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The application of electrical resistivity tomography to peatlands supports conventional coring by providing data on the current condition of peatlands, including data on stratigraphy, peat properties and thickness of organic deposits. Data on the current condition of drained peatlands are particularly required to improve estimates of carbon storage as well as losses and emissions from agriculturally used peatlands. However, most of the studies focusing on electrical resistivity tomography surveys have been conducted on natural peatlands with higher groundwater levels. Peatlands drained for agriculture have not often been studied using geophysical techniques. Drained sites are characterized by low groundwater levels and high groundwater fluctuations during the year, which lead to varying levels of water saturation. To validate better electrical resistivity tomography surveys of drained peatlands, the aim of this laboratory study is to investigate the influence of varying water saturation levels on electrical conductivity (reciprocal of resistivity) for a variety of peat and gyttja types, as well as for different degrees of peat decomposition. Results show that different levels of water saturation strongly influence bulk electrical conductivity. Distinct differences in this relationship exist between peat and gyttja substrates and between different degrees of peat decomposition. Peat shows an exponential relationship for all degrees of decomposition, whereas gyttja, in particular organic‐rich gyttja, is characterized by a rather unimodal relationship. The slopes for the relationship between electrical conductivity and water content are steeper at high degrees of decomposition than for peat of low degrees of decomposition. These results have direct implications for field electrical resistivity tomography surveys. In drained peatlands that are strongly susceptible to drying, electrical resistivity tomography surveys have a high potential to monitor the actual field water content. In addition, at comparable water saturations, high or low degrees of decomposition can be inferred from electrical conductivity.

According to the German Soil Taxonomy, the formation of cemented horizons in Podzols is restricted to the precipitation of iron oxides. However, in iron-poor sandy substrates, also illuviation of only organic compounds can form cemented horizons with penetration resistances of up to 14 kg cm−2. We present a reproducible field test for classifying pedogenic cementation in Podzols and suggest considering cemented horizons (Bmh and Bhm) in the upcoming edition of the Guidelines for Soil Mapping.

Summary Peatlands store large amounts of carbon. This storage function has been reduced through intensive drainage, which leads to the decomposition of peat, resulting in a loss of carbon. Measurements of the real (σ′) and imaginary part (σ″) of electrical conductivity can deliver information on peat properties, such as the pore fluid conductivity (σw), cation exchange capacity (CEC), bulk density (ρb), water content (WC) and soil organic matter (SOM) content. These properties change with the peat's degree of decomposition (DD). To explore the relationships between the peat properties, σ′, σ″ and DD, we focused on three different types of survey and scales. First, point measurements were made with a conductivity probe at various locations over a large area of northeast Germany to determine the degree of correlation between σ′ and DD. Second, nine of these locations were selected for sampling to determine which of the properties σw, CEC, ρb, WC and SOM predominantly influence σ′ and σ″. This multisite dataset includes the entire range of DD and was analysed in the laboratory. Third, one site was selected for a survey of σ′ including sampling, to identify which properties mainly control σ′ in a single-site approach. Statistical analysis revealed that for the multisite laboratory dataset, σw has the strongest effect on σ′, followed by CEC, whereas σ″ is mainly determined by CEC. In a single-site approach, WC followed by CEC had a dominant effect on σ′. No clear correlation could be observed between (i) DD and peat properties and (ii) DD and σ′ or σ″. This is because of the complex changes in properties with increasing DD.

Fahlerden dominate large areas of the young and old moraine landscapes of N and E Germany. Fahlerden (part of Fahlerden corresponds to Albeluvisols) and their transitional subtypes are supposed to have a higher intensity of clay illuviation than Parabraunerden (Luvisols). Besides this macroscopic feature reflecting periglacial influence, micromorphological features such as lenticular platy microstructure, vesicles, and fragments of clay coatings in Bt streaks document the initiation of Fahlerde genesis, which began in the Late Glacial. A model of Fahlerde genesis chronologically connects sedimentological and periglacial processes, vegetation development, and soil-forming processes like decalcification, clay illuviation, and humification. The classification criterion of larger differences in clay contents between E and Bt horizons to distinguish Fahlerden from Parabraunerden needs to be reconsidered, because most Fahlerden have developed in stratified parent material in periglacially influenced landscapes. The interpretation of a soil data base listing data of both soil types distributed in Brandenburg demonstrates that the difference in clay contents between E and Bt horizons may even be smaller in Fahlerden than in Parabraunerden.