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Precipitation, Plant Communities and Methane Fluxes in the Ka‘au Crater Wetland, O‘ahu, Hawai‘i

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Title:Precipitation, Plant Communities and Methane Fluxes in the Ka‘au Crater Wetland, O‘ahu, Hawai‘i
Authors:Grand, Maxime
Contributors:Gaidos, Eric (advisor)
Oceanography (department)
Global Environmental Science (department)
greenhouse gasses
Date Issued:2003
Publisher:University of Hawaiʻi at Mānoa
Place of Publication:Honolulu
Abstract:Methane emissions from the Ka`au crater tropical wetland on the island of O`ahu were
monitored from August to November 2003. Net methane emission was measured using static
chambers and the methane production and oxidation potentials of soil samples were assayed.
Environmental parameters (water table level, precipitation, temperature and
Photosynthetically Active Radiation (PAR)) were also measured. In addition, the organic
chemical composition in different soils was measured.
Average net methane emissions varied considerably among different vegetation
patterns in the wetland, ranging between 17 and 160 mg m-2 day-1
. Considering the area
covered by each pattern, the average net methane flux from the crater is 84 ± 4 mg m-2 day-1
Methane production potentials ranged between 6*10-6 and 1*10-3 mg g(dry soil)-1 day-1
Methane oxidation potentials were approximated using first order reaction kinetics and ranged
between 0.08 and 0.026 hr-1 g(dry soil)-1
Water table level was found to be the main environmental parameter influencing net
methane emissions, affecting primarily the methane generation potential of soil samples.
Methane oxidation potentials were mostly affected by ambient methane concentrations. The
variation in methanogenic activity due to the ± 0.05°C temperature variation recorded in the
soil throughout the sampling period was calculated to be 0.07%, much less than the observed
variation in net emission and methane generation potentials. No correlation was observed
between net methane emissions and PAR. Moreover, the soil organic carbon content was
similar among three of the five vegetation patterns studied.
Past changes in vegetation suggest that methane emissions may have decreased since
the early 1900s. This trend is expected to prevail in the future if the vegetation patterns
contributing the least to the overall methane flux spread. Additionally, anthropogenic
greenhouse warming is likely to reduce precipitation in Hawaii during this century which
may in turn reduce the net methane emissions from the Ka`au crater wetland even further.
Pages/Duration:83 pages
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Rights Holder:Grand, Maxime
Appears in Collections: Global Environmental Science (GES)

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