Quantitative evaluation of forest communities and effects of oak wilt in a secondary forest in western Japan.

In Japan, secondary forests associated with agriculture (satoyama) had been maintained traditionally by small-scale clearcutting and short-rotation coppice forestry. After forest management was discontinued due to modernization, shade-intolerant, deciduous trees such as Q. serrata and Q. variabilis have become dominant in many secondary forests of southwestern Japan. In recent years, however, tree death from Japanese oak wilt has become wide-spread. To identify forest communities that will be most affected by oak wilt, we investigated stand structure and species composition in a 64-ha unmanaged secondary forest in Kobe, Japan. We identified three forest communities using cluster analysis of 27 survey plots. We then analyzed and visualized vegetation similarity among the communities using non-metric multidimensional scaling (nMDS). In secondary forests, Pinus densiflora–Rhododendron macrosepalum and Quercus serrata–Quercus variabilis communities, which established after pine wilt were identified. We also found communities dominated by Cryptomeria japonica, a plantation species. We predicted that Quercus serrata–Quercus variabilis communities will experience significant vegetation change after oak wilt and become low-statured, evergreen-deciduous forests. These communities, therefore, should be prioritized for active management by small-scale clear cutting to prevent further spread of oak wilt and subsequent biodiversity decline. [ABSTRACT FROM AUTHOR]