Die Bestimmung repräsentativer Mittelwerte von Schwermetall-Konzentrationen in den Niederschlägen und im Sickerwasser von Wald-Standorten des Soiling

Heavy metals in precipitation and seepage water from forest sites in the Soiling: Determination of representative averages of heavy metal concentrations Concentrations of Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb were determined in open land precipitation, in precipitation below canopy and in seepage water in two different soil depths, over the period of 3 years, in monthly and half-yearly intervals, in a beech and a spruce forest of the Soiling mountains. The results of the concentration measurements and the element fluxes calculated from these data were treated statistically. The coefficients of variation of the concentrations and the fluxes within a given time period often exceeded 100%. It is proposed that, in order to determine meaningful average values, weighted samples are taken in half-year or year intervals, over the time span of several years, in a number of local replicates sufficient to reduce the error of the mean to less than 30%. For the investigation of time variations in the concentrations and fluxes the sampling of single rain events or of seepage water within short time periods (a few days) is suggested.     

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.     

Über die räumliche und zeitliche Variabilität scheinbar fixer Wasserhaushaltsgrößen am Beispiel von Bodenaggregaten

Temporal and spatial variability of hydrological parameters of single soil aggregates The hydrological parameters determined for a single soil profile are usually not assumed to be variable and are often taken to represent a larger area and longer period of time, without consideration of spatial and temporal changes in the environment like cultivation or weather. Naturally structured and homogenized, subsequently restructuring aggregates from a “Stagno-haplic Luvisol” (FAO, 1991) with different possibilities of swelling were analysed with regard to the characteristics of the water retention curve and hydraulic conductivity. The experiments verified that the pattern of the water retention curve with respect to single aggregates was not constant but depended on the aggregate's initial intensity and frequency of desiccation. Additionally, effects on the hydraulic conductivity were determined. The measured values varied with the amount of swelling and shrinking, to which the aggregates were exposed. Thus, the calculation of hydraulic conductivity according to the model of Van Genuchten (1987) is doubtful. Therefore, the quantification of ecological characteristics from such parameters has to be questioned. The main cause for the described effects can be seen in the induced and only partly reversible structuring process, i.g. aggregate compaction due to shrinkage and rearrangement of particles inside the aggregate during repeated swelling and shrinkage. Additionally, physico-chemical hydrophobicity was supposed to have a major influence under certain circumstances.     

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 von Stoffkonzentrationen am Grundwasserspiegel bei einem grundwasserfernen Sandstandort unter Kiefern

Spatial variability of groundwater solute concentrations at the water table under a pine stand on sandy soil with deep groundwater Aim of the study was to prove the evidence of a direct influence of solute input pattern (induced by canopy throughfall) on the pattern of groundwater solute concentration at the water table even at sites with groundwater table of 4–5 m below surface. The test site was a weakly buffered sandy soil with groundwater table ca. 4.3 m below surface (Podzol soil with some features of former gley process) under a cultivated pine stand (age ca. 60 years). Groundwater at the water table was sampled in between two rows of trees along a 30 m transect at 0.5 m intervals. As example, the results for sulfate concentration (the key solute of soil and groundwater acidification) show rather high variation along the transect. But a thorough stochastic analysis of empirical data sets reveals cyclic oszillations occurring synchronous and with same period length for sulfate concentration at the water table and for canopy coverage of the ground (and therefore for solute input). An additional long-periodic oscillation is strongly superimposing in the case of sulfate concentration. Thus the results indicate a direct influence of the pattern of canopy throughfall on the pattern of sulfate concentration at the water table. However, this influence is rather weakly pronounced at this deep groundwater site compared to corresponding shallow groundwater sites.     

Erfassung der Variabilität von Bodenmerkmalen in einem Blindversuch auf Fahlerde mittels Methoden der räumlichen Statistik

Variability of soil parameters in a uniformity trial on a Luvisol evaluated by means of spatial statistics The relationships between soil parameters and indicators of soil genesis were investigated in a uniformity trial on Luvisol by means of classical and spatial statistics. The following properties were investigated in the topsoil (0–30 cm) and subsoil (31–40 cm): content of total carbon (C_t), content of clay plus fine silt (FAT), concentrations of available potassium (K) and phosphorus (P), and pH values. The depth loamy Bt horizon and microrelief were considered as indicators of soil genesis. Smoothing of the raw data by means of block kriging eliminated the small scale variability of all parameters. In this way, the rank correlation coefficients between soil parameters increased by factor 2 and were to 0.52 for C_t–FAT; 0.69 for C_t–K, and 0.55 for C_t–P in the top soil. The maps for smoothed data allowed a much better visual analysis of spatial distribution of investigated properties compared to the raw data. The significant correlations as well as the similarity of maps and variograms suggested that the spatial variability of FAT, C_t, K, and P in the top soil was determined by the same factors. The depth of the loamy Bt horizon and the relief were the most important factors defining the distribution of the investigated soil parameters. The rank correlation coefficients of the smoothed and detrended relief with the soil parameters amount to –0.63, –0.77, –0.71, and –0.57 for FAT, C_t, K, and P, respectively.     

Die flächenhafte Variabilität bodenphysikalischer Parameter und des Corg-Gehaltes in den Pflugsohlen je eines Ton-, Sand- und Lößstandortes

Spatial variability of soil physical properties in the plow pans each of one clay, sand, and loess site Total porosity (PV), amount of micropores (< 0,2 μm; fPV) and macropores (> 10 μm; gPV) on total porosity, plant available water (nFK) and organic carbon (C_org) were measured at regular grids in the plow pans of a clay, a sand and a loess field. The variation of total porosity was remarkably low in each field (coefficient of variation v = 5.9% - 11.9%). Means of PV can therefore be estimated with a sample density of 2 per ha (1 ha = 10⁴ m²) to achieve a standard error Δa lower than 10%. More samples are needed to estimate fPV, gPV, nFK and C_org with a corresponding standard error on the clay and on the sand field (10–20 samples/ha). Comparison of block-kriging with a classical interpolation method showed that geostatistics should be applied to obtain realistic maps of the spatial distribution of soil physical properties.     

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.     

Zur räumlichen Variabilität der Gehalte ausgewählter Schadstoffe in Stadtböden Gelsenkirchens

On the spatial variability of selected contaminations in urban soils in Gelsenkirchen Principle aspects of the distribution characteristics of soil contaminations are shown by the examples of lead, benzo(a)pyren and the polychlorinated dibenzodioxins and -furans. Regions of different contamination levels are distinguishable, but are found inhomogeneous inside. The variability of contamination in urban soils can be explained by differences in the superpositon of input paths into the soil in very small areas, analytical inaccuracies, and the influence of the way of presentation respectively of the units used.     

Variabilität der Ertragsstruktur von Sommerweizenähren unter dem Einfluß von Stickstoff – Düngung,Thermoperiode und Wachstumsregulatoren

Variability of the yield structure of spring wheat ears caused by nitrogen – supply, thermoperiod and growth regulators In two years pot experiments with spring wheat, the effect of different exogenous growth factors (N - supply, growth regulators, thermoperiod) on ear development in monoculm plants was studied. All three growth factors brought about a comparible change in the internal dominance structure of the ear. Medial-dominance within the ear was diminished by both increased N supply and growth regulators whereas it was augmented by raised temperature during organogenesis of the ear. The application of growth regulators reduced the number of spikelets per ear, but did not necessarily lead to reduced fertility of the total ear. The influence of the growth regulators with anti-gibberellic effect on dominance structures in the plant is explained by an increase in respiration which improves attraction of assimilates into the ear.     

Mikroskalige Variabilität der Bodenlösungschemie - Ergebnisse eines Laborversuchs zum Vergleich von Standard- und Mikro-Saugkerzen

Microscalic variability of soil solution chemistry - results of a laboratory experiment comparing standard - with micro suction cups In a laboratory experiment with an undisturbed soil column, the chemistry of soil solution collected by a standard suction cup (Ø 2 cm) was compared with that of 20 micro suction cups (Ø I mm) installed in the same soil depth. The standard cup showed comparable concentrations of inorganic anions with the soil column leachate, because preferably the main water paths of the soil column were sampled. In contrast, about 30 % of the micro suction cups sample soil compartments that have a different solution chemistry. In these cases the differences between standard and micro suction cups decrease in the order nitrate, chloride, sulfate. Standard suction cups seem to be the right sampling device for the investigation of element fluxes through soil. To get information about plant availability of ions they are inadequate, due to their dimension. Here micro suction cups are more appropriate, because their dimension is comparable to plant roots.     

Fracht an chemischen Elementen in den Niederschlägen im Solling

Loading of chemical elements in precipitation at the Solling For the period 1969–1976 (NH₄, NO₃: 1971–1976) monthly values of concentrations and flows of the ions NH₄, H, Na, K, Ca, Mg, Fe, Mn, Al, Cl, NO₃, SO₄, P and organic bound N in precipitation are passed on. From the correlations between elements the following main ion sources are concluded: sea water (Na, Cl), combustion processes (SO₄, NO₃, NH₄), lime dust after dissolution by H₂SO₄ and HNO₃ (Ca, Mg), soil dust after dissolution by H₂SO₄ and HNO₃ (Al, Fe), leaching from plants (K, NO₃, SO₄, Mg, Ca), biogenic contaminations (P, organic N, K, NH₄, NO₃). Seasonal variations in the concentrations are most evident for Na and Cl, less for NH₄, SO₄ and NO₃. During the measuring period the flux of NH₄ is significantly increased; for H and SO₄, less for NH₄, Mg, Ca and Fe, the increasing trend was interrupted in winter 1973/74 (oil crisis). Consequences for sampling are discussed.     

Bodenvariabilität und Verhalten von Pflanzenschutzmitteln

Soil variability and pesticide behaviour The spatial variability of selected soil characteristics (organic carbon, particle size), pesticide adsorption and leaching was estimated for an agricultural location. Variograms were calculated to describe the spatial dependence of data. All parameters showed a nearly isotropic behaviour. According to variograms a kriging interpolation was done and the spatial variability of parameters was estimated. Leaching of terbuthylazine was calculated (model PRZM) with regard to soil variability and adsorption pattern (K_d-values). Leaching depth in the winter season varied between 10 and 22 cm depending strictly on soil characteristics.     

Die Abschätzung von Nitratausträgen aus landwirtschaftlichen Nutzflächen mit Hilfe von Nmin-Daten

Development and application of a method for the estimation of nitrate leaching from agricultural land For two locations in the Rhine Valley in the State of Baden- Württemberg research on the nitrate leaching from agricultural fields was carried out. The investigated sites are located on aquifers that are pumped for drinking water. A new procedure was developed in order to estimate the nitrate losses by leaching from the rooting zone of agricultural fields. The procedure uses seepage estimates from a soil water simulation model and measured nitrate contents in the soil. It is found that for both sites large amounts of nitrate are washed out and that high nitrate concentrations occur in the seepage water. The simultaneous use of the investigated areas for intensive agriculture and for drinking water supply is questioned.