question 4 page 266

The amount of rainfall affects it because the more rainfall the better kept the soil is, the less rain fall the more desert and sand there is. Also up in the northeast there is more rain and snow which is more water and rain to feed the soil and keep it fresh. But in the south-southwest there is only rain to keep the soil fresh, and with the amount of sun it gets being closer to the equator than the north it keeps the south dryer than the north.