Changes in Vegetation and Environment Over the Holocene Kaʻau Crater, Oʻahu, Hawaiʻi

Abstract

Rainfall at three mountaintop locations, two windward: Palolo (Kaʻau Crater), Poamoho, and one leeward: Mount Kaʻala, on Oʻahu, Hawaiʻi, was analyzed. Poamoho was found to receive the greatest rainfall monthly and annually, from 1920-2007, followed by Palolo and Mount Kaʻala. Kaʻau Crater sits at 460 m elevation in the southern Koʻolau Mountains and at present contains a wetland ecosystem and has accumulated many meters of sediment. At Kaʻau Crater, both rainfall and water table level were measured and were greatest between November and March. Rainfall and water table level were found to have a significant relationship. A 4.5 m sediment core retrieved from the crater dating through the Holocene, with seventeen 14C dates, contains fossil pollen including Malvaceae, a dry indicator, and wetindicator taxa such as Arecaceae Prichardia. The precipitation reconstruction derived from the pollen stratigraphy shows a drier early Holocene and a relatively wetter mid to late Holocene.