Seeds , Seedlings , and Gaps Size Matters A study in the tropical rain forest of Guyana

Growth rates of seedlings of eight tropical rain forest tree species were compared under five different canopy openness levels (FU and 50, 200, 800, 3200 m gaps). RGR exhibited a positive relation with canopy openness with species attaining their highest RGR at the 800 m (4 species) or 3200 m (3 species) gaps. Seed mass and RGR were negatively related. The increase in RGR between small and large gaps was highest for small seeded species, with these species more than doubling their RGRs. The RGR of most large seeded species remained relatively constant over all gaps. Canopy openness had opposing effects on NAR and LAR for most species. Usually as LAR decreased, NAR increased with decreasing canopy openness. However, this resulted in only marginal decreases in RGR. Small seeded species sharply increased their NAR compared with marginal increases in large seeded species. This ability of small seeded species to greatly increase their NAR is what results in their RGR being more than double that of large seeded species in the same gap size.