2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 195-8
Presentation Time: 9:50 AM

CAN SEASONAL FLOODING CONTROL THE HABITATS OF RICH FEN PLANT COMMUNITIES? : AN ECOHYDROLOGICAL CONCEPTUAL MODEL


NILSSON, Bertel1, SØRENSEN, Lærke2, EJRNÆS, Rasmus3, MØLLER, Ingelise2 and VINTHER, Erik4, (1)Department of Hydrology, Geological Survey of Denmark and Greenland, Østervoldgade 10, Copenhagen, 1350, Denmark, (2)Geological Survey of Denmark and Greenland, Copenhagen, 1350, Denmark, (3)Institute of Bioscience, Aarhus University, Aarhus, 8410, (4)Danish Nature Agency, Faaborg, 5600, Denmark

Urup Dam calcareous rich-fen in Denmark is populated with a rare orchid species (Liparis Loeselii) that is protected by the European Habitat Directive. Groundwater discharge to fens is an important factor controlling the groundwater dependent terrestrial ecosystem (GDTE). In addition, a continuous supply of cold calcium-enriched groundwater maintains a neutral pH in the fen ecosystem. Focus in this study is to understand how the fen ecosystem connects to the groundwater and the catchment to the fen area.

This study combines hydrogeological, hydrochemical, geophysical and botanical field data into a framework for assessing interaction between groundwater, GDTE habitat and surface water. The rich fen in Urup Dam was developed in a depression in the moraine terrain right after the last glaciation of Scandinavia around 11.500 years BP. The depression is situated on top a Quaternary clayey till and filled with sediments of sand, calcareous gyttja and peat on top. The peat top soil covers the entire fen area. Groundwater level fluctuates in accordance to season between 0.1 and 0.9 meter. Lowest water levels are in the dry season from May to September that is coinciding with the growing season for the orchids. Flooding of the fen arise from October/November and to March/April. The flooding in the wet season is generated by artesian groundwater pressure underneath the fen area. Groundwater discharge along a seepage face is assumed to be identical with the margin of the flooded area. The seepage face has been surveyed by differential GPS during the flooding season in 2013/2014. The spatial distribution of the orchid species has been surveyed in the growing season frequently since 1982. The locations of the seepage face in wet season and of the orchid habitat show remarkably good agreement. An ecohydrological conceptual model of the Urup Dam rich-fen shows, that the habitat of orchid species is associated with the area between the margin of the peat layer and the seepage face at wet season.

Session No. 195

T170. Physical and Biogeochemical Measurements That Characterize Groundwater–Surface Water Interactions: Where to Go from Here?
Tuesday, 21 October 2014: 8:00 AM-12:00 PM
110 (Vancouver Convention Centre-West)
Geological Society of America Abstracts with Programs. Vol. 46, No. 6, p.482
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