Abiotic And Biotic Factors Associated With Current And Long-term Native And Non-native Plant Cover Across An Invaded Hawaiian Landscape

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dc.contributor.advisorDaehler, Curtis C.
dc.contributor.authorhibit, joshua
dc.contributor.departmentBotany
dc.date.accessioned2020-07-07T19:02:12Z
dc.date.issued2020
dc.description.abstractExtended periods of disturbance and the introduction of non-native species pose major threats to native Hawaiian forests, many of which exist today as remnant patches, harboring native plant species that are on the brink of extinction. When native Hawaiian plant species are faced with competition from biogeographically cosmopolitan non-native species they are often at a disadvantage, especially in easily accessible areas and where high resource availability fuels the growth of invasive species, which can displace existing natives. However, relatively few datasets exist which can give insight into the long-term impacts of anthropogenic disturbance and species introductions on indigenous and endemic Hawaiian plant species across the myriad of abiotic site conditions that exist in the Hawaiian Islands. In addition, the importance of plant functional diversity, phylogenetic diversity, and biogeographical diversity for determining native resilience in invaded oceanic island forests has not been well established. To address this gap in knowledge I established fifty 400 m2 forest plots in the Waiʻanae and Koʻolau mountain ranges on Oʻahu, Hawaiʻi, and assessed current native and non-native plant cover trends in relation to measures of diversity and trait-mediated interactions of the constituent species in each plot. Thirty-two of these plots had also been previously surveyed, which allowed for an assessment of trends in endemic, indigenous, and non-native plant cover over time, and how these trends vary across abiotic gradients from dry to wet forest. The results of this study indicate that native Hawaiian forests may not be successfully regenerating and are being invaded by non-natives. Native and non-native plant cover values were determined by their respective diversity measures, as well as competition for light. invasion success was not related to overall trait dissimilarity, but there are likely additional traits which were not measured in this dissertation that influence competitive outcomes and/or niche filling between natives and non-natives. Non-natives exhibited a variety of successional strategies, reflecting the introduction history of tree species into the Hawaiian Islands for forestry purposes, as well as the intentional or accidental introduction histories of other herbaceous and woody species, and the diverse biogeographical origins from which these species arrived. Long-term trends showed that, as non-native plant richness and abundance has increased over time, native species in aggregate have concomitantly declined. However, this was largely the result of the loss of endemic species richness and cover, which were more susceptible than indigenous species to decline in the face of invasion, even where ungulates were excluded. Endemic species were more dependent on site conditions than indigenous species, which increased in overall cover over time, indicating that generalizations about natives as a single group may be misleading. Some of the indigenous species which increased in cover the most were early successional species, and may thus reflect disturbed or degraded conditions, rather than a trend toward recovery of natural native forests. These results suggest that an upscaling of active management efforts is needed to avoid further decline of native species, particularly endemics, and to stymie the tide of forest invasion by non-native species.
dc.description.degreePh.D.
dc.embargo.liftdate2021-01-06
dc.identifier.urihttp://hdl.handle.net/10125/68900
dc.languageeng
dc.publisherUniversity of Hawaii at Manoa
dc.subjectBotany
dc.subjectStorage batteries
dc.titleAbiotic And Biotic Factors Associated With Current And Long-term Native And Non-native Plant Cover Across An Invaded Hawaiian Landscape
dc.typeThesis
dc.type.dcmiText
dcterms.spatialHawaii
local.identifier.alturihttp://dissertations.umi.com/hawii:10606

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