ISA Certified Arborist Practice Exam

The choice of gravitational water is correct because this type of water is found within the macropores of soil. Macropores are larger soil spaces that allow water to move quickly through the soil profile. When it rains, or when irrigation occurs, excess water fills these spaces, and the force of gravity helps drain this water downward. Gravitational water doesn’t adhere strongly to soil particles and is typically not retained in the soil for long periods, making it subject to drainage.

The other options referenced do not pertain to the specifics of water drainage from macropores. Meristems refer to regions of growth in plants, particularly where new cells are produced. Buffering capacity is a measure of a soil's ability to resist changes in pH, which is not directly related to water drainage. Root pruning is a horticultural practice aimed at controlling root growth and development, rather than a type of water in the soil.