Water and heat transport in boreal soils: Implications for soil response to climate change

Department of Geological Sciences, University of Colorado, Boulder, CO 80305, USA.
Science of The Total Environment (Impact Factor: 4.1). 02/2011; 409(10):1836-42. DOI: 10.1016/j.scitotenv.2011.02.009
Source: PubMed


Soil water content strongly affects permafrost dynamics by changing the soil thermal properties. However, the movement of liquid water, which plays an important role in the heat transport of temperate soils, has been under-represented in boreal studies. Two different heat transport models with and without convective heat transport were compared to measurements of soil temperatures in four boreal sites with different stand ages and drainage classes. Overall, soil temperatures during the growing season tended to be over-estimated by 2-4°C when movement of liquid water and water vapor was not represented in the model. The role of heat transport in water has broad implications for site responses to warming and suggests reduced vulnerability of permafrost to thaw at drier sites. This result is consistent with field observations of faster thaw in response to warming in wet sites compared to drier sites over the past 30 years in Canadian boreal forests. These results highlight that representation of water flow in heat transport models is important to simulate future soil thermal or permafrost dynamics under a changing climate.

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Available from: Jason C Neff, May 28, 2014
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    • "Liquid water and convection contribute to approximately 50% of soil heat flux (Cahill and Parlange, 1998). In boreal soils where moisture is highly variable across space and through seasons, the role of water movement could be an important factor in seasonal soil energy dynamics and in the long-term response of boreal systems to changes in climate through evaporation and condensation processes (Fan et al., 2011). Soil moisture can be measured by the well-established methods of time domain reflectometry (TDR) and tensiometers, which determine volumetric content of soil water and soil matric potential, respectively. "
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    • "In contrast, drier conditions following thaw stimulate peat decomposition, releasing CO 2 to the atmosphere. However, increased CO 2 efflux may be constrained by the quantity of C (Schuur et al., 2008) or quality of thawed peat (Schuur et al., 2008; Myers-Smith et al., 2007; Jorgenson et al., 2010; Fan et al., 2011; Burke et al., 2012), or enhanced by litter input to the peat (Laiho, 2006; Walter et al., 2006; Lang et al., 2009). Enhanced decomposition may also lead to the mineralization of other elements, such as N, that stimulate plant growth (Rinnan et al., 2007; Oechel et al., 2000) and thus enhance the C sink strength (Johnson et al., 2000; Hobbie et al., 2002). "
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