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

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

PEAT-CLSM : A Specific Treatment of Peatland Hydrology in the NASA Catchment Land Surface Model

Peatlands are poorly represented in global Earth system modeling frameworks. Here we add a peatland-specific land surface hydrology module (PEAT-CLSM) to the Catchment Land Surface Model (CLSM) of the NASA Goddard Earth Observing System (GEOS) framework. The amended TOPMODEL approach of the original CLSM that uses topography characteristics to model catchment processes is discarded, and a peatland-specific model concept is realized in its place. To facilitate its utilization in operational GEOS efforts, PEAT-CLSM uses the basic structure of CLSM and the same global input data. Parameters used in PEAT-CLSM are based on literature data. A suite of CLSM and PEAT-CLSM simulations for peatland areas between 40 degrees N and 75 degrees N is presented and evaluated against a newly compiled data set of groundwater table depth and eddy covariance observations of latent and sensible heat fluxes in natural and seminatural peatlands. CLSM's simulated groundwater tables are too deep and variable, whereas PEAT-CLSM simulates a mean groundwater table depth of -0.20 m (snow-free unfrozen period) with moderate temporal fluctuations (standard deviation of 0.10 m), in significantly better agreement with in situ observations. Relative to an operational CLSM version that simply includes peat as a soil class, the temporal correlation coefficient is increased on average by 0.16 and reaches 0.64 for bogs and 0.66 for fens when driven with global atmospheric forcing data. In PEAT-CLSM, runoff is increased on average by 38% and evapotranspiration is reduced by 19%. The evapotranspiration reduction constitutes a significant improvement relative to eddy covariance measurements.Peer reviewe

A method for the separation of total discharge into base flow, overland flow and channel precipitation for water quality modelling of a small watershed in the Netherlands

For surface water quality modelling all contributing discharges, each with different loads of dissolved matter have to be considered separately. Apart from physical and (bio)chemical interactions, water quality is the result of all inputs, both in volume and mass. For this reason dynamic modelling of water quality is possible only when the processes leading to the temporal variability for each different type of input can be modelled as well. In the Netherlands almost all inland watersheds discharge considerable amounts of groundwater. During storm events however, surface runoff is an important factor even in these flat areas. Other discharge sources to be modelled are channel precipitation and effluent discharges. A dynamic one-dimensional numeric discharge model has been developed for a catchment area in the central part of the Netherlands, with distinct subareas where infiltration or seepage is dominant. Model output is dayly discharge of the three most important discharge components (groundwater discharge, overland flow and channel precipitation) and total catchment outflow. From these components groundwater discharge has been calculated using recorded levels of groundwater and surface water. Because precipitation volumes per day can be computed from meteorological data and surface water area, and effluent discharges usually are well known, overland flow discharge modelling was possible

The production and use of nitrate and phosphate in agriculture and their consequences on regional groundwater quality

The one-dimensional quantitative model MANRUU has been developed for the purpose of physical planning on a national level to calculate the overproduction of nitrogen and phosphorus in animal manure per municipality. MANRUU calculates total manure production per municipality from input data on animal-specific manure production (kg N, P2O5 per year), fertilizer use and the number of animals of various categories. Data on crop-specific fertilizer demand and on acreage of all crops grown are used to calculate the maximum amount of manure per municipality applicable from an environmental point of view. The two-dimensional model WATRUU calculates mean concentrations of nitrate and ortho-phosphate in shallow groundwater for catchment areas. It uses the output of the model MANRUU and realistic assumptions on conversion processes of nitrate and phosphate. By using watersheds, an indication can be given of the flow direction and spatial effects of the polluted shallow groundwater. The results of the calculations are displayed as maps, based on input data for 1983. Computed mean nitrate concentrations are up to 16 times in excess of the EC-standards for drinking water. Phosphate saturation down to the groundwater level is expected to occur in the soil of 145,000 ha of farming land within 25 years when no preventative measures are taken. The model results were compared with data from a detailed study of the quality of the top groundwater layer in the entire Province of Utrecht. The comparison was found to be reliable at a confidence level of 95%

West Siberian peatlands: comparative study of greenhouse gas emission in middle taiga and forest tundra climatic conditions

The study of CO2 and CH4 gas emission was carried out in two contrast bioclimatic sub-zones in the north provinces of Western Siberia. Three year measurements have shown the averaged summer fluxes to be equaled 81,6 ± 70,1 mg CH4 m~^ d~' (n = 190) and 7,56 ± 4,23 g CO2 m~^ d^^ (n = 156) for middle taiga mires. The north peatland fluxes were substantively lower and ranged from 6,1 (in lake) up to 41,0 (oligotrophic hollow) mg CH4 m~^ d^' and 1,5 g CO2 m~^ d^' (lake) to 5,4 g CO2 m~^ d^^ (paisa surface) during July-August 2005. Influence of peat temperature and water table level (WTL) were also searched on the methane and carbon dioxide fluxes. It was found statistically true regressive exponential relationship between CH4 flux and WTL for middle taiga mire. The low temperature and permafrost impact were discussed