all the rest Flashcards
(61 cards)
1
Q
5 factors affecting soil temperature
A
- aspect
- latitude / seasons
- vegetative cover
- color / albedo
- humus
2
Q
only about ____% of solar energy reaches the soil
A
10
3
Q
to increase temp. of dry soil by 1°C requires only ____
A
0.2 cal/g dry soil
(vs. 1 cal/g water)
4
Q
cooling of soil is mostly through ______
A
evaporation
5
Q
it takes ____ cal to evap. 1g of water;
energy comes from either ___ or from ____
A
540 cal; sun or soil
6
Q
movement of heat energy in soils is by _______
A
conduction;
conductivity of water > soil >>>>> air
7
Q
4 types of mulches
A
- clear plastic -> greenhouse effect = greatest heating effect
- black plastic -> absorbs heat -> radiates
- wood & other organic mulches: can cool soil, trap moisture
- permeable plastic blocks: meh
8
Q
temp. effects of changes to soil moisture (3)
A
- draining in spring alows faster warming
- wet soils stay cooler
- permeable mulch slows evaporation
9
Q
frost heaving caused by ___ ___ forming in soil and expanding ______
A
ice lenses; upwards
10
Q
temperature effects of fire
A
- greatest temps at surface due to soil water lower down
- loss of O hzn = less insulation (so greater temp variance)
- water repellent layer can form due to gases a few cm deep -> erosion w/ next rain event
11
Q
micropores are < and macropores > ___mm
A
.08
12
Q
humus has _______ charges
A
pH-dependent
13
Q
too much clay = ______
A
bad structure
14
Q
CEC = ____ & ____ of _____
A
storage & availability of nutrients
15
Q
soil water movement controlled by… (3)
A
- inputs
- soil properties
- energy
16
Q
energy = _____
A
ability to do work
high conentration -> low conc. (equilibrium)
high energy -> low energy
17
Q
potential = _____
A
- relative ability to do work
- relative to a reference
- ex: pure water @ a specific height
- relative to a reference
18
Q
Ψs = _______ = __ + __ + ___
A
soil water potential;
Ψg + Ψm + Ψo;
gravimetric + matric + osmotic
19
Q
Ψg
A
gravimetric potential
- higher in soil profile = higher energy
- typically a positive value
20
Q
Ψm
A
matric potential
- adhestion to soil particles/surfaces (+ cohesion)
- typically a negative value (b/c it req’s energy to break the bonds; stronger bonds = more negative
- @ saturation, Ψm = 0
21
Q
Ψo
A
osmotic potential
- salts can behave like a particle surface
- typically a negative value (costs nrg to break bonds)
- water moves toward concentrated salt areas
22
Q
in sandy loam, ___ dominates
in clay loam, ___ + ___
A
Ψg
Ψg + Ψm
23
Q
-15 bars = -1.5MPa = _____
A
permanent wilting point = no water available for root uptake
24
Q
saturation = _____ = __ dominates
A
all pores filled = Ψg dominates
25
field capacity = ___ \_\_\_\_ ____ = ~\_\_ hours after saturation
all macropores drained = ~48 hours after saturation
26
available water content = __ - \_\_\_
field capacity - permanent wilting point
27
what enhances water storage & availability? (4)
1. deeper soil
2. barrier @ depth to water
3. texture
4. root access to retained water
28
inputs (1) & outputs (4) to hydrologic cycle
1. precipitation
2. leaching
3. runoff
4. transpiration
5. evaporation
29
infiltration rate equation
Q / (A \* T)
quantity / (area \* time)
volume / (area \* time)
-\> depth / time
30
litterfall is mostly...
* water (75-95%)
* rest is dry matter
* 44% C
* 40% O
* 8% H
* 8% others
31
component of litterfall and decomposability
1. 40-90% quickly decomposing....
* sugars, starches, proteins
* hemicellulose
* cellulose
2. 1-10% slowly decomposing
* fat & waxes
3. 5-40% _slowest_ decomposing
* lignin
32
detrital pool = \_\_\_
* undecomposed & partially decomposed litter (O hzn)
* buildup is fx of climate, veg., organisms
* aka production vs. breakdown/decomp
* waterlogged + wet + cool = ++detrital pool
* warm + humid = --detrital pool
33
redox rxns produce (5) and are considered
\_\_\_\_\_\_ \_\_\_\_\_\_\_
1. CO2 + H2O + heat energy
2. humus
3. new microbes
4. non-humic substances
5. nutrients
-\> incomplete decomposition
34
3 parts to decomposition
1. physical fragmentation (by soil fauna)
2. leaching (of soluble components)
3. chemical breakdown & synthesis
* by microorgs & enzymes
* -\> formation & release of byproducts / nut's
* -\> forms new decay-resistant components
* humus, organic acids
35
less acidic conditions favor \_\_\_
more acidic conditions favor \_\_\_\_
bacteria & earthworms
fungi
36
factors affecting decomposition (9)
1. aeration / water
2. temperature
3. pH - too high or too low = --decomp
4. activity & availability of soil fauna & flora
5. texture: clay binds humus, stabilizing it
6. 6. litter quality: --lignin = ++decomp
7. availability of essential nut's
* N is most limiting; C:N ratio is key
* C:N ration varies w/ type of litter
* by species
* by tissue (needles take 5 yrs, wood 150)
8. toxic components (phytotoxins)
9. Humans (tend to inc. decomp rates)
* tillage, fire, slash piles
37
humus is...
a complex mixture of brownish/blackish amorphous organic substances resulting from microbial decomp. & synthesis
* humin
* humic acids
* organic acids
38
non-humic compounds are...
identifiable; ex: oxalic acid
39
benefits of humus (6)
1. high surface area (retains nut's)
2. pH-dependant charges
3. retains water
4. form aggregates (adhesives)
5. contributes to soil formation & weathering
6. hold nutrients & energy for microbes
40
muffle furnace uses ___ \_\_\_\_ ____ to measure %OM;
%C equation: \_\_\_
loss on ignition = %OM = (weight diff / initial weight) \* 100
%C = %OM / 1.78
41
nutrient = \_\_\_
element req'd for an organism's growth & completion of its life cycle
42
17/18 macro/micronutrients
CHOPKNS CaFe Mg B Mn CuZn Cl Mo**_Co_**Ni
macro: CHOPKNS CaMg
micro: Fe B Mn CuZn Cl Mo**_Co_**Ni
(_Co_ only needed by legumes)
43
macros needed in amounts greater than....
micros needed in amounts less than...
500 ppm = .05%
50 ppm = .005%
44
chlorosis = \_\_\_
insufficient production of chlorophyll, producing yellow or yellow-white discoloration; often due to low N
45
low N discoloration
yellow @ tips & small
46
low P discoloration
small & purple (in older plant parts)
47
low Mg discoloration
small, yellow -\> purple gradient
48
low K
yellow/brown tips
49
low Ca
wilted new growth b/c Ca used in _cell walls_
50
low Fe
yellow tips
51
Law of the Minimum
level of plant production can be no greater than that allowed by the most limiting essential growth factors
52
nutrient uptake rules (3)
1. uptake req's energy; plants concentrate elements
* so uptake is fighting conc. gradients
* energy comes from _respiration_
2. __uptake is selective
* plants try to exclude unwanted elements
3. uptake is electrically balanced
* export H+ to import cations
* export OH- to import anions
53
nutrient uptake factors (7)
Plant Metabolism
1. O2 supply
2. sunlight -\> sugars
3. temperature (both shoots & roots)
Soil
1. water content / O2
2. root distribution & access
3. nutrient availability
4. symbionts
5. (competition)
54
plant affects on soil (5)
1. uptakes
2. exudates
3. microorganisms
4. litter
5. **_rhizosphere_**
* --pH than surroundings
* very active zone that differs from rest of soil
* ++microbes
* just on **_fine_** roots, mostly
55
soil nutrient sources (6)
1. parent materials (weathering)
2. atmospheric deposition (dissolved in water particles)
3. soil air
4. secondary minerals (weathering)
5. OM (decomp)
6. exchange sites
availability depends on the source
soil solution \>
exchange sites \>
colloidal fraction (humus/clays) \>
coarse fraction (primary minerals)
56
3 key things to "test" for nutrient availability
1. texture - tells you about storage, exch. sites
2. humus - color & feel -\> storage & availability
3. pH - tells you what's on exch. site & how many
* effects solubility/availability
* optimal range: 6-7
57
nutrient movement & availability to roots (4)
1. mass flow: plant takes up water, nutrients enter roots w/ water
2. diffusion: no water mvmt; high conc. -\> low conc.
* ions -\> rhizosphere -\> roots
3. plant roots grow to new areas of soil
4. symbiants
58
mobile nutrients
* move readily to roots through soil
* ++conc. in soil solution
* ex: NO3, K, Ca, Mg
* ++competition w/ other plants
59
immobile nutrients
* tend to be absorbed/precipitate out of sol'n on surface
* complex, --conc. in solution
* not as soluble
* ex: PO4-3, Fe+3
* --competition
60
symbiants
* mycorrhizae: symbiotic relationship b/t fungi & roots
* very imp. for immobile nut's
* ecto: ext. to root cells (**trees**)
* endo: penetrate root cells (**grasses, crops**)
* nitrogen fixers
* bacteria, actinomycetes
* legume bacteria: rhizobium
* red alder: Frankia actinomycetes
* also by some free-living bacteria
61
soil amendments
increase nutrient availability
* liming: raise pH; lime (CaCO3); quicklime (CaO)
* fertilizers: N most common, then P
* Ammonium nitrate
* Urea (more common in forests)
* mixed fertilizers (N P K S)
* problems w/ leaching / eutrophication
* composting
* partial rotting of plant waste to make humus
* good compost:
* aerobic decomp
* moisture: 40-70%
* piled to retain heat (50-70°C)
* N: 1.2-1.6%
