The Species Composition of Soil Seed Banks in the Ooyamazawa Riparian Forest, in the Chichibu Mountains, Central Japan

シオジ,サワグルミ,カツラが林冠を構成する奥秩父大山沢渓畔林の埋土種子の種構成を発芽試験法により調べた。本渓畔林の表層土壌(深さ5cm)からは,現存植生にあるヤマアジサイ,フサザクラやミズメなどの他に,現存植生にはないフジウツギの実生が多く発芽した。本渓畔林の埋土種子組成の特徴として,優占種のシオジがほとんど含まれなかったこと,エビガライチゴやサルナシのような動物被食散布種子が少ないこと,現存植生との共通種が多いことがあげられた。渓畔林では出水を伴う撹乱によって,古い埋土種子集団が流亡するため,動物被食散布種子が蓄積されにくく,その代わりに現存植生に由来する風散布種子や重力散布種子が多いものと考えられる。We examined the species composition of soil seed banks (to 5 cm depth), using germination tests, for the Ooyamazawa riparian forest in the Chichibu Mountains. The canopy of this forest is dominated by Fraxinus platypoda. The dominant species in the soil seed bank were Hydrangea macrophylla var. acuminata, Euptelea polyandra and Betula grossa, which existed in the above-ground vegetation, and Buddleja japonica, which was not present in the above-ground vegetation. Of the buried viable seeds, there were few Fraxinus platypoda and a few zoochorous seed plants, such as Actinidia arguta and Rubus phoenicolasius. However, there were many species found in both the buried viable seeds and the current above-ground vegetation. In riparian forests, there are frequent disturbances such as flushing. It is assumed that old seed banks which included zoochorous seeds were lost in the riparian forest, while anemochorous and/or barochorous seeds were provided by parent plants near the riparian forest