Wednesday, August 8, 2007 - 8:00 AM

COS 65-1: Relationship between species richness and biomass along a hydrologic gradient in the marl prairie landscape in the southern Everglades, Florida, USA

Jay P. Sah1, Michael S. Ross1, James R. Snyder2, Pablo L. Ruiz1, and Davit T. Jones3. (1) Florida International University, (2) US Geological Survey, (3) National Tropical Botanical Garden - The Kampong

The relationship between species richness and biomass is generally represented by a hump-shaped pattern. However, this relationship is scale dependent, and the location of the peak in species richness along biomass gradients varies with resource availability and among community types. Vegetation types in the marl prairie landscape in the southern Everglades are controlled by a complex of environmental factors, including hydrology, fire and soil nutrients. Our objective was to explore the nature of a unimodal hump-shaped relationship between biomass and species richness within and among vegetation types arranged across the hydrology gradient. We sampled vegetation in 1 x 60 m plots at 906 sites distributed within the Everglades marl prairie landscape. A biomass regression model was developed from structural variables and aboveground biomass harvests at 166 sites, and then used to estimate biomass for all sites. Ten vegetation assemblages were identified and grouped into two broad categories, ‘wet prairie’ and ‘marsh’.  In the Everglades marl prairies, species richness varied from 2 to 43 per plot and the aboveground plant biomass varied from 113 to 1383 g/m2. Species richness demonstrated a hump-shaped relationship with biomass across all the sites. The relationship was maintained within vegetation types that included a relatively wide range of hydroperiods. Within vegetation types in which the hydrologic gradient was relatively narrow, the relationship was positive, negative or non-existent depending on the hydrology and biomass. The relationship was positive within the wettest marsh sites characterized by low aboveground biomass, and negative within less frequently flooded marsh sites of higher biomass. Within the short hydroperiod prairie sites, the relationship between species richness and biomass was not detected, suggesting the influence of other factors such as fire.

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