Pattern of nutrient availability and plant community assemblage in Everglades Tree Islands, Florida, USA |
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Authors: | J L Espinar M S Ross and J P Sah |
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Institution: | (1) Estaci?n Biol?gica de Do?ana (EBD-CSIC), Avda. Am?rico Vespucio s/n, Isla de la Cartuja, 41092 Sevilla, Spain;(2) Southeast Environmental Research Center, Florida International University, Modesto Maidique Campus, Miami, FL 33199, USA |
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Abstract: | We address the relative importance of nutrient availability in relation to other physical and biological factors in determining
plant community assemblages around Everglades Tree Islands (Everglades National Park, Florida, USA). We carried out a one-time
survey of elevation, soil, water level and vegetation structure and composition at 138 plots located along transects in three
tree islands in the Park’s major drainage basin. We used an RDA variance partitioning technique to assess the relative importance
of nutrient availability (soil N and P) and other factors in explaining herb and tree assemblages of tree island tail and
surrounded marshes. The upland areas of the tree islands accumulate P and show low N concentration, producing a strong island-wide
gradient in soil N:P ratio. While soil N:P ratio plays a significant role in determining herb layer and tree layer community
assemblage in tree island tails, nevertheless part of its variance is shared with hydrology. The total species variance explained
by the predictors is very low. We define a strong gradient in nutrient availability (soil N:P ratio) closely related to hydrology.
Hydrology and nutrient availability are both factors influencing community assemblages around tree islands, nevertheless both
seem to be acting together and in a complex mechanism. Future research should be focused on segregating these two factors
in order to determine whether nutrient leaching from tree islands is a factor determining community assemblages and local
landscape pattern in the Everglades, and how this process might be affected by water management. |
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