lab 18.docx-Exercise #18 LAB REPORT Name...
lab_18.docx-Exercise #18 LAB REPORT Name: Kevin
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lab 18.docx-Exercise #18 LAB REPORT Name: Kevin
lab_18.docx-Exercise #18 LAB REPORT Name: Kevin
lab 18.docx-Exercise #18 LAB REPORT...
lab_18.docx-Exercise #18 LAB REPORT Name: Kevin
Page 3
Exercise #18
The moose population peaked in the mid-1970s and then declined over the next decade. How did the
trees at each site respond in the years following the peak? Are the results for these samples surprising
given the larger data sets for tree ring-width on the previous page?
In figure A there is an inverse correlation between ring width and increase in moose population, at the
mid 1970’s the ring width decreased and as the population declined over the years, the ring width was at
its highest, and increased when moose population decreased.
How should the difference in canopy cover affect growth rates? How will the height of the trees at
each site affect their response to changes in primary productivity? The authors suggest that primary
productivity was increasing during the late 1970s and most of the 1980s
does either ring-width
index appear to reflect that change?
The moose population and ring growth are inversely proportional, where when the moose population
grows, the ring-width decreases as a result, and vice versa.
Which hypothesis do you feel is best supported by the ring-width chronologies above?
The trophic cascade hypothesis best supports the ring-width chronologies, because it is more realistic
that moose population and ring-width are inversely proportional.
What final conclusions can you draw about the interactions between each trophic level on Isle
Royale? Is control exerted from the top down, as suggested by the trophic cascade model, or are
interactions between trophic levels ultimately controlled by primary productivity?
It is control exerted from the top down, because in the primary productivity model, the moose and fir-
ring length were inversely proportional.
Design an experiment that would allow you to clarify any ambiguities from Figures 1 or 2. Why
might an experimental approach prove advantageous in this situation?
An experiment that could be done is artificially rising the population of one species and calculating the
results after some time has passed.

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