Regeneration Success of Chamaecyparis obtusa after Selection Cutting Practice in a Natural Forest without Dwarf Bamboo Undergrowth

Abstract

Natural regeneration practices via selection cutting were examined in a Chamaecyparis obtusa forest with undergrowth that lacked dwarf bamboo. The work was performed in the Akasawa Experimental Forest, Kiso District, central Japan. The forest floor light conditions were improved after selection cutting and clearing of the undergrowth of deciduous shrubs. Subsequently, the light conditions worsened due to reduced canopy gaps and undergrowth recovery, with different delayed deterioration rates depending on the location. Thirty years after cutting, the total mean density of C. obtusa seedlings and saplings amounted to hundreds of thousands ha^-1. The sapling(＞1.3 m in height) density varied widely; the relative frequency at which the sapling density exceeded 3,000 ha^-1 was no more than 38％. This variation demonstrated a mixture of successfully regenerated sites with sapling banks and unsuccessfully regenerated sites that would have had little chance of achieving sapling banks in the future. The seedling density 3-5 years after cutting did not significantly correlate with sapling density 30 years after cutting. In contrast, the seedling density and light conditions 15 years after cutting, and topographic conditions, were closely related to sapling density and sapling bank success. This relationship suggested the continuation of improved light conditions resulted in regeneration success. The prediction of successful regeneration probability is likely possible not from the initial seedling density but the light and topographic conditions.