We examined an alternative natural regeneration practice with a scarification treatment, in which removed soil is replaced on the scarified area, in northern Japan. The effect of the soil replacement on tree establishment was quite obvious; the basal area of trees, composed mostly of Betula ermanii, in the soil-replaced site was about 150-fold greater than that of the normally treated site. The greater growth rates together with higher density, both of which seemed to be enhanced by improved (i.e., deeper, tender, and nutrient-rich) soil properties, produced the marked difference to the normally treated site. The expected enhancement of species diversity owing to utilizing buried seeds in the replaced soil was not found. The current study revealed that the soil replacement could substantially improve forest restoration management with emphasis on biomass production for large nonwooded sites.

To restore nonwooded stands dominated by dwarf bamboo species (Sasa kurilensis or S. senanensis) into forests, mechanical soil scarification has been applied in northern Japan since the 1960s. The treatment is followed both by natural regeneration and artificial planting. In this study, we quantified the total carbon stock (plants plus 0.3 m depth of soil) of these stands over 35-year age-sequences.The natural regeneration stands were gradually dominated by Betula ermanii. The carbon stock increased linearly to 215.1 ± 35.2 Mg C ha -1 for 37-year-old stand formerly dominated by S.kurilensis, and 181.1 ± 29.8 Mg C ha -1 for 34-year-old stand formerly dominated by S. senanensis.The latter was similar to that of a Picea glehnii plantation, formerly dominated by S. senanensis, with comparable stand age (160.3 ± 6.7 Mg C ha -1 for 35-year-old stands). Although the carbon stock in plants quickly offset the untreated level, that in the soil remained depressed even in the older stands. This resulted in small differences in carbon stock of these stands with untreated dwarf bamboo stands. We conclude that natural regeneration following scarification could be a prime option for carbon sink management in the region. However, we should take a long rotation period (i.e. > 50-year) to ensure a carbon sink state. A potential of further improvements of the practice, including that reduce intensity of soil disturbance, was presented.