FOREST DISTURBANCE BY THE 1926 MUDFLOW AND REVEGETATION PROCESSES AT MT.TOKACHI VOLCANO

1926年在德胜火山的泥石流形成了一个巨大的裸露的陆地，具有不均匀的地形条件。森林的再生主要依靠剩余的植被岛和周围地区提供的种子。在泥石流下游和边界地区，森林遭受了轻微的破坏，植被再生是可能的。复植的森林呈镶嵌状结构，由大大小小的细长斑块组成。林地可按优势群落分类，如云杉（Picea glehnii）、p.j jezoensis、冷杉（Abies sachalinensis）和桦树（betula spp.）。纯桦树林分分布在泥流边界沉积细粒沉积物的区域。云杉林分建立在富边界土壤沉积物的中心区域。矮竹（Sasa spp.）在桦木林分中占主导地位，其快速恢复可能对桦木林分的形成起了重要作用。土壤分析清楚地表明，土壤条件与林分类型之间有很强的联系。研究认为，泥石流造成的不同立地条件可能是复生林结构差异的主要原因。

The 1926 mudflow at Mt.Tokachi Volcano created a vast, bare land mass with heterogeneous and edaphic conditions. Forests were regenerated mainly by seedings supplied from remaining vagetation islands and surrounding areas. Vagetative regrowth was possible in downstream and boundary areas of the mudflow where forests suffered light damage. Revegetated forests display a mosaic structure, consisting of small or large elongated patches. Atands can be classified by dominant soecies, such as Picea glehnii, P.jezoensis, Abies sachalinensis, and betula spp. Pure Betula stands are found at the boundary areas of the mudflow where fine sediment was deposited. Picea glehnii stands were established in the central areas of bounder-rich soil deposits. Dwarf bamboo(Sasa spp.) dominated the floor of Betula stands, and it is likely that its rapid recovery playd an important role in forming Betula stands. Soil analysis clearly indicated the strong linkage between edaphic conditions and stand types. We concluded that differences in atand structures of revegetated forests could be attributed the heterogeneous site conditions created by the mudflow.