Lec 6

Question 1

Organic matter composed of: (3)

Answer 1

1. ) Live biomass
2. ) Dead and decaying biological matter
3. ) Humic substances

Question 2

The complexity of soil is driven by two components:

Answer 2

1. ) Abiotic soil architecture

2. ) Biotic diversity

Question 3

FIVE SOIL FORMING FACTORS:

Answer 3

Climate
Topography
Organisms
Parent Material
Time

Question 4

SURFACE =

Answer 4

Parent material has been weathered

Microbial numbers are higher

Question 5

SUB-SURFACE =

Answer 5

Parent material has not been weathered by
climate
Microbial numbers are lower – why?

Question 6

Sub-surface layers: (3) (& details)

Answer 6

1.) Vadose
– Oligotrophic environment
– Unweathered parent material
– Low organic content
2.) Capillary fringe
– Area between vadose and aquifer
3.) Saturated (aquifer)
– Porous material
– Saturated with water

Question 7

What plays a major role in creating soil structure?

Answer 7

microorganisms

& roots, fungi, plant debris

Question 8

Cation Exchange Capacity =

essentially…

Answer 8

= A parameter of soil arises because of the negative charge associated with most soils
…The total of exchangeable cations that a soil can absorb

Question 9

Soil is considered to have a

Answer 9

net negative charge

Question 10

There is 2 general reasons why soil is considered to have a negative charge:

Answer 10

Isomorphic substitution = when you have one element

Ionization

Question 11

Isomorphic substitution =

Answer 11

= the change of one element for another without changing the size of the structure

Question 12

Ionization =

Answer 12

• pH dependent
• Hydroxyl groups (OH) at the edge of the lattice can
  ionize

Question 13

Cation Exchange ultimately depends on

Answer 13

the concentration of the cation in soil and the adsorption affinity of the cation

Question 14

HOW DO SOILS BIND NEGATIVELY CHARGED BACTERIA?

Answer 14

“Cation bridging”

Question 15

Most microbes in terrestrial environments exist…

Answer 15

…attached to soil particles, and not freely

Question 16

What are some benefits of being attached to a soil particle?

Answer 16

1.) Proximity of nutrients
2.) Protection from predation
3.) Protection from toxicity
4.) May create their own microenvironment in that area that could benefit them and may exclude others
▪ Some microbes have the ability to alter a microenvironment
5.) Easier to swap DNA with other cells

Question 17

Paths of dissolution and uptake of minerals in the soil: (5)

Answer 17

1) dependent on parent rock, the weathering of this – release ions into soil solution
2) cation exchange capacity
(Cations bound to a clay particle will not be part of the soil solution and won’t be available to microorgansims)
3) microbes – can uptake or release things
(Their biochemical pathways can play a role in what we have in the soil sample)
4) plant roots
(Will take up nutrients and also secrete nutrients into the environment)
5) humans – can alter what is in the environment o Fertilizers
(Run-off from irrigation o Oil and fuel spills)

Question 18

N-fixing microorganisms make…

Answer 18

…N, P, and other nutrients available for plant uptake

Question 19

SOIL pH AFFECTS

Answer 19

BACTERIAL DIVERSITY

Question 20

Autotrophs fix…

Answer 20

…their own energy from inorganic sources

Question 21

Autotrophs are….

Answer 21

…the producers in an ecosystem

Question 22

Heterotrophs depend on…

Answer 22

…energy and carbon fixed by another organism

Question 23

Heterotrophs are…

Answer 23

…the consumers and decomposers