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Presented at the NABS Annual meeting, Anchorage, Alaska, 2006
in Biogeochemistry 3
Influence of land use and seasonality on denitrification rates in three Mediterranean streams
D. Von Schiller1, E. Marti1, J.L. Riera2, A. Argerich2, M. Ribot1, and F. Sabater2.1Centre d'Estudis Avançats de Blanes (CSIC); Accés a la Cala St. Francesc, 14; 17300 Blanes; Spain, 2Departament d'Ecologia; Universitat de Barcelona; Diagonal 645; 08028 Barcelona; Spain
Recent studies suggest that denitrification in streams may be a significant sink for nitrogen in the landscape. This biogeochemical process is greatly influenced by nitrate and dissolved organic carbon concentrations, temperature and oxygen availability. Land use changes induced by human activities have altered nitrogen and carbon supply to freshwater ecosystems, while climate change is predicted to modify current temperature and precipitation regimes. We examined the influence of human-derived nutrients on denitrification rates under two contrasting environmental conditions: winter and summer. In each season, denitrification rates were determined in three streams located in the same catchment but subjected to distinct human pressures (forested, agricultural, and urban) using both laboratory sediment core incubations and whole ecosystem field 15N-nitrate tracer additions. Results from the two methods showed similar patterns. Denitrification rates were generally higher in summer than in winter, with the human altered streams (urban and agricultural) showing higher rates than the forested stream. These results suggest that seasonality may play an important role in determining denitrification patterns, and it should be taken into consideration when assessing the effects of human activities on this biogeochemical process.
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