Environmental Engineering Reference
In-Depth Information
Field Labs
Field Lab 1: The Effect of Quadrat Shape on Plant Density
and Spatial Pattern Estimates
Objectives: Be able to
...
￿ Discuss how method of observation (quadrat shape) can influence your results.
￿ Establish a sampling grid for randomly-placed plots in the field using a tape and
compass.
￿ Use a spreadsheet program to summarize your data.
￿ Use a statistical program to analyze your data.
Questions
￿ Which quadrat shape will have more variation between quadrats, leading to a
higher variance:mean ratio?
￿ Do different quadrat shapes yield significantly different plant population density
measurements?
Hypotheses
Write down hypotheses pertaining to the questions above. Think about how the
quadrat shape relates to plant shape and any environmental variation in the site.
Study system: This exercise is best conducted in a setting that has easily-
recognizable plants with somewhat aggregated (clumped) distributions. Alterna-
tively, sampling could include two different plant species, each with a different
spatial pattern (clumped, randomly, or regularly-dispersed). In any case, even if it is
a clonal plant, you will be counting individual stems (ramets). These stems should
be easily-recognizable for all students in the class, so choose the species with care.
The Set-up: Students will be collecting data at randomly-placed points within a
grid. Plan enough space for a 10
10 m plot for each pair of students in the course,
with a buffer in between each plot (Fig. 5.11 ). Students will establish a grid in the
field using meter tapes and a compass. Plant flags or stakes every 1 m to demarcate
the grid. Students can either identify pairs of points from a random number table
and work within their own plot for the lab, or they can be assigned sets of random
numbers (0-10 or 0-20 if using ½ m spacing), and sample all the plots in the class
using those same numbers. The lower left corner or center of the frame should be
placed at the random grid coordinates. Boundary decisions (how to deal with plants
on the edge of the quadrat) should be made and consistently applied within the
class. Each of the quadrats in Fig. 5.11 has a total area of 1 m 2 . Quadrats of ½ m 2
could also be used and an exploration of quadrat size effect could also be made.
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