Question

Forests are complex, evolving ecosystems. For instance, pioneer tree species can be displaced by successional species better adapted to the changing environment. Ecologists mapped a large Canadian forest plot dominated by pioneer Douglas fir with an understory of the invading successional species western hemlock and western red cedar. The two‑way table records the distribution of all 2050  trees in the plot by species and by life stage. The distinction between live and sapling trees is made for live trees taller and shorter than 1.3  meters, respectively.

	Dead	Live	Sapling	Total
Western red cedar (RC)	0.02	0.10	0.08	0.20
Douglas fir (DF)	0.16	0.16	0.00	0.32
Western hemlock (WH)	0.23	0.21	0.04	0.48
Total	0.41	0.47	0.12

What does the given data say about the current composition and the evolution of this Canadian forest?

(a) Compute the conditional probabilities that a randomly chosen tree is dead given information about its species, for each of the three tree species in this forest. (Enter your answers rounded to three decimal places.)

?(dead∣RC)=

?(dead∣DF)=

?(dead∣WH)=

What does this say about the past of this forest?

-The western hemlock is a relatively young species in this forest compared to the other two species.

-The western red cedar is a relatively young species in this forest compared to the other two species.

-None of the other options are correct.

-The Douglas fir is a relatively young species in this forest compared to the other two species.

(b) Compute the conditional probabilities that a randomly chosen tree is a sapling given information about its species, for each of three tree species. (Enter your answers rounded to three decimal places.)

?(sapling∣RC)=

?(sapling∣DF)=

?(sapling∣WH)=

Which tree species appears to be taking over and becoming dominant? What does this say about the likely future of this forest? Select the correct conclusion.

-The western hemlock proves to be a relatively young species in this forest, even though none of its trees are saplings, whereas the two other species have few to no saplings at all. The western hemlock will remain the dominant tree species in the future.

-The Douglas fir proves to be a relatively young species in this forest, with 50% of its trees as saplings, whereas the two other species have very few saplings. The Douglas fir will become the dominant tree species in the future.

-The western red cedar proves to be a relatively young species in this forest, with 40% of its as trees saplings, whereas the two other species have few or even no saplings at all. The western red cedar will become the dominant tree species in the future.

-None of the other options are correct.

Answer 1