Seed mass and light requirements for regeneration in Southeast Asian rain forest

Abstract

Seed mass values are given for 140 species of primary lowland rain forest and associated secondary forests in Singapore. Among shade-tolerant species of primary forest there is a trend for a decrease in mean seed mass with tall trees > woody climbers > small trees > shrubs > herbs; the differences between tall trees and small trees or shrubs or herbs, and between herbs and small trees or woody climbers are significant. There are a few light-demanding herbs or shrubs in the primary forest; among small trees, light demanders have significantly lower seed mass values than shade tolerators. In 9 out of 13 comparisons within taxa including both shade tolerants and light demanders the former had appreciably larger seeds than the latter. Two out of 13 comparisons involved very small seeded shade tolerators, and one a notably large-seed light demander. Many shade-tolerant herbs, shrubs, and trees have seed mass values much smaller than those of trees of secondary forest conventionally regarded as small seeded, and exploit moist, litter-free sites, e.g., steep microslopes. The trees of secondary forests on degraded soils do not differ significantly in seed mass from those on nondegraded soils. Key words: seed mass, light requirement, regeneration, tropical rain forest, phylogenetic analysis.