Terrestrial Transect Survey 2015

The Site:

Your team will select a dune area on East Beach. The location is 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 inland to locate your transect for analysis. You will notice that from the strand line toward the interior, the vegetation changes in kinds, amount, and size.

Questions to Consider:

What is the basis for the observed zonation of terrestrial plants from the strand to the interior? What are the differences in microenvironment as you move from the strand to the backdune (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 less 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 this dune? 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.

strand wrack foredune foreslope foredune crest foredune backslope interdune meadow backdune foreslope backdune crest

Figure 1. A profile of a "classic" dune showing the relative position of two dunes from the strand and the relative elevation of the two dunes above the strand. The profile is divided into several named zones.

Vegetation Survey:

You will lay out a transect line perpendicular to the strand line heading inland toward the backdune crest zone. The transect line should be held by one partner at the wrack and the line pulled taut by another partner to provide a straight pathway for the transect. You could choose the starting point at the strand, recording its GPS location, and orient the transect at 90° to the strand line. You want to select a location on the dune system that has abundant vegetation on it, and is not traversed repeatedly by walking trails. So you will be somewhat selective in positioning your 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 need an objective method for assessing environmental data for your report. So we will use the Kestrel Weather Station instrument to gather air temperature, humidity, wind-speed, and wind-direction information. This instrument will be held at the level of the top leaves in the vegetation (ignoring Uniola flower/fruit stalks) to determine parameters at plant level. The wind speed will be determined as an average over a two-minute period with the vanes directed into the prevailing wind direction. You need to record this information in your field data record.

You also need an 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 plant species inside the sampling frame are recorded in a data table in your field notebook. The sampling frame is a 1-meter × 1-meter quadrat formed by string with a knot in each corner. To get the full meter-squared area, you need to hold the knots so that all four sides are taut and the corner angles are all 90°. You also want to record where you are along the transect (strand, foreslope of the foredune, crest of the foredune, backslope of the foredune, interdune meadow, foreslope of the backdune, crest of the backdune). 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. The transect ends when the sampling frame is in the impenetrably dense sea grape thicket near the backdune crest.

Please record a separate row in your data table for each quadrat that is dedicated to only the NUMBER of Uniola paniculata flower/fruit stalks that are rooted in that quadrat. These plants will be counted twice, once in the row for Uniola number and percent cover, and once again in the row for Uniola F/F stalks. This might be useful for your paper.

With your transect data recorded, consider whether your "slice" of this environment is truly representative or not of the foredune, the interdune meadow, and the backdune communities. Walk through the dune system near your transect and record any additional species you find in a roving survey of these communities of the dune system. You need to record which zone(s) of the dune profile each new species is found as well. Be sure to discuss these rarer members of the communities in your paper!

In the GRC laboratory, you will need to observe any 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 Bahamas Flora to key out and identify your samples. This must be done before the samples deteriorate and definitely before we leave San Salvador. These identifications and reference sources are part of your Materials and Methods section (and cited in the literature section)!

Data Analysis:

With your data table fully completed, back in Connecticut, you will need to prepare some graphs to answer the natural questions for your transect. You will want to plot the number of individuals or % cover (both! in separate figures) as a function of distance along the transect. Each species would have a different line and symbol on these graphs. You need to indicate the zones of the dune profile that correlate along the x-axis! These graphs should show which species are distributed in just certain zones, and which species are more generalists. These two graphs are differently biased, one is biased for showing species with small bodies, the other is biased for showing species with large bodies!

To answer some of the questions you have chosen for study, you might need some math assistance. In each sampling frame quadrat, the diversity of species should be estimated by a value called the Shannon-Wiener species diversity index (Shannon, 1948). This index is:

H' = n
Σ 
i=1
(pi)(- log pi)

where n is the number of species in the environment, pi is the proportion of ith species individuals among the total population of all species in the environment. The index value will help you assign a number to the observed diversity in the sample frame. This value can then be plotted as a function of position along the transect. What is the lowest possible index value, and does it correspond to the most-diverse situation or the least-diverse situation? What is the highest possible index value and to what kind of assemblage would it correspond? Maybe only part of the formula can be used to answer certain questions in your project. Maybe the formula can be adapted to better address the questions you are posing! The following chart serves as an example of how to calculate the species diversity index (H') for each quadrat along your transect. Microsoft Excel or another spreadsheet program could crunch the numbers for you very easily; just watch out for how the software distinguishes natural and common logs in the formulae! The example data for this one quadrat are completely fictitious.

Taxon # or %  pi=number/total  log pi  pi(−log pi
Sesuvium50.20-0.700.14
Uniola200.80-0.100.08
Total251.00   0.22 = H'

You will need two more figures, one showing the quadrat diversity indices along the transect based on number of individuals in the quadrats as a function of distance from the strand. The other will show the quadrat diversity indices as a function of percent cover. Both need those dune profile zone indications as well! These answer the questions about the level of species diversity across this dune profile.

Another comment that, based on student papers, needs to be pointed out is that among species diversity index data, 0 is a meaningful datum. Data points of 0 values should be plotted. Thus, the values for quadrats between the strandline and the leading edge of the foredune will strongly influence your graphs! Also, please don't try to force curvilinear data into a linear regression analysis! You might try a polynomial fit of various orders to get more realistic curve fits for such data!

Reporting:

Well before the deadline due date, prepare a standard laboratory/field report on this project. You should consult the Pechenik (or Knisely) style manual, and your experience in our four core (freshman and sophomore) courses to guide you in formatting the report. Your results section should include all tables and graphs and a supportive text. One scatter (line) graph might plot the species diversity index (based on number of individuals rooted in the quadrat) for each quadrat on the Y axis and the quadrat position (meters from the strand line) on the X axis. Another graph might plot the same axes with data based on percent cover. These graphs should include information about how position from the strand relates to the dune profile (strand, foredune foreslope, foredune crest, foredune backslope, interdune meadow, backdune foreslope, backdune crest). Some smaller graphs might show several line graphs of the number of individuals per quadrate of major species in the transect as a function of distance (and dune profile) from the strand line. You should include a list of all taxa observed along the transect. Your raw data should be attached as an appendix. 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 strand to backdune crest as a summary table. Your grade will be determined, in part, by how effectively you discuss the species-diversity index values you calculate!

For those hoping to receive Bio 3** credit for the biology major/minor, you must also read pertinent articles from the bibliography, and choose wisely at least 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 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/CSE 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 pdf (preferred) or photocopy of any good and useful dune vegetation article that is NOT referenced below!

Dune Vegetation Bibliography

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.

Costa, C. S. B., C. V. Cordazzo, and U. Seeliger. 1996. Shore distrubance and dune plant distribution. Journal of Coastal Research 12: 133-140.

Doing, H. 1985. Coastal fore-dune zonation and succession in various parts of the world. Vegetatio 61: 65-75.

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. 1998. San Salvador, Bahamas. [in] CARICOMP: Caribbean coral reef, seagrass, and mangrove sites. B. Kjerfve, ed. UNESCO, Paris. 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.

Greaver, Tara L. and Leonel S. L. Sternberg. 2010. Decreased precipitation exacerbates the effects of sea level on coastal dune ecosystems in open ocean islands. Global Change Biology 16: 1860-1869.

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.

Lane, C., S. J. Wright, J. Roncal, and J. Maschinski. 2008. Characterizing environmental gradients and their influence on vegetation zonation in a subtropical coastal sand dune system. J. Coastal Res. 24: 213-224.

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.

Moreno-Casasola, P. and I. Espejel. 1986. Classification and ordination of coastal sand dune vegetation along the Gulf and Caribbean Sea of Mexico. Vegetatio 66: 147-182.

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.

Shannon, C. E. 1948. A mathematical theory of communication. Bell System Technical Journal 27: 379-423, 623-656.

Stallins, J. A. and A. J. Parker. 2003. The influence of complex systems interactions on barrier island dune vegetation pattern and process. Annals of the Association of American Geographers 93: 13-29.

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.

Appendix:

At some point during your data collection, take a break from the transect (remembering where you stopped by leaving the quadrat in place!). During this break, use the Kestrel Weather Station to collect the following environmental data. Be sure to set the unit to the proper metric units (or collect in English units and remember to convert them to metric before writing your report!). The wind speed should be measured so that the unit determines an average wind speed taken over at least two minutes (to minimize the impact of gusts).

Dune Transect Environmental Data Observation Date_______ Local Time_______
Location: East Beach, San Salvador Island, Bahamas GPS:______________________
Observers:____________________________________________________________

Dune Profile
Loc. Code
Wind Direction 2-min Average
Wind Speed
(km/hr)
Air Temperature °C Relative
Humidity %
S    
FF    
FC    
FB    
I    
BF    
BC    

When you are finished with your transect, it is time to do the Roving survey. Scan each area of the dune system, looking for plants that you did NOT pick up in your transect survey. Note the location code for each new species (obviously it is possible that multiple codes apply to some new species, but seems unlikely since you did not find it quadrats along your transect).

Roving Survey Data

Loc. Codes: S=strand F=foredune I=Interdune B = Backdune joined to F=foreslope C=crest B=backslope

e.g.: FF = foredune foreslope FB = foredune backslope

LocSpecies LocSpecies
     
     
     
     
     
     
     
     
     

Dune Transect Data                         Observation Date_______ Local Time_______
Location: East Beach, San Salvador Island, Bahamas GPS:_____________________
Observers:___________________________________________________________

Loc. Codes: S=strand F=foredune I=Interdune B = Backdune joined to F=foreslope C=crest B=backslope

e.g.: FF = foredune foreslope FB = foredune backslope

Quadrat #LocSpecies ID# individuals% cover
1S   
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     

Dune Transect Data (continued)

Loc. Codes: S=strand F=foredune I=Interdune B = Backdune joined to F=foreslope C=crest B=backslope

e.g.: FF = foredune foreslope FB = foredune backslope

Quadrat #LocSpecies ID# individuals% cover