Lecture 18: Ecosystems: Water cycle, carbon cycle, & nitrogen cycle Flashcards
Major physical and biological processes couple water movement to ____________________ and _______________ in ecosystems.
- energy transformation
- element cycling
Water movement is therefore a ______________________________________ and for understanding energy flow in an ecosystem
valuable proxy for element cycling
Direct human impacts on the water cycle
- Land conversion impacts water runoff pathways and rates
- Altered water runoff pathways and rates
Direct human impacts on the water cycle - land conversion
- Developed areas (city-building and especially concrete).
- Agricultural land conversion.
- Dams
- Irrigation.
Direct human impacts on the water cycle - Altered water runoff pathways and rates
- substantial impact on soil erosion — direct impact and indirect impact on crops
- can further impact vegetation cover,
droughts, and fire
The movement of major organic elements serves as a _____________________________
good proxy to energy flow
Carbon is ____________________________ and transferred in ___________________________________, so carbon transfer is directly coupled with energy flow.
- generated from photosynthesis
- trophic interactions and decomposition
Net ecosystem production
a measure of the balance of carbon gain and loss in an ecosystem
Positive net ecosystem production
serves as a carbon sink
carbon sink
Removes carbon, as the main “greenhouse gas”, from the atmosphere
what happens when carbon sources outweigh carbon sinks
- results in an increase in greenhouse gases and temperatures
- as we are seeing from human activity
what are the 6 major transformations that drive the carbon cycle
- photosynthesis
- respiration
- sedimentation and burial
- exchange
- extraction
- combustion
6 major transformations drive the carbon cycle - photosynthesis
Biological removal from the environment
6 major transformations drive the carbon cycle - respiration
Biological return to the environment
6 major transformations drive the carbon cycle - sedimentation and burial
carbon storage
6 major transformations drive the carbon cycle - exchange
Balanced gain/loss between ocean and atmosphere
6 major transformations drive the carbon cycle - extraction
Removal of carbon storage by human activity
6 major transformations drive the carbon cycle - combustion
- Burning of stored carbon sources
- rapid return of carbon to the environment
- and especially the atmospheric “compartment” of the carbon cycle
define residence time
Time spent in any stage of the cycle by the average carbon molecule
The global carbon cycle – Photosynthesis & respiration
- Biological exchange between the environment and organisms
- Biological material is a major “sink” for carbon
What have humans done to the carbon sink of biological material?
- Humans have reduced the amount of biological material
- Results in more carbon in the air becuase it isn’t going to the sink
The global carbon cycle – ocean-atmosphere exchange
- Physical exchange of carbon dioxide between the atmosphere and all water bodies
- Carbon dioxide uptake by the oceans and the process of sedimentation has offset the atmospheric increases from human activity.
Carbon dioxide __________________ in water at the interface between air and water, and is also lost back to the atmosphere.
readily dissolves
Oceans contain about ______ the carbon dioxide found in the atmosphere – _____________
- 50 times
- major carbon sink
The global carbon cycle – Sedimentation & burial
- Process occurs only in aquatic systems
- The excessive “consumption” of carbonate ions due to ocean acidification is also impacting shell formation in marine animals
What happens to ocean water when carbon dioxide absorption levels increase
It becomes more acidic - coral reef bleaching
explain the sedimentation process
- When carbon dioxide dissolves in water it forms carbonic acid.
- Carbonic acid dissociates into hydrogen ions (source of elevated pH!), bicarbonate ions, and carbonate ions.
- Carbonate ions combine with calcium to form calcium carbonate.
- Calcium carbonate has low solubility and precipitates out of the water to form sediment — a long-term carbon store
The average ________________ of carbon in the atmosphere is only 5 years — contrasting 31 years for autotroph material.
residence time
The ________________ and ______________________________ makes atmospheric carbon dioxide levels sensitive to increased inputs from sources outside the normal cycle — ______________________
- short residence time
- relatively low level of atmospheric carbon
- like a river bursting its banks
changes in carbon dioxide, even the steady decline to present day levels, were coupled with ___________________________________
massive shifts on global land cover and weather patterns
Emerging consequences of elevated carbon dioxide in plants
- Elevated growth for some plants
- Reduced plant quality, even if abundance is greater
- Reduced growth or die-off
- Overall, shifts in community structure, including subsequent changes in competitive dynamics
Emerging consequences of elevated carbon dioxide - elevated growth for some plants
results in important changes in relative abundance of certain species
Emerging consequences of elevated carbon dioxide - reduced growth or die-off
it is due to complex interactions with related temperature increases, and nutrient and temperature availability
define the greenhouse effect
- Carbon dioxide absorbs infrared thermal radiation from the earth and re-radiates it
- More carbon dioxide = more re-radiation.
- A steady, recorded rise in annual temperature is tightly correlated with steady rise atmospheric carbon dioxide
food production can suffer large ______ with increasingly _________________ patterns
- loses
- unpredictable weather
__________ of relatively small change in global climate patterns can have severe impact on established _______________________.
- Speed
- expectations of human activity and especially food production
Why do we care about a 1ºC increase in temperature?
Small change in mean annual temperatures may hide increasingly erratic temperature patterns
why isn’t the term global warming accurate
it hides the far more significant issue of global climate change
what is more accurate than the term global warming
global climate crisis is more accurate and all-encompassing
While we wait for global governmental efforts, individual changes do make a difference, and ________________________
collective individual efforts change markets
