MOSS AND SOIL CONTRIBUTIONS TO THE ANNUAL NET CARBON FLUX OF A MATURING BOREAL FOREST

We used input and decomposition data from C-14 studies of soils to det ermine rates of vertical accumulation of moss combined with carbon sto rage inventories on a sequence of burns to model how carbon accumulate s in soils and moss after a stand-killing fire. We used soil drainage- moss associations and soil drainage maps of the old black spruce (OBS) site at the BOREAS northern study area (NSA) to areally weight the co ntributions of each moderately well drained, feathermoss areas; poorly drained sphagnum-feathermoss areas; and very poorly drained brown mos s areas to the carbon storage and flux at the OBS NSA site. On this ve ry old (117 years) complex of black spruce, sphagnum bog veneer, and f en systems we conclude that these systems are likely sequestering 0.01 -0.03 kg C m(-2) yr(-1) at OBS-NSA today. Soil drainage in boreal fore sts near Thompson, Manitoba, controls carbon storage and flux by contr olling moss input and decomposition rates and by controlling through f ire the amount and quality of carbon left after burning, On poorly dra ined soils rich in sphagnum moss, net accumulation and longterm storag e of carbon is higher than on better drained soils colonized by feathe rmosses. The carbon fur of these contrasting ecosystems is best charac terized by soil drainage class and stand age, where stands recently bu rned are net sources of CO2, and maturing stands become increasingly s tronger sinks of atmospheric CO2. This approach to measuring carbon st orage and flux presents a method of scaling to larger areas using soil drainage, moss cover, and stand age information.