Section 1
Soil detritivores feed principally on ___.
Dead Tissues
Which of the following is (are) major sources of the carbon dioxide now being added to the atmosphere in excess of the amount taken out by plants?
A. loss of soil organic matter
B. burning of fossil fuels
C. destruction of natural forests
*D. all of the above
All of the above
Oxidation or reduction of inorganic soil constituents such as iron and sulfur is carried out by members of which group(s) of microorganisms.
Bacteria
After drying to eliminate the water in plant litter, which two elements account for about 80% of the dry weight?
C and O
Nearly all organic compounds from which living beings are made have as their backbone, chains or rings of _____ atoms.
Carbon
Soil organic matter consists of ______.
living organisms and cells, dead tissues and wastes, identifiable biomolecules , and polymerized, non-identifiable molecules
Detritus consists of ______.
Dead tissues and waste
One would expect well drained soils to have the highest organic matter contents where the climate is _______.
Cool and humid
Under natural vegetation, about 60 to 90% of soil organic matter is in the _____fraction.
Passive
An organism that subsists by eating predators would function as a(n) _____ in the soil ecosystem.
Tertiary Consumer
The fungal symbiont generally benefits from the mycorrhizal relationship by obtaining ____ from the higher plant.
None of the Above
Organisms which use carbon dioxide or carbonates for their carbon source and either sunlight or inorganic chemicals for their energy source are called ____.
Autotrophs
In which situation are the actinomycetes likely to be most dominant?
Neutral, moist, warm soil with lots of partially decomposed residues
When fresh plant residues are added to soils, the "priming effect" may result in the decomposition of _______.
Stable humus
Nitrogen is a component of which essential plant compounds?
Proteins, chlorophyll, enzymes, and DNA
Plants obtain nitrogen from the soil by taking up ______.
Soluble anions, cations, and organic compounds
Applied to agricultural crops, the term lodging refers to ________.
Plants falling over, often as a result of too much N
The great majority of nitrogen (95 to 98%) in soils can be found in the form of _____.
Organic compounds
A deficiency of N typically ______ the maturity of annual plants.
Hastens
Compared to the bulk soil in which the earthworms live, earthworm casts contain ____.
More of most plant-available nutrients
In the early stages of plant nitrogen deficiency, the most obvious symptoms are _____.
Yellowish colors in the oldest leaves
In most soils the overall population (numbers) of microorganisms changes with time, generally following changes in the _____.
Supply of decomposable organic matter
The process of ______ releases soluble nitrogen as the result of the breakdown of nitrogen-rich organic compounds.
Mineralization
The opposite process from mineralization is _______.
Immobilization
This (these) group(s) of microorganisms usually predominate(s) in sandy, acid soils.
Fungi