Sources and sinks of dissolved organic carbon in a forested swamp catchment

Abstract

Abstract. Concentrations of dissolved organic carbon (DOC) were measured in precipitation, throughfall, stemflow, and soil, peat and stream water in a 50 ha catchment with a central 5 ha swamp at Mont St. Hilaire, Quebec. DOC concentrations in precipitation were low (2.0 mg L-l), but increased in passage through the tree canopies as throughfall (9.1-14.6 mg L-l) and stemflow (23.1-30.1 mg L-l). For the period July l-November 15, 1987, 0.5 g DOC m-* was imported as precipitation, and forest canopies contributed a further 1.4-1.7 g mP2 to the soil surface. DOC concentrations were higher (46.0 and 67.6 mg L-l) in upland soil organic horizons, but decreased with depth because subsoil mineral horizons acted as a major sink of DOC. A laboratory experiment using leaf leachate revealed that subsoil horizons were able to adsorb DOC, with equilibrium DOC concentrations ranging from 3 to 19 mg L-'. Soil organic carbon appeared to be an important determinant of equilibrium DOC concentrations. The swamp was a major source of DOC. with an overall average DOC concentration of 58.6 mg L-' and showed strong spatial and temporal variations related to hydrologic and thermal regimes. During base flow periods, stream DOC concentrations were small ( < 3 mg L-l), dominated by water fed from springs draining upland soils. During high flows, stream DOC concentrations increased through the contribution of DOC-rich water originating in the swamp. Sources, sinks and transport of DOC are thus a function of a complex set of inter-related biotic and abiotic process.

Dissolved Organic Carbon in Terrestrial Ecosystems: Synthesis and a Model

“…The sorption affinity (m) and the soil carbon content are inversely related in some studies (Jardine and others Data compiled from Dalva and Moore 1991;Kaiser and others 1996;Moore and others 1992;Nodvin and others 1986;Qualls and Haines 1992;Vance and David 1992;Neff 1999. Kaiser and others 1996) and positively related in others (Moore and others 1992).…”

“…Fluxes of DOC generally decrease from the litter layer to deeper mineral hori-zons (Table 1). In virtually every soil with substantial clay content, DOC concentrations drop by 50%-90% from the surface organic layers to subsurface mineral soils (McDowell and Wood 1984;Cronan and Aiken 1985;Dalva and Moore 1991;Koprivnjak and Moore 1992;Dosskey and Bertsch 1997). Surface soil fluxes of DOC range from 10 to 85 g C m Ϫ2 y Ϫ1 ; below the surface horizons, they decline to 2-40 g C m Ϫ2 y Ϫ1 (Table 1).…”

Responses of peat carbon at different depths to simulated warming and oxidizing

“…Different from CO 2 , DOC concentration from deeper depths was not stable under 8°C-AN condition. This was probably because soil DOC concentration is dependent on a balance between production from vegetation and SOM and consumption by soil organisms (Dalva and Moore, 1991;Jones et al, 2003;Van den Berg et al, 2012). The difference in organisms may lead to different consumption, and therefore instable DOC.…”

Sources, Sinks, and Fluxes of Dissolved Organic Carbon in Subarctic Fen Catchments

“…Foster and Grieve 1982;Cronan andAiken 1985: McDowell andLikens 1988;Moore 1989: Moore andDalva 1990). These studies have shown that organic matter concentrations in water increase as precipitation passes through the forest canopy, fore st floor, and organic soil horizon but decreases when passing through the mineraI soil horizon, remaining fairly constant thereafter as the water seeps into the streams.…”