ESA ESA Soil Science & Biogeochemistry

Question 1

Which soil horizon is characterized by the accumulation of leached materials such as clay, iron oxides, and organic matter?

Accepted Answer

B horizon

Answer

O horizon

Answer

A horizon

Answer

C horizon

Question 2

The primary driver of nitrogen fixation in terrestrial ecosystems is:

Accepted Answer

Biological N2 fixation by diazotrophic microorganisms

Answer

Abiotic lightning discharge

Answer

Atmospheric deposition of NOx

Answer

Mineralization of soil organic matter

Question 3

Cation exchange capacity (CEC) of a soil is primarily determined by:

Accepted Answer

Clay content, clay mineralogy, and organic matter content

Answer

Soil bulk density

Answer

Soil pH alone

Answer

Parent material particle size

Question 4

Which process converts ammonium (NH4+) to nitrate (NO3−) in soils?

Accepted Answer

Nitrification

Answer

Denitrification

Answer

Mineralization

Answer

Assimilation

Question 5

Soil organic matter decomposition is primarily regulated by which set of factors?

Accepted Answer

Temperature, moisture, and substrate quality (C:N ratio)

Answer

Parent material and slope aspect

Answer

Vegetation type and canopy cover alone

Answer

Soil texture and bulk density alone

Question 6

Which ectomycorrhizal adaptation allows host trees to access phosphorus in organic soil layers?

Accepted Answer

Production of phosphatase enzymes by fungal hyphae

Answer

Direct root elongation into organic matter

Answer

Nitrogen fixation by fungal symbionts

Answer

Secretion of organic acids to dissolve parent rock