Wladimir Bleuten

Release of CO2 and CH4 from small wetland lakes in western Siberia

CO2 and CH4 fluxes were measured from three small wetland lakes located in the middle taiga and forest tundra zones onWest Siberian Lowlands (WSL), the world’s largest wetland area. Fluxes were measured during summer 2005 using floating chambers and were validated against the thin boundary layer model based on the relationship between gas exchange and wind speed. All studied lakes were supersaturated with CO2 and CH4, and acted on a seasonal basis as sources of these greenhouse gases to the atmosphere. Daily mean CO2 fluxes measured with chambers ranged from near the zero to 3.1 g CO2 m-2 d-1 and corresponding CH4 fluxes from 1.1 to 120 mg CH4 m-2 d-1. CH4 ebullition (0.65–11 mg CH4 m-2 d-1) was detected in two of the lakes. Total carbon evasion from the studied lakes during the active season was 23–66 g C m-2, of which more than 90% was released as CO2-C. The carbon loss per unit area from the studied lakes was of similar magnitude as previously reported values of net carbon uptake of Siberian peatlands. This emphasizes the importance of small water-bodies in the carbon balance of West Siberian landscape.

Regular Surface Patterning of Peatlands: Confronting Theory with Field Data

Regular spatial patterns of sharply bounded ridges and hollows are frequently observed in peatlands and ask for an explanation in terms of underlying structuring processes. Simulation models suggest that spatial regularity of peatland patterns could be driven by an evapotranspiration-induced scale-dependent feedback (locally positive, longer-range negative) between ridge vegetation and nutrient availability. The sharp boundaries between ridges and hollows could be induced by a positive feedback between net rate of peat formation and acrotelm thickness. Theory also predicts how scale-dependent and positive feedbacks drive underlying patterns in nutrients, hydrology, and hydrochemistry, but these predictions have not yet been tested empirically. The aim of this study was to provide an empirical test for the theoretical predictions; therefore, we measured underlying patterns in nutrients, hydrology, and hydrochemistry across a maze-patterned peatland in the Great Vasyugan Bog, Siberia. The field data corroborated predicted patterns as induced by scale-dependent feedback; nutrient concentrations were higher on ridges than in hollows. Moreover, diurnal dynamics in water table level clearly corresponded to evapotranspiration and showed that water levels in two ridges were lower than in the hollow in between. Also, the data on hydrochemistry suggested that evapotranspiration rates were higher on ridges. The bimodal frequency distribution in acrotelm thickness indicated sharp boundaries between ridges and hollows, supporting the occurrence of a positive feedback. Moreover, nutrient content in plant tissue was most strongly associated with acrotelm thickness, supporting the view that positive feedback further amplifies ridge–hollow differences in nutrient status. Our measurements are consistent with the hypothesis that the combination of scale-dependent and positive feedback induces peatland patterning.

Hydrological landscape settings of base-rich fen mires and fen meadows: an overview

ABSTRACT Question: Why do similar fen meadow communities occur in different landscapes? How does the hydrological system sustain base-rich fen mires and fen meadows? Location: Interdunal wetlands and heathland pools in The Netherlands, percolation mires in Germany, Poland, and Siberia, and calcareous spring fens in the High Tatra, Slovakia. Methods: This review presents an overview of the hydrological conditions of fen mires and fen meadows that are highly valued in nature conservation due to their high biodiversity and the occurrence of many Red List species. Fen types covered in this review include: (1) small hydrological systems in young calcareous dune areas, and (2) small hydrological systems in decalcified old cover sand areas in The Netherlands; (3) large hydrological systems in river valleys in Central-Europe and western-Siberia, and (4) large hydrological systems of small calcareous spring fens with active precipitation of travertine in mountain areas of Slovakia. Results: Different landscape types can sustain similar nutrient poor and base-rich habitats required by endangered fen meadow species. The hydrological systems of these landscapes are very different in size, but their groundwater flow pattern is remarkably similar. Paleo-ecological research showed that travertine forming fen vegetation types persisted in German lowland percolation mires from 6000 to 3000 BP. Similar vegetation types can still be found in small mountain mires in the Slovak Republic. Small pools in such mires form a cascade of surface water bodies that stimulate travertine formation in various ways. Travertine deposition prevents acidification of the mire and sustains populations of basiphilous species that elsewhere in Europe are highly endangered. Conclusion: Very different hydrological landscape settings can maintain a regular flow of groundwater through the top soil generating similar base-rich site conditions. This is why some fen species occur in very different landscape types, ranging from mineral interdunal wetlands to mountain mires.

Eco-Hydrological Functioning of the Biebrza Wetlands: Lessons for the Conservation and Restoration of Deteriorated Wetlands

Human activities have led to the loss of a large proportion of biodiversity in riverine wetlands in western Europe (Van Urk 1984; Cirujano et al. 1996). In the second half of the twentieth century, many floodplains, fens, and riparian woodlands were cultivated for agricultural purposes. In addition, the remain- ing riverine wetlands lost species due to the impact of human activities (Rich and Woodruff 1996; McCollin et al. 2000). Recently, policy has become more focused on conservation of the remaining wetlands and on rehabilitation of disturbed rivers and floodplains (Jongman 1998). The management and reha- bilitation of wetlands is difficult without adequate knowledge of the hydrolog- ical and ecological processes responsible for the functioning and biodiversity of undisturbed wetlands.

Vegetation characteristics and eco-hydrological processes in a pristine mire in the Ob River valley (Western Siberia)

Relations between vegetation characteristics and eco-hydrological processes were assessed in a pristine mire in the valley of the Ob River (Western Siberia). Along a transect from the terrace scarp to the river, field data were collected on vegetation composition, peat stratigraphy, peat chemistry, hydrology and hydrochemistry. Based on floristic composition, eight vegetation communities were distinguished. Hydraulic head measurements were used to obtain an indication of groundwater flow directions. The water balance of the mire was calculated with a two-dimensional steady-state numerical groundwater model. Water types were defined based on cluster analysis of hydrochemical data. The results revealed that the dominant hydrological factor in the Ob mire is the discharge of groundwater, which supplies about threefold more water than net precipitation. Although the discharge flux decreases with increasing distance from the terrace scarp, high water levels and a “groundwater-like” mire water composition were observed in the major part of the study site. Precipitation and river water play only a minor role. Despite dilution of discharging groundwater with rainwater, spatial differences in pH and solute concentrations of the surficial mire water are small and not reflected in the vegetation composition. Although small amounts of silt and clay were found in the peat in the proximity of the river, indicating the occurrence of river floods in former times, no river-flood zone could be recognized based on hydrochemical characteristics or vegetation composition. A comparison of the Ob mire with well-studied and near-natural mires in the Biebrza River valley (Poland) revealed substantial differences in both vegetation characteristics and the intensity and spatial pattern of eco-hydrological processes. Differences in the origin and ratios of water fluxes as well as a dissimilar land use history would seem to be key factors explaining the differences observed.

Hydrological Processes, Nutrient Flows and Patterns of Fens and Bogs

The total area of northern peatland has been estimated to be 5.8 ¥ 106 km2 (Table 9.1) A great deal, particularly in Europe, has been drained for agriculture, forestry, housing and other human use. The ability of wet, pristine peatland (mires) to accumulate atmospheric carbon, to clean water and to buffer river floods and their values of characteristic biodiversity urges for conservation action and the restoration (rewetting) of drained peatland. Hydro-ecological field data from pristine mire ecosystems will enhance modeling approaches for the prediction of effective water and land use management aimed at mire conservation and restoration. The scarce information on pristine mires leads to unjustified negative opinions and sometimes even biased scientific results. For an estimation of the world surface area of peatland, most publications refer to the data compiled by Gorham (1991). This leads to the effect that the importance of Russian peatland is strongly underestimated in climate change modeling, i.e. the depletion of atmospheric carbon by terrestrial sinks is much larger because the surface area of Russian peatland is about double the size of 1.5 ¥ 106 km2 given by Gorham (1991). Merely in Western Siberia, the surface area of peatlands is more then 1 ¥ 106 km2 (Yefremov and Yefremova 2001). Further,more then 90% of the Russian peatland is still unaffected by draining activities and is sequestering atmospheric carbon. Most of the bogs and fens in other regions have been drained by human activities aimed at lowering the groundwater table, extracting the groundwater for water supply and irrigation, regulating the river channel and discharge, etc. and can be designated today as former mires or peatland. In Europe and