PLANT COMMUNITY STUDY

• Goal: to determine the diversity and abundance of plants in an area.
• Preparation: know how to identify the plants on our plant list.
• Time Necessary: about 2-3 hours.
• Equipment: 50 meter tape, 2 meter sticks, data sheet, paper, pencil.
• Turn In: the Summary Plant Community Data Form (in html or Microsoft Word format)

OBJECTIVES:

1. To obtain experience in natural history field research and techniques.
2. To identify many of the plant species occuring here.
3. To better understand the composition of our local flora.

PROCEDURE: Quadrat Sampling Technique

• Go to starting point and lay out 50 meter tape (transect line) in a straight line.
• You will be collecting data from ten 1x2 meter plots along this transect (one plot every 5 meters along the transect).
• Establish the first plot by placing one of the two meter sticks parallel with the transect line and one meter away from the transect line and the other meter stick one meter away from the transect line on the other side of the line.
• This gives you a 1x2 meter plot.
• Within that plot, record the following data (see sample table below):
  • which species occur in the plot (any amount of the plant can occur within the plot). Record that the species occurred in the plot by recording the plot number in the plot column.
  • how many individuals of each species occur in the plot (more than half of the main stem must be in the plot to count).
  • how many centimeters of the transect line is intercepted by each species. That needs some explaining... Just look straight down from and straight up from the transect line and record how many centimeters of the transect line would touch each plant if the transect line was moved down and up. Another way to think of it is to Imagine the sun was straight overhead and the plants cast solid shadows directly below them. Now imagine your transect line running along the ground. Record the number of centimeters of the transect line that would be covered by the shadow of each plant.
• Now move 5 meters down the transect and create the next plot between the 5 and 6 meter mark on the transect line.
• Within this plot, record the same data as before, using the same table as before.
• Continue this process until you have recorded the data from all 10 plots (you should have used the following portions of the transect line -- 0-1, 5-6, 10-11, 15-16, 20-21, 25-26, 30-31, 35-36, 40-41, 45-46 meters.
  

EXAMPLE DATA: these data show that triangleleaf bursage occurred in 4 of your 10 plots, that there were 3 individuals in the first plot, 2 individuals in the fourth plot, 5 individuals in the seventh plot, and 1 individual in the ninth plot, and that shadows made by the triangleleaf bursage would cover 15 centimeters of the transect in the first plot, 24 cm in the fourth plot, 39 cm in the seventh plot, and none of the transect line in the nineth plot. Etcetera for the other species.

SUMMARY DATA:

For each species, calculate absolute and relative values of each of the following: density, frequency (not relative frequency), and cover. Round all numbers to nearest tenth (except frequecies).

Density = # individuals counted in the 20 square meters you observed (10 plots each 2 square meters in size)
          Example from above: Density for triangleleaf bursage = 11 individuals per 20 square meters
          This means that in an average 20 square meter plot, 11 triangleleaf bursages would occur.

Relative Density = take the density of a species divide by the total density of all species then multiply by 100.
          Example from above: Relative density for triangleleaf bursage = 11/16 = 68.8%
          This means that 68.8% of the plants in the area surveyed were triangleleaf bursages.

Frequency = percentage of plots in which the species occurred
          Example from above: Frequency for triangleleaf bursage = 4/10 = 40%
          This means that there is a 40% chance that there would be a triangleleaf bursage in any 2 square meter plot.

Cover = take the total intercept for the species divided by the 1000 centimeters you examined then multiply by 100.
          Example from above: 78 cm/1000cm = 7.8%
          This means that 7.8% of the ground is covered by triangle leaf bursage.

Relative Cover = take the cover of a species and divide by the total cover of all species then multiply by 100.
          Example from above: Relative Cover for triangleleaf bursage = 78 cm/260 cm = 30%
          This means that 30% of the ground that is covered by plants is covered by triangle leaf bursage.

Record these data on the Summary Plant Community Data Form (html / word) and turn in.

Back to Lab Manual