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

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.