Regeneration responses influenced by single-tree selection harvesting in a mixed-species tree community in northern Japan

摘要

The objective of this study was to assess the effects of fine-scale canopy disturbances induced by selection harvesting and its associated practices (artificial planting and machinery skidding) on the successful regeneration of tree species in a northern Japanese mixed forest. We set up 163 plots in a 6.7 ha permanent study stand where trees have been partially harvested at approximately 10-year intervals since 1974. The regeneration of trees (4324 stemsp"ha-1) occurred more frequently under closed canopies than under canopy gaps, except for a typical shade-intolerant species, Betula ermanii Cham. In particular, small canopy openings that tend to close quickly displayed higher understory tree regeneration densities likely due to the suppression of competition from dwarf bamboos. The surface soil disturbances that occurred during planting and harvesting even further enhanced understory regeneration. The results shown here should be generalized carefully because we have investigated only one stand. Nevertheless, our findings clearly indicated that the creation of small canopy gaps associated with site preparation that contains soil disturbances should be examined in management practices to maintain the community structure in this type of mixed forest.