Jutta Zeitz

Soil properties of drained and rewetted fen soils

The intensive agricultural use and consequently the drainage of fen soils have caused modifications in structure and nutrient dynamics. Pedogenetic processes result in the formation of typical soil horizons with distinctive soil properties. These are the basis for soil classification. In the present review, results are compiled. Modifications of abiotic and biotic parameters of fen soils due to drainage and rewetting are presented. Recommendations on the further use of fen soils are submitted. Bodeneigenschaften von entwasserten und wieder vernassten Niedermooren Intensive landwirtschaftliche Nutzung von Niedermooren mit einhergehender Entwasserung rufen eine starke Veranderung in der Gefuge- und Nahrstoffdynamik hervor. Pedogenetische Prozesse fuhren zur Ausbildung von typischen Bodenhorizonten mit bestimmten Eigenschaften. Eine Klassifikation bezuglich der Pedogenese wird dadurch moglich. Der Beitrag gibt einen Uberblick zu den Forschungsergebnissen. Es werden Veranderungen abiotischer und biotischer Bodenparameter von Niedermooren durch Entwasserung und Wiedervernassung aufgezeigt und Vorschlage zum weiteren Umgang mit Niedermooren unterbreitet.

Stability of soil organic matter in two northeastern German fen soils: the influence of site and soil development

PurposePeatland soils play an important role in the global carbon (C) cycle due to their high organic carbon content. Lowering of the water table e.g. for agricultural use accelerates aerobic secondary peat decomposition and processes of earthification. Peatlands change from C sinks to C sources. We characterized soil organic matter (SOM) with special attention to human impact through drainage. Our aim was to gain knowledge of SOM quality and soil-forming processes in drained fen soils in northeastern Germany.Materials and methodsThrough techniques of representative landscape analysis, we identified two typical and representative sampling sites in different stages of land use, representing the most important hydrogenetic mire types in northeastern Germany. We adapted chemical fractionation procedures which include hot water extraction (Chwe and Nhwe) for determination of the labile fraction. Furthermore, a stepwise acid hydrolysis procedure was performed to measure the chemical recalcitrant part of SOM as it is more resistant to biodegradability.Results and discussionTotal organic C decreased with increasing human impact and intensity of drainage. Conversely, Chwe and Nhwe concentrations increased with increasing drainage and human impact. In contrast, the more recalcitrant fractions increased with soil depth.ConclusionsGenerally, there is a lack of existing data about SOM quality and the factors controlling its stability and decomposition in fen soils. For northeastern German fen soils, the data are even more inadequate. Influence of drainage seems to overlap natural influences of site on SOM quality. The used extraction scheme was suitable for the chemical fractionation of SOM into labile and more recalcitrant parts.

A framework for assessing agricultural soil quality on a global scale

This paper provides information about a novel approach of rating agricultural soil quality (SQ) and crop yield potentials consistently over a range of spatial scales. The Muencheberg Soil Quality Rating is an indicator-based straightforward overall assessment method of agricultural SQ. It is a framework covering aspects of soil texture, structure, topography and climate which is based on 8 basic indicators and more than 12 hazard indicators. Ratings are performed by visual methods of soil evaluation. A field manual is then used to provide ratings from tables based on indicator thresholds. Finally, overall rating scores are given, ranging from 0 (worst) to 100 (best) to characterise crop yield potentials. The current approach is valid for grassland and cropland. Field tests in several countries confirmed the practicability and reliability of the method. At field scale, soil structure is a crucial, management induced criterion of agricultural SQ. At the global scale, climate controlled hazard indicators of drought risk and soil thermal regime are crucial for SQ and crop yield potentials. Final rating scores are well correlated with crop yields. We conclude that this system could be evolved for ranking and controlling agricultural SQ on a global scale.

Physical and hydrological properties of peatland substrates from different hydrogenetic wetland types on the Maputaland Coastal Plain, South Africa

The Maputaland Coastal Plain in KwaZulu-Natal province is home to 60% of all peatlands occurring in South Africa. These ecosystems are increasingly threatened by unsustainable agricultural utilisation, a growing population and climate change. The aim of the study was, therefore, to investigate wetland type characteristic substrates and their physical properties in order to provide more detailed knowledge about the agricultural impact on them. Six study sites were selected and detailed profile descriptions as well as in situ measurements of different physical and hydrological soil parameters were conducted. Soil samples were analysed with laboratory measurements of the saturated hydraulic conductivity, water retention characteristics and hydrophobicity. In addition, the bulk density as well as the organic carbon content were determined. Saturated hydraulic conductivity, hydrophobicity and total water retention capacity were highest for peat derived from wood, which furthermore presented the lowest bulk densities and was found to occur only in channelled and unchannelled valley-bottom wetlands and was absent in interdunal depression wetlands. It was concluded that drainage and clearance of forested valley-bottom wetlands has severe impacts on the physical peat properties. Potential subsidence of low-density peat and consolidation aggravate the danger of flooding and hydrophobicity increases the generation of surface runoff and subsequently the risk of erosion.

Greenhouse gas fluxes during rewetting of peatlands by use of effluents – a lysimeter study

Abstract The present study aims at assessing the effect of using the effluent of a wastewater treatment plant as an alternative measure for rewetting nutrient-rich fen soils over the growing season on the emission of greenhouse gas (GHG) and at discussing possible changes in the greenhouse potential as a result of this practice. In order to allow a discussion on GHG based on integrated CH4, N2O, and CO2 flux rates, fluxes were measured in our lysimeter study using the chamber methodology from May to December in 2003 and 2004. The study compares the gaseous fluxes of fen soils in lysimeters treated with the effluent and/or freshwater for rewetting. Only freshwater was applied to the control lysimeter. The source of water hardly had any statistically significant effect on trace gas fluxes. However, there was a trend towards higher CH4 emissions at the effluent lysimeters compared to the control lysimeter. Effluent usage did not decrease the greenhouse effect at the same rate, which could be observed at the control. Nevertheless, regarding gaseous emissions the use of effluents could prove to be a solution to the current problem of todays major peat oxidation and fen soil loss by drainage.

The development pathways of two peatlands in South Africa over the last 6200 years: Implications for peat formation and palaeoclimatic research:

For the first time, plant macrofossil analysis supported by detailed stratigraphic studies was used to reconstruct peatland development in South Africa. Two peat cores (4.69 and 1.5 m) from two coastal peatlands in KwaZulu-Natal were analysed for carpological macrofossils, wood and macrocharcoal. The first one, Matitimani, is an unchannelled valley bottom peatland (site VB), and the second one, KwaMazambane, an interdune depression peatland (site ID) further up in the same catchment. Radiocarbon dating reveals the peatland initiation at site VB at about 6260 cal. yr BP. Rising sea level and humid climatic conditions during that time coincide with the formation of organic gyttja (dominantly aquatic seeds like Nymphaea sp.). In ca. 4950 cal. yr BP, a change to drier condition took place, revealed by the formation of radicell peat from Cyperaceae, and an increase of fire frequency (macrocharcoal). After ca. 1200 cal. yr BP, peat swamp forest emerged, with Ficus trichopoda, Syzygium cordatum and Voacanga thouarsii forming wood peat. Site ID dates back to ca. 920 cal. yr BP. Its initiation is assumingly related to reduced drainage capacities of the catchment subsequently to the peat formation in Matitimani valley. A steady change from gyttja forming communities (Nymphaea sp.–Eleocharis dulcis) to radicell peat-forming Cyperaceae communities took place. The long-term apparent rate of carbon accumulation (LORCA) is higher for site ID (89 gC m−2 yr−1) than for site VB (55 gC m−2 yr−1). Except for the peat swamp forest period, fire occurred frequently at both sites, however less in environments with frequent inundations.

Einfluss differenzierter organisch-mineralischer Düngung auf die partikuläre organische Substanz des Bodens

Zusammenfassung Im Internationalen Organischen Stickstoff-Dauerdüngungs-Versuch (IOSDV) am Standort Berlin-Dahlem wurden nach 20 Versuchsjahren chemische und physikalische Untersuchungen der organischen Bodensubstanz durchgeführt. Die langjährig differenzierte organisch-mineralische Düngung hat die Gehalte an organischem sowie heißwasserlöslichem Kohlenstoff und Gesamtstickstoff signifikant beeinflusst. Auf physikalischem Wege wurden die organischen Bestandteile des Bodens in eine leichte, mittlere und schwere Fraktion getrennt. Die Ergebnisse zeigen ein anderes Bild als die chemische Analyse. Mineralische Stickstoffdüngung und die kombinierte organische Düngung von Stroh, Rübenblatt und Zwischenfruchtgrünmasse führten im Vergleich zur ungedüngten Kontrolle zu signifikant höheren Gehalten der leichten Fraktion (LF). Stallmistdüngung beeinflusste demgegenüber die Gehalte der schweren Fraktion (SF) positiv. Stroh-, Rübenblatt- und Gründüngung erhöhten den Gehalt der schweren Fraktion nur bei gleichzeitiger mineralischer Stickstoffdüngung. Alleinige Mineralstickstoffdüngung veränderte die schwere Fraktion hingegen nicht. Mit den Fraktionen der partikulären organischen Substanz werden andere Bestandteile der organischen Bodensubstanz erfasst als bei der chemischen Humusanalyse. Somit können zusätzliche Informationen zur Beschaffenheit der organischen Bodensubstanz gewonnen werden.

Peatland substrates in northern KwaZulu-Natal: a study of the forming environments, properties and an approach towards classification

Peatlands in South Africa are rare and fulfil important ecological functions but are threatened by degradation. Because of this peatlands have gained increasing attention from scientists during the last two decades. However, knowledge of the peatland substrates and the means to classify them is limited. This study was conducted in peatlands of the Maputaland Coastal Plain. The approach uses the German Soil Mapping directive ‘KA5’, which acknowledges the accumulation process of substrates and botanical peat types. The aims were to investigate which substrates occur, whether these have affinities to certain hydrogeomorphic wetland types (HGMTs), and to determine the physical and chemical properties. Seven peatlands in five different HGMTs were investigated along 19 transects with 141 soil profiles and 674 horizons. In total 15 different peatland substrates were encountered and characterised, amongst them raphia peat, ficus peat and peat-gyttja, which have not been described previously. Mean values were determined for organic matter content, bulk density, degree of decomposition, porosity, pH and carbon/nitrogen ratio. A substrate reference scheme was also developed and classifies the encountered substrates with respect to their occurrence in HGMTs.

Application and Verification of Techniques for Visually Assessing Pasture Conditions in Mountainous Terrain: A Test of Three Field Assessment Methods in the Kyrgyz Republic

The objective of this study was to determine a reliable and effective way to visually assess pastures under the site conditions that prevail in the Kyrgyz Republic, in particular the mountainous terrain. Such a method should make a visual evaluation of pasture conditions in the field possible and help build awareness among land users of soil and pasture degradation and the need for sustainable use of pasture areas. To this end, the Visual Soil Assessment (VSA) method was applied and verified in a research area in the Naryn district in the Kyrgyz Republic. This process included the application of 2 additional visual site assessment methods—the Muencheberg Soil Quality Rating and the method described in the Monitoring Manual for Summer Pastures in the Greater Caucasus in Azerbaijan by Etzold and Neudert in 2010, referred to subsequently as the MMSP method. A comparison of the VSA results to standard field measurements and laboratory-based analysis was also performed. The VSA method was found to be only moderately applicable under the site conditions, with low correlation between the indicator ratings and the results of the standard measurements. The MMSP method showed substantially better applicability. The results of the study suggest that further research is needed to refine the MMSP method to develop an effective visual assessment method that can be used to support sustainable use and protection of pasture areas in mountain regions.

Erarbeitung einer methode zur verwendung von altdaten der moore für die kennzeichnung von flächenbodenformen

Die Bewertung von Bodenfunktionen in Mooren ist derzeitig aufgrund fehlender Bewertungsmethoden als auch Bewertungsparameter nur unbefriedigend möglich. Das Ziel der Forschungsarbeit war die Erarbeitung einer Methode, vorhandene Altdaten für die Kennzeichnung von Flächenbodenformen in Bodenkarten so aufzubereiten, dass Idealprofile mit entsprechenden Datensätzen für die Bewertung von Bodenfunktionen bereitgestellt werden können. Zur Auswertung kamen folgende Materialien: Datensätze von verschiedenen hydrologisch‐genetischen Moortypen mit Informationen zur Stratigraphie, Art der Torfe und Mudden, Zersetzungsgrad, Tiefe der Substratwechsel, wesentliche physikalische und hydrologische Bodenkennwerte sowie digitalisierte Bodenkarten 1:25000. Die entwickelte Methode stellt eine Abfolgevorschrift mit Zuordnungsregeln dar. Informationen über den hydrologisch‐genetischen Moortyp und die Art der liegenden Schicht ermöglichen eine Vorhersage des Bodensubtyps. Zwei Stufen der Bodenentwicklung wurden beschrieben: vererdetes und vermulmtes Niedermoor. Unter Verwendung von Verknüpfungsregeln und Expertwissen ist es möglich, Idealprofile für Flächenbodenformen inhaltlich zu beschreiben. Durch Zuordnung von GIS‐Karten können dann Bodenfunktionen für definierte Flächen bewertet werden.