Effects of topsoil removal by soil-scarification on regeneration dynamics of mixed forests in Hokkaido, Northern Japan


Dwarf bamboo creates a dense carpet that prevents forest regeneration in mixed forests of Japan. Soil-scarification has been used widely to regenerate such forests. However, no study has specifically addressed the effects of soil-scarification on regeneration dynamics following such perturbation. This study analyzed the demography and community structure of the most abundant species 6 years after soil-scarification in a mixed forest stand of Northern Japan. We used canonical correspondence analysis (CCA) to analyze environmental factors effects on species distribution. Using multiple regression analysis, we determined the net balance of competition and facilitation. Abies sachalinensis and Picea glehnii are the most abundant species; Betula sp. and Salix bakko are the largest ones. Increasing distance to the edge of the scarified area is generally concomitant with decreasing seedling density, but changes in extension growth show idiosyncratic responses. These results, together with those of CCA, suggest that light is the main factor directly affecting (with high levels of irradiance) and indirectly affecting (by changing volumetric soil water content) seedling demography and structure. Multiple regression analyses show that facilitation is the most important interaction affecting seedling growth, probably by reducing excess levels of irradiance. (c) 2005 Elsevier B.V. All rights reserved.