Nutrient and energy cycling Flashcards
Ecosystem’s dynamics involve 2 main processes
- energy flow
- chemical cycling
- irregardless of ecosystem size
Laws of physices
- energy cannot be created or destroyed –>solar radiation is conserved and lost from organisms as heat
- every exchange of energy increases entropy of universe –> not completely efficient –> always some energy lost as heat
Law of conservation of mass
- matter can’t be created or destroyed
- chemicals are recycled
- ecosystem is an open system, absorbing energy and mass, and releasing heat and waste
What if nutrient’s outputs from ecosystem exceed its input?
that nutrient will limit production
2 types of biogeochemical cycles
- Perfect: fast, continuous cycling of nutrients. Involves vast, abiotic, atmospheric reservoir
- Imperfect: “lose” nutrients for a time because they are tied up in sediment or at the bottom of the ocean
Carbon Cycle
- not perfect or imperfect
- mostly photosynthesis and respiration
- needs to be dissolved in water
- sometimes tied up in unusable form
Nitrogen Cycle
-perfect cycle with big atmospheric pool
-only nitrogen fixers can use atmospheric nitrogen directly –> they turn it into ammonia for other organisms
-70% of atmosphere
-terrestrial cycling = 10x fixation
biggest pool of actively cycled N2 is in ocean
-pocket gophers bring N-poor soil to surface
-firetree in hawaii
-aquatic invertebrates recycle 15-70% of N into ammonia for plants
Phosphorus Cycle
- imperfect –> no atmospheric pool
- mostly in mineral deposits and MARINE SEDIMENTS
- slowly made available by weathering of rocks
- Release is episodic –> associated with spring snowmelt
Nutrient Spiraling
- in streams
- go downstream –> cycling doesn’t happen much in one place
- spiraling length is distance required for nutrient to complete cycle
Water cycle
- perfect cycle
- 70% oceans, 2% icecaps, 1% freshwater
- distribution is nonstatic –> relies on heat, evaporation, clouds, precipitation, consumption
transpiration
moves water into, through, and out of plants
evaporation
-surface water converts to gaseous phase
turnover time
- time required for entire body of water to be cycled
- oceans = 3100 yrs
- rivers 12-20 days
- atmosphere 9 days
nutrient pool
amount of nutrient in portion of ecosystem
nutrient sink
absorbed is greater than released
nutrient flux
movement of nutrient between pools
nutrient source
released is greater than absorbed
Photosynthesis equation
6H2O + 6CO2 + energy = C6H12O6 + 6O2
Chemosynthetic auxotrophs
bacteria on the sea floor near volcanic activity
-necessary parts of community
Net Primary Production
fixation of energy by auxotrophs in ecosystem over time (measured in biomass)
Where are the most productive places?
- tropical rainforests
- estuaries
- coral reefs
- marine ecosystems aren’t super productive, but contribute a lot because of large area
Gross Primary Production
conversion of energy (usually from light) to chemical energy of organic molecules per unit time
NPP = GPP - R (usually about 1/2 of GPP)
3 things that affect TERRESTRIAL NPP
moisture and temperature
- increases evapotraspiration
- increases PP
- soil fertility (N and P)
- especially N in dry alpine meadow
2 things that affect AQUATIC NPP
light and nutrients (more so than light)
- depth of light penetration
- N and P are often limiting nutrients
-P is positively associated with phytoplankton biomass
Eutrophication
- presence of excessive nutrients
- happens when too much phosphorus is added
- after fertilization stopped, phytoplankton went back to normal
secondary production
production of biomass by heterotrophic animals over time
detritivores / decomposers
- heterotrophs that get nutrients from dead shit
- usually prokaryotes and fungi
- affect all trophic levels
- rate of decomp is affected by temp, moisture, and chemical composition
Leave decomposition
- slower when more lignin
- faster when more nitrogen (like in streams)
Temperature and decomposition
high temp = high rate of decomp
Tropical rainforests and decomposition
- fast decomp – low soil nutrients
- most nutrients are tied up in trees
Anaerobic environments –> good or bad for decomp
bad
Litter
- high in tropical rainforests
- low in desert
- highest in high latitude boreal forests bc of slow decomp
- w/o decomp, chemicals couldn’t be recycled and GPP would go way down
Extreme pH and decomp
- bad
- Bogs accumulate peat bc acid
ultimate decomposers
- bacteria and fungi
- final degradation to CO2 and H2O
reducer-decomposers
all detritivores besides ultimate decomposers
plant material: microarthropods, nematodes, earthworms, milipedes, slugs
animal material: carion flies, beetles, crows, vultures
