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Effect of irrigation on tropical forest seedling growth and survivorship during an El Niño-related drought.
Bunker, Daniel1, Carson, Walter1, 1
ABSTRACT- Tropical forests in Central America often experience severe droughts during El Niño events, and the frequency of these droughts has increased in recent years, possibly as a consequence of global climate change. To examine the effect of these droughts on tropical forest dynamics and diversity, we irrigated seedling plots in a tropical moist forest during the 1997 El Niño-related drought. Seedling age, species habitat preference, and species rarity had the greatest effect on seedling survivorship in response to irrigation. Light availability, seedling age, and species rarity had the greatest effect on seedling growth in response to irrigation. First-year seedlings benefited most from irrigation, as did species associated with wetter forests. Rare species also benefited more so than common species. These El Niño events may enhance species diversity by alternately favoring dry-forest species during El Niño years and wet-forest species during wet years. However, an increasing frequency of drought events may lead to a decline of wet-forest species diversity and a loss of rare species at this site.
KEY WORDS: tropical forest ecology, El Niño, drought tolerance, tree seedlings