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School > EEMB 171 Cumulative > Flashcards

EEMB 171 Cumulative Flashcards

1
Q

Clay

A

Any mineral particle smaller than 2 μM

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2
Q

Aluminosilicates

A
  1. Layered
  2. High surface area, particularly 2:1 clays
  3. Electrically charged
  4. Cation Exchange Capacity (CEC)
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3
Q

Soil Organic Matter

A

Complex mix of plant debris, microbial products, humic material (fulvic, humic, humin). Behaves similarly to clays in many functional ways:

  1. Structure
  2. Water holding capcity
  3. CEC
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4
Q

Jenny State Factors

A
  1. Climate
  2. Organisms
  3. Relief
  4. Parent Material
  5. Time
  6. Humans
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5
Q

NPP

A

Net Primary Productivity = Photosynthesis – Plant Respiration

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6
Q

GPP

A

Gross Primary Productivity = Total ecosystem photosynthesis

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7
Q

NEE

A

Net Ecosystem Exchange = NPP – soil respiration

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8
Q

NEP

A

Net Ecosystem Productivity = GPP – soil respiration – leaching and harvest losses

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9
Q

Liebig’s Law of the Minimum

A
  • Growth is restricted by a single limiting factor
  • Species can adapt to adjust allocation to reduce demand, increase supply- may be co-limited
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10
Q

How does Liebig’s Law of the Minimum apply to communitiy growth?

A

Species adapted to low nutrients have low maximum growth rates, and may not be limited by nutrients, even at low nutrient supply. Fertilization will increase total community production through species replacement.

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11
Q

WUE

A

Water Use Efficiency = g production / g H2O used

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12
Q

NUE

A

Nitrogen Use Efficiency = g production / g N used

Measured by N content of senesced material

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13
Q

Tannins

A

C-rich defensive chemicals

  • Produced when C is available and N is limiting
  • Bind to proteins and make them undigestable
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14
Q

Alkaloids

A

N-rich defensive chemicals produced by plants

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15
Q

What are the four components of water potential?

A
  1. Matric potential- from interactions with surfaces and capillary pores
  2. Solute potential- from interactions with dissolved solutes
  3. Gravitational potential
  4. Pressure potential
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16
Q

Fine textured soils will have a _____ water content at a given water potential.

A

higher

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17
Q

Fine textured soils will have a _____ water potential at a given water content.

A

lower

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18
Q

Field Capacity

A

The amount of water content held in soil after excess water has drained away and the rate of downward movement has materially decreased.

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19
Q

Permanent Wilting Point

A

Point where plants wilt and die. Commonly defined as –1.5 MPa

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20
Q

Available Water

A

= Field Capcity – PWP

21
Q

While _____ may be out of equilibrium with their environment and act as a conduit for water from
moist soil to dry atmosphere,
_____ must be in equilibrium with their environment.

A

plants; microbes

22
Q

Who is responsible for decomposition?

A
  • Micro and Meso Fauna- break material down physically
  • Microorganisms (bacteria and fungi) break material down chemically
23
Q

What is the equation for exponential decay?

A

dX/dt = -k X

24
Q

How does soil water content effect the rate of decomposition?

A
  • At low water content, water availability limits decomposers
  • At high water content, soils saturate and oxygen limits decomposition
  • Water filled pore space integrates these effects, optimum at 60%
25
Q

An increase of 10 ºC increases the rate of decomposition by a rate of _____.

A

2-fold

26
Q

Describe the differences in N availability between fresh and aged litter.

A
  • In fresh litter, most N is in proteins–easy to break down
  • In old material, N may be in complex structures–hard to break down
27
Q

SUE

A

Substrate Use Efficiency

28
Q

What is the sequence of decomposition?

A
  1. Leaching of soluble material
  2. Decomposition of free cellulose – net immobilization
  3. Decomposition of lignin-cellulse complex- net mineralization
29
Q

What are the sources of SOM?

A

Leaf litter: 20-60%; Root death: 30-60%; Root exudates: 5-10%

30
Q

N-fixation

A

N2 → NH3

Importance: accounts for almost all N supplied to native ecosystems.

  • Only done by bacteria
  • Energetically expensive
31
Q

What are the types of N-fixing systems?

A
  1. Symbiotic (legume/rhizobium; actinorhizal)
  2. Associative (in rhizosphere)
  3. Free living
32
Q

Denitrification

A

NO3- → NO, N2O, N2

Importance: removes N from system, produces trace gases (NO, N<sub>2</sub>O).
 Anaerobic respiration (heterotrophs use NO<sub>3</sub><sup>-</sup> instead of O<sub>2</sub>).
33
Q

Nitrification

A

NH4+ →NO3-

Importance:
NO3- is mobile and easily lost to ecosystems
NO3- is more available for plant uptake
Nitrification produces NO and N2

34
Q

Net Mineralization

A

NM = Gross mineralization - gross immobilization

35
Q

What is a fundamental difference between the N cycle and the Phosporus cycle?

A

The main source of N is the atmosphere and N fixation. The
main source of P is mineral weathering.

36
Q

Catena Theory

A

Variation in soil and ecosystem properties down slope.

37
Q

Riparian Zones

A

Variable riparian contribution:

  1. Arid systems–flashy water flows, limited riparian zones
  2. Humid systems–more fully developed riparian zones
38
Q

Telescoping Ecosystem Theory

A

Changes in resistance and resilience varies with the component of the stream system

  • Stream: resilient
  • Parafluvial
  • Hyporheic
  • Riparian: resistant
39
Q

What are 3 methods plants use to attain Phosphorus?

A
  1. Phosphate enzymes via roots break down organic phosphate
  2. Production of organic acids to solubilize Ca+ and prevent phosphorus binding
  3. Arbuscular Mycorrhizae: form a symbiotic relationship whereby plants share carbon in exchange for phosporus
40
Q

AEC

A

Anion Exchange Capacity

41
Q

Slash and Burn Agriculture

A

A method in which plots of land are torched for the purpose of releasing bound phosphorus from living organisms and volatilizing Nitrogen, thus increasing the P/N ratio in otherwise phosporus limited areas.

42
Q

In what systems is phosporus availability the highest?

A
  • Young soils
  • Neutral soils
  • OM rich soil
  • Soils low in metal oxides
  • → much of the temperate world
43
Q

In what systems is phosphorus availability the lowest?

A
  • Old soils
  • Acidic soils
  • OM poor soils
  • Soils high in metal oxides
  • → much of the tropical world
44
Q

A mineral solution pH of ___ in soil creates optimal solubility conditions for Al, Fe and Ca.

A

≈ 6

45
Q

How do plants get their phosphorus in low P availability soils?

A
  1. Increase growth per unit P (high P-use efficiency)
  2. Reallocation of internal P (e.g. P resorption prior to leaf senescence → > 80%)
  3. Modify metabolism to bypass P-requiring steps
46
Q

How does PO43- availability compare with the pH of soil solutions?

A
  • Acid soils: Fe, Al phosphates limit
  • Alkaline soils: Ca phosphates limit
47
Q

Fe and Al ______ dissolve at low pH, thus causing what?

A

hydroxides;

Increased Fe and Al concentrations in solution, which bind to phosporus and effectively decrease its availability.

48
Q

CEC

A

Cation Exchange Capacity: the maximum quantity of total cations, of any class, that a soil is capable of holding, at a given pH value, for exchanging with the soil solution.

49
Q

Steady State Ecosystem

A

An ecosystem in which the recycling of nutrients equals its biological uptake.

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