V - Nutrient Cycling & Soils Flashcards
1
Q
Nutrient cycles
A
natural processes that involve the flow of nutrients from the nonliving
environment (air, water, soil, rock) to living organisms (biota)
& back again.
2
Q
three major types
A
Hydrologic
Atmospheric
Sedimentary
3
Q
Hydrologic
A
involving flows through the hydrosphere,
in the form of liquid water, compounds dissolved in
water, & sediments carried by water
4
Q
Atmospheric
A
involving flows through the
atmosphere, as gases or airborne particles
(particulates)
5
Q
Sedimentary
A
involving flows through the lithosphere
(Earth’s crust = soil & rock), as solid minerals
6
Q
Nutrient cycles involve
A
one–way flow of high– quality energy from the sun through the environment & recycling of crucial elements.
7
Q
Carbon main nonliving storehouse
A
Atmospheric carbon dioxide
8
Q
Carbon main forms in living organisms
A
Carbohydrates and all other organic molecules
9
Q
Carbon other nonliving storehouse
A
Hydrologic dissolved carbonate/ bicarbonate
10
Q
Nitrogen main nonliving storehouse
A
Atmospheric: nitrogen gas
11
Q
Nitrogen main forms in living organisms
A
Proteins & other nitrogen-containing organic molecules
12
Q
Nitrogen other nonliving storehouse
A
Hydrologic : dissolved ammonium, nitrate, nitrite in water & soils
13
Q
Phosphorus main nonliving storehouse
A
Sedimentary phosphate containing minerals in rocks
14
Q
Phosphorus main forms in living organisms
A
DNA, other nucleic acids- ATP -& phospholipids
15
Q
Phosphorus other nonliving storehouse
A
Hydrologic dissolved phosphate
16
Q
Sulfur main nonliving storehouse
A
Sedimentary rocks -iron disulfide & pyrite - and mineral - sulfate
17
Q
Sulfur main forms in living organisms
A
Sulfur-containing amino acids in most proteins, some vitamins
18
Q
Sulfur other nonliving storehouse
A
Atmospheric hydrogen sulfide, sulfur dioxide, sulfur trioxide, sulfuric acid
Hydrologic sulfate & sulfuric acid
19
Q
Role of water
A
• terrestrial ecosystems – major factor determining
distribution of organisms;
• aquatic ecosystems – literally matrix that surrounds &
serves as environment of aquatic organisms;
• flows of water are major means of material & energy
transport;
• water is critical for human activities – agriculture,
industry, & municipal use
20
Q
Main processes in water cycle?
A
Evaporation Transpiration Movement in atmosphere Condensation Precipitation Infiltration Percolation Flow in aquifers Runoff
21
Q
Evaporation
A
conversion from liquid to vapor form (surface
to atmosphere)
22
Q
Transpiration
A
evaporation from leaves of water extracted
from soil by roots & transported through the plant (surface to
atmosphere)
23
Q
Movement in atmosphere
A
transport as vapor
24
Q
Condensation
A
conversion of vapor to liquid droplets
25
Precipitation
movement as rain, sleet, hail, & snow
| atmosphere to surface
26
Infiltration
movement into soil
27
Percolation
downward flow through soil to aquifers
28
Flow in aquifers
belowground flow of water.
29
Runoff
surface flow downslope to ocean.
30
Human Influences on water cycles?
• withdraw large quantities of fresh water – water
diversion, groundwater depletion, wetland drainage
• clear vegetation – increase runoff, decrease infiltration
& groundwater recharge, increase flooding & soil
erosion;
• modify water quality – add nutrients (P, N…) & pollutants
31
Role of carbon
• building block of organic molecules (carbohydrates,
fats, proteins, & nucleic acid) – essential to life;
• currency of energy exchange – chemical energy for
life stored as bonds in organic compounds;
• carbon dioxide (CO
2) greenhouse gas – traps heat
near Earth's surface & plays a key role as "nature's
thermostat".
32
How is Carbon Cycled?
```
Carbon cycling
between the
atmosphere &
terrestrial
ecosystems.
```
33
Natural & synthetic admission of carbon
Volcanoes & wildfires
| Burning of fossil fuels
34
Role of ocean in carbon cycle
```
Large amounts of
carbon are buried
in sediments in the
form of calcium
carbonate (CaCO3)
```
35
Main processes in carbon cycle
```
Movement in atmosphere
Primary production
Movement through food web
Aerobic respiration
Combustion dissolving in oceans
Movement to sediments
```
36
Movement in atmosphere
atmospheric C as CO2 (0.036%
| of troposphere)
37
Primary production
photosynthesis (= carbon fixation)
| moves C from atmosphere to organic molecules in organisms;
38
Movement through food web
C movement in organic form
| from organism to organism;
39
Aerobic respiration
organic molecules broken down to
| release CO2 back to atmosphere;
40
Combustion
organic molecules broken by burning down to
| release CO2 back to atmosphere;
41
Dissolving in oceans
: C enters as to form carbonate (CO32–)
| & bicarbonate (HCO3–);
42
Movement to sediments
```
C enters sediments, primarily as
calcium carbonate (CaCO3);
```
43
Human Influences on Carbon cycle?
• removal of vegetation – decreases primary production
(decreases carbon fixation);
• burning fossil fuels & biomass (wood) – increase
movement of carbon into the atmosphere;
• the resulting increased concentration of
atmospheric CO2 is believed to be sufficient to
modify world climate through global warming
44
Role of nitrogen
• building block of various essential organic
molecules – especially proteins & nucleic acids;
• limiting nutrient in many ecosystems – typically,
addition of N leads to increased productivity.
45
How is Nitrogen Cycled?
Atmosphere
Ecosystem
Soil
46
Main processes in nitrogen cycles
```
Nitrogen fixation
Nitrification
uptake
Ammonification
Denitrification
```
47
Nitrogen fixation
conversion of N
2 (nitrogen gas) to NH
4+(ammonium), atmospheric by lightning, biological by
bacteria & blue-green algae (anaerobic), e.g., Rhizobium in
legumes;
48
Nitrification
conversion of NH
| 4+ to NO3- (nitrite) to NO3- (nitrate) by microbes
49
Uptake
by plants, forms proteins and other N containing
| organic compounds, enters food chain;
50
Ammonification
returned to NH
4+ inorganic forms by
saprophytes and decomposers;
51
Denitrification
conversion of NH
4+ to N2 by combustion or
microbes
52
Human Influences on nitrogen cycle?
• emit nitric oxide (NO), which leads to acid rain – huge quantities of nitric oxide emitted; contributes to photochemical smog; forms nitrogen dioxide (NO2) in atmosphere, which can react with water to form nitric acid(HNO3) & cause acid deposition ("acid rain")
• emit nitrous oxide into the atmosphere – nitrous oxide (N2O) is a potent greenhouse gas & also depletes ozone in stratosphere
• mine nitrogen–containing fertilizers, deplete nitrogen
from croplands, & leach nitrate from soil by irrigation
– leads to modification of nitrogen distribution in soils;
• remove N from soil by burning grasslands & cutting
forest – leads to decreased N in soils;
• add excess N to aquatic systems – runoff of nitrates &
other soluble N–containing compounds stimulates algal blooms, depletes oxygen, & decreases biodiversity;
• add excess N to terrestrial systems – atmospheric
deposition increases growth of some species (especially weeds) & can decrease biodiversity
53
Role of Phosphorus?
* essential nutrient for plants & animals
| * limiting nutrient in many ecosystems
54
Essential nutrient for plants & animals
especially building block for DNA, other nucleic acids
(including ATP; ATP stores chemical energy), various
fats in cell membranes (phospholipids), & hard calcium–
phosphate compounds (in bones, teeth, & shells);
55
limiting nutrient in many ecosystems
typically,
addition of P leads to increased productivity, especially
for fresh water aquatic systems.
56
How is Phosphorus Cycled?
Hydrospheric
| Ecosystem
57
Main processes in phosphorus cycle?
```
Weathering
Uptake
Movement through food web
Breakdown of organic forms
Leaching
Burial in ocean sediments
```
58
Weathering
P slowly released from rock or soil minerals
as phosphate (P04
3-), which dissolves in H20 & is readily
leached;
59
Uptake
by plants to form organic phosphates;
60
Movement through food web
nucleic acids (including
DNA & ATP), certain fats in cell membranes (phospholipids),
bones/teeth/shells (calcium–phosphate);
61
Breakdown of organic forms
to phosphate (P043-) by decomposers
62
Leaching
P043- from soil
63
Burial in ocean sediments
not cycled in short time scale, only over geologic time
64
Human Influences on phosphorus cycles?
• mine large quantities of phosphate rock – used for
organic fertilizers & detergents; can cause local effects from
mining & releases more P into environment;
• sharply decrease P available in tropical forests &
other ecosystems where P is limiting – deforestation
& certain agricultural practices decrease available P;
• add excess P to aquatic ecosystems – leads to
excessive algal growth, depletion of oxygen, & decrease in
biodiversity; such eutrophication ("over nourishment")
65
Role of Sulfur?
• component of some proteins & vitamins
– essential for organisms;
• limiting nutrient in some ecosystems
66
How is sulfur cycled?
Abiotically & Biotically
67
Main processes in sulfur cycle
Storage in rocks
Atmospheric input from volcanoes, anaerobic decay, & sea spray
Combustion
Movement through food web
68
storage in rocks
much of Earth's S is in rock form (e.g.,
| iron disulfides or pyrites) or minerals (sulfates);
69
atmospheric input from volcanoes, anaerobic
| decay, & sea spray
S enters atmosphere in form of
hydrogen sulfide (HS) & sulfur dioxide (SO2), & sulfates
(SO42–)
70
combustion
sulfur compounds released to the
| atmosphere by oil refining, burning of fossil fuels, smelting, & various industrial activities
71
movement through food web
movement through food web & eventual release during decay
72
Human Influences on sulfur cycles?
```
contribute about one–third of atmospheric sulfur emissions
• burning S–containing oil & coal;
• refining petroleum;
• smelting;
• other industrial processes
```
73
soil
complex mixture of inorganic material (clay,
| silt, & sand), decaying organic matter, air, water, & living organisms
74
Characteristics of soil
• rich in biological life, including bacteria, fungi, &
invertebrates;
• complex ecosystem;
• develop & mature slowly –– can take 200 to
1,00 years to develop 2.5 cm (1 inch) or topsoil
(A horizon);
• well developed soils display distinct horizons, or
soil profiles.
75
Rock cycle
```
transformations
of rock over
millions of
years.
Phosphorus cycle part of rock cycle
```
76
Main processes in rock cycle
```
Weathering
Erosion
Transportation
Deposition
Melting
Cooling
Heat & Pressure
```
77
Weathering
g
78
Erosion
g
79
Transportation
g
80
Deposition
g
81
Melting
g
82
Cooling
g
83
Heat & Pressure
g
84
Soil Profiles
Horizons, or layers, vary in number & composition,
| depending upon soil type.
85
Soils from different biomes display
different profiles.
86
Soil texture is determined by
the particular mix of
| clay, silt, & sand.
87
Types of soil textures
```
Clay
Sandy clay
silty clay
Silty clay loam
Clay loam
Sandy clay loam
Loam
Silty loam
Sandy loam
Loamy sand
Sand
silt
```
88
The pH scale is used to measure
acidity & alkalinity of water solutions.
89
pH is an
important soil property.
90
Soil Food Webs
Complex
| Many different organisms + organic debris
91
Soil Nutrient Cycling
Nitrogen, phosphorus, and potassium are among the major nutrients
92
Are ecosystems self–contained?
• immature natural ecosystems tend to have major shifts in
energy flow & nutrient cycling;
• over time ecosystems tend to reach an equilibrium with
respect to energy flow & nutrient cycling, such that these
ecosystems appear self–contained;
• however, there is considerable exchange of water &
nutrients of ecosystems with adjacent ecosystems;
• human disturbance (clear cutting, clearing, etc.) can cause
major loss of nutrients.
93
How does nutrient cycling relate to ecosystem
| sustainability?
• the law of conservation of matter enables us to understand
major nutrient cycles, and observe that given time natural
ecosystems tend to come into a balance wherein nutrients are
recycled with relative efficiency;
• modification of major nutrient cycles may lead to shift in
ecosystems, such that current ecosystems are not sustainable;
• developing a better understanding of energy flow & nutrient
cycling is critical to understanding the depth of environmental
problems.
94
Organisms found in soil food webs includes
```
flatworms
Rove beetle
Ant
Centipede
Mite
Ground beetles
Fungi
Snail
Slug
Earthworm
Sowbug
Adult fly
```
