Northern peatland carbon stocks and dynamics: a review

[摘要] Peatlands contain a large belowground carbon (C) stock in the biosphere, andtheir dynamics have important implications for the global carbon cycle.However, there are still large uncertainties in C stock estimates and poorunderstanding of C dynamics across timescales. Here I review differentapproaches and associated uncertainties of C stock estimates in theliterature, and on the basis of the literature review my best estimate of Cstocks and uncertainty is 500 ±100 (approximate range) gigatons of C(Gt C) in northern peatlands. The greatest source of uncertainty for all theapproaches is the lack or insufficient representation of data, includingdepth, bulk density and carbon accumulation data, especially from theworld's large peatlands. Several ways to improve estimates of peat carbonstocks are also discussed in this paper, including the estimates of Cstocks by regions and further utilizations of widely available basal peatages.

Changes in peatland carbon stocks over time, estimated usingSphagnum (peat moss) spore data and down-core peat accumulationrecords, show different patterns during the Holocene, and I argue thatspore-based approach underestimates the abundance of peatlands in their earlyhistories. Considering long-term peat decomposition using peat accumulationdata allows estimates of net carbon sequestration rates by peatlands, or net(ecosystem) carbon balance (NECB), which indicates more than half of peatcarbon (> 270 Gt C) was sequestrated before 7000 yr ago during theHolocene. Contemporary carbon flux studies at 5 peatland sites show muchlarger NECB during the last decade (32 ± 7.8 (S.E.) g C m⁻² yr^–1) than during the last 7000 yr (∼11 g C m⁻² yr^–1), as modeled from peat records acrossnorthern peatlands. This discrepancy highlights the urgent need for carbonaccumulation data and process understanding, especially at decadal andcentennial timescales, that would bridge current knowledge gaps andfacilitate comparisons of NECB across all timescales.

[学科分类] 地球化学与岩石