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Öko Pflanze Pils > Habitat > Flashcards

Habitat Flashcards

1
Q

The every day life definition (Webster’s New Collegiate Dictionary)

A

“The upper layer of earth which can be dug or plowed and in which plants grow”

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2
Q

This is the engineering definition of soil (Spangler and Handy, 1982)

A

“All the fragmented mineral material at or near the surface of the earth, the moon, or other planetary body, plus the air, water, organic matter, and other substances which may be included therein”

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3
Q

This geological definition of soil introduces the idea of alteration in place as a distinction between soil and sediment. (Nature 391, 12, 1998)

A

“Material altered in place at the surface of a planetary body by physical, chemical or biological means.”

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4
Q

Soil science definition (Buckman and Brady, 1970, The Nature and Properties of Soils)

Emphasizes the strong two-way interactions between biota and the soil habitat (Coleman & Crossley, 1996, Soil Ecology)

A

“A natural body, synthesized in profile form from a variable mixture of broken and weathered minerals and decaying organic matter, which covers the earth in a thin layer and which supplies, when containing the proper amounts of air and water, mechanical support and, in part, sustenance for plants”

“…with its living organisms…”

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5
Q

The pedosphere

A

the envelope of Earth where soils occur and soil forming factors are active

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6
Q

Where does the pedosphere develop?

A

where there is a close interaction between the atmosphere (soil air), biosphere(litter and organisms), hydrosphere (soil water), and lithosphere (soil and minerals)

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7
Q

Soil formation

stage 1

A
  • Bedrock is weathered into parental material (unconsolidated rock fragments)
  • Parent material can stay in one place or be transported by gravity, water, wind, glaciers
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8
Q

soil formation

stage 2

A

initial horizons are formed by additions, removals, mixing and transformations
(mixing can be done by worms)

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9
Q

soil formation

stage 3

A

mature soil is formed by further differentiation of soil horizons

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10
Q

Soils are dynamic bodies (function of time t) that respond to variety of soil forming factors (Jenny 1941):

A

S = (climate, parent material, biota, topography, vegetation)t + human (t2)

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11
Q

what does it mean that soil responds to a variety of factors?

A

that there is a considerable diversity within soils

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12
Q

Variability and complexity of soils

A
  • large variation of soil types across globe

- depth of where bedrock starts increases from arctic to tropical climate (equator)

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13
Q

soil taxonomy

A
  • 12 orders

- inceptisoil makes up 17%, most common soil type

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14
Q

A pedon

A

minimum of 3 dimensions of a soil that are necessary to describe it

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15
Q

In which layer are the most microbes?

A

…

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16
Q

Horizontal soil variability (small scale)

A

dependnet on pH, Carbon

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17
Q

What serious problem is there with the measurement of temporal patterns in soil ecology?
What examples can you think of, on what time scales?

A

???

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18
Q

“typical soil” percentage of dry weight

A

93% mineral

7% organic matter

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19
Q

organic portion of soil dry weight

A

85% dead
10% plant roots
5% Edaphon

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20
Q

soil biota percentage dry weight

A 
40% Bacteria & Actinomycetes
40% Algae & Fungi
12% Earthworms
5% other macrofauna
3% mesofauna
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21
Q

sand

A

2mm-50µm

11-227 cm^3/g

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22
Q

silt

A

50µm-2µm

454 cm^3/g

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23
Q

clay

A

<2µm
8,000,000 cm^3/g

(can be a size fraction, a texture class name or/and a class of minerals)

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24
Q

loam

A

perfect mixture of sand silt and clay

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25
Q

soil organic matter

A
  • relatively small and dynamic
  • Of multiple origins (plant, animal, microbe)
  • Incredibly chemically complex
  • Almost impossible to satisfactorily characterize chemically
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26
Q

The ecosystem perspective on the importance of soil organic matter

A
  • carbon repository

- roughly two thirds of all terrestrial carbon contained in soil organic matter

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27
Q

The soil fertility/ soil science perspective on the importance of soil organic matter

A
  • cation exchange capacity

- aggregation

28
Q

the soil microbial perspective on the importance of soil organic matter

A
  • source of carbon (for heterotrophs)
  • source of nutrients
  • A microbial product
29
Q

fractionation methods

A

SOM is described based on physical and biochemical differences of compounds

  • solubility
  • Density (polytungstate)
  • Size
  • Charge
30
Q

Fulvic acid

A

soluble in acid

soluble in alkali

31
Q

Humic acid

A

isoluble in acid

soluble in alkali

32
Q

Humin

A

insoluble in acid

insoluble in alkali

33
Q

Non-humic substances

A
  • Recognizable plant debris (this can be separated out as a separate class of SOM, the detritus)
  • All of the identifiable classes of organic compounds (such as carbohydrates and peptides)
34
Q

Humic substances (Huminstoffe: Fulvinsäuren (oder Fulvo-), Huminsäuren, Humine)

A
  • The remaining amorphous, highly transformed, darkly colored material.
  • Cannot be identified as belonging to an established group of chemical compounds
35
Q 
deffinition of humic substances
stevenson 1985 (traditional)
A

Large, multifunctional polymers which are bound to mineral surfaces via a broad range of bonding mechanisms

36
Q 
definition of humic substances
piccolo 2001 (zonal layer model)
A

small molecules with dynamic interactions

  • contact zone
  • zone of hydrophobic interactions
  • kinetic zone (outer region)
37
Q

Other organic components: carbonized materials

A

Carbonized material can either be present in soil because of
• (natural) fires (incomplete combustion),
• or because it has been added as a soil amendment

38
Q

Biochar

A
  • charcoal primarily made out of biomass for the purpose of enhancing soil carbon sequestration. Modeled after terra preta soils in the Amazon basin.
  • Two different sources of biochar: pyrolysis (high temperatures, low oxygen) or hydrothermal carbonization (aqueous, milder conditions)
39
Q

Multiple (often positive) effects of carbonized materials

A
  • soil physico-chemical properties
  • soil biota (Lehmann et al. 2012 SBB; Thies, Rillig & Graber 2015),
  • plant growth
40
Q

Soil structure:

A

The combination or arrangement of primary soil particles into secondary particles, units or peds.

41
Q

Ped:

A

A unit of soil structure, such as an aggregate, formed by natural processes.

42
Q

Clod:

A

A compact, coherent mass of soil produced artificially, usually by such human activities as plowing and digging (especially when soils are wet).

43
Q

Aggregates

A

Aggregates are (with few exceptions) hierarchically structured combinations of primary particles.

44
Q

Aggregates

2000µm

A

solids with ores

45
Q

Aggregates

200µm

A

binding agent: roots and hyphae

46
Q

Aggregates

20µm

A

binding agent: plant and fungal debris encrusted with inorganics

47
Q

Aggregates

2µm

A

binding agents: microbial and fungal debris encrusted with inorganics

48
Q

Aggregates

0.2µm

A

Amorphus alluminosilicates, oxides and organic polymers sorbed on clay surfaces and electrostatic bonding, flocculation

49
Q

AMF on soil aggregates

A

biological effects I: AMF influence microbial communities

Biological effects II: Fungal interactions with the soil food webs

Biochemical effects: release f mycelium products (glomalin etc.) from decomposing or living hyphae

Physical effects I: Hyphal enmeshment of particles/ microaggregates; altered water regime (dry wet cycle)

Physical effects II: alleigment of particles, exerting pressure

50
Q

macropores

>0.08mm

A

Allow ready movement of air and water.
• Large enough to accommodate roots and microarthropods.
• Different types
-Packing pores (spaces left between primary soil particles)
-Interped pores (spaces in between peds)
-Biopores (formed by biota; often tubular, formed by roots)

51
Q

micropores

<0.08mm

A
  • Too small to permit much air movement
  • Usually filled with water; water movement slow
  • Larger ones accommodate plant root hairs or microorganisms; small ones may be even to small for bacteria
52
Q

what is the difference between soil air and the atmosphere

A
  • soil air is almost always saturated with water vapor

- soil air slightly higher CO2 and N2

53
Q

gravitational water

A

all water that drains out of the soil

54
Q

field capacity

A

water is held in the capillary pores, macropores have air

55
Q

wilting point

A

water unavailable to plants

56
Q

why do plants wilt when the relative humidity in soil is still 0.9926?

A

Because the water is unavailable to plants. The water is in thin biofilms around aggregate.
The water potential is to low for plants to use the water (-15 bar)

57
Q

is the soil atmosphere the same everywhere?

A
  • higher concentration of CO2 near roots (respiration)
  • center of aggregates anaerobic
  • diffusion limiting factor
58
Q

why can fungi grow at the lowest water potentials?

A
  • they increase the concentration of solutes within cell so that water doesnt leave but rather is taken in. water always flows from high to low water potential
  • they have compatible solutes that do not interfere with cell processes
59
Q

Different amount of work needed to remove fractions of soil water

A
  • Adhesion of water to the soil solids (matrix) provides a matric force: reduces the energy state of water
  • Attraction of water to ions and other solutes results in osmotic forces, also lowering the energy state of water.
  • Gravity pulls water downward (energy level of water higher up in the soil profile is higher than further down)
  • Kinetic energy usually negligible
  • Soil water potential is the difference in energy levels between pure standard water and the soil water.
60
Q

Gravimetric method

A
  • Measuring soil water content

- weighing soil and knowing dry weight

61
Q 
Neutron scattering (probe)
Measuring soil water content
A
  • Fast neutrons are emitted
  • When fast neutrons encounter hydrogen atoms (like in water), they get slowed down and scattered
  • Slow neutrons are counted with a detector
  • Need access hole
62
Q

Time-domain reflectometry (TDR)

Measuring soil water content

A
  • Measures the time (picoseconds; 10-12 sec) it takes for an electromagnetic impulse to travel along two buried metal rods;
  • The transmission time is dependent on the dielectric constant of the medium (soil) in which the waveguides are buried.
  • Relatively expensive; small sensing volume
63
Q

FDR Frequency-domain reflectometry

Measuring soil water content

A
  • changes in soil moisture are detected by changes in circuit operating frequency
  • advantage: cheap (relatively!)
  • like TDR, small sensing volume
64
Q

Tensiometers

Measuring soil water potentials (Saugspannung)

A
  • Water-filled tube with a porous ceramic cup at the bottom, and at the top an air-tight seal (Keramik-Kerze);
  • Vacuum develops and is measured with a pressure gauge as water leaves the tensiometer at the bottom
65
Q

Thermocouple psychrometry

Measuring soil water potentials (Saugspannung)

A
  • Water potential of the liquid phase of a soil is inferred from measurements within the vapor phase in equilibrium with the liquid phase
  • Water potential is directly related to relative humidity
  • Relative humidity is measured extremely accurately (why is that necessary?)
  • This is done by actually measuring a temperature decrease due to evaporation of a water droplet (which is formed by condensation in the first place by cooling down the thermocouple); evaporation is proportional to humidity

Öko Pflanze Pils (7 decks)

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