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Activity Two
Annual Wetland Plant Diversity Survey

Objectives
The student will use a standard method for calculating the diversity of a plant community and determine whether purple loosestrife population density is correlated to the diversity of the community.

Method
One square meter quadrats will be selected randomly in a wetland containing areas of differing levels of loosestrife invasion. The numbers and areas covered by each species of plants will be recorded and used to calculate a diversity index using the formula

diversity = -pr ln pi (see print version)

where pi is the number of individuals of one species divided by the total number of individuals in the sample. The diversity values obtained will be plotted in a scatter plot versus the percentage of the total plant population represented by loosestrife.

Background
One of the major problems with the presence of loosestrife often cited by researchers and others is that it tends to crowd out other wetland plants and reduce the diversity. This reduces the variety of available foods for herbivores, space for nesting of wetland birds, and turns the infested area into a "biological desert". If this is true, students should see a very strong negative effect of loosestrife density on the diversity index. If the expected relationship does not appear, this will provide a chance for further research or refinement of techniques.

Materials
Six clipboards, one ten meter tape measure, five quadrat markers made of 1" plastic pipe or meter sticks taped together at the corners, four corner stakes (60" each), hip boots or old sneakers, tally sheets and site maps, calculator and graph paper. [Optional: aerial photos of the study site and/or maps, camera to record operations and allow later checking for accuracy] 

Procedure
Locate an area of marsh in which some areas are heavily infested with purple loosestrife, other areas have some plants and some areas are not yet infested. Otherwise conditions in the areas should be as similar as possible with regard to wetness, soil type, drainage, etc. Show the students the quadrat markers and ask for volunteers to place them and record notes. Locate a ten meter quadrat in each of the areas described and stake the corners. Measure diagonals to ensure a square. Position one student in the center and one in each corner and have them carefully position the quadrat markers in the center and four corners. Have the students draw a picture of the plot and their location labeled 1,2,3,4 in any order around the perimeter. Complete the field notes forms with a count of the number of stems per square meter for each plant species found. Rotate the quadrat by 45 degrees and repeat using a different group of students. Combine the field notes to calculate the percentage of stems of loosestrife in the plot. Also use the data to calculate the diversity index for each plot. On a piece of graph paper, plot the diversity index for each quadrat as a function of the density of purple loosestrife in the one meter squares.

Extensions
Using standard references, find and use different diversity indices to compare the plots. Remove all loosestrife plants from the same ten meter square plot as soon as growing plants can be identified in the spring and keep the loosestrife plants from growing by periodic weeding during the summer. Calculate the diversity index for the same plot the following September.

Evaluation
Student performance in this activity may be evaluated by: 1) observation during the activity, 2) informal questioning and discussion before, during and after the activity 3) Asking the students to discuss in written form the reason for doing this activity, the expected result and what was actually observed.4) asking the student to predict the results of releasing Galerucella so. In the study plots and justify the prediction. 5) Have each student write up the activity as a formal scientific report and evaluate using the standards used for other lab write-ups.

Activities: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10