B.F. Bachelor of Forestry Forest Soils 1 — Questions and Answers
Question 1: What is the O horizon in a forest soil profile primarily composed of?
- Mineral particles and clay
- Decomposed and partially decomposed organic matter (Correct answer)
- Weathered bedrock fragments
- Leached minerals and iron oxides
Correct answer: Decomposed and partially decomposed organic matter
The O horizon consists of organic matter in various stages of decomposition, including leaf litter, twigs, and humus, and sits above the mineral soil.
Question 2: Which soil texture has the highest water-holding capacity?
- Sand
- Sandy loam
- Clay loam (Correct answer)
- Gravel
Correct answer: Clay loam
Clay loam has fine particles with a large surface area that allows it to hold significantly more water than coarser-textured soils.
Question 3: What is the downward movement of water through soil that carries dissolved minerals called?
- Translocation
- Leaching (Correct answer)
- Eluviation
- Pedogenesis
Correct answer: Leaching
Leaching is the process by which percolating water carries soluble minerals and nutrients downward out of the upper soil layers.
Question 4: Which soil order is most commonly associated with highly weathered, nutrient-poor soils found under humid subtropical forests in the southeastern US?
- Mollisols
- Ultisols (Correct answer)
- Entisols
- Histosols
Correct answer: Ultisols
Ultisols are highly weathered, acidic soils with low fertility and a clay-enriched B horizon, common in the humid southeastern United States.
Question 5: What does cation exchange capacity (CEC) measure in forest soils?
- The rate at which water infiltrates the soil
- The soil's ability to hold and supply positively charged nutrient ions (Correct answer)
- The total amount of organic carbon stored in the soil
- The percentage of clay particles present in the soil
Correct answer: The soil's ability to hold and supply positively charged nutrient ions
CEC measures the soil's capacity to retain cations such as calcium, magnesium, and potassium, which are essential plant macronutrients.
Question 6: Which soil order is most commonly associated with productive temperate deciduous forests in the eastern United States?
- Aridisols
- Alfisols (Correct answer)
- Gelisols
- Oxisols
Correct answer: Alfisols
Alfisols are moderately leached, fertile soils that develop under deciduous forests and maintain high base saturation, supporting productive tree growth.
Question 7: What is soil porosity?
- The resistance of soil to penetration by plant roots
- The ratio of void space volume to the total soil volume (Correct answer)
- The capacity of soil to adsorb and retain nutrients
- The distribution of particle sizes in a soil sample
Correct answer: The ratio of void space volume to the total soil volume
Soil porosity is the proportion of the total soil volume occupied by pore spaces, which controls the soil's capacity to hold air and water essential for plant growth.
B.F. Bachelor of Forestry Forest Soils 1
What is the O horizon in a forest soil profile primarily composed of?