Recent acceleration of carbon accumulation in a boreal peatland, south central Alaska

Abstract

[1] The ongoing warming in high-latitude regions may be causing rapid changes in the structure and functioning of terrestrial ecosystems. Of particular concern is the fate of belowground soil organic carbon stored in peat-accumulating wetlands, as these large carbon pools are sensitive to temperature and moisture conditions. Despite their important role in the global carbon cycle, considerable uncertainty remains over the carbon balance of northern peatlands in a changing climate. Here we examine the response of vegetation and carbon dynamics in a wet boreal peatland to recent climate warming using empirical peat core data and a new modeling approach. We observed a widespread shift from herbaceous Carex fen peat to Sphagnum moss peat around 100 years ago that was accompanied by a sharp increase in carbon accumulation rate. The observed apparent carbon accumulation rates over the past 100 years (96.8 g C m -2 yr -1 ) were almost 10 times greater than those over the past 4000 years (11.5 g C m -2 yr -1 ). Once differential decomposition history was considered using three modeling approaches, the expected long-term accumulation rate of recent peat was still 2-6 times greater than that of the past 4000 years. We propose that recent warming has led to Sphagnum establishment, which rapidly altered the peatland surface chemistry and hydrology, further promoting Sphagnum growth and enhancing the carbon sink capacity of this peatland. Longer and warmer growing seasons could also have stimulated plant growth. Our results imply that accelerated carbon accumulation under global warming in some wet peatlands might offset some of the carbon losses experienced from other peatland types.

Experimental warming differentially affects microbial structure and activity in two contrasted moisture sites in a Sphagnum-dominated peatland

“…Other studies indicated that climate change can further diminish C sequestration by promoting the growth of vascular plants which, in turn, depress the productivity of peat mosses (Breeuwer et al, 2009;Bragazza et al, 2013). In contrast to these studies, Loisel and Yu (2013) and Charman et al (2013) indicated that the C accumulation rate of many northern peatlands could increase in response to a warmer climate in the future, as long as moisture is not a limiting factor. These examples illustrate the ongoing debate on the fate of C in peatlands in response to climate change.…”

Application of palaeoecology for peatland conservation at Mossdale Moor, UK

“…A lack of Sphagnum remains observed in the plant macrofossil samples when Sphagnum spores are present may suggest high decomposition rates causing the loss of preservation of plant material at these depths (below 65 cm depth), also supported by high levels of UOM (Loisel and Yu, 2013).…”

Higher recent peat C accumulation than that during the Holocene on the Zoige Plateau

“…The carbon balance of peatlands is determined by the joint effect of frequently changing biogeochemical processes of photosynthesis and respiration, so the peat carbon sequestration often shows great fluctuation over a wide range of timescales. Peat core data indicated that carbon accumulation rate varies over millennial (Frolking and Roulet, 2007;Yu et al, 2010), centennial (Craft and Richardson, 1998;Malmer and Wall en, 2004;Ali et al, 2008) and decadal timescales (Craft and Richardson, 1998;Wieder, 2001;Gao et al, 2010;Loisel and Yu, 2013), which can be attributable to many factors, such as climate change (Ise et al, 2008;Cai et al, 2010;Yu, 2011), geological and human disturbances (Yu et al, 2010;Hooijer et al, 2010), landscape morphology (Belyea and Baird, 2006) and self-regulation mechanisms (Wu, 2012). Overall, climate change, which is ubiquitous in the whole world, turns out to be a crucial element in determining carbon accumulation rate of peatlands over different timescales (Friedlingstein et al, 2006;Cai et al, 2010;Yu et al, 2010).…”

“…Because we did not have enough data to model the decay coefficient (a) to reconstruct accurate NCU for the other sites, we estimated their NCU by assuming that they had the same decay coefficient (a) with Huahu peat core. The remaining modern peat masses after 25, 50 and100 yr decomposition were assumed to be equivalent to 60%, 44.4% and 29.6%, respectively, of the initial mass (Loisel and Yu, 2013). Assuming the surface peat decay rate of QTP peatlands as 0.0244 yr À1 reported by Loisel and Yu (2013), we used the recent C accumulation rate obtained from peat cores, which represents the remaining C mass after 25 yr decomposition, to back calculate the initial peat C mass.…”