© 2004 Heron Publishing—Victoria, Canada
Photosynthesis, carbohydrate storage and survival of a native and an introduced tree species in relation to light and defoliation
S. M. Gleason (1, 2) and A. Ares (1, 3, 4)
1. Department of Natural Resources and Environmental Management (NREM), University of Hawaii, 1910 East-West Road, Honolulu,
HI 96822, USA / 2. U.S. Army Garrison, Hawaii, Directorate of Public Works, Environmental Division, Pohakuloa Training Area, P.O. Box 6346, Hilo,
HI 96720, USA / 3. Weyerhaeuser Company, 505 N. Pearl Street, Centralia, WA 98531, USA / 4. Corresponding author (adrian.ares@weyerhaeuser.com) / Received April 25, 2003; accepted February 28, 2004; published online August 2, 2004
Summary
Fraxinus uhdei (Wenz.) Lingelsh (tropical ash), a species introduced to Hawaii from Mexico, invades forests of the endemic tree Acacia koa A.Gray (koa). We examined physiological and morphological characteristics of koa and tropical ash to explore possible mechanisms
that may facilitate invasion of koa forests by tropical ash. Seedlings of both species were grown in a greenhouse in three
light treatments: 100% photosynthetic photon flux (PPF); 18% PPF; and 2% PPF inside the greenhouse. Light compensation point,
maximum CO2 assimilation rate and dark respiration rate of seedlings differed significantly among light treatments, but were similar
between species. A defoliation experiment indicated that tropical ash was better able to survive defoliation than koa, especially
under high-light conditions. Tropical ash seedlings allocated more carbon (C) and nitrogen (N) to storage per unit PPF than
koa seedlings. Total nonstructural carbohydrates were positively correlated with plant survival in both species. The patterns
of C and N allocation associated with tropical ash seedlings favor their survival in high light, under intense herbivory and
on sites where N availability is seasonal or highly variable. Variation in carbohydrate storage between koa and tropical ash
greatly exceeded variation in photosynthetic performance at the leaf level.
Keywords:
Hawaii, invasive species, nitrogen-use efficiency, nonstructural carbohydrates.
