ISA Certified Arborist Practice Exam

The term for air-filled soil macropores is indeed macropores. Macropores provide essential spaces in the soil structure that allow for the movement of air, water, and nutrients. These pores are typically larger than 0.08 millimeters in diameter and are crucial for aeration and drainage within the soil. They play a significant role in the overall health of the ecosystem, facilitating root development and the conditions necessary for microbial activity.

In contrast, buffering capacity refers to the soil's ability to maintain a stable pH level when acids or bases are added. Gravitational water is the term used for water that drains through the soil due to gravity, and field capacity describes the amount of moisture retained in the soil after excess water has drained away and the rate of downward movement has slowed. Understanding these distinctions helps clarify why macropores specifically relate to the air-filled spaces in soil.