A high-resolution record of carbon accumulation rates during boreal peatland initiation

[摘要] Boreal peatlands are a major global C sink, thus having important feedbacksto climate. A decreased concentration in atmospheric CO₂7000–10 000 yr ago has been linked to variations in peatland C accumulation ratesattributed to a warm climate and increased productivity. Yet, this periodalso corresponds to early stages of peatland development (as peatland wasexpanding) following retreat of ice sheets and increases in C storage couldbe associated with wetland evolution via lake filling or following marineshoreline emergence. Unravelling past links amongst peatland dynamics, Cstorage, and climate will help us assess potential feedbacks from futurechanges in these systems, but most studies are hampered by low temporalresolution. Here we provide a decadal scale C accumulation record for a fenthat has begun transformation from salt marsh within the last 70 yr on theisostatically rebounding coast of James Bay, Québec. We determined timeframes for wetland stages using palynological analyses to reconstructecological change and ²¹⁰Pb and ¹³⁷Cs to date the deposit. The averageshort-term C accumulation rates during the low and high tidal marsh and incipient fenstage (42, 87 and 182 g C m⁻² yr⁻¹, respectively) were as much as sixtimes higher than the global long-term (millennial) average for northernpeatlands. We suggest that the atmospheric CO₂ flux during the earlyHolocene could be attributed, in part, to wetland evolution associated withisostatic rebound, which makes land for new wetland formation. Future climatewarming will increase eustatic sea level, decrease rates of land emergenceand formation of new coastal wetlands, ultimately decreasing rates of Cstorage of wetlands on rebounding coastlines.

[学科分类] 地球化学与岩石