Diversity of naturally regenerating tree species in the overstorey layer of Larix kaempferi plantations and abandoned broadleaf coppice stands in central Japan

Abstract

Forestry, Vol. 83, No. 3, 2010. doi:10.1093/forestry/cpq011 For Permissions, please email: journals.permissions@oxfordjournals.org Advance Access publication date 12 May 2010 Introduction One-quarter of Japan’s land area is occupied by plantations (10.4 million ha in 2001). In many plantations, active management or ‘tending’ (weeding and thinning) of the forests has been abandoned due to declining timber prices and an aging workforce. Consequently, the extension of plantation rotation periods has become an increasingly common means of producing more valuable timber in maturing stands and of maintaining biological diversity. Species diversity in forests is strongly affected by the kinds of forest management interventions employed, and the impacts of these interventions can have a marked and variable effect on the structure and functioning of different forest ecosystems (e.g. plantations, coppice forests). Studying the effects of forest management is considered an important aspect of sustainable ecological forest management because it promotes an understanding of the relationship between stand structure and species composition (Kerr, 1999; Cummings and Reid, 2008). Since stand age can also influence the species composition of forest stands, a chronosequence approach is increasingly being applied to studies of how stand age and stand management practices influence stand composition (Hunt et al., 2003; Nagaike et al., 2006a). Plantations would be designated for ecological restoration when it is recognized that they were established on sites that are unsuitable for timber production and where there is a need for conserving biological diversity (Zerbe, 2002; Masaki et al., 2004; Cummings and Reid, 2008). The change in species composition associated with stand age in plantations differs with that in naturally regenerated stands since different regeneration processes (i.e. planting vs natural regeneration) and tending procedures (e.g. weeding and thinning) are employed. Stand age of plantations is important because it is directly related to the amount of timber produced and the cutting rotation employed in a landscape. When considering the requirements of ecological restoration initiatives, it is important to set the end points of either natural or historical conditions as a target for the restored forests (Stanturf, 2005) and establish baseline data for the composition of naturally regenerated tree species in the subject plantations. In addition, as another end point, the plantations should also be compared with natural forests as the end points, which represent the natural condition of forests in a region. Forest management (e.g. directly removing trees and shrubs by thinning and weeding) is known to affect each stratum of the forest differently (Nagaike et al., 2003; Diversity of naturally regenerating tree species in the overstorey layer of Larix kaempferi plantations and abandoned broadleaf coppice stands in central Japan