Early-stage vegetation recovery in forests damaged by oak wilt disease and deer browsing: effects of deer-proof fencing and clear-cutting

摘要

Oak wilt disease and deer browsing have depleted the canopy and forest floor of secondary Quercus serrata and Quercus variabilis forests in Japan. Small-scale clear-cuttings enhance sprouting, and are, therefore, recommended for restoration of the damaged forests. However, most damaged forests are composed of mature stands, and it is not clear whether they would sprout successfully when cut. Moreover, little is known about the regeneration of forests damaged by both oak wilt disease and deer browsing. To determine the appropriate treatment for restoration of damaged Q. serrata and Q. variabilis forests, we established a study site with three different treatments (10 x 30 m each) in Kyoto City: clear-cut and fenced, removed dead oak trees and fenced, and removed dead oak trees and unfenced. After 1-year treatment, the number of species and individual saplings tended to increase at the lower slope of each treatment site with dominance of Ilex pedunculosa. The largest species and individual numbers were observed at the clear-cut fenced site, where pioneer species such as Mallotus japonicus were found. A few seedlings of Q. serrata were found at each treatment site, and no Q. variabilis was recorded. The emergence of Q. serrata seedlings was explained by their location at the slope and not by the treatment. Moreover, many sprouts of Q. serrata and Q. variabilis were observed at the clear-cut fenced site. Although further monitoring is needed, clear-cutting and fencing appear to be an effective method for the rehabilitation of depleted forests.