Survival and recruitment of Sasa kurilensis culms in response to local light conditions in a cool temperate forest

Dwarf bamboos (Sasa spp.) are clonal plants and are known to inhibit tree regeneration. In natural conditions, however, culm dynamics in response to local light conditions is not fully understood. In this study, we examined the relationship between local light conditions and culm survival or recruitment of Sasa kurilensis in an old-growth beech forest in Japan. We identified 1466 S. kurilensis culms with lengths ≧0.5 m in forty 2 × 2 m quadrats in 2014 and recorded their survival rate and the number of newly recruited culms in 2015. From 2014 to 2015, the number of dead and recruited culms in 160 m² area were 179 and 118, respectively. Our model indicated that the recruitment density was not influenced by the horizontal light intensity, and it increased as the number of pre-existing culms increased. In contrast, culm survival rate increased with an increase in the horizontal light intensity just above the Sasa layer and with a decrease in the degree of shading by the conspecific leaves. This finding suggests that the life span of S. kurilensis culms both horizontally and vertically varies in response to local light variations in the old-growth beech forest.