FM FM Soil Science & Hydrology 2 ā Questions and Answers
Question 1: Which soil property is the best indicator of compaction risk from heavy logging equipment?
- Soil pH
- Cation exchange capacity
- Bulk density (Correct answer)
- Soil color
Correct answer: Bulk density
Bulk density measures the mass of dry soil per unit volume; higher bulk density indicates less pore space and greater compaction, which restricts root growth and water infiltration.
Question 2: In forest hydrology, Best Management Practices (BMPs) are primarily designed to:
- Maximize timber volume removed per acre
- Protect water quality during and after harvesting operations (Correct answer)
- Eliminate riparian wildlife habitat
- Increase surface runoff to improve stream flows
Correct answer: Protect water quality during and after harvesting operations
BMPs are operational guidelines that minimize soil disturbance and protect water quality by reducing sediment, nutrient, and chemical inputs to streams during forestry activities.
Question 3: What is 'interflow' (also called throughflow) in a forest watershed?
- Water flowing overland across the soil surface
- Lateral subsurface water movement through the soil during storm events (Correct answer)
- Deep percolation to the water table
- Capillary rise from groundwater into the root zone
Correct answer: Lateral subsurface water movement through the soil during storm events
Interflow is the lateral movement of water through upper soil horizons during rainfall events when vertical percolation is slower than infiltration, contributing to streamflow without reaching the surface.
Question 4: Which process in the forest nitrogen cycle converts atmospheric nitrogen (Nā) into plant-available forms?
- Denitrification
- Nitrification
- Mineralization
- Nitrogen fixation (Correct answer)
Correct answer: Nitrogen fixation
Nitrogen fixation, carried out by specialized bacteria (e.g., Rhizobium, free-living Azotobacter) and some cyanobacteria, converts inert Nā gas into ammonia that plants can use.
Question 5: In a forested watershed, the water table typically exhibits which seasonal pattern?
- Remains constant year-round
- Rises during summer when trees are actively transpiring
- Drops in winter when precipitation is highest
- Rises in winter/fall when trees are dormant and falls in summer (Correct answer)
Correct answer: Rises in winter/fall when trees are dormant and falls in summer
During dormancy, tree transpiration nearly stops, allowing precipitation to recharge groundwater and raise the water table; in summer, high transpiration draws water down.
Question 6: What type of soil erosion is most commonly associated with forest roads and skid trails?
- Sheet erosion across flat surfaces
- Wind erosion from exposed areas
- Rill and gully erosion from concentrated flow (Correct answer)
- Splash erosion from raindrop impact
Correct answer: Rill and gully erosion from concentrated flow
Forest roads concentrate runoff into channels where water velocity increases, carving rills and gullies that deliver large sediment loads to nearby streams.
Question 7: What is the primary soil-related concern when logging operations are conducted during wet soil conditions?
- Increased fire risk
- Soil compaction and rutting that reduce long-term site productivity (Correct answer)
- Decreased organic matter accumulation
- Elevated soil pH levels
Correct answer: Soil compaction and rutting that reduce long-term site productivity
Wet soils have less structural strength, making them highly susceptible to compaction from heavy equipment, which reduces pore space, water infiltration, and root growth for future tree crops.
FM FM Soil Science & Hydrology 2
Which soil property is the best indicator of compaction risk from heavy logging equipment?