A new model of Holocene peatland net primary production, decomposition, water balance, and peat accumulation

Abstract

Abstract. Peatland carbon and water cycling are tightly coupled, so dynamic modeling of peat accumulation over decades to millennia should account for carbon-water feedbacks. We present initial results from a new simulation model of long-term peat accumulation, evaluated at a wellstudied temperate bog in Ontario, Canada. The Holocene Peat Model (HPM) determines vegetation community composition dynamics and annual net primary productivity based on peat depth (as a proxy for nutrients and acidity) and water table depth. Annual peat (carbon) accumulation is the net balance above-and below-ground productivity and litter/peat decomposition -a function of peat hydrology (controlling depth to and degree of anoxia). Peat bulk density is simulated as a function of degree of humification, and affects the water balance through its influence on both the growth rate of the peat column and on peat hydraulic conductivity and the capacity to shed water. HPM output includes both time series of annual carbon and water fluxes, peat height, and water table depth, as well as a final peat profile that can be "cored" and compared to field observations of peat age and macrofossil composition. A stochastic 8500-yr, annual precipitation time series was constrained by a published Holocene climate reconstruction for southern Québec. HPM simulated 5.4 m of peat accumulation (310 kg C m −2 ) over 8500 years, 6.5% of total NPP over the period. Vascular plant functional types accounted for 65% of total NPP over 8500 years but only 35% of the final (contemporary) peat mass. Simulated age-depth Correspondence to: S. Frolking (steve.frolking@unh.edu) and carbon accumulation profiles were compared to a radiocarbon dated 5.8 m, c.9000-yr core. The simulated core was younger than observations at most depths, but had a similar overall trajectory; carbon accumulation rates were generally higher in the simulation and were somewhat more variable than observations. HPM results were sensitive to centuryscale anomalies in precipitation, with extended drier periods (precipitation reduced ∼10%) causing the peat profile to lose carbon (and height), despite relatively small changes in NPP.

Limited response of peatland CH<sub>4</sub> emissions to abrupt Atlantic Ocean circulation changes in glacial climates

“…An alternative approach would involve predicting the accumulation of peat as a function of environmental controls (e.g. Frolking et al, 2010;Kleinen et al, 2012;Spahni et al, 2013).…”

Transient simulations of the carbon and nitrogen dynamics in northern peatlands: from the Last Glacial Maximum to the 21st century

“…For example, recent models representing peat evolution over the Holocene (Bauer, 2004;Heinemeyer et al, 2010;Frolking et al, 2010) include feedbacks and influences of hydrology, plant communities, and peat properties on peat accumulation. These models are applied at individual peatland sites and simulation results were then compared with peat-core data.…”

“…The parameterization of acrotelm decomposition includes a temperature modifier, based on soil temperature at 0.25 m depth, and a constant soil moisture modifier of 0.35 as in LPJ-WHy (Wania et al, 2009b Frolking et al (2010):…”

The role of hydrological transience in peatland pattern formation

“…Our results indicate that this memory effect is important to the formation of patterning in the ponding model and should be investigated directly in future studies, perhaps via the use of cohort-based peat accumulation models (e.g. Frolking et al, 2010;Morris et al, 2011Morris et al, , 2012.…”

“…The inclusion of these processes in patterning models would also help to address the question raised above of ecological memory effects, and suggests the need to unify models of peatland surface patterning such as those considered here, and cohort models of long-term peatland development (e.g. Frolking et al, 2010;Morris et al, 2011Morris et al, , 2012.…”