Population structure and spatial patterns for trees in a temperate old-growth evergreen broad-leaved forest in Japan

The population structure and spatial pattern of major tree species in a war m-temperate old-growth evergreen broad leaved forest in the Tatera Forest R eserve of Japan were investigated. All stems greater than or equal to 5 cm in diameter at breast height (DBH) were mapped on a 4 ha plot and analyses were made of population structure and the spatial distribution and spatial association of stems in different vertical layers for nine species. This wa s done in the context of scale dependency. The plot was located on a very g entle slope and 17.1% of its canopy layer was in gaps. It contained 45 wood y plant species and 4570 living stems with a basal area of 63.9 m(2) ha(-1) . Castanopsis cuspidata var. sieboldii. the most dominant species fur the b asal area, had the maximum DBH among the species present, fewer smaller ste rns and a lower coefficient of statistical skewness of the DBH distribution . The second most dominant species, Dystilium racemosum, had the highest st em density (410 ha(-1)), more abundant smaller stems and a relatively highe r coefficient of skewness. Most stems in different vertical layers showed a weakly aggregated distribution with loose colonies as basic units. Gap dep endency for the occurrence of stems under the canopy layer was weak. Maximu m slope degree of the plot also weakly affected the occurrence of stems. Sp atial associations varied among intra- and interspecific cohorts in the dif ferent layers and spatial scales examined, and positive associations among cohorts were found more frequently as the scales examined became larger. Th is tendency suggests that key factors forming observed spatial associations might vary with the spatial scales.