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Flashcards in Organic Soils Deck (10)
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1

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.

2

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)

3

What climates would tend to be more acidic?

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

4

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.

5

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

24:1

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

6

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.

7

What is an important aspect of "Indian pipe."

It does not photosynthesize and gathers nutrients by decomposing OM.

8

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

9

Which nitrogen molecule is most desired by plants?

NH4
And
NO3

10

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

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