Intra-Island Distribution of Soil Phosphorus Forms in Everglades Tree Islands.

The Florida Everglades is considered a phosphorus (P) limited ecosystem, however large amounts of P are accumulated in tree island soil throughout the system.  Recent literature has suggested tree islands may play an important role in soil nutrient distribution dynamics in the landscape as focal points of potential P sequestration and redistribution.  Little data is available regarding the specific forms of P present in tree island soil and how P forms may be distributed at the intra-island scale.  Tree island ecosystems in the Everglades offer a unique opportunity to study distribution of soil P forms to determine if P accumulation occurs in discrete regions of islands, or diffusely throughout the areal extent of an island.  Characterization of soil P forms can provide insight of P source, and potential mobility.  Surface soil (0-5 cm) from different locations within tree islands in the Central Everglades was sequentially extracted with distilled deionized water, 1 M KCl, 0.1 M NaOH, and 0.5 M HCl to quantify the proportions of different forms of soil P.  Total and HCl extractable P (slowly available P) were highest (p < 0.05) in the head region.  The proportion of soil P extracted by HCl was ~50% of the total P measured in head region, which was roughly five times higher than the percentage of HCl P in the middle and tail regions.   The high proportion of slowly available soil P observed in the head region as compared to other areas within tree islands suggests current nutrient redistribution hypotheses may be accurate.  Accumulation of slowly available soil P in the head region may provide a nutrient reservoir which could foster both island development and P sequestration within the ecosystem.