Responses of carbon dioxide flux and plant biomass to water table drawdown in a treed peatland in northern Alberta: a climate change perspective

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.

Integrating peatlands into the coupled Canadian Land Surface Scheme (CLASS) v3.6 and the Canadian Terrestrial Ecosystem Model (CTEM) v2.0

“…The model errors were larger for sites with unusual soil properties or vegetation cover. Long-term decline of water table depth can also shift the vegetation in peatlands from mosses and grasses to shrubs and trees Munir et al, 2014;Talbot et al, 2010). Taking into account such effects could improve the performance of the model (Sulman et al, 2012).…”

Behind the stability of boreal bog carbon sink: Compositional and functional variation of vegetation across temporal and spatial scales

“…Plant species typical for the dry end of the water table gradient, hummock Sphagna and dwarf-shrubs, are known to have lower photosynthesis rate than sedges or lawn and hollow Sphagna (Leppälä et al 2008;Laine et al 2011). Despite this, hummocks are known to often have higher photosynthesis than the wetter plant communities due to their generally higher photosynthesizing leaf area Munir et al 2014). Since plant biomass usually decreases from the dry end of the water table gradient towards hollows (Vasander 1982;Moore et al 2002), also autotrophic respiration can be expected to follow the same pattern.…”

Carbon accumulation in a drained boreal bog was decreased but not stopped by seasonal drought

“…Silvola et al 1996, Flanagan and Syed 2011, Ballantyne et al 2014, Munir et al 2014. However, many studies have shown only a weak or no impact of WT on RECO, whereas soil temperature has been driving the respiration fluxes (Lafleur et al 2005, Nieveen et al 2005, Juszczak et al 2013, Olefeldt et al 2017.…”