A simple model for simulation of water content, soil frost, and soil temperatures in boreal mixed mires

Abstract

Abstract. In this paper we present a model that can reconstruct water table position and soil temperature profiles to 3 m depth in boreal mixed mire systems using the readily available climate data on air temperature and precipitation as driving variables. The model simulates complete, multiple annual cycles including winter conditions and freeze-thaw processes. The major requisite for an accurate description of the soil heat flux in a mire is an accurate description of the water content of the profile because of the high porosity of the soil and the thermal properties of water. The soil moisture profile in this model is described as a function of water table position The necessity of correctly describing water content over time in modeling heat flows and ice formation in arctic soils was discussed by Waelbroeck [1993]. In peat-forming mires it is even more important to have a correct water content description for calculating heat fluxes because of the high water content in the saturated zone and the large variation of the water content in the unsaturated zone. Accurate water content de-

In situ measurements of the thermal properties of a northern peatland: Implications for peatland temperature models

“…While all peatland temperature models incorporate energy transfer by conduction, the advective liquid heat flux is incorporated within some peatland temperature models [Kellner, 2001;Grant and Roulet, 2002], but is excluded from others [Zhang et al, 2002;Granberg et al, 1999]. The vertical advective liquid heat flux has not been directly measured within poorly decomposed Sphagnum peat.…”

“…For example, methane (CH 4 ) production [Dunfield, 1993;Crill, 1991] is related exponentially to temperature, and CH 4 oxidation is exponentially/linearly related to temperature [Dunfield et al, 1993;Whalen et al, 1990] provided oxygen is not limiting [Grant, 1999]. Current peatland temperature models do not adequately simulate soil temperatures [Zhang et al, 2002;Kellner, 2001;Granberg et al, 1999]. Errors in these models may result from errors in their parameterization or errors in the representation of heat transfer processes (i.e., the model may ignore important mechanisms of heat transfer or only partly describe a mechanism).…”

“…Accurate simulation of temperatures is particularly important in the upper peat layers which are the most important for peat decomposition and CH 4 production [e.g., Daulat and Clymo, 1998]. Until now, measurements of the thermal properties of peat have been limited to well-decomposed peat [de Vries, 1963;Farouki, 1986;Lauren, 1997], and the empirical equations used to parameterize current peatland temperature models have not been independently tested within poorly decomposed Sphagnum peat: the type of peat most often found near the peatland surface [Zhang et al, 2002;Kellner, 2001;Granberg et al, 1999]. Therefore detailed in situ measurements of the thermal properties of poorly decomposed Sphagnum peat are required to parameterize accurately peatland temperature models.…”

“…[3] Granberg et al [1999] suggest that a better understanding of the soil thermal properties is required if peat soil temperatures are to be better modelled. Accurate simulation of temperatures is particularly important in the upper peat layers which are the most important for peat decomposition and CH 4 production [e.g., Daulat and Clymo, 1998].…”

Nitrogen and methanogen community composition within and among three Sphagnum dominated peatlands in Scandinavia

“…The main factors controlling the rates of methane production in peatlands are the water table fluctuations, plant functional type composition, and peat temperature and chemical characteristics (Svensson and Sundh, 1992;Granberg et al, 1999;Ward et al, 2013). The abundance of methanogens differs between areas with high and low water table, however, the variation in the methanogenic community composition among peatlands is mainly explained by peat pH and temperature, where the hydrogenotrophic pathway has been found to be dominant at acidic peat pH and low temperature (Kotsyurbenko et al, 2007;Yavitt et al, 2011).…”