More than 20 million Ponderosa pines died in Arizona and New Mexico following bu

Question

More than 20 million Ponderosa pines died in Arizona and New Mexico following bug attacks between 2001 and 2003. Defoliators eat the leaves and needles of trees, whereas bark beetles kill trees by burrowing under the bark and damaging them so that they can no longer transport water to their needles. As a consequence, trees with limited access to water are more vulnerable to bark beetles. Consider the graph below:

1) How did mortality (acres damaged) of pine trees due to bark beetles change through time?

a) decreased then increased

b) increased linearly

c) increased exponentially

d) was variable but relatively constant until 2003 and then increased dramatically

2) Were observed patterns of tree damage the same in Arizona and New Mexico?

a) yes

b) no

c) yes for defoliators; no for bark beetles

d) no for defoliators, yes for bark beetles

3) Relative to historical averages, local precipitation amounts were likely __________ over this time interval?

a) higher than normal

b) lower than normal

c) more variable than normal

d) unchanged

4) Ecological effects of bark beetles in this region are likely to include increases in the __________ of disturbance due to wildfires caused by lightening strikes.

a) intensity and scale

b) intensity and frequency

c) scale and frequency

d) intensity, scale, and frequency

5) Wildfires function as a density-__________ factor that __________ tree population growth.

a) dependent; regulates

b) dependent; limits

c) independent; regulates

d) independent; limits

Explanation / Answer

1) mortality (acres damaged) of pine trees due to bark beetles change through time was increased exponentially. Option c is correct.

2)The observed patterns of tree damage were not similar for defoliators and similar for bark beetles in Arizona and New Mexico. Option d is correct.

3) Relative to historical averages, local precipitation amounts were likely lower than normal over this time interval. Option b is correct. This is because of the death of several trees.

4) Ecological effects of bark beetles in this region are likely to include increases in the intensity, scale, and frequency of disturbance due to wildfires caused by lightening strikes. Option d is correct.

5) Wildfires function as a density- independent factor that limits tree population growth. Option d is correct.

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