Study of Long-Term Climate Change and Plant and Ecosystem Processes in Hawai‘i Using Copper Oxide Chemistry of Organic Sediments
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2014-09-26
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University of Hawaii at Manoa
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Native plant litter from the Pēpē‘ōpae Bog (Moloka‘i) was collected, as well as organic soil cores from Ka‘ala mountain (O‘ahu) and Pēpē‘ōpae, as these sensitive environments are relatively pristine and where organic matter and plant lignin are preserved. The objective of this study was to examine whether plants differ in their lignin chemistry and identify any changes in plant-derived lignin compounds in two contrasting peat profiles. Plant lignin compounds in plant litter and soil profiles were isolated using copper oxide (CuO) extraction to investigate lignin types and the stages of lignin degradation. Studying long-term plant inputs and organic matter decomposition using lignin chemistry was successful; plant lignin concentrations ranged from 421-92,700 μg/ g C, and plants from 660-14,00 μg/ g C. A Principal Components Analysis (PCA) of lignin concentrations results showed diverse and distinct lignin chemistry between plant litter types and soil depths. Lower plants – Dicranopteris and Lycopodiella – consisted of greater p-Hydroxyacetophenone concentrations than other species – Styphelia, Machaerina, Vaccinium, and Metrosideros – which consisted more of S-compounds. Down-core results revealed that these peat-forming ecosystems formed 12,000 (Ka‘ala) and 9500 (Pēpē‘ōpae) years ago, and lignin chemistry suggest woody and vascular plants dominated first, and lower plants dominated later in the Holocene. The drier site at Ka‘ala may also be showing a more sensitive climate response, as its C:N and total lignin concentrations had greater variability compared to the wetter Pēpē‘ōpae site. Further work will be done on these sites for more detailed lignin data and radio-carbon dates.
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vii, 38 pages
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