Effects of canopy openings on tree seed germination in a Malaysian dipterocarp forest

ABSTRACT The germination of 43 tree species native to the lowland forests of Malaysia was monitored on forest soil in trays placed in closed-canopy forest, an artificial forest gap, and a large clearing. Germination varied significantly among habitats, with only seven species germinating well in all three sites. Seed germination of most species demonstrated clear patterns of shade tolerance or intolerance identical to those long recognized for tree seedlings. Favoured locations for germination were similar to known distributional patterns of adult individuals in mature and secondary forests. Most forest canopy species germinated in the gap, but germination in the large clearing was dramatically reduced or nil; the regeneration of these species in large clearings will be severely retarded even when seeds are present. Canopy-induced inhibition of germination was apparent in several pioneer species; seeds moved from the forest into the gap or clearing germinated rapidly. Results indicate that natural treefall gaps do not inhibit the germination of most species, but do allow pioneer species to germinate, and therefore regenerate. Although germination occurred in all three locations, the level of germination for particular species varied greatly among habitats. We conclude that germination requirements play a very important role in controlling the species composition of regeneration in forest understorey, gap, and large clearing habitats.