Development and Stability of Everglades Tree Islands, Ridge & Slough, & Marl PrairiesEntry ID: USGS_SOFIA_willard_tree_islands_04
Abstract: Analysis of 209 pollen assemblages from surface samples in ten vegetation types in the Florida Everglades form the basis to identify wetland sub-environments from the pollen record. This calibration dataset makes it possible to infer past trends in hydrology and disturbance regime based on pollen assemblages preserved in sediment cores. Pollen assemblages from sediment cores collected in different ... vegetation types throughout the Everglades provide evidence on wetland response to natural fluctuations in climate as well as impacts of human alteration of Everglades hydrology. Sediment cores were located primarily in sawgrass marshes, cattail marshes, tree islands, sawgrass ridges, sloughs, marl prairies, and mangroves. The datasets contain raw data on pollen abundance as well as pollen concentration (pollen grains per gram dry sediment).
Everglades restoration planning requires an understanding of the impact of natural and human-induced environmental change on wetland stability, and this project focuses specifically on three wetland types: tree islands, the sawgrass ridge and slough system, and marl prairies. Tree islands are considered key indicators of the health of the Everglades ecosystem because of their sensitivity to both flooding and drought conditions. Tree islands also act as a sink for nutrients in the ecosystem and may play an important role in regulating nutrient dynamics. Although management strategies to restore and even create tree islands are being formulated, the published data on their age, developmental history, geochemistry, and response to hydrologic alterations is limited. To address these issues, this project integrates floral and geochemical data with geologic and vegetational mapping activities to establish the timing of tree-island formation and impacts of both flooding and droughts on tree islands throughout the Everglades.
Data Set Citation
Dataset Originator/Creator: Debra Willard William H. Orem
Dataset Title: Development and Stability of Everglades Tree Islands, Ridge & Slough, & Marl Prairies
Dataset Release Date: 2006
Data Presentation Form: spreadsheetsOnline Resource: http://sofia.usgs.gov/projects/tree_islands/
Start Date: 1962-01-01Stop Date: 2007-12-31
Quality Pollen data from surface samples collected during the 1960s:
Column A (the sample ID) refers to the sites listing. Line 1 lists taxa identified in the samples. For lines 2-13, original raw data on total pollen grains were unavailable, so back-calculation from percentages to original counts was not possible. The numbers provided in these lines are percent abundances. ... For all other samples, the number of grains counted for each taxon was determined by back-calculation from percentages and total grains counted, as provided by Riegel, 1965.
Pollen from surface sample collected in 1995 and 1998:
Column A (sample ID) refers to the sites listing. Line 1 identifies taxa identified in the samples. Numbers provided for all taxa represent raw counts. Numbers of exotics counted refers to number of Lycopodium grains counted during each pollen count. For each sample, one tablet of Lycopodium grains was added before processing. Each tablet contains 12, 542 +/- 416 Lycopodium grains. Sample weight refers to the dry weight of sample processed. Pollen concentration (pollen grains/gram dry sediment) was calculated using the formula
pollen grains/gram dry sediment= [(pollen counted/exotics counted) x 12542]/sediment weight
Sampleing site locations were determined using GPS.
Core Collection and Sampling
We collected sediment cores using a piston corer with a 10 cm diameter core barrel. The core barrel was pushed through the sediments until it contacted the underlying limestone at all sites except in Loxahatchee NWR, where peat thicknesses in excess of 2 meters would require alternative coring strategies. After core collection, we extruded sediment from the core barrel and sampled it at 1 cm increments for the upper 20 cm and at 2 cm increments at greater depths. We described sediment lithology as samples were extruded. We dried samples in a 50 deg C oven and subsampled sediments at the base of each core and at 20 cm increments above the base for radiocarbon dating. Bulk peats were dated using conventional radiocarbon dating
Age models for the last century of deposition are based on 210Pb (lead-210) and, where applicable, first occurrences of pollen of the exotic plant Casuarina which was introduced to south Florida in the late 19th century (Langeland, 1990). Lead-210 (210Pb) activity was measured by alpha spectroscopy using the method outlined in Flynn (1968) in which 210Pb and its progeny, polonium-210 (210Po), are assumed to be in secular equilibrium. Supported 210Pb activity was determined by continuing measurements until activity became constant with depth. Excess 210Pb activity was calculated by subtracting the supported 210Pb activity from the total 210Pb activity. Accumulation rates were calculated by fitting an exponential decay curve to the measured data using least squares optimization and making the assumptions of a constant initial excess lead-210 concentration (the CIC [constant initial concentration] model).
In pre-20th century sediments, models are derived from linear interpolation between radiocarbon data points obtained on bulk sediment samples, which were calibrated to calendar years using the Pretoria Calibration Procedure (Stuiver et al., 1993; Talma and Vogel, 1993; Vogel et al., 1993). The shorter hydroperiods and shallower water depths on tree-island heads result in seasonal drying and oxidation of sediments. We have noted that radiocarbon dates from tree-island head sediments appear to be artificially old relative to those in the tail and adjacent marsh. Cores collected in the near tail, directly downstream from the head, have radiocarbon dates and vegetational trends that are consistent both internally and with adjacent wetlands. Therefore, we used cores from the near tail as our representative sites to detect vegetation changes on teardrop-shaped tree islands and for comparison with patterns documented in the adjacent marsh.
Analysis of Pollen Assemblages
Approximately 0.5-1.0 gram of dry sediment was used for palynological analysis. Pollen and spores were isolated from these samples using standard palynological techniques (Traverse, 1988; Willard et al, 2001a,b). After drying and weighing samples, Lycopodium marker tablets with known concentrations of Lycopodium spores were added to approximately 0.5 g of sediment for calculation of absolute pollen concentrations (Stockmarr, 1971). The samples were first acetolyzed (9 parts acetic anhydride : 1 part sulfuric acid) in a hot-water bath (100 deg C) for 10 minutes, then neutralized, and treated with 10% KOH in a hot-water bath for 15 minutes. Neutralized samples were sieved with 10 µm and 200 µm sieves, and the 10-200 µm fraction was stained with Bismarck Brown, mixed with warm glycerin jelly, and mounted on microscope slides. Raw data for pollen samples are reposited in the North American Pollen Database (NAPD) at the World Data Center for Paleoclimatology in Boulder, CO (http://www.ngdc.noaa.gov/paleo/pollen.html) and at the US Geological Survey South Florida Information Access (SOFIA) site (http://sofia.usgs.gov).
Pollen and spore identification (minimally 300 grains per sample) was based on reference collections of the United States Geological Survey (Reston, VA) and Willard et al. (2004). Absolute pollen concentrations were calculated using the marker-grain method described by Benninghoff (1962). Marker tablets of Lycopodium spores were the source of the exotic grains, and the quantity of Lycopodium spores in the marker tablets was determined by the manufacturer with a Coulter Counter following the procedures of Stockmarr (1973). Absolute pollen concentration was calculated using the formula (Maher, 1981):
Where: Pconc = pollen per gram dry sediment; R=pollen grains counted/marker grains counted; M=marker grains added; V=dry weight of sediment
Our interpretations of past plant communities are based on the quantitative method of modern analogs (Overpeck et al., 1985). 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 and this research) 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. We divided cores into pollen zones based on a combination of visual inspection, objective zonation using CONISS (Grimm, 1992), and modern analogs.
Access Constraints None
Use Constraints None
Data Set Progress
Distribution Format: MS Excel
Role: TECHNICAL CONTACT
Phone: (703) 648-5320
Fax: (703) 648-6953
Email: dwillard at geochange.er.usgs.gov
Email: dwillard at mailrvag2.er.usgs.gov
MS 926A National Center U.S. Geological Survey
Province or State: VA
Postal Code: 20192
Role: DIF AUTHOR
Email: alicia.m.aleman at nasa.gov
Goddard Space Flight Center Code 610.2
Province or State: MD
Postal Code: 20771
Willard, Debra A., Weimer, Lisa M., 1997, Palynological Census Data from Surface Samples in South Florida, USGS, Open-File Report, 97-0867, Reston, VA, U.S. Geological Survey http://pubs.usgs.gov/pdf/of/ofr97867.html
Willard, Debra A., 1997, Pollen Census Data from Southern Florida: Sites Along an Nutrient Gradient in Water conservation Area 2A, USGS Open-File Report, 97-0497, Reston, VA, U.S. Geological Survey http://pubs.usgs.gov/pdf/of/ofr97497.html
Willard, Debra A., Bernhardt, Christopher E.; Weimer, Lisa (deceased); Gamez, Desire; Cooper, Sherri R.; Jensen, Jennifer, 2004, Atlas of Pollen and Spores of the Florida Everglades, Palynology, 28, Arlington, TX, American Association of Stratigraphic Palynologists, Posted with permission from Palynology and the American Association of Stratigraphic Palynologists http://sofia.usgs.gov/publications/papers/pollen_atlas/
Marshall, Curtis H., Pielke, Roger A., Sr.; Steyaert, Louis T.; Willard, Debra A., 200401, The Impact of Anthropogenic Land-Cover Change on the Florida Peninsula Sea Breezes and Warm Season Sensible Weather, Monthly Weather Review, v. 132, n. 1, Boston, MA, American Meterological Society, Permission to post a copy of this work on the SOFIA server has been provided by the American Meterological Society
Willard, Debra A., Weimer, Lisa M.; Riegel, W.L., 2001, Pollen assemblages as paleoenvironmental proxies in the Florida Everglades, Review of Palaeobotany and Palynology, v. 113, n. 4, Amsterdam, The Netherlands, Elsevier Science B.V., The full article is available via journal subscription or single article purchase. The abstract may be viewed on the Science Direct website by selecting the volume and issue number. http://www.sciencedirect.com/science/journal/00346667
Willard, D.A., Holmes, C.W.; Korvela, M.S.; Mason, D.; Murray, J.B.; Orem, W.H.; Towles, T., 200302, Paleoecological Insights on Fixed Tree Island Development in the Florida Everglades: I. Environmental Control, Dordrecht, Netherlands, Kluwer Academic Publishers, in Tree Islands of the Everglades, Sklar, F.H. and van der Valk A. (editors) http://sofia.usgs.gov/sfrsf/rooms/wild_wet_eco/tree_islands/index.html
Bernhardt, C.E., Willard, D.A.; Marot, M.; Holmes, C.W., 2004, Anthropogenic and natural variation in Ridge and Slough pollen assemblages, USGS Open-File Report, 2004-1448, Reston, VA, U.S. Geological Survey. http://sofia.usgs.gov/publications/ofr/2004-1448/
Willard, D.A., Holmes, C.W.; Weimer, L.M., 2001, The Florida Everglades Ecosystem: Climatic and Anthropogenic Impacts over the Last Two Millenia, Bulletins of American Paleontology, v. 361, Ithica, NY, Paleontological Research Institute, in Paleoecology of South Florida, B.R. Wardlaw, ed.
Grimm, E.C., 1992, CONISS: a Fortran 77 program for stratigraphically constrained cluster analysis by the mothod of incremental sum of squares, Computers & Geosciences v. 13, issue 1, Amsterdam, The Netherlands, Elsevier Science, Ltd., The abstract may be viewed online at the Science Direct website. The full article is available for purchase from the Science Direct website. http://www.sciencedirect.com/science/journal/00983004
Traverse, A., 1988, Paleopalynology, Boston, MA
Unwin Hyman, Stockmarr, J., 1971, Tablets with spores used in absolute pollen analysis, Pollen et Spores, v. 13, Paris, France, Museum national d'histoire naturelle
Overpeck, J.T., Webb, III, T.; Prentice, I.C., 1985, Quantitative interpretation of fossil pollen spectra: Dissimilarity coefficients and the method of modern analogs, Quaternary Research, v 23, issue 1, Amsterdam, Netherlands, Elsevier Science, Ltd., The abstract may be viewed online at the Science Direct website. The full article is available for purchase from the Science Direct website. http://www.sciencedirect.com/science/journal/00335894
Riegel, W.L., 1965, Palynology of environments of peat formation in southwestern Florida, Doctoral thesis, University Park, PA, The Pennsylvania State University
Willard, D.A., 2004, Tree Islands of the Florida Everglades- Long-term stability and response to hydrologic change, USGS Fact Sheet, 2004-3095, Reston, VA, U.S. Geological Survey. http://pubs.usgs.gov/fs/2004/3095
Bernhardt, C.E, Willard, D.A., 2007, Marl prairie vegetation response to 20th century hydrologic change, report, USGS Open-File Report, 2006-1355, Reston, VA, U.S. Geological Survey, http://pubs.er.usgs.gov/usgspubs/ofr/ofr20061355
Willard, D.A., Cronin, T.M., 2007, Paleoecology and ecosystem restoration: case studies from Chesapeake Bay and the Florida Everglades, Frontiers in Ecology and the Environment, vol. 5, issue 9, Ithica, NY, Ecological Society of America, The full article is available via journal subscription or single article purchase. The abstract may be viewed at the URL below by selecting the article.,
Willard, D.A., Bernhardt, C.E.; Holmes, C.W.; Landacre, B.; Marot, M., 2006, Response of Everglades tree islands to environmental change, Ecological Monographs, v.76, n.4, Ithica, NY, Ecological Society of America, The full article is available via journal subscription or single article purchase. The abstract may be viewed at the URL below by selecting the article. http://www.esajournals.org/perlserv/?request=get-toc&issn=0012-9615...
Langeland, K., 1990, Exotic Woody Plant Control Florida, Circular, 868, Florida, Florida Coooperative Extension Service
Flynn, W.W., 1968, The determination of low levels of polonium-210 in environmental materials, Analytica Chimica Acta, v. 43, Amsterdam, The Netherlands, Elsevier B. V., The abstract may be viewed online at the Science Direct website. The full article is available for purchase from the Science Direct website.
Stuiver, M., Reimer, P.J., 1993, Extended 14C database and revised CALIB 3.0 14C age calibration program, Radiocarbon, v.35, n.1,
Talma, A.S., Vogel, J.C., 1993, A simplified approach to calibrating C14 dates, Radiocarbon, v.35, n.2, Tucson, AZ, University of Arizona
Creation and Review Dates
DIF Creation Date: 2008-04-28
Last DIF Revision Date: 2009-02-06