Soil Science & Analysis Flashcards
7 cards from real SAF practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Soil Science & Analysis flashcards as text
During a forest road construction project, a forester observes mottling (rust-colored and gray spots) in a soil profile at 45 cm depth. What does this indicate?
Answer: Seasonal or periodic water saturation causing anaerobic conditions
Mottling results from alternating oxidizing and reducing conditions caused by fluctuating water tables, indicating seasonally saturated soils.
What is the significance of the C:N ratio in forest floor organic matter for nutrient cycling?
Answer: A high C:N ratio indicates slow decomposition and potential nitrogen immobilization
When C:N exceeds 30, microbial decomposers immobilize nitrogen for their own growth, making it temporarily unavailable to trees.
Which method is most appropriate for estimating fine root biomass distribution in a forest soil profile?
Answer: Soil core extraction and root washing with sequential sieving
Soil core extraction followed by washing and sieving allows quantitative separation and measurement of fine roots by diameter class across soil depths.
A silviculturist notes that a harvested site has poor natural regeneration and compacted soils. Which soil remediation technique is most appropriate before replanting?
Answer: Subsoil ripping or deep tillage to fracture compacted layers
Subsoil ripping fractures compacted hardpans, restoring macroporosity and allowing root penetration and water infiltration.
What role does soil organic matter play in water repellency (hydrophobicity) sometimes observed after wildfires?
Answer: Heat volatilizes organic compounds that recondense in cool soil layers, creating hydrophobic coatings
Fire volatilizes hydrophobic organic compounds from litter; these gases move downward and condense on cooler soil particles, forming water-repellent layers.
Which soil order typically supports the most productive temperate broadleaf forests in the eastern United States?
Answer: Alfisols
Alfisols have high base saturation and a clay-rich argillic horizon, providing good moisture and nutrient retention for productive hardwood forests.
What does a field test using 10% HCl (hydrochloric acid) on a soil sample indicate if it fizzes vigorously?
Answer: Presence of carbonates such as calcium carbonate
Vigorous effervescence with dilute HCl indicates the presence of carbonates (CaCO₃), signaling alkaline soil conditions and possible calcium excess.