METHANE AND CARBON-DIOXIDE DYNAMICS IN TYPHA-LATIFOLIA (L.) WETLANDS IN CENTRAL NEW-YORK-STATE

I examined differences in the biogeochemical cycles of CH4 and CO2 (fl uxes, concentrations, production, CH4 oxidation) in Typha latifolia we tlands on silty clay sediment versus organic peat soil in central New York State to determine whether variation in the amount of organic mat ter in sediment or soil, or plant production on sites with different o rganic matter content, affected variation in CH4 and CO2. I found very high temporal variation in CH4 within each site, precluding the detec tion of variation in CH4 as a function of sediment or soil organic mat ter content. In 1994, CH4 efflux from two peat sites to the atmosphere averaged 7 and 87 nmol m(-2) s(-1) compared to 89 and 408 nmol m(-2) s(-1) for two sediment sites. Mean CO2 efflux from the peat sites was 0.40 and 1.51 mu mol m(-2) s(-1) compared to 1.02 and 1.65 mu mol m(-2 ) s(-1) for the sediment sites. I assessed the role of plant productio n by experimentally removing T. latifolia shoots from small plots: thi s lowered CH4 efflux from the sediment site by 85%, suggesting that pl ants foster CH4 production in low organic matter sediment, but CH4 eff lux was 14-times greater following shoot removal on one peat site. Sho ot removal had no effect on CO2 efflux. Variations in temperature, dis solved organic carbon, and pCH(4) in sediment or soil porewater explai ned the variation in CH4 efflux among the four study sites, whereas va riation in net primary production explained the variation in CO2 efflu x.