Tree Survey Assignment (1) (1)
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University of Arkansas *
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Geology
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Dec 6, 2023
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LAB 5: GEOLOGY & BIODIVERSITY
100 points
Due at the beginning of lab next week.
LEARNING OUTCOMES
At the end of this lab, you will be able to:
1.
Describe how to perform an arboreal survey.
2.
Calculate quantitative measures of biodiversity.
3.
Discuss environmental and other controls on tree biodiversity.
INTRODUCTION
For this lab, we will sample tree species composition and productivity in the woodland
area behind the Clinton House Museum on the University of Arkansas campus. We will sample a
series of 1/20-hectare circular plots (8.62 m radius), the measure the number of trees per
hectare (ha), the cross-sectional area of the tree stems per hectare (i.e., basal area), and several
other variables (Figure 1).
Geology and Biodiversity StoryMap Presentation
Figure 1: A) Illustration of a 1/20-hectare sample plot.
A tree must be at least
10 cm in diameter at breast height (DBH)
to be included. If at
least half of the tree trunk is in the plot, the tree should be included in the analysis.
After the data are collected, you will make a series of calculations to determine:
1
-
Tree absolute density (number of trees per hectare for all species)
-
Tree relative density (percent trees per hectare for each species)
-
Number of tree species encountered on the transect (measures biodiversity)
-
Basal area per species
-
Combined basal area for all species
-
Relative species dominance
-
Total basal area in m
2
per hectare (measures productivity)
These calculations will allow you to make quantitative interpretations about biodiversity on a
wild part of campus. Each calculation is described in more detail within the assignment
questions.
Identifying trees
There are several species of trees on campus, but you may not know how to identify
them. Below is a quick tree identification reference. If you have trouble, please refer to various
online resources, a tree ID app, or the book “Trees of Arkansas.” Identify trees to the genus level
(Oak, Maple, Ash, etc.). If a species is unidentified, note it as “unknown” in your tables below.
2
Oak (
Quercus
)
Maple (
Acer
)
Ash (
Fraxinus
)
Pine (
Pinus
)
Sweetgum (
Liguidambar
)
Dogwood (
Cornus
)
3
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Tuliptree (
Liriodendron
)
4
LAB 8: GEOLOGY AND BIODIVERSITY
Name: _____________________________
Section: _____________________________
Perform the following calculations, show your work, and answer the questions [100 pts].
Part 1: Set up plots
In groups, set up three 1/20 hectare plots in the wooded area pictured below. For
each plot, note the latitude/longitude coordinates of the centroid, then measure
8.62 meters from the centroid to the edge of the circle, and mark the boundaries
of the plot. You can use field tape here to help visualize the plot. Mark the
approximate location of each plot on Figure 1.
Figure 1
: Google Earth image of measurement area.
5
Part 2: Data
collection (30 pts)
Draw a stem map of all trees sampled within each plot (e.g., Figure 1), noting DBH
and species (or at least genus: do the best you can here). Only indicate those trees
10 cm > DBH.
Plot 1
Centroid Coordinates:
6
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Plot 2
Centroid Coordinates:
7
Plot 3
Centroid Coordinates:
8
Part 3: Calculations
1)
Stem
density
: count the total number of trees in each plot, then multiply by 20 to get stems
per hectare. Add the total stems per hectare together then divide by 3 (the number of plots)
to get the average. [15 pts]
Plot 1:
Total number of trees:
Stems per hectare (total # x’s 20):
Plot 2:
Total number of trees:
Stems per hectare:
Plot 3:
Total number of trees:
Stems per hectare:
AVERAGE NUMBER OF STEMS PER HECTARE:
2)
Basal area
: use the DBH to get basal area for each randomly sampled tree in each plot using
the formula for the area of a circle,
π(DBH/2)
2
. DBH should be in cm. Basal area will be in
cm
2
. [15 pts]
PLOT 1
TREE #
TREE SPECIES
DBH (cm)
BASAL AREA (cm
2
)
9
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PLOT 2
TREE #
TREE SPECIES
DBH (cm)
BASAL AREA (cm
2
)
PLOT 3
TREE #
TREE SPECIES
DBH (cm)
BASAL AREA (cm
2
)
3)
Relative Frequency
: The number of trees per species divided by the total number of trees
measured; e.g., 12 shagbark hickories / 20 total trees = 0.60 (decimal form) or 60% (the sum
of your percentages should equal 100%). [10 pts]
TOTAL # OF TREES (ALL 3 PLOTS)
: ___________________
SPECIES
TOTAL NUMBER OF TREES
FOR THAT SPECIES
% FREQUENCY
10
4)
Relative dominance
: List the total basal area from each species (found in question 2; you’ll
need to add up the basal area for trees of the same species). Which is the most dominant,
by percentage (total basal area per species/total basal area of all trees)? [10 pts]
SPECIES
TOTAL BASAL AREA (cm
2
)
% DOMINANCE
Dominant species:
Questions
1.
[5 pts] What is the exposure of the survey site? How do exposure and slope affect growth and
biodiversity in the survey area?
2.
[5 pts] Besides exposure and slope, what other factors might influence the types of trees that
are growing in the survey area?
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