大雪山小泉岳北東の残雪凹地における雪田消失過程 Disappearance of a snowpatch in the hollow of the northeastern slope of Mt. Koizumidake, the Daisetsu Mountains, Central Hokkaido
大雪山小泉岳北東の残雪凹地において, 1994-1997年の消雪過程を調査し, 植生および砂礫地の分布や推定気温との関係を検討した。各年とも5月下旬には, ハイマツは完全に雪から解放されていた。また, 5-6月に消雪した地表面は, 強風砂礫地もしくは風衝地矮性低木分布地となっていた。1994, 1996, 1997年には7月中旬までに, 1995年には8月上旬までに消雪した地表面は, 雪田植物分布地となっており, それ以降に消雪した地表面は, 残雪砂礫地となっていた。雪田は1994年には8月中旬に, 1996, 1997年には8月末～9月初頭に消失したが, 1995年には越年した。雪面低下速度は,7月中旬から8月上旬に速く, これは推定気温が最も高い時期に対応する。残雪東縁の後退速度は, 推定気温が最も高い時期に速く, また推定気温の最も高かった1994年に最も速かった。いっぽう, 残雪西縁では, 気温との対応はみられなかった。各年の消雪時期は, 気温の変化による残雪東縁の後退速度の影響が大きいといえる。
Retreats of snowpatch margins were investigated in 1994, 1995, 1996, and 1997, and snow surface lowering were measured in 1996 and 1997 at a snow accumulation hollow in the Daisetsu Mountains. Discussions on ablation were made in relation to air temperature and distribution of vegetation cover and bare ground. In the area where snow disappeared in May or June, alpine wind-blown dwarf scrub or wind-beaten bare ground are dominant. In the area where snow disappeared by late July in 1994, 1996, 1997, and middle August in 1995, alpine snowpatch vegetation was dominant. In the area where snow disappeared after these dates, development of vegetation cover was not observed. This snowpatch finally disappeared by late August in 1994, 1996, 1997, while it turned into a perennial one in 1995. The lowering rates of snow surface were the greatest (15cm/day) in a period from middle July to early August. As variation of the lowering rate and that of the air temperature corresponds well, it may be said that the lowering rate is to be controlled by the air temperature. Snow-margin retreat rate on the western margin of this snowpatch was constant about 0.5m/day in 1994 and 1995. However, as far as 1996 and 1997, the rate increased near the end of August in 1996 and 1997. On the other hand, the rate fluctuated widly at the eastern margin. The rate was the fastest (1.5m/day) from middle July through to early August. During these periods, air temperature were also the highest of all the measurement period. Air temperature during the observed period in 1994 was the highest (18°C) of the four years, and the rate during the period at the eastern margin is also the fastest (1.8m/day). These results show that the retreat rates on the eastern margin are greatly controlled by air temperature, but that the rates on the western margin were not because of topographical influence.
- 季刊地理学 = Quarterly journal of geography
季刊地理学 = Quarterly journal of geography 51(2), 134-144, 1999-06-15
The Tohoku Geographical Association