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RENR 210 > FINAL > Flashcards

FINAL Flashcards

1
Q

What is soil organic matter and what does it do?

A

0-10% of soil volume
In surface soils
Driver of soil life
Improves physical characteristics (structure, porosity and Db), increases water holding capacity, soil structure and aggregation, decreases bulk density while increasing porosity
Improves chemical characteristics, increases CEC and makes soil more resistant to pH changes
Improves biological activity – slow release fertilizer for N, P, K and S
Supports large and varied microbial communities

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2
Q

inorganic vs organic C

A

Inorganic C: CO2 in soil and air and carbonates (in lithosphere) – ex. Ca, Mg, K, Na
Organic C: soil organic matter and carbon

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3
Q

What are the typical sizes of carbon reservoirs?

A

Active pool = 3000Pg
Turnover: CO2 - CHO - CO2
Sedimentary rocks = 10^8Pg
Turnover: geologic - active - geologic
Ocean and lakes: 36000Pg
Lithosphere: 75MPg
Atmosphere: 800Pg
Hydrosphere: 36000Pg

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4
Q

What is soil health?

A

the continued capacity of the soil to function as a vital living ecosystem that sustains plants, animals and humans through nutrient cycling, water, filtering, buffering, physical stability/support and as a habitat for biodiversity

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5
Q

SOC vs SOM

A

SOC = 0.58SOM
SOM = 1.72SOC

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6
Q

How is SOC measured?

A

Measurement of SOC = dry combustion (20mg)
Carbon released measured as CO2
Analytical

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7
Q

How is SOM measured?

A

SOM = measured by loss on ignition (5g)
Gravimetric

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8
Q

What is SOM composed of?

A

58% C
3-5% H
30-40% O
2-5% N
Living biomass, humus, residues/detritus, non-humic substances and humic substances

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9
Q

What is decomposition?

A

chemical reaction occurring during the decay of plant/animal remains
Altered chemical composition to produce E

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10
Q

What is mineralization?

A

release of soluble or gaseous inorganic constituents during decomposition

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11
Q

What is humification (old vs new theory)?

A

decomposition results in black, greasy OgM
Old theory: condensation reaction – low molecular weight biopolymer to high MW biopolymer
New theory: stabilization of SOC by 3 mechanisms

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12
Q

What is cellulose?

A

linear polymer of glucose units (polysaccharide, carbohydrate) – about 30% of plant material (cell wall)

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13
Q

What is hemicellulose?

A

branched polymer of different sugars (glucose, fructose, polysaccharide) – about 20% of plant material

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14
Q

What is lignin?

A

branched, aromatic polymer (volatile) – about 20% of plant material (woody material)

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15
Q

What are lipids?

A

fats/waxes – about 20% cellular material

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16
Q

What is protein?

A

amino acids (N is present), biochemical machine (photosynthesis) – high N content, about 5% of plant material

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17
Q

What is the old theory of humification?

A

theoretical framework derived from analytical methods – alkali extraction method produced 3 fractions – theory of C stability determined from this data

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18
Q

In order of increasing complexity and decreasing N

A

Protein > hemicellulose > cellulose > lignin > fats

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19
Q

What are humic fractions?

A

Operationally defined fractions: humin, humic acid and fulvic acid
Historic method for examining soil fertility
Fractions are artifacts of extraction procedure

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20
Q

What is the SOM stabilization theory?

A

Contemporary theory
Based on decreasing molecular size
Stabilization in aggregates and on mineral surfaces
Generates a lot of data saying old theory is wrong – we can have very old C in soil but made up of labile constituents – humus doesn’t exist, it is made up of identified biopolymers

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21
Q

What is the soil carbon model?

A

Plant residue to microbe using an enzyme system to SOM (mineralization and stability)

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22
Q

Low vs high C:N

A

Lower ratio = implies labile plant residue or fertile/easily decomposed SOM
High ratio = implies resistant plant residue or less fertile/harder to decompose SOM

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23
Q

What is mean residence time?

A

time of atoms to cycle through pools – plant residue (biopolymers, some chemical resistance) – affects turnover

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24
Q

What are the SOM theoretical pools?

A

chemical/physical protection and organo-mineral associations

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25
What are the E sources?
Photo = suns E Chemo = E from organic C Litho = E from soil redox reaction People = chemo-heterotrophs Plants = photoautotrophs Fungi = chemo-heterotrophs Bacteria = everything (capable of alternate metabolism
26
What are the C sources?
Autotrophs use CO2 Heterotrophs use organic C
27
What are some facts about N fixation?
Most N gas is unavailable to most organisms About 78% in atmosphere chemical/biological conversion of N to R-NH2 = organic N Can be chemically fixed by lighting/man Can be biologically fixed by symbiotes (bacteria/plants), mutualistic (pleurozomes) and by free living bacteria
28
organic vs inorganic N
Organic N: C-NH2 Inorganic N: N2, NH4, NO3, N2O
29
Where does the majority of biological N fixation occur?
<1% by free living bacteria – important in some ecosystems >99% by symbiotic relationships between plants and bacteria Bacteria – genus associated plant family Rhizobium: pea family Frankia: alder family Nitrogenase: enzyme that catalyzes N fixation (must be protected from O2, therefore nodule forms) – leghemoglobin scrubs O2 out of the nodule
30
What kinda fixation do diff organisms use?
Heterotrophs use SOM for building biomass Ammonifiers use SOM for electron acceptor (chemo) Autotrophs: use CO2 for building biomass Nitrifiers: use HN4 as electron acceptor (litho)
31
What is ammonification?
mineralization/immobilization: SOM to inorganic N back to SOM as mediated by bacteria Microorganisms decomposing SOM for E and building blocks for biomass C/N is low, net accumulation of ammonium Surplus ammonium leads to nitrification
32
What is nitrification?
By lithoautotrophs (bacteria/archaea) Organisms: bacterial genuses Step 1: nitrosomonas/nitrosospira Step 2: nitrobacter/nitrospira
33
What is denitrification?
Anaerobic process NO2 species are being used as electron acceptors in the absence of O2
34
What is mineral fixation?
NH4 binding to clay particles (irreversible) Not CEC, not just electrostatic charges are being shared Internal covalent bond to mineral structure Especially in clay dominated soils
35
What is a major source of pollution?
nitrogen fertilizer
36
Natural vs Human N fixation
Natural N fixation Lighting = 5-10Tg/yr Biological = 90-140Tg/yr Total: 95-150Tg/yr Human N fixation Fertilizers = 80 Leguminous crops = 30-50Tg/yr Combustion of fossil fuels = 20Tg/yr Land clearing, burning of forests and draining of wetlands = 60Tg/yr Total = 190-210 Tg/yr (1.5x natural amount)
37
What is the haber bosch process?
CH4 + N2 + H2O = NH4 + CO2 + H2O Natural gas – E source to break triple covalent NN bond 1 kg NH3 = 1.75L diesel fuel equivalent
38
What is eutriphication?
Definition: increase in nutrient (N and P) in surface waters Causes algae growth Decreases oxygen content in water Increases turbidity Decreases water quality N concentrations that cause eutrophication: fresh water = 0.5-1mg/L Marine water <0.5mg/L
39
What is the P cycle?
no redox From lithosphere No organic form Always PO43- Order: Mineral dissolution Uptake from solution leaching/runoff Organic matter release Precipitation (of insoluble precipitates)
40
What is the main source of loss of P?
leaching and runoff
41
What is Ps availability and pH?
max phosphates available at pH 6.5 Never higher than 20% distribution Increased pH = fixation by Ca phosphates Decreased pH = fixation by hydrous oxides (Fe, Mn, Al)
42
What is the K cycle?
No redox, from lithosphere Macronutrients: N, P, K, S, Ca, Mg
43
What is the S cycle?
Organic forms of S C-S carbon bond COS ester bond Electron acceptor in anaerobic environments
44
What are the important micronutrients in soil?
Trace metals Need to chelate in solution - organic complex that helps with solubility Cycle up to plants then back into SOM, go into the available pool Needed in very small quantities Absence of them can result in poor growth/performance Important for some biochemical functions
45
What is the law of the minimum?
Crop productivity is limited by the most limiting resource Liebig barrel Most limiting in AB = water
46
What is the concept of fertility (ag vs wildlands)?
Agriculture: monocultures, known plant requirements Possible to measure limitation (water, salinity, nutrients) NPKS, maximize yield Wildlands Multiple species, functional types Does not work well Not possible to know or define limitations Microbial function Bioavailable nutrient profile SOM quality all contribute
47
What is an edatopic grid?
System for identifying different ecosystems Nutrient regime – soil, OgM quality Moisture regime: slope, soil texture, depth of the water table
48
What are the soil food web levels?
Ogm and plants Fungi, nematodes and bacteria Protozoa, nematodes and arthropods Arthropods, nematodes Birds and animals
49
What is megafauna?
rodents, gophers, ground squirrels, rabbits and pica Cause bioturbation and are predators
50
What is macrofauna?
millipede, centipede, ant, termite, beetle Main contributors to bioturbation, do predation on a smaller size class and are OgM shredders to decrease particle size
51
What is special about earthworms?
non-native invasive species, good for agricultural and garden soils, bad for forest soils as they eat the organic layer (LFH) that some rare plants require for habitat and germination
52
What is mesofauna?
mites – shredders, OgM consumers and predators High diversity and high prevalence in grassland and forest ecosystems
53
What is microfauna?
nematodes, protozoa (both are eukaryotes = have a cell nucleus and membranes around their organelles – their feeding appendages will differ
54
What are protozoa and what are the 3 types?
Have large diversity, consume bacteria and fungi, influence nutrient cycles and are aerobic organisms in aqueous environments Ciliates: single celled, amorphous with small hairs (largest) Amoebae: flowing cytoplasm – medium sized Flagellates: whip-like appendage – smallest
55
What are testate amoebae?
dormant organism that makes a shell to protect itself (from CaCO3)
56
What is microflora?
(no membranes around organelles) Fungi: eukaryotes, filaments (each called a hyphae) – some can be symbiotic with plants (mycorrhiza) Bacteria: prokaryotes, capable of alternative metabolism, some can be symbiotic with plants (BNF) Archaea: prokaryotes, capable of alternative metabolism, live in extreme environments (thermal vents)
57
What are yeasts (fungi)?
important human services – go through fermentation processes to make things such as bread, vinegar and alcohol
58
What is mycorrhizal fungi?
help with aggregation, structure and content of the soil (symbiotic)
59
What is mycorrhizal symbiosis?
trade sugars for water and mineral nutrition, increases the area of soil exploration
60
What are the types of mycorrhiza?
Ecto (outside shell) – general Ericoid (species specific) Arbuscular (inside cell) Orchid (species specific)
61
How many bacteria in a bit of soil?
One gram of soil = 1 billion bacteria = thousands of species Soil is the most biologically diverse ecosystem in the world More work is needed in promoting soil health Diverse as very high habitat drivers, carbon diversity
62
What are the microbial size classes from biggest to smallest?
Nematodes Protists Fungus Bacteria Virus Clay particles
63
How do we count and how did we used to count bacteria?
Historic: plate counting and culturing (but only less than 1% of bacteria can be cultured) Modern: DNA extraction from soil then amplified the 16S gene which can determine functional groups
64
What are some definitions of soil health?
The continued capacity of soil to function as a vital living ecosystem that sustains plants, animals and humans. Healthy soil gives us clean air and water, bountiful crops and forests, productive grazing lands, diverse wildlife and beautiful landscapes. Functionality: health, broadly, can be defined as the condition of an organism in which it performs its vital functions normally or properly (functionality to promote utility) Vitality: the peculiarity distinguishing the living from the nonliving (soil is a living system) Sustainability or resilience: a final essential element of purported definitions of health is that of sustaining (a healthy soil supports ecosystem functioning into perpetuity)
65
What are some principles of soil health?
minimize disturbance, maximize biodiversity, maximize soil cover, maximize living roots
66
What are the 6Cs for soil health?
compassion reduction, conservation tillage, continuous living plants, crop and animal diversity, cover crops and compost and amendments
67
What are some threats to soil health?
Erosion (loss of topsoil) Organic matter decline: erosion not adding C to soils Depletion of nutrients: crop removal, nutrient mining Low plant productivity: annual crops, no cover crop Contamination Biodiversity loss Salinization Desertification

RENR 210 (3 decks)

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