Significance and limitation of scarification treatments on early establishment of Betula maximowicziana, a tree species producing buried seeds: effects of surface soil retention

摘要

We compared early establishment of B. maximowicziana, a commercially valuable tree species producing buried seeds, among the standard scarification and three alternative treatments in which surface soil was retained (soil replacing, screening, and plowing). We found the efficiencies of the soil retention for the seedling emergence were clearly different among the treatments; the replacing and plowing caused significantly richer seedling emergence, whereas the screening resulted in lower emergence than the standard treatment. In total, the most abundant seedling emergence was estimated to have occurred in the case of higher soil water content with lower soil hardness. These seemed to be attributed to soil properties, induced differently by each treatment, and relatively high water demand characteristics of B. maxomowicziana. On the other hand, plowing showed low seedling density at the end of the second growing season despite its greater emergence, probably because of suppression from understory vegetation recovered from undisturbed root system. We conclude that replacing would be a best alternative for regeneration of B. maxomowicziana. The scarification treatments in which surface soil is retained can be evaluated to be positive or negative according to the site conditions, physiological characteristics of the target tree species, and recovery of other vegetation.