Effect of sika deer on forest recovery after clear-cutting conifer plantations in warm temperate regions of western Japan: from a field experiment of deer exclosure and planting of Quercus acutissima

A field experiment was conducted involving deer exclosures and planting of Quercus acutissima, a deciduous oak, to reveal forest recovery patterns and factors following clear-cutting at overcrowded conifer plantation sites. Sites were selected in a warm temperate region in western Japan, which is dominated by deciduous broad-leaved secondary forests and extensive conifer plantations. Thirteen years after clear-cutting in the study area, naturally regenerated stands were established with exclosures. The exclosures housed vegetation dominated by pioneer trees, such as Mallotus japonicus or Zanthoxylum ailanthoides. In contrast, naturally regenerated stands without exclosures had limited pioneer trees present. Vegetation dominated by pioneer shrubs (e.g. Aralia elata) was established in these stands. Reduced canopy height and total basal area were observed for vegetation outside the exclosures. In stands where Q. acutissima was planted immediately after clear-cutting, the vegetation that is dominated by this species in the canopy layer was established in both stands with and without exclosure. Most of tree species that emerged after clear-cutting across all stands were of the frugivore seed dispersal type. However, results from this study suggest that these frugivore seed dispersal type trees are more vulnerable to deer browsing than trees from the Fagaceae family. Natural forest recovery following plantation clear-cutting could be inhibited due to deer herbivory at relatively low deer density if a major source of tree regeneration in clear-cut plantations is non-Fagaceae trees.