SPATIAL-DISTRIBUTION OF EURYA-JAPONICA IN AN OLD-GROWTH EVERGREEN BROAD-LEAVED FOREST, SW JAPAN

The spatial distribution of Eurya japonica, an evergreen understorey s pecies, was studied on a 4-ha permanent plot in an old-growth, tempera te, evergreen broad-leaved forest in southwestern Japan. The pattern o f spatial dispersion varied with size class, the environmental heterog eneity produced by tree-fall gaps and microtopography and the scale of observation. Seedlings (0.05 to < 0.5 m high) had the most clumped di stributions, followed by saplings (0.5 to 1.3 m high) and adults (grea ter than or equal to 1.3 m). individuals were more clumped at the smal lest grid size, 1.56 m x 1.56 m, and became less clumped as grid size increased for all size classes. On grids of less than 6.25 m x 6.25 m, no spatial correlations were found between seedlings and lar er size classes; positive spatial correlations were found between saplings and adults at this scale. Abundant seedlings appeared in tree-fall gaps f ormed by uprooted trees, but seedlings were frequent on ridge tops and upper slopes. Saplings and adults also occurred on upper slopes, but their spatial distribution had little relation to current tree-fall ga ps. The spatial distribution of E. japonica individuals was largely at tributed to the distribution of tree-fall gaps and the differential re sponses to microtopographic variation by individuals at different size classes.