EDGE EFFECTS: DEPENDENCE OF VEGETATION DENSITY
ON INSECT ABUNDANCE
Hypothesis
HO: Insect abundance does not depend on vegetation abundance.
HA: Insect abundance is dependent on vegetation abundance.
Prediction
Insects living in a grassland environment are more inclined to be present in more
vegetative areas since vegetation gives insects shelter/camouflage (against some elements and
predators) and vegetation provides as a food source in themselves, thus it is predicted that more
insects will be found in areas of greater vegetation abundance. Due to inherent edge effects,
vegetation will increase in copiousness from the edge of the grassland toward the middle. So, if
insect abundance is dependent on vegetation density, there will be a trend in insect abundance in
correlation with edge effects of the density of vegetation.
Materials
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Dry pitfall traps (x10)
Shovels (x4)
Transect tape (x2)
1mx1m quadrat (x2)
Methods
Beginning at the edge of the grassland, a 25m transect line going towards the middle of
the grassland will be laid out. A 1m by 1m quadrat will be placed on the transect line and a
pitfall trap hole will be dug in the middle of that quadrat. Percent coverage of vegetation
abundance in the quadrat surrounding the dry pitfall trap will be estimated. This process will be
repeated for a total of 5 holes, therefore 5 pitfall traps, where these pitfalls traps will be 5 meters
apart. On the opposite side of the grassland, the opposite edge, another 25m transect line will be
going towards the middle of the grassland, simultaneously carrying out the same process for
another 5 pitfall traps, therefore ten pitfall traps in total will be laid out. These pitfall traps will
be laid out for two hours and upon completion of two hours, each pitfall trap will be examined
for trapped insects. Only number of insects caught will be tabulated, forgoing species.