ESA Soil Science & Biogeochemistry Flashcards
6 cards from real ESA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 ESA Soil Science & Biogeochemistry flashcards as text
Which soil order in the US Soil Taxonomy is characterized by a permanently frozen subsurface layer (permafrost)?
Answer: Gelisols
Gelisols are defined by the presence of permafrost within 100 cm of the surface and are dominant in arctic and subarctic regions.
The soil water potential component that describes water held by capillary and adsorptive forces in the soil matrix is called:
Answer: Matric potential
Matric potential (always negative or zero) quantifies the energy required to extract water held in soil pores and on particle surfaces.
Arbuscular mycorrhizal fungi (AMF) are most important for plant acquisition of which nutrient?
Answer: Phosphorus
AMF dramatically extend the effective root surface area and are the primary pathway for phosphorus acquisition in most terrestrial plants.
Methane (CH4) is produced in anaerobic soils and sediments primarily by:
Answer: Methanogenic archaea
Methanogenic archaea are strict anaerobes that produce CH4 as a metabolic end product during the decomposition of organic matter in anoxic environments.
Net ecosystem production (NEP) is calculated as:
Answer: Gross primary production minus total ecosystem respiration (autotrophic + heterotrophic)
NEP = GPP − (Ra + Rh), representing the net carbon balance of the ecosystem after accounting for all respiratory carbon losses.
Which biogeochemical process links the carbon and sulfur cycles in marine sediments under anoxic conditions?
Answer: Sulfate reduction coupled to organic matter oxidation
Sulfate-reducing bacteria oxidize organic carbon using SO42− as the electron acceptor, producing H2S and coupling carbon mineralization to the sulfur cycle.