Download Honors Biology Laboratory INVESTIGATING FOREST

Honors Biology Laboratory
INVESTIGATING FOREST SUCCESSION
Introduction:
In nature, communities of organisms experience frequent change. Sometimes, existing plants create
environmental conditions in an ecosystem that promote the growth of a new and different community of
producers. The replacement of a community by another is called “ecological succession.” Many different factors
initiate succession in forest ecosystems. And many different environmental variables influence the types of trees
that grow to replace an existing forest. Nevertheless, by studying a forest one can infer much about the history of
the ecosystem. And by analyzing the age structure of different species, one can also predict how the forest will
change over time. In this investigation you will learn to “read” the dynamics of a forest community.
Materials:
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Masking tape
Pen/pencil
String
Meter sticks (2-4 per group)
Plastic bag for collection of leaves
Graph paper- for drawing of “plot” made by group
Field guide to local trees
Lab books for data collection
Data Collection:
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Working in groups of 5-6, you will study an area in the forest that is approximately 5meters by 5meters.
To approximate your “grid” you will use the meter sticks and string provided to mark off your area of
study.
Within the 5x5meter area, you will identify and count numbers of species of every tree. It is critical not to
skip trees. If you are having trouble identifying a species because it is so tall or otherwise challenging,
seek help from other students or the teacher.
Also every identified tree must be categorized by an estimate of its age. Tree ages will be estimated using
their diameter at breast height (DBH). These are the categories:
Sapling
Young
Adult
Mature
Old
Over mature
Less than 1 cm @DBH
1 to 7.5 cm
7.6 to 12.5 cm
12.6 to 22.5 cm
22.5 to 37.5 cm
Greater than 37.5 cm
Jobs:
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Data keeper- has their lab notebook to record data
Grid drawer- uses graph paper to draw out their “plot”
Measure width of tree- corresponding to number of tree (see below)
Leaf collection- everyone in group other than data keeper. Collect and tag, using masking tape, according
to the # of tree on plot (example below) If you can’t reach the leaf, make a drawing of your leaf and “tag”
it.
You will determine the genus and species name in laboratory later after data collection.
3
1
2
4
5
Data analysis:
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Lab groups will pool data to come up with class totals. (Why is this a good idea?) Devise a system with
other students to do this efficiently. (Wiki anyone?)
Calculations- using class data
a. Total tree density (total of all trees/square meter)
b. Density for each species (total of each species/square meter)
c. For each species, percentage at each age.
Graphs- using class totals
a. Choose 5 of the species that yielded the most data. For, each, graph the distribution by age
b. Graph the distribution of all species by density
Lab Write-up: (in lab notebook)
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An introduction: Explain, discuss the concepts of the lab (such as ecological succession)
Procedure followed
Data- spreadsheet, calculation results, graphs
Analysis and conclusions
a. Discuss and explain your results
b. Refer to data in your explanations
c. Address the following in your conclusion:
i. What was this forest like (in terms of species composition, species densities) 50 to 100
years ago?
ii. Predict what the forest will be like in the future
iii. Why is the forest changing?
iv. How confident are you about the data?
Sample Date Table: __________________________________________________
Species
Saplings
Young
Adult
Mature
Old
Over-mature
Ex : Maple
Acer
saccharum
7
4
2
1
1
0