THE ARCHITECTURE AND ALLOMETRY OF MANGROVE SAPLINGS

1. The architecture and allometry of eight populations of mangrove tre e saplings of seven species (1.5-3 m in height) were studied at Sungei Merbok, Kedah, Peninsular Malaysia. Three populations (Bruguiera cyli ndrica, Bruguiera parviflora and Rhizophora apiculata) were growing in shaded conditions, the other five (Avicennia alba, Rhizophora apicula ta, Rhizophora mucronata, Sonneratia alba and Xylocarpus granatum) wer e in the open. 2. Comparisons were made between the population specifi c allometric regressions for dimension pairs of the form ln y = b1 ln x + b0. The bifurcation ratio (R(b)) for the-branching system of each sapling was calculated. 3. In the majority of the allometric regressio ns the populations differed significantly in b0 but not b1, though som e significant slope differences were found, particularly for regressio ns involving root dry weight. 4. The allometric analysis showed that f or saplings of the same height, those growing in the shade had lower s hoot dry weight and lower dry weight and area of leaves than the open- grown ones. The shaded saplings also exhibited a greater accumulation of foliage at the top of the plant. 5. Xylocarpus granatum was notable for a low investment in leaves, which was probably explained by recen t flushing, and in roots, which may reflect the limited development of pneumatophores in this species. The shaded Bruguiera populations show ed a relatively high root investment probably because of their abundan t pneumatophore development. 6. When compared to published results of allometric analyses for shaded saplings from lowland tropical rain for est and warm temperature rain forest it was found that the shaded mang roves were consistently more similar to the unshaded mangroves than to the rain-forest saplings. This may be because the shaded mangroves we re growing under higher average irradiances than those from the rain f orests. It is argued, however, that mangrove species are inherently mo re likely to show an architecture better suited to high irradiance con ditions than the majority of broad-leaved evergreen rain-forest trees.