Abstract
This study shows the use of subalpine meadow soil stratigraphy to establish the time of disappearance of past snow patches. Growth periods of plants are too short in places where the snow disappears late in the season, such as at the centers of snow patches. Therefore, plant growth and the subsequent increase of organic content in the soil will indicate the disappearance of snow patches in early summer. Key tephras indicated that a series of buried peat layers on Mt. Zarumori in northeastern Japan accumulated after ca. 1200 yBP, and were buried after 915 AD, showing that the organic content in the surface soil increased ca. 1000yBP. The increase in carbon content probably indicates an increase in litter and stable surface condition. This was likely due to an early snow disappearance and longer snow-free period during the Medieval Warm Period. Snow disappearance before mid July is needed for the formation of buried peat, thus the buried peat layers on Mt. Zarumori probably indicate that the size of summer snow patch in 1000 yBP was smaller than those of recent snow patches.
