Gap‐Phase Regeneration in a Tropical Forest

Abstract

Gap—phase regeneration of trees was described for the first 5—6 yr of regrowth in 30 treefall gaps (20—705 m 2 ) in tropical moist forest on Barro Colorado Island, Panama. Trees were classified as pioneers (saplings found only in gaps) or primary species (saplings found in gaps and in the understory of mature forest). In most of the gaps studied, stem densities rose rapidly after gap formation, then levelled off or declined by years 3—6. This pattern was particularly marked in some large gaps (>150 m 2 ), where pioneers attained high densities, then experienced heavy mortality. Stem density of primary species did not vary with gap size. In large gaps the mean rate of growth in height was greater for pioneers than for primary species, size—class distribution broadened more for pioneers than for primary species, and early recruits of both regeneration types grew faster than later ones. Gap formation fosters regeneration of pioneer and primary species and, in this forest, produces patches that differ markedly in tree population dynamics, species composition, and growth rate.