Land-use and hydroperiod affect kettle hole sediment carbon and nitrogen biogeochemistry.
Kettle holes are glaciofluvially created depressional wetlands that collect organic matter (OM) and nutrients from their surrounding catchment. Kettle holes mostly undergo pronounced wet-dry cycles. Fluctuations in water table, land-use, and management can affect sediment biogeochemical transformations and perhaps threaten the carbon stocks of these unique ecosystems. We investigated sediment and water of 51 kettle holes in NE Germany that differ in hydroperiod (i.e. the duration of the wet period of a kettle hole) and land-use. Our objectives were 1) to test if hydroperiod and land management were imprinted on the isotopic values (δ13C, δ15N) and C:N ratios of the sediment OM, and 2) to characterize water loss dynamics and kettle hole-groundwater connectivity by measuring the stable δ18O and δD isotope values of kettle hole water over several years. We found the uppermost sediment layer reflected recent OM inputs and short-term processes in the catchment, including land-use and management effects. Deeper sediments recorded the degree to which OM is processed within the kettle hole related to the hydroperiod. We see clear indications for the effects of wet-dry cycles for all kettle holes, which can lead to the encroachment of terrestrial plants. We found that the magnitude of evaporation depended on the year, season, and land-use type, that kettle holes are temporarily coupled to shallow ground water, and, as such, kettle holes are described best as partially-closed to open systems.
Leibniz Centre for Agricultural Landscape Research (ZALF), Institute of Landscape Biogeochemistry, Eberswalder Str. 84, 15374 Muencheberg, Germany. Electronic address: kai.nitzsche@zalf.de.
Kai Nils
KN
Nitzsche
Leibniz Centre for Agricultural Landscape Research (ZALF), Institute of Landscape Hydrology, Eberswalder Str. 84, 15374 Muencheberg, Germany. Electronic address: tkalettka@zalf.de.
Thomas
T
Kalettka
Leibniz Centre for Agricultural Landscape Research (ZALF), Institute of Landscape Biogeochemistry, Eberswalder Str. 84, 15374 Muencheberg, Germany; Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Chemical Analytic and Biogeochemistry, Mueggelseedamm 310, 12587 Berlin, Germany. Electronic address: premke@igb-berlin.de.
Katrin
K
Premke
Leibniz Centre for Agricultural Landscape Research (ZALF), Institute of Landscape Hydrology, Eberswalder Str. 84, 15374 Muencheberg, Germany; Institute of Earth and Environmental Sciences, University of Potsdam, Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany.
Gunnar
G
Lischeid
Leibniz Centre for Agricultural Landscape Research (ZALF), Institute of Landscape Biogeochemistry, Eberswalder Str. 84, 15374 Muencheberg, Germany; Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zuercherstrasse 111, 8903 Birmensdorf, Switzerland; Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB), 14195 Berlin, Germany. Electronic address: gessler@wsl.ch.
Arthur
A
Gessler
Leibniz Centre for Agricultural Landscape Research (ZALF), Institute of Landscape Biogeochemistry, Eberswalder Str. 84, 15374 Muencheberg, Germany; USDA Forest Service, Northern Research Station, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA. Electronic address: zkayler@fs.fed.us.
Zachary Eric
ZE
Kayler
Biogeochemical transformations; Depressional wetlands; Evaporation; Landscape functioning; Stable isotopes; Wet-dry cycles