Factors Controlling Seasonal Nutrient Profiles in a Subtropical Peatland of the Florida Everglades
- M. S. Koch-Rose *,
- K. R. Reddy and
- J. P. Chanton
Research Dep., South Florida Water Management District, P.O. Box 24680, West Palm Beach, FL 33416(currently Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149); Soil Science Dep., Univ. of Florida, Gainesville, FL 32611; Dep. of Oceanography, Florida State Univ., Tallahassee, FL 32306. Abstract
Approximately 75% of soil nutrients in the Everglades are stored in the organic form; thus, factors affecting seasonal organic matter and associated nutrient mineralization will influence nutrient availability to marsh vegetation. To assess the factors controlling mineralization in the field, pore water nutrients including NH+4, NO−3 and, soluble reactive P (SRP) were determined along with soil Eh, pH, temperature, and water levels at eutrophic, mesotrophic, and oligotrophic sites through a dry and rainy season. Indicators of anaerobic microbial activity, SO2−4, methane (CH4), CH4-stable isotope signatures, and dissolved inorganic carbon (DIC) were sampled at all three sites. At the enriched site, SRP and NH+4 levels were 95 and 706 µM during summer months and 11 and 26 µM spring concurrent with N/P ratios of three and maximum macrophyte growth. Low seasonal variability in SRP was found at oligotrophic sites where pore water N/P ratios ranged from 39 to 551 throughout the year. During the spring dry season, Eh exceeded 300 mV at all three sites. In all other seasons, soils remained flooded and Eh averaged −100 to −200 mV. Methane and DIC, and isotopic 13C ratios in the eutrophic sites, relative to those found under oligotrophic conditions, suggest greater microbial production rates at enriched sites. Oligotrophic Everglades soils appear to have limited microbial activity and consequently, dampened seasonal pore water nutrient levels in response to fluctuating Eh, pH, water level, and temperature regimes.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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