Effect of difference of floor vegetation cover on regeneration of trees on an old-growth cedar and cypress plantation

Abstract

Number and height of regenerated trees were investigated on three different covers(1%, low cover site(LC); 30%, middle cover site(MC); 80%, high cover site(HC))of floor vegetation inside and outside of three deer-proof fences in an old-growth cedar and cypress plantation diminished by sika deer for 12 years after selection logging. Understory relative Photosynthetic Photon Flux Density increased with selection logging on three sites inside the fences. Floor vegetation cover also increased with selection logging, and LC needed 4 years to increase as well as HC. Both species richness and number of individuals following selection logging were most on LC. The number of regenerated trees over 1m in height was 11,873 saplings /ha on LC, 7,499 saplings /ha on MC, and 2,083 saplings /ha on HC at 12 years after selection logging. These results indicated that many regenerated trees invaded, established and grew on LC. In contrast, outside the fence 12 years after selection logging, there was no difference among sites for species richness or number of individuals, and both were less than inside the fence. Therefore I conclude that control of both floor vegetation and sika deer in addition to overstory tree density control was needed to regenerate trees on the overbrowsed old-growth plantation.