FE Ch 7. These are due Monday, Nov 26^th at the beginning of class. Write your answers neatly and legibly on a separate piece of paper that you will turn in. Be prepared to discuss your answers with your study group.

You may need to access outside resources to completely answer these questions.

Read chapters 6-8 in The World of Northern Evergreens.

1. You are hiking in southern Oregon coast range through a forest that is pretty diverse and seems to vary in composition in different patches of forest. You suspect that fire and perhaps other disturbances may have resulted in the forest you see. What clues would you look for to determine the fire history of this forest, and what would they tell you?


For questions 2 and 3, you don’t need to limit yourself to diseases and insects that affect western forests, you may look at ones from other parts of the country if you are interested in them.

2. Select one tree disease and outline its basic life history, the type of damage it does to the tree and forest, and its potential for creating disturbance in the forest ecosystem­does it create small-scale disturbances or large-scale ones? What are the conditions that "setup" the forest for a large disturbance by this disease?
3. Select one insect and outline its basic life history, the type of damage it does to the tree and forest, and its potential for creating disturbance in the forest ecosystem­does it create small-scale disturbances or large-scale ones? What are the conditions that "setup" the forest for a large disturbance by this insect?
4. One of the biggest disturbances that the Earth has experienced is the asteroid impact described on p. 102 in your Forest Ecology book. Available evidence suggests that about 20% of the asteroid’s mass ended up as dust spread uniformly over the Earth after eventually settling out of the upper atmosphere. This dust amounted to about 0.02 g/cm² of Earth’s surface. The asteroid very likely had a density of about 2 g/cm³. How large was the asteroid? Give the mass in kilograms and the diameter in kilometers (assume it is a sphere). Useful data: Earth’s surface area = 5.1 x 10¹⁴ m², volume of a sphere (V)  where R is the radius of the sphere.
5. In addition to the dust from the asteroid, material from the impact crater was also blasted into the atmosphere. One estimate of the total mass of dust ejected into the atmosphere is 6.22 x 10¹⁸ g. The amount of sunlight blocked out by the dust would depend on the size of the dust particles produced. If all the dust were in one large lump in the atmosphere, it would block only a tiny fraction of the incoming sunlight. To explore this, assume each dust particle is spherical with a density of 2 g/cm³. Assume that the radius of each dust particle is 5 x 10^-7 m. To determine the size of the shadow cast by a dust cloud, you need to determine the shadow of one dust particle and then multiply this by the total number of particles. The shadow of a sphere is the cross-sectional area (the area of a circle that goes through the equator of the sphere, area of a circle = 1 R² where R is the radius of the circle). Compare your answer to the total surface area of the Earth (given above). Could the dust totally shade the Earth? (Hint for an approach to this problem if you’re totally stuck is on the web page).