Modeling the effects of hydrology on ecosystem respiration at Mer Bleue bog

Abstract

[1] The ecosys model was applied to examine the effects of peatland hydrology on soil respiration and ecosystem respiration at Mer Bleue peatland, Ontario, Canada. It was hypothesized that a decrease in near-surface microbial respiration in peat hummocks resulting from water table (WT) drawdown and subsequent desiccation of the uppermost peat would offset an increase of soil respiration at depth with improved aeration (respiration offsetting mechanism). In contrast, shallower water table in hollows would not allow near-surface desiccation to offset increased soil respiration at depth during drying. However, increased hollow soil respiration with WT drawdown would be offset by decreased aboveground moss respiration with near-surface desiccation in hummocks. Model results for microbial respiration were tested against independent laboratory experiments and ecosystem respiration against hourly eddy-covariance measurements of bog

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

“…The errors in MB-Bog were consistent over time, which was likely a result of the difference between the observed and modelled peat surfaces. The difference in height between hummocks and hollows at the MB-Bog is about 0.25 m (Lafleur et al, 2005) and the bottom of the fibric peat lies at 0.35 and 0.10 m below the peat surface for hummock and hollow respectively (Dimitrov et al, 2010). The parameterized MB-Bog, with 0.10 m of fibric peat, is therefore closer to a hollow (Table 1).…”

A pore-size classification for peat bogs derived from unsaturated hydraulic properties

“…Dimitrov et al, 2010;Sulman et al, 2012;Wu and Blodau, 2013;Mezbahuddin et al, 2016). However, the investigation of the WRC of organic soils has revealed bimodal pore-size distributions which have been found for different but limited pressure head ranges (Rezanezhad et al, , 2010(Rezanezhad et al, , 2016Quinton et al, 2008Quinton et al, , 2009Kettridge and Binley, 2011), and have so far rarely been expressed in terms of effective SHP over the full pressure head range.…”

Coupled eco-hydrology and biogeochemistry algorithms enable the simulation of water table depth effects on boreal peatland net CO<sub>2</sub> exchange

“…Mettrop et al (2014) in a controlled incubation experiment found that the rates of microbial respiration in a nutrient-rich Dutch fen had initially increased with peat drying and consequent improved aeration before excessive drying and consequent peat desiccation reduced microbial respiration efficiency, growth and biomass. While modeling the CO 2 exchange of a northern temperate bog using ecosys, Dimitrov et al (2010a) found that a decrease in desiccated near-surface peat respiration partially offset increased deeper peat respiration when the WT deepened below a threshold of 0.6-0.7 m from the hummock surface. The desiccation of near-surface peat layers with WTD drawdown below a threshold level also caused reduced plant water uptake from those layers which were colonized by most of the vascular root systems and all of the belowground biomasses of nonvascular mosses (Eqs.…”

“…Continued WTD drawdown can also cause near-surface peat desiccation from inadequate recharge through capillary rise from deeper WT. The desiccation of near-surface shallow peat layers can cause a reduction in microbial decomposition that can partially or fully offset the increased decomposition in the deeper peat layers, thereby yielding indistinct net effects of WTD drawdown on R e (Dimitrov et al, 2010a).…”