Die Datenbestände der im LfULG verfügbaren Stoffdaten von Böden (Messnetze, Sondermessnetze, Auenmessprogramm, Bodenkundliche Landesaufnahme, Fremddaten) werden in geochemischen Übersichtskarten im Maßstab 1:400.000 als Rasterdaten dargestellt. Für die Oberböden liegen Probendaten von über 15.000, für die Unterböden von über 12.000 Standorten vor.
Verdichtungsempfindlichkeit des Unterboden unter typischen Bedingungen des Ackerbaus im Winter, d.h. im langjährigen Durchschnitt (1975-2005) für den Zeitraum Oktober bis April. Die Klassifikation reicht von sehr geringer bis sehr hoher Verdichtungsempfindlichkeit. Bodenverdichtungen sind bereits seit längerem ein Problem des Bodenschutzes, das durch den Einsatz von immer schwereren Maschinen vor allem in der Landwirtschaft und in der Bauwirtschaft verschärft wird. Diese Karten können als Instrument des vorsorgenden Bodenschutzes z. B. die Frage beantworten, ob ein Erntetransport, der im Juli/August relativ risikolos war, im Oktober bereits ein hohes Risiko für Bodenschadverdichtungen birgt. Um möglichst viele Fragestellungen mit verschiedenem räumlichen Bezug zu bedienen, stehen Karten in sechs verschiedene Maßstabsebenen bereit: 1 : 2.000 für die konkrete Landbewirtschaftung oder Bauausführung vor Ort oder für eine hochaufgelöste Planung 1 : 10.000 für eine parzellenscharfe Planung 1 : 25.000 für Planungen auf Gemeindeebene 1 : 100.000 für Planungen in größeren Regionen 1 : 250.000 für eine landesweit differenzierte Planung 1 : 1000.000 für eine landesweite bis bundesweite Planung Weitere Kartenserien zur potentielle Verdichtungsempfindlichkeit existieren für den Zeitraum Oktober- April sowie für die Grünlandnutzung.
Magnetic resonance tomography (MRT) on microcosm soil cores (200 mm Ø) used for CeMiX, comprising naturally stacked subsoil down to 700 mm plus topsoil from CeFiT, will be implemented at a laterally partially open Split 1.5 T magnet, with intended final in-plane spatial resolution of 200 Micro m. Three-dimensional biopore distributions and dynamics of their formation within the cores will be determined non-invasively and compared to complementing CT analyses of SP 2. One major aim is a non-invasive differentiation of the biopores into earthworm- and root system-originating ones and currently air-, water-, root- and earthwormfilled ones, based on NMR relaxation parameters. Attempts will additionally be made to classify different wall coatings of the biopores with regard to their water affinity. Dynamics of water distribution within the microcosm core and its biopore structures, starting from initial values taken from CeFiT (SP 3), will be documented with an in-plane resolution of 5 mm, in parallel to measurements of root growth dynamics for calculation of biomass and root surface area. Special emphasis will be put on the role of the plant root system for a re-distribution of water/D2O (and solutes) between different soil layers. Finally we will attempt MRT-controlled sample collection from the microcosm cores, to get - together with our research unit partners of SPs 4-8 - repeated access to minimally invasively acquired data on nutrient and microorganism distributions in concert with non-invasively collected water and root distribution data as a basis for dynamic modelling of water and solute circuits in SP 10. Beside the microcosm cores, flat rhizotrons as used in SP 3 will be employed to enable measurements of root and shoot hydrostatic pressure profiles with pressure probes, in addition to MRT measurements. In this way water distributions and corresponding driving forces and growth dynamics will be measured altogether in a minimally invasive manner.
Subsoils are an often neglected nutrient source for crops. The mobilisation and use of this potential nutrient source is an important factor in sustainable land use. Nutrient accessibility, release, and transport are strongly dependent on soil structure and its dynamics controlled by spatiotemporally variable physical functions of the pore network. A well structured soil, for example, with numerous interconnected continuous biopores will enhance root growth and oxygen availability and hence nutrient acquisition. In contrast to soils with a poorly developed structure nutrient acquisition is limited by restricted root growth and reduced aeration. The goal of this research project is to investigate different preceding crops and crop sequences in developing characteristic biopore systems in the subsoil and to elaborate their effect on the functional performance of pore networks with respect to nutrient acquisition. The main research question in this context is how soil structure evolves during cultivation of different plant species and how structure formation influences the interaction of physical (water and oxygen transport, shrinking-swelling) biological (microbial activity, root growth) and geochemical processes (e.g. by creating new accessible reaction interfaces). In order to study and quantify pore network architectures non-invasively and in three dimensions X-ray computed microtomography and 3D image analysis algorithms will be employed. The results will be correlated with small- and mesoscale physical/chemical properties obtained from in situ microsensor (oxygen partial pressure, redox potential, oxygen diffusion rate) and bulk soil measurements (transport functions, stress-strain relationships) of the same samples. This will further our process understanding regarding the ability of various crop sequences to form biopore systems which enhance nutrient acquisition from the subsoil by generating pore network architectures with an efficient interaction of physical, biological and geochemical processes.
Most soils develop distinct soil architecture during pedogenesis and soil organic carbon (SOC) is sequestered within a hierarchical system of mineral-organic associations and aggregates. Permafrost soils store large amounts of carbon due to their permanently frozen subsoil and a lack of oxygen in the active layer, but they lack complex soil structure. With permafrost thaw more oxidative conditions and increasing soil temperature presumably enhance the build-up of more complex units of soil architecture and may counterbalance, at least partly, SOC mineralization. We aim to explore the development of mineral-organic associations and aggregates under different permafrost impact with respect to SOC stabilization. This information will be linked to environmental control factors relevant for SOC turnover at the pedon and stand scale to bridge processes occurring at the aggregate scale to larger spatial dimensions. We will combine in situ spectroscopic techniques with fractionation approaches and identify mechanisms relevant for SOC turnover at different scales by multivariate statistics and variogram analyses. From this we expect a deeper knowledge about soil architecture formation in the transition of permafrost soils to terrestrial soils and a scale-spanning mechanistic understanding of SOC cycling in permafrost regions.
Dissolved organic matter (DOM) is one major source of subsoil organic matter (OM). P5 aims at quantifying the impact of DOM input, transport, and transformation to the OC storage in the subsoil environment. The central hypotheses of this proposal are that in matric soil the increasing 14C age of organic carbon (OC) with soil depth is due to a cascade effect, thus, leading to old OC in young subsoil, whereas within preferential flowpaths sorptive stabilization is weak, and young and bioa-vailable DOM is translocated to the subsoil at high quantities. These hypotheses will be tested by a combination of DOC flux measurements with the comparative analysis of the composition and the turnover of DOM and mineral-associated OM. The work programme utilizes a DOM monitoring at the Grinderwald subsoil observatory, supplemented by defined experiments under field and labora-tory conditions, and laboratory DOM leaching experiments on soils of regional variability. A central aspect of the experiments is the link of a 13C-leaf litter labelling experiment to the 14C age of DOM and OM. With that P5 contributes to the grand goal of the research unit and addresses the general hypotheses that subsoil OM largely consists of displaced and old OM from overlying horizons, the sorption capacity of DOM and the pool size of mineral-associated OM are controlled by interaction with minerals, and that preferential flowpaths represent 'hot spots' of high substrate availability.
For surface soils, the mechanisms controlling soil organic C turnover have been thoroughly investigated. The database on subsoil C dynamics, however, is scarce, although greater than 50 percent of SOC stocks are stored in deeper soil horizons. The transfer of results obtained from surface soil studies to deeper soil horizons is limited, because soil organic matter (SOM) in deeper soil layers is exposed to contrasting environmental conditions (e.g. more constant temperature and moisture regime, higher CO2 and lower O2 concentrations, increasing N and P limitation to C mineralization with soil depth) and differs in composition compared to SOM of the surface layer, which in turn entails differences in its decomposition. For a quantitative analysis of subsoil SOC dynamics, it is necessary to trace the origins of the soil organic compounds and the pathways of their transformations. Since SOM is composed of various C pools which turn over on different time scales, from hours to millennia, bulk measurements do not reflect the response of specific pools to both transient and long-term change and may significantly underestimate CO2 fluxes. More detailed information can be gained from the fractionation of subsoil SOM into different functional pools in combination with the use of stable and radioactive isotopes. Additionally, soil-respired CO2 isotopic signatures can be used to understand the role of environmental factors on the rate of SOM decomposition and the magnitude and source of CO2 fluxes. The aims of this study are to (i) determine CO2 production and subsoil C mineralization in situ, (ii) investigate the vertical distribution and origin of CO2 in the soil profile using 14CO2 and 13CO2 analyses in the Grinderwald, and to (iii) determine the effect of environmental controls (temperature, oxygen) on subsoil C turnover. We hypothesize that in-situ CO2 production in subsoils is mainly controlled by root distribution and activity and that CO2 produced in deeper soil depth derives to a large part from the mineralization of fresh root derived C inputs. Further, we hypothesize that a large part of the subsoil C is potentially degradable, but is mineralized slower compared with the surface soil due to possible temperature or oxygen limitation.
It is well established that reduced supply of fresh organic matter, interactions of organic matter with mineral phases and spatial inaccessibility affect C stocks in subsoils. However, quantitative information required for a better understanding of the contribution of each of the different processes to C sequestration in subsoils and for improvements of subsoil C models is scarce. The same is true for the main controlling factors of the decomposition rates of soil organic matter in subsoils. Moreover, information on spatial variabilities of different properties in the subsoil is rare. The few studies available which couple near and middle infrared spectroscopy (NIRS/MIRS) with geostatistical approaches indicate a potential for the creation of spatial maps which may show hot spots with increased biological activities in the soil profile and their effects on the distribution of C contents. Objectives are (i) to determine the mean residence time of subsoil C in different fractions by applying fractionation procedures in combination with 14C measurements; (ii) to study the effects of water content, input of 13C-labelled roots and dissolved organic matter and spatial inaccessibility on C turnover in an automatic microcosm system; (iii) to determine general soil properties and soil biological and chemical characteristics using NIRS and MIRS, and (iv) to extrapolate the measured and estimated soil properties to the vertical profiles by using different spatial interpolation techniques. For the NIRS/MIRS applications, sample pretreatment (air-dried vs. freeze-dried samples) and calibration procedures (a modified partial least square (MPLS) approach vs. a genetic algorithm coupled with MPLS or PLS) will be optimized. We hypothesize that the combined application of chemical fractionation in combination with 14C measurements and the results of the incubation experiments will give the pool sizes of passive, intermediate, labile and very labile C and N and the mean residence times of labile and very labile C and N. These results will make it possible to initialize the new quantitative model to be developed by subproject PC. Additionally, we hypothesize that the sample pretreatment 'freeze-drying' will be more useful for the estimation of soil biological characteristics than air-drying. The GA-MPLS and GA-PLS approaches are expected to give better estimates of the soil characteristics than the MPLS and PLS approaches. The spatial maps for the different subsoil characteristics in combination with the spatial maps of temperature and water contents will presumably enable us to explain the spatial heterogeneity of C contents.
Der Datensatz beinhaltet Daten vom LBGR über die relative Bindungsstärke für Schwermetalle für den grundwasserfreien Bodenraum Brandenburgs und wird über je einen Darstellungs- und Downloaddienst bereitgestellt. Diese Karte basiert auf den Legendeneinheiten der Bodenübersichtskarte mit entsprechender Zuordnung von parametrisierten Flächenbodenformen. Diese stellen je Legendeneinheit eine Bodenformengesellschaft dar. Die einzelnen (Flächen-)Bodenformen wurden mit Parametern belegt, auch jenen zur Berechung der Bindungsstärke für Schwermetalle (s. Hennings 2000, Kap. 2), die durch Gelände- und Laboruntersuchungen bestimmt wurden. Dazu wurden für gleiche Horizont-Substrat-Kombinationen die entsprechenden Parameter (Bodenart, Humusgehalt, pH-Wert) statistisch abgeleitet (i.d.R. der Medianwert). Die Abfolge von Horizont-Substrat-Kombinationen in den Flächenbodenformen mit ihren Parametern (Bodenart, Humusgehalt, pH-Wert, Obergrenze des Go-Horizontes) bildeten die Grundlage für die Berechnung der relativen Bindungsstärke gegenüber Schwermetallen (s. Hennings 2000, Verknüpfungsregel 7.1 bis 7.3). Die folgenden Themenkarten weisen jeweils für die Schwermetalle Fe(III), Hg, Pb, Cr(III), Cu, Al, Zn, Co, Ni, Cd und Mn die metallspezifische relative Bindungsstärke für verschiedene Tiefenbereiche aus. Diese Karte stellt die relative Bindungsstärke für das jeweilige Schwermetall im grundwasserfreien Bodenraum bzw. bis zur Obergrenze eines Go-Horizontes oder bis 2 m unter GOF für die beteiligten Flächenbodenformen dar. Dazu werden Oberboden (einschließlich der Auflagehorizonte bis 3 dm unter GOF) und Unterboden getrennt behandelt. Für den Oberboden wird der Kennwert wie oben bis zum Schritt der Ordinalskalierung ermittelt. Für den Kennwert des folgenden Tiefenbereiches bis 2 m unter GOF bzw. bis zur Obergrenze des Go-Horizontes je Bodenform wird der Horizont mit der höchsten pH-abhängigen Bindungsstärke betrachtet, wenn dieser > 3 dm mächtig ist. Anderenfalls wird von dem unmittelbar hangenden bzw. liegenden Horizont derjenige nach seiner Mächtigkeit gewichtet zur Mittelung des Kennwertes herangezogen, der von diesen beiden Horizonten die höhere pH-abhängige Bindungsstärke aufweist. Anschließend werden Zuschläge für entsprechende Humus- und Tongehalte hinzugerechnet. Die so ermittelten Kennwerte für Ober- und Unterboden werden addiert und ordinal in den Stufen 0 bis 5 skaliert, wobei der maximale Wert auf 5 begrenzt wird. Bei unterschiedlichen Ergebnissen für die Bodenformen einer Legendeneinheit wurden die flächenhaft dominierenden und die subdominierenden ordinal skalierten klassifizierten Kennwerte angegeben (s. Hennings 2000, VKR 7.3).
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