Document Type

Article

Publication Date

January 2010

Abstract

Natural tropical wetlands constitute an important but still poorly studied source of atmospheric methane, a powerful greenhouse gas. We measured net methane emission, soil profiles of methane generation and oxidation, and related environmental parameters in a tropical wetland occupying the Ka'au extinct volcanic crater on the Hawaiian island of O'ahu. The wetland has a fluctuating water table with dynamics that can be reproduced using precipitation data and a simple model. Median net methane flux was 117 mg m-2 day-1 and is consistent with measurements at other tropical sites. Net methane flux in the Commelina diffusa—dominated vegetation pattern (honohono) was significantly higher than that of the invasive Psidium cattleianum—dominated pattern (strawberry guava). Net methane emission in the honohono vegetation pattern was also significantly higher during the "wet" season compared with the "dry" season, although we did not find a clear correlation between net methane emission, water table level, or precipitation. We show that the measured fluxes are consistent with the integrated potential methane generation over the uppermost 30 cm of soil and consumption of ∼50% of that methane in the soil. Absence of a correlation between net methane emission and water table level may be due to suppression of the activity of strictly anaerobic methanogens by dynamic redox conditions in the upper layers of soil and varying rates of methane oxidation by facultive methanotrophs.

Comments

This article was published in Pacific Science, volume 64, and can also be found online at this link.Copyright of Pacific Science is the property of University of Hawaii Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.SJSU users: Use the following link to login and access the article via SJSU databases.

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