Studying Plant Populations:
Quadrat Sampling
Names: ______
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Class: ______
Date: ______
Introduction:
The world is too large for ecologists to study without sampling. Even a smaller area such as a park or marsh may be too large for counting methods. One of the most convenient ways to measure ecological variables (like abundance, species diversity or biomass) is by sampling with quadrats. Quadrats are small, identically-sized plots which are placed randomly over a study site. Whenever a field study is planned, scientists must answer a few important questions: What size quadrat should I use? What shape quadrat should I use? How many quadrats should I use? The answer to these questions depends on the resources available for sampling (either time or money is always the limiting factor in fieldwork). It also depends on the underlying spatial distribution pattern of the variable being measured (whether clumped, randomly or uniformly distributed, and whether common or rare).
Purpose:
We will build square quadrats with a total area of 0.25 m2. We will use these quadrats to study the density and distribution of leaves at Westmount Park. You will have one period to assemble your quadrats, and one period to collect data which will be analyzed and presented in a report.
Materials:
- wooden slats: 1 long and 2 short
- string: 6 m
- scissors
- hand saw
- metric measuring tape
- screws (8)
- hand drill and drill bits
- clamps
- carpenter’s square
Diagram:
Figure A: Quadrat Design
Procedure:
Cutting the Workpieces to Length
1. Obtain a short slat of wood. Using a metric measuring tape, measure a distance of exactly 50 cm from the straight cut edge.
2. Use a carpenter’s square to draw a straight line at your 50 cm mark.
3. Repeat steps 1 and 2 with your second short slat of wood.
4. Using 2 wooden handscrew clamps or a C-clamps, affix your workpiece on both ends to the work bench. Ensure that a scrap piece of wood is clamped under your workpiece to avoid sawing the tabletop.
5. Using a backsaw, carefully cut along the line you have drawn on your workpiece.
6. Repeat with the second workpiece.
7. Using a metric measuring tape, measure the thickness of your 50 cm wooden slats.
8. Calculate the length of the longer slats by adding 50 cm + the thickness of the other 2 shorter slats combined.
9. Using a metric measuring tape, measure the distance you have calculated above.
10. Use a carpenter’s square to draw a straight line at your measured mark.
11. Using 2 wooden handscrew clamps or a C-clamps, affix your workpiece on both ends to the work bench. Ensure that a scrap piece of wood is clamped under your workpiece to avoid sawing the tabletop.
12. Using a backsaw, carefully cut along the line you have drawn on your workpiece.
13. Now, measuring from the cut you have made, repeat steps 9-12.
Drilling Holes in the Workpieces
14. Label the two 50 cm pieces with the letter “i”, since they are your interior slats. Label the two longer pieces with the letter “e” since they are your exterior slats.
15. Draw a straight line lengthwise down the center of your 50 cm “i” pieces. Using a metric tape measure, make a mark every 10 cm along your drawn line. These will be your drilling points later on. Put these pieces aside.
16. Draw a straight line lengthwise down the center of your longer “e” pieces. Draw a straight line indicating the edge where your interior slat will meet your exterior slat. Measuring from this drawn line, make a mark every 10 cm along your center line. These will be your drilling points later on.
17. Using the table vice, secure your workpiece to the table with your drilling points facing upwards.
18. Use an electric hand drill with a 1/8” drill bit installed by your teacher, drill a hole right through the workpiece at each of your drilling points.
19. Repeat step 18 with all of your remaining workpieces.
Assembling your Quadrat Frame
20. Dryfit your pieces together, ensuring that your exterior pieces are on the outside and your interior pieces are on the inside.
21. You will use two screws to affix each corner. This kind of joint is called a butt joint.
22. Using two clamps, affix your workpieces to the table so that they a joined at the corner of the tabletop. Show your teacher before proceeding to the next step.
23. Using a hand drill with a 1/8” drill bit installed by your teacher, you will drill two pilot holes for each corner. Repeat for each butt joint.
24. Re-clamp two adjoining workpieces and using a Robertson screw driver, assemble your frame.
Stringing your Quadrat
25. Tie a large knot in one end of your string. String the quadrat according to Figure B: Stringing Technique.
26. Pull the string taught, and tie off your string.
27. Repeat steps 25-26 for the perpendicular string, ensuring that you use an ‘over-under’ technique (like a badminton racket).
Construction Sketch (with dimensions)
Draw a sketch to show how you will construct your quadrat. Include the dimensions and the placement of fixed links (screws), the location of holes for string placement, as well as indicating the tools that will be used for each job.
Construction Sketch (with dimensions) continued...
Pre-lab analysis: Brainstorm the answers to these questions as a group.
1. What would be the advantage of increasing the number of quadrats sampled? What would be the disadvantage or cost of increasing this number?
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2. What would be the advantage of increasing the size of quadrats sampled? What would be the disadvantage or cost of increasing the size?
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3. How should you arrange your quadrats? What would be the best method for determining where they should be placed?
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Evaluation:
5 / 4 / 3 / 2 / 1 / 0Design Plan / Is complete, organized and neat. Will produce the desired product. / Plan is nearly complete, is organized and neat. Will produce the desired product. / Plan is complete, fairly neat and organized. Will produce the desired product with some revision. / Plan is incomplete, but on the right track. Needs significant modification. / Plan is incomplete, disorganized or messy. Needs significant modification.
Team Organization / Team has organized itself effectively and evenly to complete all tasks. / Team has organized itself effectively to complete all tasks. / Team has worked together effectively with teacher assistance in organization. / Team has had major conflicts but has completed all tasks. / Team has only completed some objectives as a result of ineffective organization.
Construction / The best tools for the job were used carefully, with little waste materials. / Adequate tools were used carefully with little waste generated. / Adequate tools were used with mistakes that led to some waste. / Adequate tools were used with mistakes that led to major waste. / Inappropriate tools were used , or misused, leading to suspension of tool privileges.
Product
Specifications (Specs.) / Product conforms to all specs. & is attractive & functional. / Product conforms to all specs. & is functional. / Product conforms to most specs. & is attractive and functional. / Product conforms to most specs. and is functional. / Product does not conform to most specs. &/or does not function.
Group Self-Evaluation
Describe one conflict that your group encountered, and how you resolved the problem:
Each student in your group must respond to each of the following:
1. Explain exactly what you contributed to the first part of this project.
2. What are some of your strengths/talents that you used in this part of the project?
3. What are some of your weaknesses that you feel you need more practice to improve on?