Answer to Question 1
The answer will vary based on the chosen soil. The characteristics of most state soils can be understood by consideration of climate and vegetation and, in some cases, parent material. In some cases, forest soils are found in areas that were extensively cleared for agriculture so that soil characteristics do not necessarily match current vegetation (a good discussion opportunity).
Answer to Question 2
The B soil horizon contains an abundance of soil aggregates. They form because mild surface charges cause clay particles to adhere together when they come into contact with one another. Soil aggregates are not abundant in the other soil horizons because the other horizons do not have an abundance of clay particles. The soil aggregates are important because their formation aids in the formation of cracks between the particles. These cracks are important pathways for downward transport of water, clay particles, and organic matter from above. Roots preferentially grow along the cracks.