Correlating the Current and Potential Ranges of Hawaiʻi’s Declining Native Plant Species in Relation to Slope and Aspect on the Summit of Puʻu Kōnāhuanui on the Island of Oʻahu

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2024-05-10

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The Koʻolau mountain range on Oʻahu, Hawaiʻi, is home to an exceptional amount of endemic plant life. However, the mountain range’s unique biodiversity is under threat from drought and the spread of invasive species, which is exemplified by declining rainfall patterns (Giambelluca et al., 2013). Since rainfall in Hawai’i is strongly related to the dominant trade wind pattern and orographic uplift, this study focused on understanding where certain Koʻolau endemic species are likely to be found and most resistant to these threats based on the aspect of slopes in relation to Oʻahu’s prevailing trade winds. The study surveyed species communities on the summit of Puʻu Kōnāhuanui, with the primary study site being the north, and east-facing aspects of the mountain. Labordia hosakana and Lobelia gaudichaudii subsp. gaudichaudii were the two species surveyed for this study, as both are considered to be high-risk wink-out species, meaning there is no other habitat for them to migrate to in the event their habitat becomes too degraded for their survival (Fortini et al., 2013). The data from the surveys was subsequently used to predict the most viable windswept habitats, in order to provide range information to natural resource managers on Oʻahu. The data showed that only the steepest slopes, ranging from 47.5º - 85º, and the most northerly to easterly aspects, ranging from 30º - 127.5º, proved to harbor the windswept species of concern, with the primary habitats being located between a slope of 40-60º and an aspect between 55-95º. The research findings were used to provide resource managers within the Plant Extinction Prevention Program (PEPP) the best information for protecting rare and declining plant species on the windswept Koʻolau summit from encroaching noxious weeds and for making informed management decisions regarding species of concern in the future, potentially establishing new habitats in other suitable locations throughout the range. Recommendations from the PEPP included future on-the-ground work to survey for species, targeted weed treatment to protect rare plant populations, and fencing, which has not been implemented anywhere in the southern Koʻolau mountains.

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Presentation slideshow and written report

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Rare plants, Plant Extinction Prevention Program, Plant Habitat, Invasive Species

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23

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Creative Commons

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Ragone, Noah L.

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