Nitrogen cycling in Everglades peat soils

Meera Krishnan Nair, Florida International University


Nitrogen transformation processes in Everglades peat soils were investigated using isotopic dilution methods. The nitrogen mineralization and immobilization potentials of Everglades peat soil were calculated as 1.91 $\pm$ 1.15 $\mu$g g$\sp{-1}$ soil h$\sp{-1}$ and 1.54 $\pm$ 1.05 $\mu$g g$\sp{-1}$ soil h$\sp{-1}$, respectively. In the absence of plants, approximately 76% of the ammonium produced was consumed in the soil itself. The net production of ammonium accounted only for 20% of the gross production. Phosphorus addition to the soil increased both ammonium production and ammonium consumption about 1.5 times. Incubation temperature also had significant effect on ammonium production and consumption. Potential nitrification rates were estimated using a nitrification inhibitor N-Serve (Nitrapyrin) and the nitrification potential ranged from 0.04 to 0.33 $\mu$g g$\sp{-1}$ soil h$\sp{-1}$. When compared to many other aquatic systems nitrification was slow in Everglades soils and phosphorus addition did not affect the nitrification potential. When nitrate was added to the soil 29% of the added nitrate was reduced to ammonium. Litter mineralization studies indicated that surface litter can serve as a sink for nitrogen during its early decomposition process. A comparative study of the sawgrass decomposition process with algae and glycine showed the following results: (i) while decomposition of sawgrass caused inorganic N depletion of the soil, algal and glycine treatment resulted in nitrogen accumulation (ii) early decomposition of all materials resulted in an increase of biomass nitrogen. Gross rate estimates of the nitrogen transformation process give us a more clear picture of nitrogen cycling process than the net process estimates. There is sufficient mineralization of nitrogen in Everglades peat soils to sustain the system in terms of nitrogen. Phosphorus addition to the system can affect not only phosphorus cycling but also nitrogen cycling in these peat soils. Low nitrification and high nitrate ammonification potential of the soils help to conserve nitrogen in these soils. In a marsh like the Everglades, sawgrass litter decomposition can result in temporary immobilization of inorganic nitrogen making it unavailable to other transformation processes and thus conserving nitrogen in the organic matter.

Subject Area

Biogeochemistry|Ecology|Soil sciences

Recommended Citation

Nair, Meera Krishnan, "Nitrogen cycling in Everglades peat soils" (1996). ProQuest ETD Collection for FIU. AAI9625357.