JACOBI: Metrosideros DIEBACK IN HAWAI'I

Approximately 50,000 ha of native wet Metrosideros forest on the island of Hawai'i experienced a drastic reduction (dieback) of the tree canopy between 1954 and 1977. Two general hypotheses have previously been suggested to explain this phenomenon: 1) Metrosideros dieback has resulted from recently introduced pathogens, and 2) the dieback has naturally occurred previously in Hawai'i, and is related to plant succession under periodic conditions of climatic instability which effect the soil moisture regime. Plant species composition, vegetation structure, and general substrate characteristics (lava flow type and soil drainage) were sampled on adjacent dieback and non-dieback rain forest stands. Although the only primary difference identified between these two forest stands was lava flow structure, both the soil drainage conditions and the plant communities which had developed on the two sites were found to be considerably different. The results of this study lend support to the successional hypothesis of Metrosideros dieback.