CS08 Biogeochemical Cycles
Date: Tuesday, June 11, 2002
Location: Poster Session - VCC
 
InglettPW, Wetland Biogeochem. Lab., University of Florida, Gainesville, FL, USA, pinglett@ufl.edu
Reddy, K, R, Wetland Biogeochem. Lab., University of Florida, Gainesville, FL, USA, krr@mail.ifas.ufl.edu
 
STABLE ISOTOPIC INDICATORS OF PHOSPHORUS LOADING IMPACTS ON WETLAND NITROGEN CYCLING
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Spatial patterns of nutrients and natural abundance levels of stable nitrogen (N) isotopes were measured at ten stations along a nutrient enrichment gradient in the Florida Everglades. Sampled components included surface soil (0-10cm) and live leaves of the dominant macrophytes, Sawgrass (Cladium jamaicense) and Cattail (Typha domingensis). Natural abundance N-isotopic ratios (expressed as per mil relative to atmospheric standard) were found to vary for all components sampled, ranging from approximately 2 per mil in the unimpacted marsh zones to approximately 4, 6, and 8 per mil for sawgrass, soil, and cattail, respectively, in areas affected by high-nutrient discharges. These per mil increases occurred in the absence of any observed change in soil or plant N content, but correlated well with measured total phosphorus of plants (r=0.81, p<0.0001) and soil (r=0.53, p<0.001). The exact mechanism responsible for the N-isotopic patterns is unclear, however, two potential hypotheses concerning microbial N cycling and plant N uptake are presented.