ENSCI 2510 Exam 5

Iowa State University

________ matter (particularly humus) makes soil dark or black.

Organic

What describes the dwindling global supply of phosphorus?

Peak phosphorus

The rate of net primary productivity can be limited directly by the availability of

inorganic nutrients in the soil solution.

What is a significant and powerful greenhouse gas?

N2O (Nitrous oxide)

When the amount of water in soil exceeds what the pore space can hold, the soil is

saturated

What breaks down the slowest during decomposition?

lignin

Bacteria and fungi secrete ________ into plant and animal tissues to break down the complex organic compounds.

enzymes

In the plant-soil feedback model, harmful feedbacks cause what phenomenon?

plant turnover

How can minerals captured via immobilization be released back into the soil?

via microbivores

Material with a C:N ratio around 10:1 would decompose _________ than material with a C:N ratio of 160:1?

faster

The process by which organic nutrients are converted to inorganic forms is ________.

 

mineralization

True or False: Epiphytic plants are always parasitic

False

Epiphytes are ________.

plants that grow on other plants but typically do not obtain nutrients from their hosts

What is not needed by the bacteria in biological nitrogen fixation in the rhizobia-legume system?

oxygen

The smallest soil particle is ___________.

clay

True or False: the species richness of terrestrial plants and animals generally increases with elevation.

False

Which of the following is a common soil anion?

NO3- (Nitrate)

What term refers to the number of species in a specific area?

Species richness

"Liming" (adding carbonates to the soil) is a management technique used to _________soil pH.

increase

High nutrient environments tend to be dominated by plant species that

squander nutrients

You have a fertilizer bag labeled 10-20-10. The first number refers to

the concentration of nitrogen atoms

Dinitrogen fixation is most likely to occur in this type of environment?

High light

True or False: The biogeochemical cycles of one ecosystem are typically independent from those of other ecosystems.

True

True or False: Salt is beneficial to plants.

False

Nitrification in soil is performed by 

aerobic and lithotrophic prokaryotes

True or False: Microorganisms contribute to the formation of soils.

True

The production of NH3 from various forms of nitrogen is called

volatilization

Cultivation _____________ soil organic matter.

decreases

What is the Haber-Bosch process?

process for creating nitrogen fertilizers

Which of the following terms refers to the diversity of habitats within a geographical area?

ecosystem diversity

Plants have 17 essential nutrients. What 3 nutrients make up 96% of the plant tissue (dry mass)?

Carbon (C), Hydrogen (H), and Oxygen (O)

The most abundant plant essential nutrients are C, H, and O. There are 17 total. What are the other 14 nutrients called?

mineral nutrients

You have a fertilizer bag labeled 10-20-10. The second number refers to

the concentration of Phosphorus atoms

You have a fertilizer bag labeled 10-20-10. The third number refers

the concentration of Potassium atoms