Variably saturated flow and heat transport simulations of an Interior Alaskan fen

Thesis (M.S.) University of Alaska Fairbanks, 2010"The objectives of this research are: to identify the applicably and limitations of a one-dimensional coupled model to simulate variably saturated hydrologic and energy transport processes in peat; to assess the sensitivity of the hydrologic input parameters and water fluctuations on heat transport; and to test an in situ frequency domain method of soil freezing characteristics versus a statistical approach. Soil temperatures and energy transfer through soils and hydrology are interrelated. Chemical, macro- and microbiological activities are largely dependent on both of these processes in peatlands. It is important to model these processes to assess the interaction of hydrology and soil temperature dynamics under current and future climate conditions. Modeling was accomplished using the van Genuchten model for soil moisture characteristics and hydraulic conductivity, coupled with thermal conduction, convection, and latent heat to study the effects of the vadose zone on heat transfer in peat. The model was calibrated with 40 days of data from 2005, in a fen site in Interior Alaska. Diurnal model verification was conducted with data from 2006, 2008, and 2009. The results of this study demonstrated that the coupled numerical solutions applied to the fen performed well over a variety of environmental conditions. The application of a statistical method of characterizing variably saturated processes suggested variability in moisture distribution in the unsaturated zone. Errors in winter simulations were most likely caused by hysteresis indicating a need for a non-symmetric solution to compensate for the latent heat of phase change in ice"--Leaf iiiNational Science Foundation (DEB-0724514), The Bonanza Creek Long-term Ecological Research Program, NSF (DEB-0620579) and the USDA Forest Service, Pacific Northwest Research (PNW01-JV11261952-231