Distribution of water-soluble organic carbon in an aspen forest soil

The purpose of this study was to characterize the quantity, distribution, and variance of water-soluble organic C (WSOC) in a soil under trembling aspen (Populus tremuloides Michx,) in the southern boreal forest of Canada, WSOC was determined monthly from May to October 1994 in the forest floor horizons (L,F,H) and mineral soil (Ae) of an aspen stand in Prince Albert National Park, Saskatchewan. The concentration of WSOC varied considerably with profile depth but varied little among the slope positions and aspects. The L horizon had the highest WSOC concentration (425-8690 mg . kg(-1) ovendried soil), following by the F, H, and Ae horizons. The concentration of WSOC in the Ae horizon was significantly related to the concentration in forest floor horizons above. Water-soluble organic C in the Ae horizon likely was derived from the overlying organic layer by leaching. In a laboratory incubation, the rate of WSOC release (the net result of release and uptake) during incubation decreased continuously over time, but in the field, the rate of WSOC release decreased slightly early in the growing season, but increased later in the season as new litter fall reached the forest floor. This indicates that litter fall is a major factor in the replenishment of WSOC in aspen forest stands.