HR: 0800h
AN: C21A-0053    [Abstracts]
TI: Impacts of tundra fire on active layer condition and estimation of true resistivity value of soil in Seward Peninsula, Alaska
AU: * Harada, K
EM: haradak@myu.ac.jp
AF: School of Food, Agricultural and Environmental Sciences, Miyagi University, 2-2-1, Hatatate, Taihaku-ku, Sendai, 9820215, Japan
AU: Sawada, Y
EM: ysawada@pop.lowtem.hokudai.ac.jp
AF: Institute of Low Temperature Science, Hokkaido University, N19 W8, Kita-ku, Sapporo, 0600819, Japan
AU: Narita, K
EM: knarita@ed.akita-u.ac.jp
AF: Faculty of Education and Human Studies, Akita University, 1-1, Tegata-Gakuen, Akita, 0108502, Japan
AU: Fukuda, M
EM: mfukuda@pop.lowtem.hokudai.ac.jp
AF: Institute of Low Temperature Science, Hokkaido University, N19 W8, Kita-ku, Sapporo, 0600819, Japan
AB: In Seward Peninsula, southwest Alaska, large tundra fires were occurred in 1997 and 2002, and a discontinuous permafrost area burned widely near the Kougarok River. After fires, a vegetation condition was destroyed and a ground surface thermal condition was changed. Then, field observations were conducted at burned and unburned sites in summer 2005, 2006 and 2007, in order to clarify impacts of the tundra fire on thermal and water conditions of active layer. From pit surveys, ground temperatures at burned sites showed 4-5 °C higher values than those at unburned sites. Soil water contents at burned sites showed relative high values in 2005, but low in 2006. Active layer thicknesses were significantly different between burned and unburned sites, about 60cm and 40cm, respectively. There is no significant increasing of the thickness between 2005 and 2006, however, the thickness in 2007 at north-facing sites increased to 80cm at the burned site and 50cm at the unburned site, respectively. Apparent electrical resistivity values up to 1m deep were obtained from electrical soundings in 2006, and values at burned sites were lower than those at unburned sites due to the thick active layer whose resistivity value is relatively low. As an apparent resistivity value is generally produced from the combination of a true resistivity value and a thickness of a layer, a simple calculation was carried out in order to estimate a true resistivity value of unfrozen mineral soil in the active layer. The calculated results showed that the true resistivity at burned sites was higher than that at unburned sites, which was seemed to correspond to a relative low water condition. This result is in agreement with the measured result of water content in 2006. Using this method, the apparent resistivity may show a soil water condition.
DE: 0702 Permafrost (0475)
DE: 0706 Active layer
DE: 0718 Tundra (9315)
DE: 0768 Thermal regime
DE: 0925 Magnetic and electrical methods (5109)
SC: Cryosphere [C]
MN: 2007 Fall Meeting