Midterm (lect.1-12) Flashcards
System definition
a collection of things that have a relationship (linkage) between each other and are contained within an identifiable boundary
Linkage definition
any relationship between the “things” of a system.
cause and effect, exchanges of material or energy
can be unidirectional or reversible
arrows in visual representation –> one direction (unidirectional linkage) and two ways
Boundary definition
the limits of end of a system
difficult to define for most systems (may not be entirely closed (can allow for passage of energy or material outside the boundary)
boxes in visual representation (dotted lines matter)
Types of systems
open
closed
isolated
open system
both energy and matter can move across the system boundary
the most common natural system
closed system
only energy can move across the system boundary
matter is excluded from crossing
rare in natural systems
ex. boiling pot of water with proper lid
isolated system
both energy and matter are excluded from crossing the system boundary
rare, mainly theoretical in natural systems
System dynamics
Understanding the behavious of a system in action
Quantifying the movement of energy and matter within a system, or into and out of a system
The state of a system can vary over time
States of a system
transient
steady
transient state
Input and output across the boundary are unequal
results in change to the size of the reservoir inside the boundary
Most natural systems are transient
Transient systems can appread to be in a steady state over specific time scales (important to define the time scale you are studying your system in)
steady state
input and output across boundary are equal
reservoir inside the boundary remains unchanged over time
Continuity equation
variation S/variation t=F1-F0
S=reservoir size
F1=input
F0=output
Reservoir time
Average length of time a substance remains in a reservoir at a steady state
Reservoir time=reservoir volume/flow rate
Positive coupling (or positive linkage)
Change in component A leads to a change in component B in the same direction
If A increases, B also increases
Solid arrow (with arrowhead)
Negative coupling (or negative linkage)
Change in component A leads to a change in component B in the opposite direction
If A increases, B decreases
Open circle arrowhead
Feedback mechanism
A sequence of interactions in which the final interaction influences the original one
Feedbacks occur in loops
Feedback loop
A linkage of two or more system components that forms a round-trip flow of information
Leads to the establishment of equilibrium states
Negative feedback
An interaction that reduces or dampens the response of the system in which is it incorporated
Self-regulating; diminishes the effect of pertubations (never bounces to extremes)
Establishes stable equilibrium states
Positive feedback
Interaction that amplifies the response of the system in which it is incorporated
Gets bigger and bigger (snowball effect)
Self-enhancing; amplifying
How to figure out if a system is a negative or positive feedback loop
Multiplication rule: if you multiply the number of positive and negative loops –> positive = +, negative=-
Albedo definition
The reflectivity of a surface
The fraction of total suhnlight reflected from a surface
High albedo=high reflection
Examples of high albedo: fresh snow, thick cloud
Equilibrium state
The state in which the system will remain (unless something disturbs it)
Can be stable or unstable
Stable equilibrium states
Negative feedback loop
Are resistant to a range of perturbations
A modest disturbance (short-term pertubation) –> response that tends to return the system to its equilibrium state
Unstable equilibrium states
Positive feedback loop
The slightest disturbance may lead to system adjustments that carry the system further and further from that state
Radiation law 1: As temperatures increase, wavelength ____?
decreases
Wavelength and temperature are inversely proportional
Solar radiation
shortwave, visible
radiation is most intense at a wavelength of 0.5 micrometers
Terrestrial radiation
longwave, infrared
radiation is most intense at a wavelength of 10 micrometers
Stefan-Boltzman Law
The energy flux emitted by an object is proportional to the fourth power of its temperature
That energy flux is what this infrared camera measures to give a temperature reading
Exchange of energy of Earth
Provides the input of energy to the planet’s surface and its atmosphere (geothermal heat is negligible in comparison)
69% of the radiation is absorbed
Some (31% albedo of planet) is reflected, and terrestrial radiation is emitted, balancing the budget.
Earth emits as much energy as it absorbs
The effect of the atmosphere on radiation
The atmosphere is a relatively thing layer of gas
Air, dust and clouds in the atmosphere affect global radiation –> reflect some light (energy loss)
The atmosphere affects invisible radiation differently than it does visible radiation
Four layers of the atmosphere (closest to furthest)
Troposphere: temperature goes down as we go higher
Stratosphere: temperature increases back because there is heat absorption
Mesosphere
Thermosphere
Greenhouse effect
Greenhouse gases in the atmosphere absorb a significant portion of the terrestrial radiation. Some of that energy is then reemitted back to the surface, raising the surface temperature.
The absorption of terrestrial radiation is mainly by water vapour and clouds (not GHG but acts as one)
GHG examples
methane
carbon dioxide
ozone
nitrous oxide
water vapour
Latent heat and energy definition
energy released during a change (fusion evaporation) in phase (physical phase)
example: water melting, or evaporating
Global energy balance cycle (explain)
Incoming solar radiation (shortwave)
- Absorption by H2O, dust, ozone
- Backscatter by air (albedo)
- Absorption by clouds
- Backscatter by clouds, reflected by earth’s surface
- Absorption of direct solar radiation
- Absorption of diffuse sky and cloud radiation
Outgoing radiation
- Net long-wave re-radiation
- Net absorption by GHG
- Emission by clouds
- Emission by H2O, CO2, ozone
- sensible heat flux (hot dry air) and latent heat flux (water vapour) –> convective mixing
Is the energy distribution at the surface equal?
No, the equatorial latitudes receive more energy than the polar latitudes due to the angle that the radiation hits the surface.
List three reasons why air moves?
Pressure gradient force
Interplay between pressure, density, and temperature
Pressure gradient force definition
air accelerates from high to low pressure areas
Where does the pressure of air come from?
The pressure of air is due to the weight of the column of air above, pushing on the air below
If there is more mass of air above, air pressure wil be larger
Air mass and air pressure is directly proportional
What is the relation between temperature and density of air?
Warm air is less dense than cold air –> warm air rises and cold air sinks
Temperature and density are inversely propotional
(remember PV=nRT ideal gas law)
What happens if an entire column of air is warmed
It will expand (becoming less dense, it needs more space), typically vertically
In other words, warming a column of air will have to take more volume
The direct thermal circulation
1) Start with two identical columns of air
- P1=P2 and same pressure at surface
2) Warm P1, it expands (gas law)
-P1(hot)>P2(cold)
-P1 expands –> more air above level of column 1
-Same pressure at surface
3) Flow aloft emptires warm column
-air flows from column 1 to column 2
-this changes pressures at lower levels
4) The direct circulation in steady state
- Air flows from hot column at the top moves down cold column, then moves back to hot column at the bottom, moves up hot column
Explain the feedback loop associated with the thermal circulation (begin at solar heating)
- Uneven solar heating
positive coupling - Temperature contrasts between air columns
positive coupling - Air movement between columns
negative coupling
Temperature contrasts between air columns
As long as there are temperature differences in the horizontal, air will circualte as a result
The Coriolis Effect
Because we are on a rotating Earth, straight paths appear curved to us, as if a “force” was pulling on moving objects.
Trajectories curve to the right in the Northern Hemisphere, and to the left in the Southern.
What happens to air when it moves vertically?
Air that goes up expands (and contracts when going down)
Pressure on the parcel diminishes with height –> parcel can take more space
Air that expands cools (and warms when it contracts) because expansion requires internal energy, taken away from heat
Air that goes up expands+air that expands cools=air that goes up cools (warm air rising cools in the proces, yet remains warmer than its surroundings)
What happens when the amount of vapor per unit volume exceeds a specific threshold called “saturation”
Net condensation to liquid or deposition to solid occurs
What happens when air is saturated with humidity?
No net flux
What happens when air is sub-saturated?
Net evaporation
What happens wehn air is super-saturated?
Net condensation
What is the link between water vapour saturation and air circulation?
The saturation point decreases as air cools
Saturated air rises, expands, and cools –> it becomes super-saturated (clouds)
If it descends, compresses, warms, it becomes sub-saturated (no clouds)
Cloud formation explanation
Clouds are made of tiny droplets of liquid or small crystals of ice
They from when humid air cools and becomes super-saturated
Almost all clouds are formed by cooling due to rising of moist air, and subsequent condensation
Descending motion brings drier air from aloft and tends to surpress cloud formation
General circulation is the tropics, also known as Hadley cell
Warm moist equatorial air rises and moves towards the poles, leading to cloud formation
There is a sinking motion at about 30 degrees latitude in both hemispheres
How are surface winds connected to general circulation?
Average surface winds consist of trades and easterlies (winds coming from the east) in the equatorial and polar latitudes, and westerlies at mid-latitudes
(look at picture on slide 19 lect. 5 for reference)
Do high pressure systems have a lot of clouds?
No, because the descending motion of air supresses cloud formation
What drives surface ocean circulation?
wind: through friction, momentum is transferred from winds to ocean currents
loops (known as gyres) are created because water hits land masses and needs to go somewhere, helped by winds, friction, and Earth’s rotation
All water moves west from the equator (east to west)
Why is ocean circulation (oceanic temperature patterns) important?
important in global energy redistribution
- Heat exchange with the atmosphere (dampens seasonal and diurnal temperature swings)
- Moisture exchange (evaporation) patterns (warmer water can evaporate more readily than colder water)
Is deep ocean circulation caused by wind-driven surface currents?
No, deep ocean circulation is independent of and superposed on the wind-driven surface currents
Deep ocean circulation arises from what properties?
Salinity of oceans: seawater contains dissolved salts; concentration varies with location. This salinity affects density and therefore water movement.
Temperature: temperature varries with location and surface currents. Temperature affects density, and therefore water movement.
What happens when ocean water evaporates?
The salt stays in the oceans
What happens when ocean water freezes?
Much of the salt stays in the liquid and the resulting ice is less salty
Why does ice float on top of liquid water?
Because solid water (ice) is less dense than liquid water
What happens to the melting point of water when salt is added?
The melting point lowers (oceans it is approximately -4 celcius)
What is more dense: salty of sweet water?
Salty water is denser
What happens when heat arrives at the ocean surface from above?
90% of radiation entering oceans is aborbed in the top 100 m
Warm water is less dense than cold
Surface +/-200 m is well mixed and seperated from deeper water
Cold, salty, dense water forms the “bottom water” (more salt, heavier water, tends to sink)
Ocean stratification layers (from surface) Name 3.
Thermocline
Halocline
Pycnocline
Sea surface temperature is primarily determined by what?
Transport and energy exchange between space and the atmosphere
What affect surface salinity?
Evaporation and precipitation
Therefore, regions with a lot of precipitation dilute salty water, making it more fresh (e.g. tropical areas have warm, fresher, lighter water, vs. poles that have cold, salty denser water).
Surface water density varies geographically, with the densest water located in the Northern Atlantic.
What is the relationship between polar regions, ice and deep water circulation?
Cold conditions in polar regions create dense, cold water and ice
Ice formation increases salinity because salt is excluded from the ice
Increased salinity increases density
Cold, salty, high-density water sinks, flows along coean floor to deep ocean
Polar regions hence appread to be the main drivers of the deep ocean circulation
Explain the thermohaline circulation, also known as the ocean conveyor belt
- Warm, low density water from the tropics moves towards the poles driven by surface ocean circulation. As the water gets closer, it gets cooler.
- At the poles, the water freezes, and the liquid water becomes more salty and dense, and sinks to the deep oceans.
- Density gradients move the dense water towards less dense regions in the tropics
Explain heat movement in the Equatorial Pacific Basin
- The cool water from the pole arrives at the eastern tropics, and begins to warm as it travels across the equator towards the west
(note: the warm water at the west causes rainy weather in the west, and the east side is normally more dry) - The warm water expands, and begins to cool as it moves to the pole
Hence, east=cooler, dry; west=warmer, rainy
Explain el Niño
Winds bringing water from east to west are reduced.
Warm water forms earlier
Atmospheric circulation is broken down (split circulation in 2)
Less cold water on the east side
Water will keep getting warmer and stay in the East
More precipitation on eastern side, drier on western side
Explain la Niña
Stronger winds bring warm water more West
Circulation becomes stronger
Brings stronger winds East
More cold water arrives East
More cold water pushes more water West
Positive feedback loop
Weather definition
day-to-day (or hour-to-hour) changes in atmospheric conditions (weather forecasts)
Temperature, precipitation, winds, etc. in the next few days
Dictacted by the movement of high and low pressure systems, showers, and atmospheric instabilities
Climate definition
long-term averaged weather, and departures from this average.
Deals with statistics
Determined by radiation, global circulation, land, etc.
Determine what is normal and rare to see in any given location (a normal event in one place/time can be sever in another)
What gives rise to seasonality? How does this relate to solar heating?
The tilt in Earth’s axis of rotation gives rise to seasonality
The annual cycle of solar illumination is more pronounced at higher latitudes
Not only are the temperatures colder at higher latitudes, they are more contrasted between summer and winter
What is the relationship between seasonality and atmospheric response?
As a result of seasonality in solar heating, surface temperatures and atmospheric circulation also vary with seasons.
As the Hadley cell of the global circulation moves, so do rainy and dry areas
Does land or ocean warm faster?
Because of mixing, the warmed layer from sunlight hitting the surface is much thicker in oceans.
On land, only thin layer is being warmed
Land areas both warm and cool faster than the ocean surface
Higher diunral and seaonsal temperature range (land)
What kind of climates do warm waters induce?
often rainier and milder climates (example Florida)
What kind of climates do colder waters induce?
coler and drier climates (example California)
How does snow/ice affect temperatures on land?
Snow and ice stays better on land than on water.
Ice albedo effect –> reflectance/whiteness of snow furthers cooling in winter on continents
How does orography (mountains) affect climate?
Colder/windier at high altitudes
Mountain barrier force air up, remove the moisture of air (via clouds, precipitation) –> lots of clouds/rain on the upwind side, sunny/dry on the downwind side
Dominant winds go from east to west (and so the east side of mountains have a lot of precipitation and so a lot of forests compared to drier deserts on the western side of mountains)
What is the residence time of water in the atmosphere?
11 days
What are some roles of the hydrological cycle
Movement of water=movement of energy and movement of matter
Important in energy redistribution, nutrient movement, weathering and sediment movement, water availability, photosynthesis
Water cycle couples with physical climate and biogeochemical systems
Roles of hydrological cycle in landscape and habitat development
Takes place globally but effects are more regional
Connection between hydrosphere, atmosphere, lithosphere, and biosphere
Affects a broad range of landscape shaping processes
River systems, glacier systems, groundwater systems, shoreline systems are subsystems of the hydrological cycle
Hydrological cycle and biogeochemical cycling
Evapotranspiration (ET) from plants is a key hydrological flow that is linked with atmospheric carbon capture by plants to allow for photosynthesis
Soil water flows contribute to movement of nitrogen and phosphorous. Nitrogen is critical for building of chlorophyll. Both elements are essential for photosynthesis.
Plant anatomy and physiology often reflect adaptions to ET and efficient use of water
Population definition
organisms of the same species living in the same place at the same time
Community definition
coexisting populations of different species (at the same place at the same time)
Ecosystem definition
Community of organisms and their physical environment
All organisms in an area + physical environment + biotic/abiotic interactions
Primary producers
Autotrophic: make their own food using either solar energy (photoautotrophs) or chemical energy (chemoautotrophs) and nutrients around them
Decomposers
Break down feces and dead organisms to recycle matter so that it is available for primary producers
Simplest ecosystem
One species that produces its own food from inorganic compounds + one species that decomposes wastes of the first species
(primary producer + energy source + decomposer)
Photoautotroph
Uses solar energy to make their own food
Chemoautotroph
Using chemical energy to make their own food
Primary consumers
Heterotrophic: get matter from consuming others
Herbivores: feed directly on primary producers
Secondary consumers
Carnivors: feed directly on primary consumers
Name the trophic levels from bottom to top
Producers
Primary consumers
Secondary consumers
Tertiary consumers
+ decomposers
Omnivores
Organisms that feed on multiple trophic levels
Can feed on both primary producers and primary consumers
What composes 78% of the atmosphere
Nitrogen (N2)
Can most living things utilise N2? Why or why not?
No, N2 has a triple covalent bond (strongest bond). It is hard to break the bond
Very stable
Nitrogen fixation
Bacteria in plant roots (rhizobium) and soil bacteria take N2 from the atmopshere and convert it to ammonium (NH4+) (which is far more accessible)
Nitrification
Certain bacteria take ammonium (NH4+) and convert it to nitrites (NO2-)
nitrification
Nitrifying bacteria take nitrites (NO2-) and convert it to nitrates (NO3-)
Assimilation
Nitrates are taken into the tissues of plants (roots in soil can suck up nitrates)
Plants can also take ammonium.
Make amino acids and nucleic acids and turn it into DNA, RNA, proteins
Consumption
Animals consume the nitrogen in plants
Ammonification
Decomposers take the nitrogen-containing organic compounds from dead animals/plants and from urine/litter, and turn it back into ammonium
Denitrification
Denitrifying bacteria takes nitrates and brings it back into the atmosphere to form nitrogen N2
Explain the nitrogen cycle
- Nitrogen fixation from bacteria in plant roots and soil bacteria converts nitrogen to ammonium
- Through nitrification, ammonium is converted to nitrites. Nitrifying bacteria turn nitrite into nitrate
- Through assimilation, plants take up the nitrate (and also ammonium) and convert it to energy that is consumable.
- Animals consume the nitrogen
- Decomposers take animals and plant waste/ dead matter and convert this nitrogen back to ammonium through ammonification
- Denitrifying bacteria take nitrate and convert it back to N2 and release it in the atmosphere
What is Liebig’s law of the minimum?
biological growth is not controlled by total resource availability, but rather by the availablity of the scarcest resource.
What is the limiting factor in Liebig’s law of the minimum
The scarce resource
Limiting factors can be environmental conditions (temperature, water, sunlight during different seasons, and nutrients)
What are redfield ratios?
the ratio of inorganic nutrients in phytoplankton biomass.
106 carbon: 16 nitrogen: 1 phosphorous
While ratios measured by scientists may vary by conditions and locations, this is the general nutrient proportion found throughout the world’s marine systems.
How does water limit primary production in terretrial systems?
When water is scarce, photosynthesis stops
CO2+H2O+sunlight–>glucose+O2
How do nutrients limit terrestrial production?
Fertilizers stimulate crop production
N is often the limiting nutrient
How do nutrients limit aquatic systems?
Especially in open oceans
Inadvertent addition of nutrients may stimulate unwanted production.
Trophic groups in aquatic environments
Primary producers
Herbivores
Carnivores
Top carnivores
What happens to trophic cascade with bottom up controls?
Increased production results in greater productivity at all higher trophic levels.
Everyone benefits with bottom-up controls
As we increase nutrients, we increase primary producers, which means more food for primary consumers –> more food for secondary consumers
What happens to the trophic cascade with top-down controls?
Consumers depress the trophic level on which they feed, indirectly increasing the next lower trophic level.
As we increase secondary consumers, we increase primary producers
The relative biomass of trophic levels alternate
What happens to biomass of the other trophic levels if the population of piscivores increases? (top-down controls)
Population of planktivores goes down
Population of herbivores goes up
Population of planktivores go down
Name ways in which nitrogen can enter an ecosystem
N2 fixation
Industrial fixation
Lightning
Rainfall
Plant and animal residues
Fertilization
Name ways in which nitrogen can leave an ecosystem
Plant loss
Leaching
Organic matter
Ammonia volatilization
What is the role of vegetation in nutrient cycles?
Vegetation aids nutrient retention
- Uptake of nutrients before they are leeched
- Store more nutrients in biomass rather than soil
Vegetation is also important to hold onto water. Removing trees changes precipitation
During the Hubbard Brook Study, what nutrient was lost 60 hold?
nitrates
Productivity definition
The creation of new organic matter
The change in biomass per unit time (gm^-2 yr^-1)
THe change in energy per unit area per unit time (kcal m^-2 yr^-1)
What is the 1st law of thermodynamics?
Conservation of matter and energy: in any physical of chemical process, matter and energy are neither created nor destroyed but merely transformed.
Is energy transferrable in ecosystems?
Yes, energy is transferred along food chains from one trophic level to the next.
Ecosystems are transformation systems (“input-output machines”) for energy and matter.
Changing froms from being useable to non-usable
Fixed amount of energy in the Universe
On average, how short of food chains? Why are they usually this short?
4 trophic levels
- Longer chains tend to be unstable (more dependencies on every level, chain reaction if something bad happens on one level)
- Increasingly less energy reaches higher trophic levels.
Is all energy retained when it moves from one trophic level to the next? Why or why not?
No, not all energy consumed by an animal is retained. Some energy is excreted and some is respired as waste heat.
Feeding inefficiencies exist (not all of the available food is consumed)
What is the 2nd law of thermodynamics?
Energy Degradation (entropy): energy moves from an organized, useful from to a disorganized, less useful form. Energy cannto be recycled to its original state of organized, high-quality usefulness.
What is meant when we say that energy is lost as respiration?
Cellular respiration
Energy=ATP+heat
ATP used as energy currency at cellular level
Eventually, all energy in ATP is lost as heat
(ATP is useable energy for humans)
Energy balance equation
i=o+d+r+e
where, i=input
o=output
d=detritus (death)
r=respiration
e=excrements
What goes in=what goes out
Secondary production definition
the rate of transformation (through consumption) of one’s food into your own biomass
Production efficiency definition
Fraction of energy stored in food that is used for secondary production (not used for cellular respiration)
Production efficiency equation
production efficiency=(secondary production/production consumed)x100%
What is the production efficiency of insects and mircoorganisms?
averaging 40%
What is the production efficiency of fishes (ectotherms)?
averaging 10%
What is the production efficiency of birds and mammals?
averaging 1-3%
Why is the production efficiency of birds and mammals so low compared to other species?
They need energy to warm their blood
What does the amount of energy reaching each trophic level depend on?
The net primary production
The energy transfer efficiency
Energy transfer efficiency equation
=consumption (at trophic level n)/production (at trophic level n-1)
What is the 10% rule of food pyramids?
Approx. 10% of the energy harvested at a lower trophic level is transferred up to the next higher trophic level
Does biomass tend to increase or decrease up the food chain?
Decrease
Why are some biomass pyramids inverted?
Biomass pyramids are inverted when the biomass of producers is consumed rapidly and is replaced rapidly.
Although biomass may be small, the rate at which it is produced may be very large.
More common in aquatic (freshwater and marine) food webs than terrestrial
What is Allen’s Paradox?
K.R. Allen found that there was insufficient invertebrate prey in a New Zealand stram to support the trout population he sampled, but the population still exists.
How do we explain Allen’s paradox?
- Allen measured only the prey that was present at a given time of sampling. However, the insect population reproduced many times during the year.
Taking a snapshot at the wrong time–seems as though they are not a lof of the species. - Energy subsidies from connected ecosystems (terrestrial resource use by a fish increases with vegetation cover in terrestrial catchments)
Is fish biomass supported by terrestrial primary production?
Yes, 1/3 of fish biomass is supported by terrestrial primary production
Can energy pyramids be inverted?
No, never (as opposed to biomass pyramids which can be inverted)
Gross primary production (GPP)
The amount of CO2 fixed by the plant through photosynthesis
Respiration (R)
The amount of CO2 lost through metabolic activity
Net primary production (NPP)
The net amout of PP after the cost of plant respiration
NPP=GPP-R(p)
The rate of accumulation of plant biomass
Net ecosystem production
- Carbon gained by photosynthesis - carbn lost from the ecosystem (through community respiration)
- Net carbon storage in the ecocsyem
NEP=GPP-(Rp+Rh+Rc+Rd)
NEP=GPP-(Rp+Rhet)
NEP=NPP-Rhet
where Rp=respiration by plants and Rhet=respiration by heterotrophs
When the NEP>0, the ecosystem is a sink of source for carbon?
Sink (biomass accumulates)
When the NEP<0, the ecosystem is a sink or source for carbon?
Source (example: newly-tilled field, a forest disturbed by a fire)
If NEP=0, what happens with carbon?
Carbon is transferred to the ecosystem and atmosphere at equal rates
Residence time of energy
Rt=energy in biomass/NPP
What is the residence time for forests?
20-25 years
What is the residence time for grasslands?
3-5 years
What is the residence time in lakes and oceans?
10-15 days
Disturbance definition
Any discrete removal of biomass
Natural components of all ecosystems, and the resident organisms are typically well-adapted to that system’s natural disturbance regime
For most ecological systems, the natural disturbance regime is a mix of large infrequent events, and small frequent events (not necessarily the same disturbance type)
Every ecosystem has disturbances
Natural disturbances
Not “bad”
Play a large role in shaping ecosystems
Fire, wind, floods, landslides, volcanos, earthquakes, etc.
Eliminated from, introduced to, and/or drastically changed in many ecological systems
Anthropogenic disturbances
Typically “bad”
Most often detrimental –> little evolutionary adaption
How can disturbances change ecosystems?
They can alter fundamental properties
Example: fire in a temperate deciduous forest
- Loss of principal habitat structure (tree canopy)
- Loss of understory diversity (mosses, shrubs)
- Release of stored nutrients
–> End result: conversion of forest to grassland
Carbon general information on molecular structure
All planetary carbon was first created in space
Now a closed system
Chemical properties of carbon make it an extremely useful element for forming molecules
- Carbon can form 4 strong bonds with other elements
- Carbon bonds can enter ring formations
Carbon can form a wide range of versatile and diverse molecules (from diamonds to fats)
Carbon and life
Essential for life
Central element of all organic compounds that form the physical structures of life
Involved in energy acquisition and use in biological life (conversation thermal energy to biological energy)
Maintains the long term stability of the global climate
The carbon cycle
The movement of the element carbon through abiotic and biotic reservoirs on the planet
Reservoir definition
A source of stored carbon
Linkage definition
process linking two reservoir of carbon
Source definition
a reservoir which releases more carbon than it receives through linkages
Sink definition
A reservoir which receives more carbon than it releases through linkages
The carbon cycle units
carbon is usually represented as Gt (billions of tons)
Can be Gt of CO2 or Gt of just elemental carbon (1 Gt carbon approx. 3.666 Gt CO2)
Inorganic carbon cycle definition
The cycling of carbon between the oceans, rocks, and the atmosphere
Takes place on the order of millions of years
Existed before there was biological life on the planet
In the modern carbon cycle, interacts with the organic processes of the carbon cycle
Inorganic carbon cycle reservoirs
Oceans
Atmosphere
Rocks
Inorganic carbon cycle linkages
Volcanism
Solubility pump
Chemical weathering
Subduction
Volcanism definition
Melting of rocks as a result of intense heat and pressure from the interior of the planet
Melted rock and gasses rise towards the surface, ultimately reaching the crust and emerging into the atmosphere
How does volcanism participate in the carbon cycle?
Chemical composition of rocks undergoing melting will produce different by-products
- Carbonate rocks release CO2 when broken down
- CO2 gas is released along with heat and melted minerals during volcanic activity
Volcanism is infrequent, but regular (large amounts of CO2 are released each time)
(A less dratamtic but gradual version: hydrothermal vents)
What role does the solubility pump play in the carbon cycle?
The direct exchange of carbon between the atmosphere and the ocean
CO2 can move both ways (both enter oceans or leave)
CO2 is soluble in water
- Where the ocean touches the atmosphere, CO2 will dissolve in water
- Reacts with water to produce a reversable reaction involving carbonic acid, bicarbonate ions, carbonate ions, and H+
Chemical weathering definition
The chemical breakdown of minerals
During this breakdown, elements, ions, and molecules can be released
Products of chemical weathering depend on the initial chemical make-up of the mineral being weathered
What is the role of chemical weathering in the carbon cycle?
Releases specific ions from weather rocks (theses ions are part of the carbon cycle)
Releases other elements, ions, and molecules which are not a part of the carbon cycle. This moves carbon in the atmosphere down in the oceans
Chemical weathering in the carbon cycle steps
1) CO2 reacts with H2O in the atmosphere.
- forms carbonic acid (H2CO3), a weak acid
2) Carbonic acid falls with rainwater.
- reacts with exposed sedimentary rock
- results in production of calcium ions and bicarbonate ions (HCO3-)
- in the rock is a calcium silicate, also results in the production of silicates
3) Rainfall washes bicarbonate ions and calcium ions into the ocean
- where carbonate ions have also been produced as a result of the solubility pump
- the solubility pump and chemical weathing act together
4) In the ocean, calcium ions and carbonate ions combine in solutino to form calcium carbonate (limestone)
5) In the modern carbon cycle, most calcium carbonate is made by shell-producing life forms. (necessary in shell formation). Calcium carbonate can also form spontaneously in solution (hoe the carbon cycle funcioned before life evolved)
6) Calcium carbonate settles on the ocean floor
- as animals with shells die and settle
- over time naturally as calcium carbonate suspended in the ocean settles on the sea floor
7) Forms mineral deposit of calcium carbonate (carbonate rocks)
Subduction definition
When one tectonic plate is pushed under another
The plate being subducted eventually melts as a result of the heat in the interior of the planet
Minerals and organic matter within the tectonic plate melt and join layers of the mantle
What is the role of subduction in the carbon cycle?
Carbonate rocks from ocean deposits melt during subduction and converts CO2 gasses (as well as other elements)
What happened during snowball earth
Complete freezing of the ocea surface several times in Earth’s ancient past
Positive feedback (apprx. 750 million years ago)
- Continents were mainly at the equator
Increased weathering from rainfall pulled more CO2 from the atmsophere and lowered temperature. - Continents increase albedo (reflect more than dark ocean) and also contribute to lower temperature.
- Ice formation starts at poles, and spreads towards equator further increasing albedo.
- Oceans frozen, slowdown in rate of precipitation on Snowball Earth
How did the planet leave Snowball Earth? How could the carbon cycle function without the availability of oceans and slow precipitation?
Volcanism continues
Low rate of precipitation (no method to remove CO2 from the atmosphere)
CO2 is a GHG
Increasing concentration of CO2 in the atmosphere heats the Earth
Temperatures increase, the snow melts, oceans open again
The long term carbon cycle can resume
Why is there no carbon cycle on Venus?
Venus had tectonic activity
Presence of carbon, but no water to remove the CO2
Why is there no carbon cycle on Mars?
Mars had water at some point (still some ice)
Some point had active volcanism in the plnet (currently no more)
All of carbon is locked in rocks (no volcanism to bring the CO2 back into the atmosphere
Organic carbon cycle linkages
Biological life
Photosynthesis
Decomposition
Cellular Respiration
Fossil fuels
Upwelling/downwelling
Biological pump
Calcium carbonate life
Photosynthesis definition
The process where thermal energy is used to convert atmospheric CO2 into sugars and oxygen
Primary producers providing energy for higher trophic levels in food chains
What is the role of photosynthesis in the carbon cycle
Removes atmospheric CO2
Fixed carbon (sugar) can then be used by the plant or other life forms (directly as energy, carbon available as a building block for other organic molecules)
Cellular respiration definition
The converstion of sugars to biological energy (ATP)
Decomposition definition
The breakdown of complex organic molecules into simpler molecules through the action of living things
What is the role of respiration in the carbon cycle?
All aerobic life practices cellular respiration
- Heretotrophs fuel cellular respiration through the sugars consumed from primary producers
- Plants fuel cellular respiration through the sugars produced from photosynthesis
Takes place in mitochondria
As sugars are converted to energy (ATP), gaseous CO2 is released as a byproduct to the atmosphere as waste product (animals respire, plants release gas through pores on leaves)
What is the role of decomposition in the carbon cycle?
Complex organic molecules broken down into simpler compounds release atmospheric CO2 through cellular respiration.
Some carbon is deposited in the soils as humus.
Humus definition
Organic component of soil
Composed of partially decomposed organic molecules
Fossil fuels definition
Reservoirs of concentrated carbon formed in the ancient geological past from the remains of plant and animal life which did not fully decompose
Natural gas, petroleum, coal
Fossil fuel formation
Happen over long geological timescales
1) Dead organic matter buried by sedimentation before it can be fully decomposed
2) Increasing uild-up of sediments –> increasing weight compressing organic matter, moves organic matter deeper within the crust (increasing heat exposure)
3) Increased compression and heat –> removes trapped water and gases, transforms larger carbon molecules to smaller ones
4) What remains is concentrated carbon with a minority of other elements
- coal: 60-80% carbon
- oil: 80-85% carbon
What is the role of fossil rules in the carbon cycle
Represent long term organic carbon storage in the crust
- Many deposits are older than 200 million years
Can be returned to the atmosphere through natural processes (long timescale)
How does ocean life contribute to the carbon cycle?
Biological pump
Photosynthetic marine life
- primary producers in many marine ecosystems
- utilizes CO2 for photosynthesis
Marine animals
- Releases CO2 during cellular respiration
- Decomposition (possible fossil fuel formation)
Shell-forming marine life actively builds calcium carbonate during shell formation
- dissolved carbon dioxide and Ca2+ present in the ocean as a result of chemical weathering and the solubility pump
Thick mineral deposits of calcium carbonate build up over time
Most remain buried in ocean environments (tectonic plate movements can bring calcium carbonate deposits onto land)
What is the biological pump? How does it contribute to the carbon cycle?
Cycle of photsynthesis, cellular respiration, decomposition, and fossil fuel formation that takes place in marine habitats
Pumping CO2 through the different levels of the oceans through living organisms
Coccolithophores (algae) affect in oceans
Sometimes form blooms at the ocean surface which reflect visible light
These organisms reflect nearly all visible light –> Increase the ocean’s albedo (causing less solar radiation to be absorbed and stored as heat in the ocean)
How does carbon moves between surface waters and deep waters in oceans?
Natural upwelling and downwelling of dissolved CO2
Movement of living organisms between surface and deeper waters
(As currents move through the ocean, they take CO2 with them. As marine life rises at night to feed on shallow surface organisms, they eat and bring that carbon (food) down in the deep oceans)
Why is the organic side of the carbon cycle seen in the regular and cyclical changes in atmospheric carbon? Why are there seasonal changes?
Exceptionally large impact of plant life
- Plants do not consume CO2 throughout the year (depends on the season)
What happens to the relationship between plants and carbon during the spring and summer?
Plant life engages in growth (plants need sugar to grow, taking a lot of CO2 out of the atmosphere)
- Photosynthesis rate increases, takes up atmospheric CO2
- Atmospheric CO2 may be fixed in long term organic structures (wood)
What happens to the relationship between carbon and plants during the fall and winter?
Plant growth slows down and ultimately stops (plants become dormant)
Processes involving cellular respiration become the primary process involving CO2 (decomposition of fellan leaves, animal respiration)
Is plant growth equal in all regions?
No, plant growth is not equal in all regions of the globe
Where are seasonal changes in atmospheric CO2 the greatest?
The Northern hemisphere
Poles=larger variations in temperature
More land in the Northern Hemisphere (more CO2 being released in the north than the south)
Oceans are less sensitive to seasonality, and so where the continents are located have an impact on global climate
What are some ways in which human activity participates in CO2 being released back into the atmosphere?
Burning of land biota
Farming (from soil)
Fossil fuel burning
Name major anthropogenic linkages in the carbon cycle
Burning fossil fuels for energy
- excessive use of fossil fuels are returning to the atmosphere at a much faster rate than it would naturally
Changing land use
- Removing established vegetation
- Modifying existing rates of photosynthesis, respiration, and decomposition
- Creating concrete from limestone (especially in developing nations)
Ocean acidification
Atmospheric CO2 concentrations affect ocean pH as a result of the solubility of CO2 in water (CO2 is soluble in water)
- More CO2 in the atmosphere, more CO2 will ultimately dissolve in oceans
How much CO2 released is currently absorbed by oceans?
25-50%
How does ocean acidification affect the natural process of shell formation?
Marine life needs both dissolved Ca2+ and CO3(2-) (carbonate) to build calcium carbonate for shell formation
Increasing H+ concentration in marine environments binds with available carbonate in solution, resulting in bicarbonate (HCO3-)
Removes reservoir of dissolved carbonate for formation of calcium carbonate
H+ has a higher affinity for carbonate than does Ca2+
- At high enough concentrations of H+, existing molecules of CaCO3 can actually break apart
- Existing calcium carbonate shells have been found to dissolve at low pH (calcium carbonate was pulled away by the hydrogen)
What is the Greening Hypothesis
CO2 is a fertilizer (not a pollutant) that, when increased will be absorbed by the biosphere, stimulate greater plant productivity and expand forests
What is CO2 fertilization (in relation to the Greening Hypothesis)?
Atmospheric CO2 acing as a fertilizer to enhance plant growth
Free Air Carbon Dioxide Enrichment (FACE) systems
Large scale experimental exposure of plants in real world conditions to elevated atmospheric CO2 levels
What happens to NPP during FACE experiment?
Initially increases, then declines over time
(curb on slide 39 lecture 12)
Wha observations were made during the FACE experiments
Elevated CO2 can impact nurtient cycles and microbial communities
- Increased growth can modify what is the limiting nutrient for growth (get to the point where run out of all other nutrients and so have excess CO2)
Soil microbes can modify whether a plant uses increased atmospheric CO2 for biomass or stores excess carbon in the soil (plants feed the carbon to symbiotic fungi)
What happens to plant growth under high CO2 and wet conditions?
Less water use, more nitrogen fixation, more yield
What happens to plant growth under high CO2 and dry conditions?
More water use, less nitrogen fixation, less yield
Junk food effect
Increased sugar production in plants results in decrease in production of other organic molecules and reduction in mineral uptake
Plants exposed to CO2 increase –> plants are less healthy (decrease of all other nutrients)
Since 1950, nutrient levels have already fallen in our food
Evaluate the Greening Hypothesis
NPP can increase initially, but returns to standard levels over time
- Other elements are limiting on growth (nitrogen, water)
Increased atmospheric CO2 can make plants more vulnerable to heat and drought stress
Increased sugar production –> reduced uptake of minerals and production of other biomolecules
Increased atmospheric CO2
- Reduce yields and nutrition of crops
- Increased stress on native plant ecosystems
