Abstract Introduction Marl Prairie Habitat & Community Everglades Hydrologic History > Methods Results Discussion Conclusions Acknowledgements References Figures & Tables PDF

Using a 10 cm diameter piston-coring device, we collected five cores in the Rattlesnake Ridge area of Big Cypress National Preserve (Fig. 4, Table 1). Because only a thin veneer of calcitic sediment (<5 cm) covers most of the marl prairie, we collected a series of sediment cores from solution holes in the limestone bedrock. These solution holes ranged up to 73 cm in depth and provided sufficiently wet sites for accumulation and preservation of organic and calcitic sediments with minimal loss due to drying and oxidation. Four of the five cores consisted of a basal peat overlain by marl; the fifth core (core 03-9-16-3), which penetrated 73 cm of sediment, consisted entirely of peat. We hypothesize that the latter solution hole was sufficiently deep to maintain permanent standing water, facilitating preservation of peat throughout. Cores were sampled in 1 cm increments, and samples were dried and subsampled for radiocarbon dating and pollen analysis. This report focuses on pollen records from two sediment cores (03-9-16-3 and 03-9-16-6).

Chronology of the cores is based on a combination of radiocarbon dating on bulk sediment from core 03-9-16-6 (Table 2) and occurrence of the biostratigraphic indicator Casuarina equisetifolia (Australian pine) in both cores. Casuarina equisetifolia was introduced to South Florida ~1900 AD; calibration of its pollen with ²¹⁰Pb geochronologies in a series of cores from Florida and Biscayne Bays indicates that C. equisetifolia pollen first occurred in south Florida sediments at 1910 +/- 15 years, becoming common after 1940 (Duever and others 1986, Langeland, 1990; Wingard and others, 2003). An additional biostratigraphic indicator is the decrease in Pinus pollen. We interpret this as the pollen signature of Pinus logging during the late 1930's based partly on historical records (Duever and others 1986) and patterns exhibited in sediment cores with excellent ²¹⁰Pb dating (Wingard and others, 2003).

Figure 4. Map of core localities in Big Cypress National Preserve. See Table 1 for information on core location and sediment depth. Sites analyzed in this study are indicated by yellow dots. [larger image]

Table 1. Location of cores collected in marl prairie west of Shark River Slough, Big Cypress National Preserve. Map with site locations is provided in Fig. 4. [click here to see entire table]

Table 2. Radiocarbon dates obtained on samples from core 03-9-16-6, marl prairie habitat in Big Cypess National Preserve. Core location is 25° 42.931' N, 80° 52.336' W. [click here to see entire table]

We isolated pollen from the sediment cores and surface samples using standard palynological preparation techniques (Traverse, 1988; Willard and others, 2001a). For each sample, one tablet of Lycopodium spores was added to between 0.5 grams to 1.5 grams of sediment. Samples were processed with HCl and HF to remove carbonates and silicates respectively, acetolyzed (1 part sulfuric acid: 9 parts acetic anhydride) in a boiling water bath for 10 minutes, neutralized, and treated with 10% KOH for 10 minutes in a water bath at 70° C. After neutralization, residues were sieved with 149 µm and 10 µm nylon mesh to remove the coarse and clay fractions, respectively. When necessary, samples were swirled in a watch glass to remove mineral matter. After staining with Bismarck Brown, palynomorph residues were mounted on microscope slides in glycerin jelly. At least 300 pollen grains were counted from each sample to determine percent abundance and concentration of palynomorphs (Table 3, Table 4). Identifications were made using reference material at the US Geological Survey and descriptions contained in Willard et al. (2004). Abundance data are available through the USGS SOFIA website (http://sofia.usgs.gov) and the North American Pollen Database (NAPD) at the World Data Center for Paleoclimatology in Boulder, CO (http://www.ngdc.noaa.gov/paleo/pollen.html).

Reconstruction of past plant communities is based on statistical comparison of fossil and modern assemblages from different wetland communities throughout the Everglades (Willard and others, 2001b). Using the modern analog technique (Overpeck and others, 1985), we statistically compared modern and fossil assemblages to those that share similar vegetation and environmental parameters. We calculated squared chord distance (SCD) between down-core pollen assemblages and a suite of 197 surface samples collected throughout southern Florida in the early 1960s and 1995-2002 (Willard et al., 2001b, 2006) to define the similarity between each fossil and modern pollen assemblage. Internal comparison among surface samples from ten vegetation types indicates that samples with SCD values < 0.15 may be considered close analogs (Willard et al., 2001b). If analogs were present for a fossil assemblage, we identified the source vegetation for the fossil assemblage as one of the twelve types represented in the modern database.

Table 3. Abundance of pollen grains of individual taxa in sediment core 03-09-16-3, marl prairie in Big Cypress National Preserve. Numbers indicate raw counts from pollen assemblages. [click here to see entire table]

Table 4. Abundance of pollen gains of individual taxa in sediment core 03-9-16-6, marl prairie in Big Cypress National Preserve. Numbers indicate raw counts from pollen assemblages. [click here to see entire table]