NSF Award Abstract - #0223271

AWSFL008-DS3

RUI: Carbon Accumulation in the Fens of Boreal, Western Canada

Abstract

Boreal and subarctic peatland ecosystems cover about 3-4 % of the earth's land surface and store about 1/3 of the world's soil C as peat. Peatlands represent a major global C pool, yet it is unclear whether they function as sources or sinks of atmospheric C, both today and into the future. Based on a recent inventory of peatlands in boreal western Canada (Alberta, Saskatchewan, and Manitoba), peatland ecosystems collectively cover 365,157 km 1 of the land surface and store 42 Pg (10 15 g) of C as peat. Previous research, including our own, has focused on continental bog, permafrost bog, and internal lawn (areas of recent permafrost melt) peatland features in boreal western Canada, but we now know that 2/3 of the peatland area and C storage are not in these types of systems, but rather are in fens, peatlands hydrologically connected to surface water and groundwater systems. We propose to use approaches that we have used to study bogs in boreal western Canada to compare carbon accumulation and carbon cycling between continental bogs, poor fens and rich fens of boreal western Canada.

We will address three specific objectives: 1) to characterize and compare recent C accumulation through coring, 210Pb-dating and modeling; 2) to quantify moss production and decomposition rates and gaseous C fluxes, and 3) to characterize the long-term historical development of C accumulation through coring, macrofossil analysis, 14C dating and modeling. Results will test an overall working hypothesis that net C accumulation is greater in continental bogs than in poor or rich fens. High accumulation in bogs is attributed to the resistance of Sphagnum fuscum to decomposition, despite a relatively thick aerobic acrotelm (upper, aerobic, non-saturated peat layer) in bogs. Although poor fens and rich fens also accumulate C, they do so at comparatively lesser rates - fen Sphagnum and brown mosses decompose comparatively rapidly very near the surface, but because of high water table positions, the acrotelm is thin. It is the thin acrotelm that promotes C accumulation in fens. Differences in C accumulation rates are determined more by differences in decomposition than by differences in NPP. Findings from this research will improve our estimate of the extent to which peatland ecosystems of boreal western Canada do or do not represent a net sink for atmospheric CO2.