Abstract
The abundance and composition of native trees established on young conifer plantations with stand ages of 10-30 years were investigated in 210 plots of 10 x 50 m within a watershed of 1000 ha, in Shizukuishi Town, Iwate Prefecture, northern Japan. Established native trees generally indicated low values in relative basal area because of the successful establishment of conifer plantations, reflecting the relatively mild snow conditions (ca. 150 cm in maximum snow depth). The dominant species of established native trees differed according to previous forest types: Pinus densiflora was dominant in plantations made by cutting P. densiflora secondary forest; Quercus serrata and Castanea crenata in plantations made by cutting Quercus crispula and Q. serrata secondary forest; Betula maximowicziana, Swida controversa, Magnolia hypoleuca, etc. in plantations made by cutting natural forests composed of Thujopsis dolabrata var. hondai, Fagus crenata, Aesculus turbinata, etc. These species are also reported to be dominant in other regions of Japan. However, Fagus crenata was scarcely found in conifer plantations in this region although this species is reported to be dominant in some regions, suggesting regional differences. The seeds of some of these dominant species were dispersed over long distances by wind or birds, or some species had soil seed banks, while large-sized seeds of others were dispersed by rodents.
