Effect of canopy openness on growth, specific leaf area, and survival of tree seedlings in a temperate rainforest of Chiloé Island, Chile

Abstract

Tree species of intermediate-shade tolerance may regenerate in canopy gaps as well as in the forest understory. However, seedling performance may vary widely between shaded and open habitats. In this study, we assessed the differences in relative growth rate (RGR), specific leaf area (SLA), and survival of seedlings of the tree species Drimys winteri (Winteraceae) and Gevuina avellana (Proteaceae) planted in three forest habitats differing in light availability: (1) forest interior, (2) forest edge, and (3) tree-fall gap (1%, 6%, and 12% of canopy openness, respectively). A total of 60 3-month-old seedlings of each species were monitored over 16 months (December 2001-April 2003) in the three habitats of a Valdivian rainforest fragment on Chiloé Island, southern Chile. RGR was greatest in the tree-fall gap in both species. Allocation to leaves was proportionally higher in the forest interior. SLA tended to be lower in the tree-fall gap, intermediate in the forest edge, and greater r in the forest interior in both species. In addition, SLA of D. winteri seedlings was always greater than that of G. avellana in all three habitats. Survival of both species was greatest under the canopy gap and lowest in the forest interior. Survival of seedlings of the larger-seeded species, G. avellana, was greatest during the first few months of the experiment in the forest interior, but then dropped significantly in the period during which seedlings of the smaller-seeded species, D. winteri, survived in greater numbers. Our comparative study of two intermediate-shade-tolerant tree species documented wide variation in growth and survival of seedlings among habitats differing in canopy openness