In order to trace water infiltration and heat transport processes in unsaturated zone, field experiments were conducted at two sites, one with and another without tree, in a typical sand dune at Tottori, Japan since May 1998. TDRs and thermometers were set to measure changes of water contents and temperatures in sand dune. It was found that the depth at which water infiltrates into for every event was no more than 200cm in winter. At this period, water content was decreased continually below 300cm from the surface. Field observations showed that vertical distribution of temperature in sand dune has a very close relation with the water content and responded well to the water movement during the events. Groundwater is not recharged for every event, but only in snow-smelt period when the temperature was high. Comparing both water content and soil temperature in the sites with and without tree, it was found water content in the former was less than later. As a result, the responding depths of soil temperature during snow-smelt were different between two sites.
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