Wolves, Moose, and Trees Case Study
Group Members: Ayesha, Ailin, Peace, Chen, Sadie
PART I – Introduction
1) We would expect to see a positive correlation between the population densities of each
trophic level under the primary productivity hypothesis.
2) We would expect to see a negative correlation between the population densities of
each trophic level under the trophic cascade hypothesis.
3) Under the primary productivity hypothesis, we would expect to see less plant growth
with wolf removal. Under the trophic cascade hypothesis, we would expect more plant
growth with wolf removal.
4) We are assuming that the only factor that affects the growth rates of balsam fir is
herbivores consuming the foliar biomass. We do not consider fluctuations in energy
available to the trees like changes in temperature or precipitation. We are assuming
that the trees will essentially become smaller over time as herbivores continue to
consume them. This assumption can be warranted as moose are the only large
herbivore so there is not another consumer that is competing for food. The assumption
for the growth rate is less stable as there is no evidence the researchers took
fluctuations in energy sources into account.
PART II – Trophic System Data
1) The purpose of figures A and B are to tell you the wolf and moose population. Figures C
and D are telling you the ring width from firs on each end of the island. Figure E tells you
the actual evapotranspiration rates from April to October. An unclear term is what do
evapotranspiration rates even tell us. Why are they useful to know?
2) The maxima and minima for the ring width of firs on the west are inversely correlated
with the moose population while those on the east are positively correlated. As the
moose population increased, the ring width of firs on the west end decreased while the
ring width of the firs on the east side increased along with the moose population. It is
possible they support the trophic cascade hypothesis if the moose stayed on the west
side of the island and ate more of the balsam firs than on the east side.
3) The east firs respond in the same way to changes in moose density. This is possible if the
moose stayed on the west side of the island and ate more of the balsam firs than on the
east side.
4) They respond inversely, so when moose are at their highest, wolves are at their lowest
and vice versa.
5) The primary productivity hypothesis is supported. AET is positively correlated with the
fir tree populations.
Group Members: Ayesha, Ailin, Peace, Chen, Sadie
PART I – Introduction
1) We would expect to see a positive correlation between the population densities of each
trophic level under the primary productivity hypothesis.
2) We would expect to see a negative correlation between the population densities of
each trophic level under the trophic cascade hypothesis.
3) Under the primary productivity hypothesis, we would expect to see less plant growth
with wolf removal. Under the trophic cascade hypothesis, we would expect more plant
growth with wolf removal.
4) We are assuming that the only factor that affects the growth rates of balsam fir is
herbivores consuming the foliar biomass. We do not consider fluctuations in energy
available to the trees like changes in temperature or precipitation. We are assuming
that the trees will essentially become smaller over time as herbivores continue to
consume them. This assumption can be warranted as moose are the only large
herbivore so there is not another consumer that is competing for food. The assumption
for the growth rate is less stable as there is no evidence the researchers took
fluctuations in energy sources into account.
PART II – Trophic System Data
1) The purpose of figures A and B are to tell you the wolf and moose population. Figures C
and D are telling you the ring width from firs on each end of the island. Figure E tells you
the actual evapotranspiration rates from April to October. An unclear term is what do
evapotranspiration rates even tell us. Why are they useful to know?
2) The maxima and minima for the ring width of firs on the west are inversely correlated
with the moose population while those on the east are positively correlated. As the
moose population increased, the ring width of firs on the west end decreased while the
ring width of the firs on the east side increased along with the moose population. It is
possible they support the trophic cascade hypothesis if the moose stayed on the west
side of the island and ate more of the balsam firs than on the east side.
3) The east firs respond in the same way to changes in moose density. This is possible if the
moose stayed on the west side of the island and ate more of the balsam firs than on the
east side.
4) They respond inversely, so when moose are at their highest, wolves are at their lowest
and vice versa.
5) The primary productivity hypothesis is supported. AET is positively correlated with the
fir tree populations.
