BELOWGROUND AND ABOVEGROUND ALLOMETRIES OF SHADE-TOLERANT SEEDLINGS IN A JAPANESE WARM TEMPERATE RAIN-FOREST

1. A comparative study has been made of the allometric relationships a mong below-ground and above-ground dimensions of seedlings (6.5-27 cm tall) of 14 abundant shade-tolerant species taken from the forest floo r in a warm-temperate rain forest on Yakushima Island, southern Japan. 2. The allometric lines between below-ground dimensions are significa ntly different between species, which reflects the differentiation bet ween the species developing tap-roots and those developing horizontal fine roots in the same forest. The difference correlates with a differ ence in seed size, but not with height at maturity or habitat (ridge v s slope or gully). It is hypothesized that the differences in root arc hitecture are related to 'choices' in microsite for establishment, the large-seeded tap-rooted species being better suited to soft soil and deep litter, and the small-seeded lateral rooters to rocky soil and a lack of litter. 3. The allometric relationship relating below- and abo ve-ground dry mass is not sufficient to characterize a species' archit ecture; a species may have a large ratio of root mass to shoot mass bu t a low ratio of fine-root length to leaf area. 4. Interspecific diffe rentiation in below-ground allometries at the seedling stage is not co rrelated with that in above-ground allometries at the seedling stage o r with that in above-ground allometries at the sapling stage with deve loped branching architecture. Allometric 'design' in architecture at t he sapling stage (related to earlier or later canopy-gap formation) is variously combined with that at the seedling stage (related to the mi crosite of establishment).