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Natural History Event Species List

PLANT COMMUNITY STUDY

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 [USE THE RAW DATA SHEET)

  1. Go to starting point and lay out 50 meter tape (transect line) in a straight line.
  2. You will be collecting data from ten 1x2 meter plots along this transect (one plot every 5 meters along the transect).
  3. 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.
  4. This gives you a 1x2 meter plot.
  5. Within that plot, record the following on your raw data sheet (Word, pdf):
    1. Frequency: which species occur in the plot (any amount of the plant can occur within the plot). The most common species in the area already have a row created for them.  If it is one of those species, record that the species occurred in the plot by recording a Y in the first box in the Frequency column in that row and record a N if the species does not occur in the plot.  If there are other species in the plot that are not already written on your sheet, create a new row for them and put a Y in the first box.
    2. Density: how many individuals of each species occur in the plot (more than half of the main stem must be in the plot to count).  For each species, record this in the first box of the Density column.
    3. Cover: how many centimeters of the transect line is intercepted by each species. 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 (use the outside of the plant as measured from a straight line from outer branches). Another way to think of it is to imagine the sun was straight overhead and the plants cast solid shadows directly below them (from their outside margins). Now imagine your transect line running along the ground. In the first box in the Cover column, record the number of centimeters of the transect line that would be covered by the shadow of each plant of that species.
  6. Now move 5 meters down the transect and create the next plot between the 5 and 6 meter mark on the transect line; record the same data as before, but in the second box for each column.
  7. 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 meters

5-6 meters

10-11 meters

15-16 meters

20-21 meters

25-26 meters

30-31 meters

35-36 meters

40-41 meters

45-46 meters

EXAMPLE DATA


Species

Present? Y/N  = Frequency

# Individuals = Density

Transect Intercept = Cover

Triangleleaf Bursage

Y

N

N

Y

N

3

0

0

2

0

15

0

0

0

0

N

Y

N

Y

N

0

5

0

0

0

0

39

0

9

0

Frequency: These data show that triangleleaf bursage occurred in 4 of your 10 plots: the first (0-1 meters), the fourth (15-16 meters), the seventh (30-31 meters), and the ninth (40-41 meters.)
Density: There were 3 individuals in the first plot, 2 individuals in the fourth plot, 5 individuals in the seventh plot, and no individuals in the ninth plot.  Note that even though the species was present in the ninth plot, there were no individuals inside the plot – the tree’s branches were hanging over into the plot, but its stem was not more than halfway inside.  
Cover: Shadows made by the whitethorn acacia would cover 15 centimeters of the transect in the first plot, none of the transect line in the fourth plot, 39 cm in the seventh plot, and 9 cm in the ninth plot.  Note that even though two individuals were inside the fourth plot, none of the branches actually intersected the transect line running down the center of it.  Also note that even though there were no individuals present in the ninth plot, the branches hanging over into the plot did intersect the transect line for 9 cm.

PROCEDURE: DATA SUMMARY [USE THE SUMMARY DATA SHEET]

For each species, calculate overall frequency, density and cover. Round density and cover to the nearest tenth (one decimal place.) Then calculate the total density and cover for all species, by adding up values for all species. Finally, calculate the relative density and the relative cover. Again, round to the nearest tenth (one decimal place.)

Frequency = percentage of plots in which the species occurred
Calculate as: # of plots containing the species times 10
Example from above: Frequency of Triangleleaf Bursage = 4 X 10 = 40%. This means that there is a 40% chance that there would be a triangleleaf bursage within any 2 square meter plot.

Density = # individuals counted in the 20 square meters you observed (10 plots each 2 square meters in size)
Calculate as: sum of # of individuals for that species
Example from above: Density for triangleleaf bursage = 3 + 2 + 5 = 10 individuals per 20 square meters

This means that in an average 20 square meters, 10 triangleleaf bursages would occur.

Add densities for all species to get the Total Density.

Cover = % of transect line covered by that species
Calculate as: take the total intercept for the species divided by the 1000 centimeters you examined then multiply by 100.

Example from above: 15 cm + 39 cm + 9 cm = 63 cm/1000cm = 6.3%. This means that 6.3% of the ground is covered by triangleleaf bursage.

Add Cover for all species to get the Total Cover.

Relative Density = % of all individuals that are of that species
Calculate as: Species Density divided by Total of all densities times 100 (round to nearest tenth)
Example from above: Say that a total of 16 individuals of all species were observed (Total Density.) Relative density for triangleleaf bursage = 10/16 = 62.5%. This means that 62.5% of the plants in the area surveyed were triangleleaf bursages.
Total of all Relative Densities = close to 100

Relative Cover = % of all plant cover that is of that species
Calculate as: Species Cover divided by Total of all covers times 100 (round to nearest tenth)
Example from above: Say that the sum of the cover for all species was 260 cm (Total Cover.) Relative Cover for triangleleaf bursage = 63 cm/260 cm = 24.2%. This means that 24.2% of the ground that is covered by plants is covered by triangle leaf bursage.
Total of all Relative Covers = close to 100

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

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