Fossil carbon/nitrogen ratios as a measure of peat decomposition

Net accumulation rates of carbon in a 9000 calendar year record of Sphagnum fuscum peat in western boreal Canada range from 13.6 to 34.9 g.m-2 yr-1. The depth vs. age curve is slightly convex due to generally declining net productivity at the site. Fossil carbon/nitrogen ratios of bulk Sphagnum fuscum peat and its components are used to calculate the rate and total amount of decay in the deeper anoxic peat deposits. The pro- portional rate of decay in the catotelm of the peatland declines linearly over time. Carbon loss from the catotelm is estimated at 50% after 1700 calendar years and 65% after 7500 calendar years. Carbon has been added to the catotelm at an average rate of 28.0 g.m-2*yr-1 over the last 1174 years, whereas, at present, the cumulative loss of carbon over the entire catotelm is 19.4 g.m-2*yr-1. The peatland continues to represent a sink for carbon.