Possible Change of Water and Nitrate Cycles Associated with the Frost-Depth Decrease Under Climate Change

摘要: Amounts of snowfall in early winter have increased recent years because climate change, thereby insulating soil from cold air and decreasing the frost depth during last 20 Tokachi region northernmost Japan. To reveal water movement winters, field observations were conducted for 5 at an experimental this region. Soil froze to 0.2 m two winters a frozen layer was absent three other periods. Substantial amounts infiltrated deep both unfrozen suggesting that thin did not impede snowmelt infiltration years. simulate past conditions, we removed snow replaced it after reached desired value. An approximately 0.4-m-thick greatly impeded spring period. During period, nitrate control plot, where natural conditions maintained throughout maximum 0.1 m, carried deeper than snow-removal treatment plot greater amount plot. These results imply dramatic change period region, presumably resulting change.