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
Which soil water potential component describes the binding of water to soil particle surfaces and organic matter?
Answer: Matric potential
Matric potential (also called capillary or pressure potential) results from adhesion of water to solid surfaces and capillary forces, and is always negative in unsaturated soils.
A soil lab report shows a base saturation of 25% for a forest soil. What management implication does this have?
Answer: The soil has low fertility with significant acidic cation (H⁺, Al³⁺) dominance on exchange sites
Low base saturation means exchange sites are dominated by acidic cations (H⁺ and Al³⁺), indicating poor nutrient status and potential aluminum toxicity concerns.
What is the role of actinomycetes in forest soil nutrient cycling?
Answer: They decompose recalcitrant organic compounds like lignin and chitin, releasing nutrients
Actinomycetes are filamentous bacteria that break down tough organic compounds including lignin, cellulose, and chitin, playing a key role in humus formation.
In the context of forest soil surveys for site index prediction, which soil property has the strongest correlation with site productivity in many temperate forest types?
Answer: Available water-holding capacity of the rooting zone
Available water-holding capacity integrates soil depth, texture, and structure into a measure directly related to how much water trees can access, strongly predicting site index.
Which type of clay mineral predominates in highly weathered Ultisols and Oxisols typical of southeastern US forests, and what are its fertility implications?
Answer: Kaolinite with low CEC and limited nutrient retention capacity
Kaolinite dominates highly weathered soils because it is a stable 1:1 clay that resists further weathering; its low CEC means these soils have poor nutrient retention.
A forester is evaluating a site for potential nitrogen limitation to stand productivity. Which field indicator would most strongly suggest nitrogen deficiency?
Answer: Thick, slowly decomposing Oe/Oa horizon with low pH and high C:N ratio
A thick, slowly decomposing organic horizon with high C:N indicates that nitrogen is being immobilized in organic matter rather than mineralized and made available to trees.
When interpreting a particle size analysis (mechanical analysis) for a forest soil, which result would classify the texture as 'sandy clay loam' using the USDA textural triangle?
Answer: 60% sand, 10% silt, 30% clay
Sandy clay loam requires approximately 45-80% sand and 20-35% clay with insufficient silt to classify otherwise; 60% sand and 30% clay falls within this class.