HR: 0830h
AN: B41C-0906    [PDF]
TI: Rainfall, Plant Communities and Methane Fluxes in the Ka`au Crater Wetland, Oahu, Hawaii
AU: * Grand, M
EM: maxime@hawaii.edu
AF: University of Hawaii, Department of Geology and Geophysics 1680 East-West Road POST 701, Honolulu, HI 96822-2219 United States
AU: Gaidos, E
EM: gaidos@hawaii.edu
AF: University of Hawaii, Department of Geology and Geophysics 1680 East-West Road POST 701, Honolulu, HI 96822-2219 United States
AB: Tropical wetlands constitute a major source of methane, an atmospheric greenhouse gas. Net methane emission in freshwater settings is the result of organic matter decomposition under anaerobic conditions modulated by aerobic methane oxidation and is thus also an indicator of wetland ecosystem processes. This study is monitoring the methane flux from the Ka`au crater wetland on the island of Oahu (Hawaii) and correlating it with environmental parameters such as precipitation and sunlight. We are obtaining precipitation, Photosynthetic Active Radiation (PAR), and water table level data with data loggers and are correlating these data with static chamber methane flux measurements and measurements of soil methane production potential. Additionally, our research is studying the effects of changes in vegetation type, i.e., of the invasive strawberry guava tree (Psidium Cattleianum) on the wetland methane emissions. Changes in soil chemistry and in the transport of gases by roots that accompany such vegetation change are a potential driver of methane flux modifications that have not been previously examined. Strawberry guava forms dense mats of surface roots that may change soil gas exchange and prolific fruiting may raise the soil organic content. We collected soil samples along a 30 meter transect that extends through two vegetation patterns; the strawberry guava canopy and the sedge meadow (Cladium Leptostachyum). Samples were incubated for 24 hours to estimate their methane generation potential. Our preliminary results show that methane generation potential is greater under the strawberry guava canopy. However, 2 of the 15 samples collected in the sedge meadow section of the transect did not match this pattern. Soil organic carbon content is slightly higher in the strawberry guava than in the sedge. We recorded a 90% decrease in methane generation potential in sedge meadow soils during a dry period relative to a wet period 2 months earlier. We propose that this change reflects a difference in the relative activity of microorganisms in the oxic and anoxic parts of the soil column. We will use environmental molecular technique to compare the microbial community component responsible for the production of methane in the different wetland soils.
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2003 Fall Meeting