Your team will select either a dune area (such as found on East Beach) or a headland area (such as found at North Point). Both choices are well-exposed to the sun, so bring your sunscreen and hat! You will need to bring with you a transect line, a sampling frame, your field notebook, pencil, and sampling bags and/or tape. You will choose a specific site that goes from the strand line (or cliff-edge) inland to locate your transect for analysis. You will notice that from the strand line or cliff-edge toward the interior, the vegetation changes in kinds, amount, and size.
What is the basis for the observed zonation of terrestrial plants from edge to the interior? What are the differences in microenvironment as you move from beach to headland (think of temperature, light exposure, wind, salinity, fresh water availability, soil or substrate type, etc.)? What percentage of the ground (substrate) is covered by vegetation? Why are certain sites not suitable for plant growth? How many individual plants of each species are found in each microenvironment? What is the dominant species of plant? Which of the microenvironment parameters seem to be most important in determining which species become dominant? What characteristics of the dominant plants permit them to be competitive in these environments? Which adaptations are missing in the rarer species? Which microenvironments lead to greater species diversity? How did these species arrive on San Salvador? Which characteristics (protoadaptations) allowed certain species to become established in their habitat? Which species are colonizing new areas? What are these colonizers doing to the substrate? Is succession completed or is it underway? Is there a climax community on San Salvador? Would a similar transect elsewhere on the island provide different findings? Obviously many of these questions cannot be answered with certainty, but evidence can be gathered to support various points of view. This list of questions is meant only generate ideas for your discussion and can be expanded or truncated as you find it desirable.
You will lay out a transect line from the strand line or cliff edge heading inland. The transect line should be held by one partner at the edge and the line pulled taut by another partner to provide a straight pathway for the line. You could choose the starting point and the compass direction of the line randomly, but for our purposes here, we just want to select a location that has abundant vegetation on it, and is not traversed repeatedly by walking trails. So we will be somewhat selective in positioning our transect line. The transect line is simply knotted at 1-meter intervals; you might want to secure the line at each end to some vegetation or other structure during your analysis. You will want to record in your notebook your observations about the site of the transect; be sure to include some description of the environmental factors you are noticing.
You will want to develop some objective method for assessing the plants found along the transect. Generally the sampling frame is laid at the knot on a particular side (your choice) of the transect line. At each meter-interval, the kinds, numbers, height, and percent-cover of individual plants inside the sampling frame are recorded in a data table in your field notebook. For plants that cannot be identified in the field, you will need to take a sample with stem, leaf, flower, and fruit (if possible) present to key out later in the laboratory. The sample should be labeled with tape and/or bagged so that it can be kept together until your return to the lab. When recording a sample's transect information, you can use its sample label name (Species A for example) in the table temporarily.
You may need to reset your line to extend your transect further into the interior. Also if the distance between the edge and either the back-dune thicket or the roadside coppice is quite long, you may need to also set your sampling frame down at a longer interval (perhaps every third or fifth meter knot) along the transect.
In the laboratory, you will need to observe your sample clippings and correct your table entries with correct taxonomic names. Use your field guides and, if necessary, the large Correll and Correll tome on the Bahama Flora to key out and identify your samples. This must be done before the samples deteriorate and definitely before we leave San Salvador.
With your data table fully completed, you will need to prepare some demonstrations to answer the questions you are posing for your transect (see above). Perhaps you will plot the number of individuals or % cover (etc.) as a function of distance along the transect.
To answer some of the questions you have chosen for study, you might need some math assistance. In a particular sampling frame the diversity of species can be estimated by a value called the Shannon-Wiener species diversity index. This index is:
| H' = |
n Σ i=1 | (pi)(- log pi) |
| Taxon | Number | pi=number/total | log pi | pi(-log pi) |
|---|---|---|---|---|
| Sesuvium | 5 | 0.20 | -0.70 | 0.14 |
| Strumpfia | 20 | 0.80 | -0.10 | 0.08 |
| Total | 25 | 1.00 | 0.22 = H' |
Back in Connecticut you will prepare a standard laboratory report on this dune project or on the intertidal zone project. You should consult the Pechenik style manual, and your experience in Bio 221 and Bio 234 to guide you in formatting the lab report. Your results section should include all tables and graphs and a supportive text. It should include a list of all taxa observed along the transect. Your discussion should integrate the observed results with your environmental observations of substrate, exposure, soil moisture, etc. The discussion should address the characteristics of the vegetation along the transect. Your discussion should present a general progression of taxa from edge to interior as a summary table. Your grade will be determined, in part, by how effectively you discuss the species-diversity index values you calculate!
You must also read pertinent articles from the bibliography, and choose wisely five articles that best support your project! Most of these articles are available for downloading on the course website: http://plantphys.info/Bahamas/. For access to these copyrighted materials you need the username:________________ and password:_____________________. Another major part of your grade is how well you compare, contrast, and integrate into your discussion, the findings in the five articles you choose from the bibliography. To do this, you need to at least scan all of the articles to make intelligent selections from the bibliography (yes, those choices count in your grade too!). So you want to be selective! Deductions will be made for listing articles not actually cited, and for making a citation without having thoroughly read the article! Yes, faculty can tell when you cite something you have not actually read! Your literature cited section should provide complete citations in CBE style of all library references and all field guides that you do choose to incorporate into your paper…in alphabetical order. The style below is acceptable. Bonus points will be issued to students providing a clean photocopy of the complete articles referenced below marked with an * or for any good dune vegetation article that is NOT referenced below!
Anonymous. 1999. Beach Dune, Coastal Strand, and Maritime Hammock [in] Sam D. Hamilton. South Florida multiple species recovery plan. S.E. Regional US Fish and Wildlife Service, Bethesda, MD. http://www.fws.gov/verobeach/Programs/Recovery/vbms5.html (5-16-2007).
Arens, S. M. 1996. Patterns of sand transport on vegetated foredunes. Geomophology 17: 339-350.
Asprey, G. F. and R. G. Robbins. 1953. The vegetation of Jamaica. Ecological Monographs 23: 359-412.
* Cousins, S. H. 1991. Species diversity measurement: choosing the right index. Trends in Ecology & Evolution: 6: 190-192.
Espejel, I. 1987. A phytogeographical analysis of coastal vegetation in the Yucatan peninsula. Journal of Biogeography 14: 499-519.
Gerace, D. T., G. K. Ostrander, G. W. Smith. Undated. San Salvador, Bahamas. [in] Environment and development in coastal regions and in small islands website. UNESCO. http://www.unesco.org/csi/pub/papers/gerace.htm (5-16-2007)
* Greaver, Tara L. and Leonel L. Sternberg. 2006. Linking marine resources to ecotonal shifts of water uptake by terrestrial dune vegetation. Ecology 87(9): 2389-2396.
Herwitz, S. R. 1992. Quaternary vegetation change and dune formation on Bermuda: a discussion. Global Ecology and Biogeography Letters 2(3): 65-70.
Howard, R. A. 1950. Vegetation of the Bimini Island group: Bahamas, B. W. I. Ecological Monographs 20: 317-349.
Liddle, M. J. and P. Grieg-Smith. 1975. A survey of tracks and paths in a sand dune ecosystem. II. Vegetation. The Journal of Applied Ecology 12: 909-930.
* Maun, M. A. 1998. Adaptations of plants to burial in coastal sand dunes. Canadian Journal of Botany. 76: 713-738.
Moreno-Casasola, P. 1988. Patterns of plant species distribution on coastal dunes along the Gulf of Mexico. Journal of Biogeography 15: 787-806.
Oosting, H. J. and W. D. Billings. 1942. Factors effecting vegetational zonation on coastal dunes. Ecology 23: 131-142.
Ripley, B. S. 2001. The ecophysiology of selected coastal dune pioneer plants of the eastern Cape. PhD Dissertation, Rhodes University, South Africa.
Rodgers, J. C. 2002. Effects of human disturbance on the dune vegetation of the Georgia sea islands. Physical Geography 23: 79-94.
Thomas, M. L. H. and A. Logan. 1992. A guide to the ecology of shoreline and shallow-water marine communities of Bermuda. Bermuda Biological Station for Research Special Publication #30. Ferry Reach, Bermuda. Pp. 189-203.
* Whittaker, R. H. 1972. Evolution and measurement of species diversity. Taxon 21: 213-251.
Willis, A. J., B. F. Folkes, J. F. Hope-Simpson, and E. W. Yemm. 1959. Braunton Burrows: the dune system and its vegetation. The Journal of Ecology 47: 1-24.