Nitrogen Fixation (Acetylene Reduction) Associated with Decaying Leaves of Pond Cypress (Taxodium distichum var. nutans) in a Natural and a Sewage-Enriched Cypress Dome

Forrest E. Dierberg, Patrick L. Brezonik
1981 Applied and Environmental Microbiology  
Surface litter from a natural and a sewage-enriched cypress dome in northcentral Florida showed a pronounced seasonal pattern of nitrogenase (acetylene reduction) activity associated with seasonal leaf fall from deciduous trees in the domes. Samples of peat from cores indicated negligible nitrogenase activity below the surface layer. Integrating the monthly rates of nitrogen fixation (based on the theoretical molar ratio of 3:2 for C2H4/NH3) yielded 0.39 and 0.12 g of N/mi2 per year fixed in
more » ... litter of the natural and sewage-enriched domes, respectively. The nitrogen fixed in the first 3 months after leaf fall in the natural dome represented about 14% of the nitrogen increment in the decomposing cypress leaves, but fixation contributed a negligible amount of nitrogen (<1%) to decomposing litter in the sewage-enriched dome. Cypress domes are small subcircular swamps that are found throughout the pine-palmetto woodlands of the southern Atlantic and the Gulf Coastal plain. The domes vary in area from about 1 ha to more than 10 ha (usually less than 5 ha) and are a common geomorphological landforn in the region. Odum et al. (18) proposed using cypress ecosystems as an alternative to conventional tertiary treatment of sewage effluent, and feasibility studies on this proposal have been under way near Gainesville, Fla., for the past 6 years. Ewel and Odum (5) recently concluded that the use of cypress wetlands for tertiary treatment of sewage is favorable for several reasons, including: (i) lower cost, compared with physicochemical methods; (ii) better filtration and less ecosystem change, compared with upland disposal; and (iii) higher adaptability to high nutrient and low dissolved oxygen levels, compared with disposal into rivers and lakes. Recycling treated sewage into cypress wetlands can save waste treatment costs and maintain a high-quality timber product. This alternative for treatment of sewage effluent and storn water runoff is being considered on a caseby-case basis in Florida. The disposal of treated sewage into cypress swamps stimulated studies of nutrient cycling processes in natural as well as sewage-affected t Present address:
doi:10.1128/aem.41.6.1413-1418.1981 fatcat:z2nex7vnsraanddhldja3lhmpa