Lec 6 Flashcards
(23 cards)
Organic matter composed of: (3)
- ) Live biomass
- ) Dead and decaying biological matter
- ) Humic substances
The complexity of soil is driven by two components:
- ) Abiotic soil architecture
2. ) Biotic diversity
FIVE SOIL FORMING FACTORS:
Climate Topography Organisms Parent Material Time
SURFACE =
Parent material has been weathered
Microbial numbers are higher
SUB-SURFACE =
Parent material has not been weathered by
climate
Microbial numbers are lower – why?
Sub-surface layers: (3) (& details)
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
What plays a major role in creating soil structure?
microorganisms
& roots, fungi, plant debris
Cation Exchange Capacity =
essentially…
= A parameter of soil arises because of the negative charge associated with most soils
…The total of exchangeable cations that a soil can absorb
Soil is considered to have a
net negative charge
There is 2 general reasons why soil is considered to have a negative charge:
Isomorphic substitution = when you have one element
Ionization
Isomorphic substitution =
= the change of one element for another without changing the size of the structure
Ionization =
- pH dependent
- Hydroxyl groups (OH) at the edge of the lattice can
ionize
Cation Exchange ultimately depends on
the concentration of the cation in soil and the adsorption affinity of the cation
HOW DO SOILS BIND NEGATIVELY CHARGED BACTERIA?
“Cation bridging”
Most microbes in terrestrial environments exist…
…attached to soil particles, and not freely
What are some benefits of being attached to a soil particle?
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
Paths of dissolution and uptake of minerals in the soil: (5)
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)
N-fixing microorganisms make…
…N, P, and other nutrients available for plant uptake
SOIL pH AFFECTS
BACTERIAL DIVERSITY
Autotrophs fix…
…their own energy from inorganic sources
Autotrophs are….
…the producers in an ecosystem
Heterotrophs depend on…
…energy and carbon fixed by another organism
Heterotrophs are…
…the consumers and decomposers
