Growth and survival of tall tree seedlings 6∼8 years after soil scarification in hokkaido

Abstract

Scarification is widely conducted in northern Hokkaido to remove understory dwarf bamboos in degraded forests, and to replace it with tree species. We investigated height growth and survival during 6∼8 years after the treatment for nine major tree species naturally established in a site, and examined their contributing factors (competition or facilitation).The height growth and survival rate were higher in Phellodendron amurense and Sorbus commixta, besides lower in Picea glehnii. The results of generalized linear model or generalized linear mixed model suggested that facilitation effects of surrounding broadleaved trees or understory vegetation were dominant for growth of many tree species. Regarding Betula platyphylla, however, the facilitation effect, which had been found in the former period (3∼5 years after scarification) ,was changed into competition effect. For seedling survival, although negative effects of surrounding conifers were found, effects of broadleaved trees and understory vegetation were unclear. We concluded that weeding and cleaning treatments were ineffective for enhancing species richness in the site in this stage of stand development.