Concentration and Fluxes of Dissolved Organic Carbon (DOC) in Three Norway Spruce Stands along a Climatic Gradient in Sweden

Abstract

Leaching of dissolved organic carbon (DOC) from the forest floor and transport in soil solution into the mineral soil are important for carbon cycling in boreal forest ecosystems. We examined DOC concentrations in bulk deposition, throughfall and in soil solutions collected under the O and B horizons in three Norway spruce stands along a climatic gradient in Sweden. Mean annual temperature for the three sites was 5.5, 3.4 and 1.2°C. At each site we also examined the effect of soil moisture on DOC dynamics along a moisture gradient (dry, mesic and moist plots). To obtain information about the fate of DOC leached from the O horizon into the mineral soil, 14 C measurements were made on bulk organic matter and DOC. The concentration and fluxes of DOC in O horizon leachates were highest at the southern site and lowest at the northern. Average DOC concentrations at the southern, central and northern sites were 49, 39 and 30 mg l À1 , respectively. We suggest that DOC leaching rates from O horizons were related to the net primary production of the ecosystem. Soil temperature probably governed the within-year variation in DOC concentration in O horizon leachates, but the peak in DOC was delayed relative to that of temperature, probably due to sorption processes. Neither soil moisture regime (dry, mesic or moist plots) nor seasonal variation in soil moisture seemed to be of any significance for the concentration of DOC leached from the O horizon. The 14 C measurements showed that DOC in soil solution collected below the B horizon was derived mainly from the B horizon itself, rather than from the O horizon, indicating a substantial exchange (sorption-desorption reactions) between incoming DOC and soil organic carbon in the mineral soil.

The impact of four decades of annual nitrogen addition on dissolved organic matter in a boreal forest soil

“…Rappe-George, unpublished data, 2012). Moreover, there is support that water flux through the (Fröberg et al, 2006;Kalbitz et al, 2007;Schmidt et al, 2010). In accordance with our hypothesis regarding DOC concentration in mineral B horizon, DOC approximately doubled in both sampling years in response to both N treatments, N1 and N2.…”

“…Acid/base effect of N fertilizer (Evans et al, 2008) and ecosystem-specific response of the microbial community (Waldrop and Zak, 2006) have been proposed to explain between-site differences of DOC response to N addition. Fröberg et al (2006) identified a positive correlation between O horizon leachate mean annual DOC concentration and aboveground biomass across a gradient of climate and primary productivity in Sweden. We observed a similar relationship in our study (Fig.…”

Properties of dissolved and total organic matter in throughfall, stemflow and forest floor leachate of central European forests

“…Dissolved organic matter (DOM), often described as the solutes that can pass through a filter with < 0.45 µm pore size, contributes substantially to the biogeochemistry of carbon (C) and nitrogen (N) in forest ecosystems Michalzik and Matzner, 1999;Fröberg et al, 2006;Kindler et al, 2011). While many investigations have addressed the nature and dynamics of DOM in terrestrial ecosystems (e.g.…”

Dissolved organic carbon concentrations under conditions of different forestcomposition

“…Accumulation of DOC in the mineral soil often represents a major carbon pool (Callesen et al 2003). DOC is also released from the mineral soil to the soil solution (Fröberg et al 2006). These processes are affected by soil temperature and moisture (Christ, David 1996;Gödde et al 1996).…”