Abstract
Abstract. Northern peatland ecosystems represent large carbon (C) stocks that are susceptible to changes such as accelerated mineralization due to water table lowering expected under a climate change scenario. During the growing seasons (1 May to 31 October) of 2011 and 2012 we monitored CO2 fluxes and plant biomass along a microtopographic gradient (hummocks-hollows) in an undisturbed dry continental boreal treed bog (control) and a nearby site that was drained (drained) in 2001. Ten years of drainage in the bog significantly increased coverage of shrubs at hummocks and lichens at hollows. Considering measured hummock coverage and including tree incremental growth, we estimate that the control site was a sink of −92 in 2011 and −70 g C m−2 in 2012, while the drained site was a source of 27 and 23 g C m−2 over the same years. We infer that, drainage-induced changes in vegetation growth led to increased biomass to counteract a portion of soil carbon losses. These results suggest that spatial variability (microtopography) and changes in vegetation community in boreal peatlands will affect how these ecosystems respond to lowered water table potentially induced by climate change.
Highlights
Northern peatlands, functioning as carbon (C) sink ecosystems of the boreal forest over millennia, have stored approximately one third of global soil carbon (Tarnocai, 2006; Tarnocai et al, 2009; Turunen et al, 2002)
Ten years after initial drainage, the water table at the drained site was as much as 80 cm lower than that at the control site (Fig. 2)
In 2012, the reduction in rainfall by 121 mm led to a decrease in water table level at control and drained hollows by 4.5 and 4.3 cm and at control and drained hummocks by 8.0 and 7.2 cm, respectively (Fig. 2)
Summary
Northern peatlands, functioning as carbon (C) sink ecosystems of the boreal forest over millennia, have stored approximately one third of global soil carbon (Tarnocai, 2006; Tarnocai et al, 2009; Turunen et al, 2002). These peatlands dominate the Canadian and Albertan landscape with coverage of 12 and 16 %, respectively and contain almost twice as much C per unit area (115 kg m−2) as tropical forests (Carlson et al, 2010; Vitt et al, 2009). Drought/warming-induced water table drawdown could have a significant impact on the sustainability and ecosystem functions of boreal peatlands
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