LAUSR

Abstract The montane region of Hokkaido, northern Japan, was originally dominated by mixed forests of broad-leaved trees and conifers. Since the 19th century, human disturbance has eliminated most of the original conifers. During the second half of the 20th century, after the clearcutting of the degraded natural forests dominated by broad-leaved species, the native conifer species Abies sachalinensis was planted. We have investigated the understory vascular plants in mature planted A. sachalinensis stands (aged 47–61 years) and in neighboring natural stands to identify the importance of the planted conifer forests as habitats for understory species. Often the planted A. sachalinensis forests are mixed with broad-leaved trees retained in the planted area. Species composition was associated with elevation, thinning history, and overstory types (evergreen conifers or deciduous broad-leaved trees), and split into six community types using the non-metric multidimensional scaling (nMDS) analysis. The understories of the stands dominated by broad-leaved trees were commonly covered with Sasa spp. and the species richness was low. At the same time, some species exhibit a positive association with the basal area of the broad-leaved trees and coverage of Sasa spp. Alternatively, the closed canopies of the A. sachalinensis kept Sasa from dominating the understory. Variable thinning operations can also lead to provide a variety of habitats for understory plants. Thus, planted conifer forests can provide habitats for various understory plants through the diversity of forest management, such as retention of broad-leaved trees and thinning operations.