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FOREST ECOLOGY Powered By Docstoc

Forests are important ecosystems. In this laboratory exercise, you will be
simulating the methods used by forestry scientist in determining the ‘tree density’,
‘dominance’, and ‘frequency’. Each of these forest variables tells you something
slightly different about the makeup of the forest. In this exercise, you will come to
learn what each of these different values tells you about the forest.


1. You should understand what forest data is used to determine ‘tree density’,
   ‘dominance’, and ‘frequency’, as well as understand the importance of each of
   these measures in determining the ecology of the forest.


Basal Area & Species Data

                     Sample     Sample    Sample     Sample
                       1          2         3          4

         Area           0.1       0.1       0.1        0.4
 NE       (ft2)

        Species       Hickory   Red Oak   Red Bud    Red Oak

         Area           0.1       0.2       2.6        0.3
 SE       (ft2)

        Species      Red Bud    Red Oak   Burr Oak   Hickory

         Area           4.1       0.2       0.4        0.1
SW        (ft2)

        Species      Burr Oak   Hickory   Red Oak    Red Oak

         Area           0.5       0.2       0.4        0.1
NW        (ft2)

        Species      Red Oak    Red Oak   Burr Oak   Red Oak


1. In order to estimate the ‘tree density’ in the forest given, you will be simulating
    a standard method called the Point Quarter Method. Before applying this
    method, we need to identify random points within the forest from which data
    will be collected. Locate the following points using the values given below
    and identify each point by making a small dot within the forest picture

   For Example, for sample point 1, measure over 4.5 centimeters using the
   scale on the bottom of the forest, and measure up 3.0 centimeters using the
   scale on the left side of the forest. Draw a dot where these two measures
   converge in the forest.

                               Horizontal Distance Vertical Distance

             Sample Point 1             4.5                  3.0

             Sample Point 2            12.5                  2.0

             Sample Point 3             11                   8.5

             Sample Point 4              3                   8.0

2. After finding each of the sample points, imagine two lines traveling through this
    each point, a vertical north-south line and a horizontal east-west line. These
    two lines would break the area surrounding each point into four quadrants, a
    northeast quadrant (NE), southeast quadrant (SE), southwest quadrant (SW),
    and northwest quadrant (NW). Hopefully you now understand why they call it
    the Point Quarter Method. It might be beneficial for you to lightly sketch in
    these imaginary lines through each sample point.

3. Next, measure the distance in meters (one centimeter equals one meter) to
   the nearest tenth of a meter from each sample point to the nearest trees in
   each of the four quadrants surrounding it. Record the measurements in
   meters in the data table provided in question 1.

   For example, you may measure the distance from sample point 1 to the
   nearest tree in the NE quadrant as 1.5 centimeters. You would convert this to
   1.5 meters and record it in the data table under sample 1, NE quadrant.

4. Next, determine the average distance from sample points to the nearest tree in
    each quadrant by adding each of the distance measurements in the data
   table in question 1 and the dividing by 16 (the total number of
   measurements). Record this value in the appropriate space below the data
   table in question 1.

5. Next, to determine the average open area surrounding each tree in the forest
   in square feet, 1) square the value determined in step 4, and then 2) multiply
   the value determined by 10.6 (there are 10.6 ft 2 per square meter). Record
   this value in the appropriate space below the data table in question 1.

6. Finally, to determine the ‘tree density’ in acres, plug in the value calculated in
    step 5 in the following equation. Record this final ‘tree density’ in trees per
    acre in the appropriate space below the data table in question 1.

         43,560 ft2 / average open area in ft2 = Density of Trees per acre

7. Answer question 2.

Basal Area & Species Data

1. The Point Quarter Method is used to determine more than an estimate of the
    density of trees in a forest. It is also used to determine ‘tree dominance’ and
    ‘tree frequency’. ‘Tree dominance’ is determined by adding up the basal
    area values for each species of tree in the samples taken. Since we are
    simulating this laboratory exercise this data is given to you in the “Basal Area
    & Species Data Table’ in the materials section. Use this data, determine the
    total basal area for each tree species and record it in the table provided in
    question 4.

2. For 2 point extra credit (so that you know how the values in the table were
   calculated), determine the basal area in square feet of the log at the front of
   the class, and record the value in question 5.

   1) Measure the circumference of the log in feet to the nearest tenth of a foot
      (1 foot 6 inches would equal 1.5 feet).
   2) Use the following formula to determine the basal area in square feet.
                          Area circle =  (circumference / 2)2

3. Answer question 6.

4. To determine the ‘tree frequency’, determine the number of individuals for a
   given species and divide that number by the 16 (the total number of trees in
   the sample). To express your value as a percentage multiple your value by
   100%. Determine the tree frequency for each tree species and record it in the
   table provided in question 7. Your percentages should add up to 100%.

5. Answer question 8.
                                      Name: ____________________________


1. Distance Measurements Data Table

                                Distance Measurements (cm)

                       Sample       Sample        Sample       Sample
         Quadrant        1            2             3            4





   Average Distance       = _________________ meters

   Average Open Area      = _________________ square feet

   Tree Density           = _________________ trees / acre

2. What does the tree density tell you about a forest? What would be different
   about forests having a lesser or greater tree density?
3. Do you think old growth forests may have a different density than young
   forests? Explain.

4. Tree Dominance Data Table

                                  Total Basal Area
                                    (square feet)

                       Burr Oak

                       Red Oak


                       Red Bud

5. Extra Credit

   Basal Area     = _______________ square feet

6. Based on the ‘Basal Area Data’ for each species which species would you
   consider to be the most dominant species? The least dominant species?
7. Tree Frequency Data Table

                                   as a percentage
                        Burr Oak

                        Red Oak


                        Red Bud

8. Based on the ‘Tree Frequency Data’ for each species, which species do you
   consider to be the most dominant species? The least dominant species?

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