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Flashcards in Organic Soils Deck (10)
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Does humus contain nutrients?

No. It's acts as a nutrient storage site in a similar fashion to clay, but with a much higher cation exchange capacity, upward of 10 times.


The rate of organic matter decomposition is a function of...

Type of organic matter present

Presence of fungi and soil organisms

The sites climatic conditions
(Moist and warm = fast decomposition and thinner soils)


What climates would tend to be more acidic?

Cold environments due to less bacteria, and slower chemical reactions.


Why does heat increase chem reaction rate?

When molecules heat up they expand and the valence shells react more easily. Heat also creates a more favourable environment for soil organisms and bacteria.


What is a typical carbon to nitrogen ratio required by bacteria ?


Requires 8 C to 1 N but 2/3 is exhaled during respiration


As a forest stand matures, what happens to the forest floor?

Biomass accumulates on the forest floor leading to thickness as a stand matures in a typical conifer forest. Relatively slow decomposition rate due to less bacteria and more fungi, ( fungi are slower decomposers ).

Deciduous stands offer better conditions for bacteria (more sun and heat), therefor faster decomposition rates and typically thinner soils.


What is an important aspect of "Indian pipe."

It does not photosynthesize and gathers nutrients by decomposing OM.


Which bacteria associates with red alder and fixes atmospheric nitrogen?

Frankia - Rhizobium Genus
Atmospheric N is absorbed by tree and transported to the root system where Frankia nodules fix nitrogen into NH4 and make it available to plants


Which nitrogen molecule is most desired by plants?



What is the main stipulation for something to be considered organic?

Any compound with a high content of carbon that originated as an organism.