RECENT VEGETATION CHANGE IN DRY, LEEWARD HABITATS OF THE HAWAIIAN ISLANDS: ALIENS REPLACING ALIENS

Curtis C. Daehler

University of Hawai'i, Honolulu HI 96822

Beginning with the arrival of Polynesians over a millennium ago, most dry, leeward areas of the Hawaiian Islands have been disturbed by humans, and native vegetation has been replaced by aliens. Egler (1942) predicted that native vegetation would return if leeward areas were protected from frequent human disturbance. Two alternatives are 1) stable alien vegetation types have developed, or 2) alien vegetation types remain transitory, being replaced over time with new alien vegetation types. To examine which of these alternatives best describes the situation during the last half-century, we compared the current leeward vegetation in conservation areas with that described from surveys made 30-50 years ago. We found numerous changes in vegetation patterns and species dominance. A number of former vegetation types, including those dominated by Chloris bartata (swollen finger grass) and Rhynchelytrum repens (natal red top) have declined dramatically during the last half-century. Other formerly absent or rare aliens now dominate (e.g. Cenchrus ciliaris, Pennisetum setaceum, Panicum maximum). In general, the current vegetation types appear to attain higher standing biomass, resulting in greater fire hazards than the former alien vegetation. We found no evidence for a natural succession to native vegetation.

 

Abstract from: 43rd Symposium of the International Association for Vegetation Science, July 23-28, 2000, Nagano, Japan.


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