Soil Organism Interactions

Within any particular climate, the rate of organic matter decomposition is primarily dependent upon

• the chemical composition of the organic matter
• the species diversity of the decomposer community
• which decomposer microbes are present
• All of these are correct

_______ levels of disturbance often increase above-ground diversity, while the most diverse soil communities are associated with _____ levels of disturbance.

• intermediate, low
• high, low
• high, intermediate
• low, intermediate

The highest above-ground diversity is typically associated with ______ levels of productivity.

• none of these are correct – above-ground diversity is not related to productivity
• intermediate
• low
• high

The highest soil organic matter content would be expected

• In cold environments, due to low decomposition
• In hot environments, due to high plant productivity
• Soil organic matter content is ultimately not a function of climate
• In temperate environments, due to the balance of intermediate decomposition and plant productivity

Why do soil microbes have to excrete their digestive enzymes to the outside of their cells?

• dead organic matter polymers are too large to pass through microbial membranes otherwise
• dead organic matter polymers often must be de-toxified prior to microbial uptake
• dead organic matter polymers contain a high proportion of low energy compounds that may be removed prior to microbial uptake
• dead organic matter polymers contain a high proportion of low nutrient compounds that may be removed prior to microbial uptake

Which of these abilities is most critical for early colonizers of a newly formed soil?

• Nitrification
• N mineralization
• N fixation
• Denitrification

Most organic matter entering the soil ultimately gets converted to

• carbon dioxide
• microbial tissues
• soil aggregates
• plant-available nutrients

Nutrient mineralization is the

• microbial enzyme-catalyzed conversion of organic nutrient forms to mineral nutrient compounds
• mineral-catalyzed conversion of insoluble organic nutrient forms to soluble nutrient compounds
• 
  precipitation of soluble mineral nutrient compounds out of solution
• 
  adsorption of charged nutrient compounds onto mineral surfaces

A filamentous growth form is a favorable strategy for soil fungi and bacteria because it allows them to

•  take advantage of patchily distributed resources
• come into contact with more potential hosts
• regrow more quickly after predation
• all of these are correct

Tags

NGSS.MS-LS2-1

N fixation involves the bacterial conversion of _________ into compounds that can be incorporated into biological tissues.

• dinitrogen gas
• insoluble organic N
• nitrate
• ammonium