Spatial distribution of Eurya japonica in an old-growth evergreen broad-leaved forest, SW Japan

The spatial distribution of Eurya japonica, an evergreen understorey species, was studied on a 4-ha permanent plot in an old-growth, temperate, evergreen broad-leaved forest in southwestern Japan. The pattern of spatial dispersion varied with size class, the environmental heterogeneity produced by tree-fall gaps and microtopography and the scale of observation. Seedlings (0.05 to < 0.5 m high) had the most clumped distributions, followed by saplings (0.5 to 1.3 m high) and adults (greater than or equal to 1.3 m). individuals were more clumped at the smallest 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 formed 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 gaps. The spatial distribution of E. japonica individuals was largely attributed to the distribution of tree-fall gaps and the differential responses to microtopographic variation by individuals at different size classes.