| Species diversity in tropical forests is a major concern of ecology and conservation. This study introduces a novel approach for the study of tropical tree regeneration by experimentally creating a light gradient continuum through stand thinning. Replicates of four stand thinning treatments were implemented in 144 m2 plots within one secondary forest in the Peruvian Amazon: (a) 0% basal area cut and removed, (b) 60% cut, (c) 80% cut, (d) 100% cut. Light environments were significantly different among all four treatments, among replicate plots within treatments, and among different locations within replicate plots at both six and sixteen months after thinning. In addition, variation within and among the study plots spanned a fine-scaled, habitat continuum ranging from 0.8% to 16.7% canopy openness. Consequently, this approach supports research designs that either quantify canopy cover as a continuous variable, or classify habitat into specific treatment classes.; Seeds of native tree species were planted across the experimental light gradient. For thirteen of fifteen species, light environment predicted species-specific probabilities of successfully flushing the first set of leaves. Although successional class was not predictive of species' establishment probabilities, species with higher cotyledon specific mass in general established more readily in the shade and were less influenced by light environment.; Observations of juvenile growth revealed the value of using a continuous habitat gradient. Variation in canopy openness explained patterns growth for fourteen of sixteen species. Six of the species were of particular interest because their relationships between light environment and growth were described by curvilinear models. Three of these species grew most in intermediate light environments, while the other three species approached thresholds where additional increments in canopy openness did not result in increased growth.; The overall conclusion of this work is that regeneration niche diversity among tropical tree species is much higher than previously thought. The high diversity of tropical tree species includes a broad range of complex relationships between plant morphology, seedling establishment and growth, and light environment. Understanding those relationships is key to the management of secondary forests for the recovery and maintenance of a high diversity of native species. |
