Natural Regeneration of Tree Species after Clear-cutting in a Coniferous Plantation

To study the regeneration process of tree species after clear cutting, we investigated the density of seedling occurred after 1 year in the coniferous forest of Sikotuko Hokkaido, northern Japan that was clearcut after windthrow damage due to typhoon. As the results, 25 species of tree seedlings were growing and the density of seedlings and sprouts was $9.8trees/m^2$ ($1.25tres/m^2{\sim}54.44trees/m^2$) in the area of clear cutting. The 87% ($8.6/m^2$) of all seedlings was current seedlings and non-animal dispersal seedlings (average density $7.2tree/m^2$) were about 5 times more than animal-dispersal seedlings ($1.4tree/m^2$). The seedling density was beyond $6tree/m^2$ within 10m and $2{\sim}9tree/m^2$ in 150~250m from a natural forest. Number of non-animal dispersal seedlings were decreased along the distance from a natural forest but there was not such a tendency in animal dispersal seedlings. The variation in seedling density was higher in non-animal dispersal seedling than in animal dispersal seedling. In natural regeneration of tree species after clear-cutting, the possibility that pioneer species like Betula spp. etc. will be composed of the major species is high. Therefore, in order to maintain the species diversity, the nurture work for reducing competition among the individuals is necessary.

침엽수(針葉樹) 인공조림지(人工造林地) 개벌(皆伐) 후의 교목류(喬木類) 천연갱신(天然更新)

개벌 후의 교목류 천연갱신 과정을 연구하기 위하여 개벌상의 태풍피해를 입은 북해도 시코츠코지역 침엽수 조림지에서 1년 후에 발생된 치수를 조사하였다. 그 결과 25종의 교목류 치수가 자라고 있었으며 치수밀도는 9.8주/$m^2$였다. 그 중 1년생 치수가 87%(8.6주/$m^2$)였으며, 비동물산포종(7.2주/$m^2$)이 동물산포종(1.4주/$m^2$)보다 5배 정도 많았다. 인접한 천연림으로부터 100m이내에서는 치수 밀도가 6주/$m^2$이상이었으며 150~250m에서는 2~9주/$m^2$였다. 비동물산포종은 천연림으로부터 멀어질수록 치수발생량이 감소하였으며 동물산포수종에 비하여 밀도 변이폭이 크게 나타났다. 개벌 후 교목류의 천연갱신에서는 자작나무류와 같은 선구수종이 우점할 확률이 높다. 따라서 수종구성을 다양하게 유지하기 위해서는 경쟁을 완화시키는 보육작업이 필요하다.