Factors influencing early vegetation establishment following soil scarification in a mixed forest in northern Japan

Abstract

Scarification is widely conducted in northern Japan to remove understory dwarf bamboo species in degraded forests for replacement with tree species. To explore ways to enhance species diversity and restoration of mixed forest at the treated site, we clarified the mechanisms that lead to compositional heterogeneity of plant species. We evaluated the relative importance of environmental factors (scarification properties, soil properties, light conditions, litter cover, and presence of canopy trees) for the demography of tall tree species (emergence, mortality, and growth) and whole vegetation structure (species diversity and composition) over the two growing seasons immediately following scarification. Of tall tree species, Betula spp. were dominant (60% in total density), followed by Abies sachalinensis (Fr. Schm.) Masters, Acer mono Maxim., and Phellodendron amurense Rupr. Light intensity was an important factor, having mostly negative effects on the demography of these species. Soil factors (e.g., nitrogen content, moisture) affected the demography mainly of shade-intolerant or hygrophilous species. In general, extreme environmental conditions led to the dominance of grasses, forbs, and lianas rather than tall trees. Maintenance of canopy cover, which limits light and supplies seeds as well as litter, proved to be most important in promoting plant species diversification on the scarification site.

Variation in understory structure and plant species diversity influenced by silvicultural treatments among 21- to 26-year-oldPicea glehniiplantations

“…A typical natural (or seminatural) forest in this area has a low density of overstory trees [e.g., less than 200 stems, with diameter at breast height (DBH) ≥10 cm/ha] (Yoshida et al 2005b). Low densities are possibly related to low rates of recruitment resulting from heavy snowfall, negative effects of partial logging (Noguchi and Yoshida 2004), and severe windthrow events (Uryu Experimental Forest, unpublished).…”

“…The area of site preparation significantly influenced the sapling density of Quercus crispula. Coefficients were positive, indicating that fewer opportunities exist for this species to establish itself in nonscarified areas (Yoshida et al 2005b). It has also been reported that machinery site preparation is necessary to increase tree regeneration (Wurtz and Zasada 2001;Beland et al 2002;Yoshida et al 2005b).…”

Changes in carbon stock following soil scarification of non-wooded stands in Hokkaido, northern Japan

“…Although many larger trees were found in the plantations (Table 4) due probably to silvicultural practices (e.g. weeding and thinning) to promote the growth of planted individuals (Nagai and Yoshida 2006), dense establishment and rapid growth of a B. ermanii, a common pioneer tree species across the region (Umeki 2003;Yoshida et al 2005), compensated the carbon accumulation. Naturally, the use of faster growing species for plantation would reduce the difference, but the advantage of natural regeneration is certainly dependable if we consider management costs.…”

“…Based on actual measurement at the two-year-old S. senanensis scarified stand, we found that the scarification treatment removed surface soil to 0.1 m depth (also see Yoshida et al, 2005), and the piling process (to make mounds) reduced the volume of scarified soil to about 60% by machinery compaction. With considering the usual mound shape (semi cylindrical shape with 0.6 m height), we could assume that the scarified soil (600 m 3 ha -1…”

Stand structure and composition of a 60-year-old larch (Larix kaempferi) plantation with retained hardwoods

“…Species diversity indices for canopy-layer (dbh >= 10 cm) and shrub-layer (dbh < 10 cm and h > 2 m) trees in the three distance classes (distance from the nearest retained tree). (Sato and Hiura 1998) and can colonize and grow preferably in disturbed sites (Wurtz and Zasada 2001;Yoshida et al 2005). This species often compensates for the decline of planted trees in plantation forests (Hasegawa 1998;Kodani 1999).…”