Final answer:
The soil profile referred to is the pedosphere, with the A horizon being the topsoil and the B horizon as the subsoil. These layers are essential for plant growth and contain various nutrients and organic matter.
Step-by-step explanation:
The soil profile described in the question refers to the layered structure of the soil above the parent bedrock. Each layer, known as a horizon, has distinct physical and chemical properties. The term for this soil profile is the pedosphere, which is part of the larger biosphere.
Within the soil profile, the A horizon is considered the topsoil. This layer is rich in organic matter and is crucial for plant growth due to its nutrient content and the microbial processes that take place within it. The B horizon, or subsoil, is the accumulation of fine materials that have been transported downward from the A horizon and tends to be more mineral-rich and less fertile as compared to the topsoil.