THE IMPACT OF PHYSICAL DAMAGE ON CANOPY TREE REGENERATION IN TROPICAL RAIN-FOREST

(1) This study assesses the frequency, rates of occurrence, and consequences of physical damage to individuals of nine canopy tree species in primary tropical rain forest at the La Selva Biological Station, Costa Rica. (2) For all species combined, frequency of damage varied from 9 to 27% among five size classes. Frequency of damage was negatively correlated with diameter growth rates for stems 1-30 cm in diameter. (3) Rates of damage due to falling litter ranged from 1 to 7% year-1 for trees up to 30 cm in diameter. Calculated half-lives until death or damage due to falling litter increased from 10 years for stems less-than-or-equal-to 1 cm in diameter to 63 years for stems 10-30 cm in diameter. (4) Rates of mortality were higher in damaged individuals than in undamaged plants for stems up to 10 cm in diameter. Absolute rates of mortality decreased with increasing stem diameter, but the relative contribution of physical damage as an agent of mortality increased with stem diameter. Litterfall caused at least 20% of the mortality of stems less-than-or-equal-to 1 cm in diameter, and accounted for 41% of the deaths of stems 1-30 cm in diameter. (5) Damage and death due to falling litter are important factors affecting plant regeneration throughout the humid neotropics. Future studies are likely to show that the same is true for temperate-zone closed-canopy forests.