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