FM Soil Science & Hydrology Flashcards

Which soil property most directly determines water infiltration rates in forest soils?

Answer: Soil texture

Soil texture (the ratio of sand, silt, and clay) controls pore size distribution, which determines how quickly water can move into and through the soil.

Which soil horizon typically contains the highest concentration of organic matter in a forest soil profile?

Answer: A horizon

The A horizon (topsoil) accumulates organic matter from decomposing plant material above and supports the highest biological activity.

What is 'field capacity' in the context of forest soil hydrology?

Answer: The amount of water soil retains after gravitational drainage

Field capacity is the water content remaining in soil after excess gravitational water has drained away, representing the upper limit of plant-available water.

Which process describes the downward movement of water through soil layers toward groundwater?

Answer: Percolation

Percolation refers to the gravitational movement of water downward through soil pores and fractures toward deeper layers and the water table.

In a mature, undisturbed forest watershed, what approximate percentage of annual precipitation typically becomes streamflow?

Answer: 10–30%

Mature forests intercept, evaporate, and transpire the majority of precipitation, so only 10–30% typically reaches streams as streamflow under normal conditions.

What is the primary hydrological function of riparian buffer zones in forest management?

Answer: Filter sediment and nutrients from runoff before it enters streams

Riparian buffers trap suspended sediments and absorb nutrients from upslope runoff, protecting stream water quality and aquatic habitat.

Which soil classification system is the standard used in US forest soil surveys and management?

Answer: USDA Soil Taxonomy

The USDA Soil Taxonomy is the official classification system used by the NRCS and US Forest Service for describing and mapping forest soils across the country.