Release of Carbon in Different Molecule Size Fractions from Decomposing Boreal Mor and Peat as Affected by Enchytraeid Worms

Terrestrial export of dissolved organic carbon (DOC) to watercourses has increased in boreal zone. Effect of decomposing material and soil food webs on the release rate and quality of DOC are poorly known. We quantified carbon (C) release in CO2, and DOC in different molecular weights from the most common organic soils in boreal zone; and explored the effect of soil type and enchytraeid worms on the release rates. Two types of mor and four types of peat were incubated in laboratory with and without enchytraeid worms for 154 days at + 15 A degrees C. Carbon was mostly released as CO2; DOC contributed to 2-9% of C release. The share of DOC was higher in peat than in mor. The release rate of CO2 was three times higher in mor than in highly decomposed peat. Enchytraeids enhanced the release of CO2 by 31-43% and of DOC by 46-77% in mor. High molecular weight fraction dominated the DOC release. Upscaling the laboratory results into catchment level allowed us to conclude that peatlands are the main source of DOC, low molecular weight DOC originates close to watercourse, and that enchytraeids substantially influence DOC leaching to watercourse and ultimately to aquatic CO2 emissions.