HR: 0800h
AN: B41D-0752    [Abstracts]
TI: Where does boreal stream DOC come from? – Quantifying the contribution from different landscape compartments using stable C isotope ratios.
AU: * Brink Bylund, J
EM: jenni.brink@geo.su.se
AF: Department of Geology and Geochemistry, Stockholm University, Stockholm, 106 91, Sweden
AU: Bastviken, D
EM: david.bastviken@geo.su.se
AF: Department of Geology and Geochemistry, Stockholm University, Stockholm, 106 91, Sweden
AU: Morth, C
EM: magnus.morth@geo.su.se
AF: Department of Geology and Geochemistry, Stockholm University, Stockholm, 106 91, Sweden
AU: Laudon, H
EM: hjalmar.laudon@emg.umu.se
AF: Ecology and Environmental Science, Umea University, Umea, 901 87, Sweden
AU: Giesler, R
EM: Reiner.Giesler@emg.umu.se
AF: Ecology and Environmental Science, Umea University, Umea, 901 87, Sweden
AU: Buffam, I
EM: Ishi.Buffam@sek.slu.se
AF: Department of Forest Ecology, Swedish University of Agricultural Sciences, Umea, 901 83, Sweden
AB: Stable carbon isotope (δ¹³C) ratios are frequently used as a source tracer of e.g. organic matter (OM) produced in terrestrial versus aquatic environments. To our knowledge there has been no previous attempt to quantify the relative contribution of dissolved organic carbon (DOC) from various landscape compartments in catchments of different sizes. Here, we test to what extent δ¹³C values can be used also to quantify the relative contribution of DOC from wetlands/riparian zones along streams, and off stream forest habitats, respectively. We present data on spatial and temporal variability of DOC concentrations and δ¹³C-DOC values, during the year of 2005 in Krycklan catchment, a boreal stream network in northern Sweden. Ten stream sites, ranging from order 1 to 4, were monitored in sub catchments with different wetland coverage. Spatial variation of DOC concentration showed a weak but statistically significant relationship with wetland area, with higher concentration with increasing percent of wetland in the drainage area. During base flow the difference in δ¹³C-DOC values was significantly different between forest (-27.5‰) and wetland (-28.1‰). This spatial pattern disappears during spring peak flow when higher discharge flushing upper soil layer and the riparian zone on DOC in the catchments. A simple mixing model using DOC and δ¹³C-DOC showed that stream water DOC could be describe as a mixture of DOC coming from forest (deep) groundwater and wetland/riparian zone water. The result indicates that during spring peak flow almost all stream DOC (84-100%) is derived from wetlands and riparian zones. The wetland/riparian water dominates the stream DOC flux at all hydrological events, except for two sites, one forest dominated and one mixed catchment, where the forest groundwater dominated the DOC transport during base flow. Although the total wetland area in Krycklan catchment only represent 8.3%, it contributed, together with riparian zones, to as much as 83% of the yearly DOC transport. This study shows that there is a great potential in using stable carbon isotopes to quantify the relative contribution of DOC from various landscape compartments in catchments. Quantitative patterns are crucial for several reasons. It is for example necessary in predicting the response to global warming which will result in a changed hydrology and shifts in the relative area of the landscape compartments in boreal environments. KEY WORDS carbon isotopes; dissolved organic carbon; streams; boreal; landscape compartments; wetland; groundwater
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1637 Regional climate change
SC: Biogeosciences [B]
MN: 2007 Fall Meeting