvisol as compared to the Standard soil 2.2 which again unterlines that for this type of experiments a fresh soil should be used. In conclusion, the variation of the soil water content did not have a pronounced influence on the mineralization rates of atrazine, but did influence the metabolism and the formation of certain metabolite fractions.     

Spatial and temporal variations in resistance of loess-derived soils to ephemeral gully erosion

Planners would like a simple means of describing spatial and temporal variations in soil erodibility accurately. We have done a series of concentrated flow detachment experiments to investigate the feasibility. Four different soil horizons, typical of loess‐derived soils in Belgium, were sampled seven times during one year, so that a representative range of initial soil moisture contents was obtained. Undisturbed soil samples were subjected to five different combinations of slope gradient and concentrated flow discharge. Results showed that for a given soil horizon, variations in detachment rate could be related well to temporal variations in initial soil moisture content. For a given initial soil moisture content the ploughed topsoil horizon (A_p) and the underlying clay‐enriched horizon (B_t) had only one fifth of the erodibility of the loess horizon whether decalcified (C₁) or still calcareous (C₂). Combining knowledge on spatial distribution of soil profiles and initial soil moisture content allowed us to explain observed spatial and temporal variations in resistance to ephemeral gully erosion for soils in loess. Also, differences in ephemeral gully morphology (cross‐sections) could be explained from differences in initial soil moisture content and soil horizon. In the short term these results have important implications for spatial and temporal variations in erosion, while in the medium or long term information on spatial distribution of soil profiles is crucial when predicting the volumes and patterns of (ephemeral gully) erosion. Finally, the importance of combining the effect of water and tillage erosion with respect to soil profile evolution and consequent erosion risk is stressed.     

Lateral flow in loamy to sandy Kandiudults of the Upper Coastal Plain of Georgia (USA)

Interest in site-specific agronomic management in intensively cropped regions necessitates characterization of subsurface water movement for efficient water management (irrigation timing) and control of off-site agrichemical movement. Soils formed in fluvial sediments in portions of the Upper Coastal Plain of Georgia (USA) are extensively used for peanut, cotton, and corn production. Certain proximate soils in this region possess contrasting subsoil properties, and it was hypothesized that these differences would have major effects on water redistribution across the landscape. This could be important in irrigation management, where soils possessing increased impedance to vertical flow could require decreased irrigation as opposed to soils without vertical flow restrictions. At a site near Plains, GA. (USA), hydraulic properties of soils with differences in overlying sand thickness and contrasting argillic horizon textures (sandy vs. loamy) were evaluated. The soils were predominantly in loamy and sandy families of Typic, Arenic, and Grossarenic Kandiudults. Laboratory measurements, field monitoring of matric potentials under simulated and natural rainfall, and modeling (VS2DT) were utilized to evaluate soil hydraulic properties. Reduction in vertical K_s occurred in horizons containing higher clay (argillic horizon). Changes in tension and build ups in hydraulic gradients associated with infiltration and redistribution events existed above and within horizons with low K_s. Evidence suggested there was less groundwater recharge occurring in the loamy than in the sandy pedons, suggesting more pronounced lateral flow occurred in the loamier soils. Model simulations of water movement across a slightly sloping (1%) simulated landscape indicated lateral gradients of flow existed within the solum of these soils. Analyses of tracer (Br) movement suggested a very slight lateral redistribution occurred within a relatively short monitoring period within the sandy pedon's Bt1 horizon, and the Bt2 and Bt3 horizons of the loamy pedon. Evidence suggested both loamy and sandy argillic horizons slightly, but not overwhelmingly, induced lateral flow on these landscapes.     

Measuring interlayer potassium release rates from soil materials. II. A percolation procedure to study the influence of the variable ‘solute K’ in the < 1…10 μM range

Release rates of nonexchangeable K from Ap material of a Luvisol (‘Eckerde’ loess, 15% clay) are determined using a percolation procedure which avoids the common artifacts due to shaking or stirring soil suspensions and thus provides less biased kinetic data. CaCl₂ solution (10 mM_c. 20 °C. pH 5.8) is percolated through packages of soil aggregates (0.5–1 mm grain size, 0.5 g samples) with 0.02 to 25 ml h^?1. Solute K (C_K) was varied between < 1 and > 10 μM and is shown to have a dominant influence on the rates of interlayer K release. These increase exponentially below 3.5 μM (no steady state but steady decrease of release rates in each sample). The difference between the related C_K between moderate and high release rates is as small as 1 μM K. The average rates, of a 10-day-interval, starting after 1.3 times the exchangeable K had been removed, are 40 μmol K kg^?1 soil d^?1 at 4 μM C_K and 240 μmol kg^?1 d^?1 at 3 μM C_K, respectively. It is concluded that larger quantities of interlayer K become plant available in the studied soil if the of soil solutions gets below 3.5 μM (for 10 mM_c Ca, 20 °C, pH 5.8), probably because the dominant dioctahedral illites start to join the release process below this critical limit. The higher K concentration range was accounted for by K-Ca exchange isotherms which, by alteration of shape, indicate that K_nex release becomes measurable below 10 to 20 μM K. It is further argued that existing diffusion or reaction kinetics approaches towards K release are incomplete because the influence of solute K is not considered.     

Effects of fresh and aged copper contaminations on soil microorganisms

The aim of the investigation was to compare effects of fresh and aged amendments of copper (Cu) on the active, aerobic, heterotrophic microbial biomass by respiration and potential‐nitrification measurements and on microbial‐community structure by means of phospholipid‐fatty‐acid (PLFA) analyses. An A_p horizon (10–20 cm) of a Luvisol was used for the experiments. Fresh copper amendments were carried out by spraying a CuCl₂ solution on the soil. Aged heavy‐metal amendments were achieved by mixing the control soil with monocontaminated soil derived from an abandoned site in Denmark which has been used as a wood‐preservation plant. As expected, fresh contaminations were more effective to reduce potential nitrification and respiration than aged contaminations if the total Cu concentration (Cu_t) in soils is considered. There were no differences between aged and fresh contaminations if their effects were referred to NH₄Cl‐extractable concentrations (Cu_AN). The lowest concentration reducing cumulative substrate‐induced respiration (C_R) amounted to 0.33 mg Cu_AN (kg dm)^–1. PLFA analyses revealed Cu contaminations to decrease mainly aerobic bacteria. Effects were more pronounced using the contaminated soil as an inoculum. Apparently the duration of contamination is more important to the change of microbial‐community structure than the actual availability of the contaminant.     

Pyrolysis methylation—mass spectrometry of whole soils

In-source pyrolysis field ionization mass spectrometry (Py-FIMS) and Curie–point pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) have been applied to the characterization of whole soils methylated off–line and on–line by two methylation reagents. Samples of a gleysolic Ap–horizon and a podzolic Bh horizon (C_org concentrations 2–3%) were investigated by conventional on–line and developed off–line methylation with tetramethylammonium hydroxide (TMAH) and by off–line methylation with diazomethane. For the first method, the soils were dried, milled and pretreated with TMAH for 10 min at 250°C at ambient pressure outside the pyrolyzers. For the second method, the dried and milled soils were methylated with an ether solution of diazomethane for 12 h at room temperature (～20°C). Pyrolysis methylation with TMAH enabled aliphatic C₂–C39 monocarboxylic acid methyl esters, C4–C₃₀ dicarboxylic acid dimethyl esters and benzenecarboxylic acid methyl esters to be detected. Methoxybenzenes from phenols, benzenediols and benzenetriols, methoxybenzenecarboxylic acid methyl esters from phenolic acids and furancarboxylic acid methyl esters from carbohydrates were also identified. Nitrogen–containing compounds in soil organic matter were obtained as N,N–dimethylamides. Using diazomethane as methylation reagent, distinct Py-FIMS signals were observed for aliphatic C₂–C₃₂ monocarboxylic acid methyl esters and C₃–C₂4 dicarboxylic acid dimethyl esters. Additionally, methoxybenzenes originating from lignins, methoxybenzenecarboxylic acid methyl esters from phenolic acids and N,N–dimethylamides from amides were detected. The more acid podzolic Bh horizon showed higher relative intensities for dicarboxylic acid dimethyl esters and methylated phenolic acids compared to the gleysolic Ap horizon. Similarly, benzenecarboxylic acids are connected mainly by ester linkages to the macromolecular network of soil organic matter. Both methylation procedures support conventional Py-FIMS and Py-GC/MS and give valuable additional information on the occurrence of aliphatic and aromatic carboxylic acids, substituted phenols, benzenediols, benzenetriols, phenolic acids and amides in soil organic matter.     

Electrostatic method to separate roots from soil

Complete removal of roots from soil samples is a prerequisite for most of the chemical and biological analyses. A simple electrostatic method of separating roots from sieved, largely mineral soil substrates was optimized and examined by the addition of ¹⁴C labeled fine roots to sandy, silt loamy and clay loamy samples. Depending on soil texture, between 40% and 50% of fine roots can be removed from 100 g of sieved soil in less than 10 minutes. The root‐free soil substrate and the extracted roots can be used for analyzes or experiments immediately after the separation. The proportion of the mineral particles remaining in the root fraction depends on duration of separation, distance between the charged plate and the sample, and soil texture. The proportion of separated mineral particles is about 90%—95% (w/w) in sandy and 70%—85% in silt loamy and clay loamy substrates. The electrostatic method of root separation may take place before the analysis of C_t and N_t contents, and is suitable for soil samples preparation for incubation experiments.     

Humusveränderungen nach Einbringung von Buche und Eiche in Kiefernreinbestände

Humus changes after introduction of beech and oak into Scots‐pine monocultures Medium‐ and long‐term (16 to 83 years) effects of an introduction of broadleaf‐tree species (Common beech [Fagus sylvatica] and European‐Sessile Oak [Quercus robur/petraea]) into mature Scots‐pine (Pinus sylvestris) stands on humus type and chemical properties of the Oh layer (pH value, base saturation, C : N ratio) were studied on 16 sites in Bavaria/Germany. The sites investigated covered a large range with respect to elevation, climate, parent material, and soil type. At most sites, the introduction of beech resulted in a significant change of the soil humus type from biologically inactive humus types to more active ones. The strongest changes occurred on the poorest sites, where forest floors under pure pine were particularly biologically inactive. In most cases, the changes in humus type were accompanied by significant increases in the pH value and the base saturation and significant decreases in the C : N ratio of the Oh layer. However, the latter effect was not noticed at most sites with initial C : N ratios higher than 30. In contrast to beech, the introduction of oak did not result in a systematic change of the humus type, the pH value, or the base saturation of the Oh layer. In spite of the considerable change of humus type under beech to biologically more active types, the introduction of broadleaf trees did not result in a systematic change of the thickness or the mass of the forest floor. A decrease in the mass of the Of layer was compensated by an increase of the Oh‐layer mass. All studied sites considered, the introduction of broadleaf trees into Scots‐pine monocultures resulted on average in an 8% decrease of the total amount of organic carbon (C_org) in the forest floor; the C_org amount in the uppermost 10 cm mineral soil increased by 9%. At 35% of all investigated sites, broadleaf tree introduction resulted in increased (+5% to +18%) topsoil (forest floor and uppermost 10 cm mineral soil) C_org stocks. At 30% of the sites, the stock changes were less than ±5%, and on 35% of all sites, soil C_org stocks decreased by –5% to –36%. The average change in the topsoil C_org stock for all studied sites was –5%. The introduction of beech into Scots‐pine monocultures resulted in an ecologically desired translocation of soil organic matter from the forest floor into the mineral topsoil. It is an effective and sustainable silvicultural measure to restore and revitalize acidified, nutrient‐depleted topsoils with biologically inactive humus types.     

Bodenphysikalische Untersuchungen zum Nachweis der spätpleistozänen Bodenbildung in rheinisch-westfälischen Lößgebieten

Soil physical investigations proving the late pleistocene pedogenesis in loess areas of Northrhine-Westfalia Balancing the structure of typical Braunerde- and Parabraunerde-profiles in the loess-regions of Northrhine-Westfalia soil physical investigations had confirmed that the biggest part of the solum has been clearly compacted als related to parent material. Above C-horizon there has been found a small part of Bv-horizon without compaction, characterized by distinctly increasing pore volume, especially by that of the 10–50 μm fraction, following the carbonate losses. This horizon represents an important mark in soil genesis, probably dating the border between preholozene and holozene soil forming processes. Because the disturbing effects of permafrost conditions the preholozene soil genesis is of definite importance in soil mapping and describing properties of the soils.