Soil Phosphorus Forms In Tree Islands of the Florida Everglades.

Tree island ecosystems in the Florida Everglades offer a unique opportunity to study partitioning of forms of soil phosphorus (P).  The relatively high soil P concentrations reported in some Everglades tree islands warrants investigation of soil P forms to elucidate biogeochemical function of tree islands.  Recent data suggests tree islands play an important role in soil nutrient distribution dynamics as P sinks in the P-limited landscape of the Everglades.  However the relative proportions of P forms within tree island soil have not fully described.  Variation in ecological attributes among tree islands, such as physical and chemical soil properties, size, vegetative species composition, wildlife use, fire frequency, anthropogenic alteration, and hydroperiod cumulatively complicate the potential for generalized characterization of P forms and origin. Here we show inorganic P, specifically calcium or magnesium bound P, represents the majority of the soil P, particularly in islands with relatively high soil TP concentrations.  Sequential chemical extraction of six operationally defined soil P forms was conducted to determine the proportion of specific P forms in tree island soil.  This study focused determining the portions of soil P forms within the head region of tree islands and provides a general indication of soil P availability.  These results suggest deposition, or in-situ formation, of Ca- or Mg-P soil constituents correlate with elevated tree island soil P.  These results can be used to help explain differential soil P patterns observed among islands in the Everglades and are valuable for restoration planning and resource management.