HR: 17:55h
AN: B24A-08    [Abstracts]
TI: Controls on DOC Concentrations in Peatlands During Droughts
AU: * Clark, J M
EM: geojmcl@leeds.ac.uk
AF: School of Geography,Univeristy of Leeds, Woodhouse Lane, Leeds, LS2 9JT United Kingdom
AU: Chapman, P J
EM: p.j.chapman@leeds.ac.uk
AF: School of Geography,Univeristy of Leeds, Woodhouse Lane, Leeds, LS2 9JT United Kingdom
AU: Adamson, J K
EM: jka@ceh.ac.uk
AF: Environmental Change Network, Centre for Ecology and Hydrology, Lancaster Environment Centre, Lancashire, LA1 4AP United Kingdom
AU: Lane, S N
EM: s.n.lane@durham.ac.uk
AF: Department of Geography, University of Durham, South Road, Durham, DH1 3LE United Kingdom
AB: The role of droughts in controlling the production of dissolved organic carbon (DOC) from peatlands has received much attention recently. Although some experimental work suggests drying should increase DOC production, several field studies have shown reduced concentrations of DOC in stream water during drought years. Several theories have been suggested about the factors controlling DOC under these extreme conditions. These include (i) low hydrologic flows, (ii) physio-chemical changes in peat structure delaying/inhibiting peat re-wetting and (iii) enhanced biological degradation of DOC to carbon dioxide (CO$_{2}$). Few have considered the role of chemical changes in peat soil water as a mechanism for DOC suppression, even though (i) acidity and ionic strength increase in peat waters during droughts in response to the oxidation of reduced sulphur and (ii) both pH and ionic strength affect DOC solubility. Analysis of a 10-year time series (1993-2002), collected as part of the UK Environmental Change Network (ECN) programme, has shown a strong link between sulphate (SO$_{4}$) and DOC dynamics under drought conditions. A statistical model including a function to account for DOC suppression due to drought-induced acidification explained more of the variability of DOC in soil solution (R$^{2}$ = 0.81) than temperature alone (R$^{2}$ = 0.58). This model of peat soil solution DOC at 10 cm depth was extended to explain 74 % of the variation in stream water DOC. As future climate change scenarios suggest an increase in the magnitude and frequency of drought events, these results suggest there is potential for a similar increase in DOC suppression resulting from episodic drought-induced acidification.
DE: 1812 Drought
DE: 1890 Wetlands
DE: 1030 Geochemical cycles (0330)
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting