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Approximately 50,000 ha of native “ohia lehua” (Metrosideros polymorpha) dominated rain forest on the windward side of the island of Hawaii experienced a dieback of the tree canopy (”ohia dieback”) during the 1960´s and 1970´s. The forests affected were located between 600 and 1,500 m elevation. Dieback stands were found in a variety of different substrates ranging from 500-10,000 years in age. In 1977, the first wave of rapid expansion had come to a halt. In recent years, new dieback areas appeared, e.g. near Mauna Loa Road and Ocean View (SW Hawaii). The Hawaiian forest decline is, obviously, still a relevant phenomenon.
In the mid-1970´s, 62 plots (20x20m relevés) were established in dieback and non-dieback forest stands to assess tree vigor, composition and structure of the vegetation, and to describe substrate characteristics. The plots are located in the National Park (Kilauea, Olaa), the Puu Makaala area, along the Saddle Road, and in the Wailuku River area. Metrosideros population structure and tree vigor were resampled on 25 permanent plots in 1982, 1986, 1990, and 1995. Ohia regeneration was quantified in sixteen 3x5m subplots systematically established within each relevé. The fifth reassessment of the permanent plots started in 2002. The Ohia Project has now become a long-term study of Hawaiian rainforest dynamics.
Todays research questions include: Do the Ohia populations regenerate? Did invasive alien species take advantage of the forest decline? If “yes”: How did/will they change the native forest? Is the prediction of future rainforest dynamics possible? And there are more questions still remaining open... . |
