Winfrid Kluge

Ecohydrological characterisation of a degenerated valley peatland in Northern Germany for use in restoration

Abstract Present environmental policy aims to restore wetlands for multifunctional purposes and requires quantitative information on the spatially interrelated biohydrochemical processes which allow wetlands to regulate water- and nutrient flow on different scales. For this purpose, this study presents an ecohydrological system analysis as a basis for a future management concept of the Eider valley peatland. This study combines field data with existing knowledge to set up different modelling techniques to study hydrological processes and nitrogen transformations. The Eider valley of northern Germany is a riverine freshwater wetland of 150 ha. Mire genesis was dominated first by river water inflow from the upstream catchment area, and in a later successional stage by groundwater inflow at the mire margins. Drainage, land use intensification and river regulation have resulted in severe degeneration of the peatland. Altering of the water flow patterns led to the mobilisation of nutrients and resulted in eutrophication of the sites. Abandonment of the mown or grazed sites led to the establishment of species poor Urtica dioica stands. The scenario calculations of the nitrogen budget of the peatland with a process oriented nitrogen model indicate that a water level increase of 30 cm is not sufficient to reduce peat loss due to oxidation. On the basis of the system analysis, restoration prospects for the Eider valley peatland are discussed where the historical subsurface flow pattern can be a long term restoration goal. Due to irreversible changes in peat hydraulic conductivities combined with subsidence, it is only possible to restore surface flow on top of the peat. Raising river water level will result in a shallow lake system. The limnic stage is a draw-back in the genesis of the valley, but necessary for the restoration of wetlands as self-evolving landscape entities.

FEUWAnet: a multi-box water level and lateral exchange model for riparian wetlands

Abstract Riparian wetlands as typical aquatic-terrestrial interfaces control, in a very specific way, nonpoint water and related chemical fluxes exchanging between catchment areas to their respective water systems (streams, lakes). The existing groundwater and soilwater flow models reveal gaps in dealing with the complex behaviour of processes and the considerable spatial and temporal heterogeneity of riparian wetlands. Based on long-term experience gained through field observations and the interpretation of model produced data, a multi-box aggregation of processes which determines lateral as well as vertical flows and, as a whole, water balance, is used to discretise a generic riparian wetland transect situated between an upland aquifer and a receiving water body. The resulting mathematical model, FEUWAnet, endowed also with an original methodology to adapt parameters, has been applied to a riparian alder wetland adjacent to Lake Belau (northern Germany). Results of simulations illustrate a good fit between calculated water levels and observed values and an accordance of calculated water balance to previous independent evaluations. This confirms that the sound simplifications of real situations performed by the FEUWAnet mathematical model are a promising way to deal with hydrological complexity of riparian zones. Moreover, FEUWAnet permits, to a certain extent, one to unravel the spatial heterogeneity and temporal variation of lateral (from catchment area to water systems) and vertical (from canopy to groundwater zone) water fluxes typical of riparian ecosystems: this is the necessary step to undertake when developing integrated models capable of assessing the effectiveness of riparian systems in controlling the fluxes of nonpoint pollution discharging in the open water bodies.

Parameter acquisition for modelling exchange processes between terrestrial and aquatic ecosystems

Abstract In the Bornhoved Lakes Ecosystem Research Project fluxes of water, nutrients and other substances from the surrounding upland into Lake Belau are studied. The investigation of different transition subsystems requires the application of both spatially distributed models and lumped box models. Present knowledge of processes and parameters, the types of models and the availability of measured data decide if parameter calibration can be carried out. Without altering the model structure the sets of calibrated parameters refer to different time scales. Case studies show how to improve the efficiency by careful coordination of measurement, modelling and different parameter acquisition methods.

Transport Processes between Lake Belau and its Drainage Basin

Air and water are the fluid media transporting dissolved and particulate mineral and organic substances between terrestrial and aquatic ecosystems. With respect to the physics of such flow processes, two theoretical approaches are distinguished in general. Using Euler’s concept, the multidimensional partial flow transport equations are solved simultaneously for all points in space at a given time. Lagrange’s approach describes mainly the temporal change of tracking particles which can shift along flowlines within catchments and may be subject to transformation processes. Although both approaches, from a theoretical point of view, are equivalent, labouring under the apprehension of non-turbulent flow and yielding compatible results (e.g. in groundwater hydraulics), the Lagrange approach provides a detailed description in direct correspondence with the water and material cycles in ecological systems and catchment areas. Between the origin, e.g. the entry into a terrestrial system, and the spatially distinct and temporally retarded effect in the subordinate systems, e.g. the entry into an aquatic system, a direct correlation is established (Kluge et al. 2003).

General Concept of the Research Pogramme and Methodology of Investigations

The integrative biological and geoscientific examination of both the nature of physical and biotic environments which make up ecosystems, and the interactions between these sub-systems, has substantiated the conception that a thorough knowledge of the ecosystem and its unifying position between ecology and environmental science is essential for a coherent understanding of environmental issues and large-scale problems in the biosphere. Recent developments in ecosystem theory have created a challenge to the development of recipes for a sustainable management of ecosystems and regions. It is increasingly considered in the disciplines of conservation biology, in the assessment of ecosystem health, integrity and sustainability, in ecological engineering, and in ecological economics in order to solve practical environmental management problems. In all of these fields modelling plays an essential role, since models provide for opportunities to develop strong transdisciplinary ties between the ecological community and the agency management personnel. A wide variety of illustrative examples of such approaches is provided by the International Biological Programme (IBP) and, in particular, by UNESCO’s Man and the Biosphere Programme (MAB) which, together with the German concept of a comprehensive ecological surveillance system (Ellenberg et al. 1978), contributed to define the concept and structure of the Bornhoved Project. They are summarized in the first part of the present Chapter while, in a concise form, the second part provides information about the practices, procedures and instrumentation used when implementing the ecosystem research scheme in the Bornhoved Lake District.