PARENT SESSION
Oral Session # 4: Forest Ecology I: Diversity, Suppression, and Release.
Presiding: B Schamp
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 103.
Suppression and release during canopy recruitment of five tropical tree species of differing shade tolerance.
Baker, Patrick1, 1 Institute of Pacific Islands Forestry, USDA Forest Service, Hilo, HI
ABSTRACT- How trees reach the upper canopy of tropical forests is poorly understood due to the lack of long-term growth data. In temperate forests, ecologists have identified several different patterns of canopy recruitment using tree-ring analyses. To determine if similar patterns of canopy recruitment occurred in tropical tree species, I analyzed annual growth rings from 92 canopy trees (>20 cm dbh) of five species in a mature stand of species-rich seasonal dry evergreen forest in western Thailand. The species included Neolitsea cambodiana (Lauraceae) and Vitex peduncularis (Verbenaceae), two relatively shade tolerant species, Toona ciliata (Meliaceae) and Chukrassia tabularis (Meliaceae), two moderately shade intolerant species, and Melia azederach (Meliaceae), a highly intolerant gap species. Mean tree age was 67 y (range: 23-129 y). Mean annual growth rates were positively correlated with relative shade tolerance; however, there was wide variation in radial growth rates within and amongst trees and species. Growth release patterns differed among species. The number of minor growth releases (i.e., growth increases of >50% sustained for 10 y) was positively correlated to shade tolerance; however, the number of major releases events (i.e., radial growth increases of >100% sustained for 10 y) were similar for all species, except Melia which showed no releases. Qualitative assessments of the tree-ring series showed several different patterns of canopy recruitment that varied in relative abundance amongst species. These included (1) direct recruitment to the canopy, (2) a period of prolonged suppression followed by growth release into the canopy, (3) multiple periods of suppression and growth release prior to canopy recruitment, and (4) continuous suppressed growth without growth release. These patterns are similar to ones described for temperate forests and further underscore similarities in stand development patterns between temperate and tropical forests.
Key words: annual growth rings, canopy disturbance, stand dynamics, Thailand