BIO220 Lecture 21 Flashcards
Biochemical cycles
Connection between nuclear weapons & ecological research
Cold War: Us vs. USSR
- use nuclear weapons
- radiation enter food chains -> affect crops, fish, livestock
Use radioactive tracers to see where chemicals go in natural communities
___ Project is the collaborative “big science” model that ecologists try to follow.
Manhattan
Manhattan Project
Group that produced atomic bombs
N cycle is a ___ cycle
gaseous
Human intervention in N cycle
N fertilizer, HB process, combustion of fuels
P cycle is a ___ cycle
sedimentary
human intervention in P cycle
- mining
- pollution
- fishing
- sewage & agriculture runoff
- erosion
HYDROLOGIC CYCLE
water cycle
hydrologic cycle ____ and ___
pools & fluxes if time permits
human intervention in hydrologic cycle
freshwater diversion (used in agriculture)
cycle for large organic molecules
synthesized, consumed, broken down
cycle for chemical elements
not synthesized, but instead move around and change oxidation states/compartments
cycle comprises of…
pools & fluxes
____ can persist as much as elements, but experience phase changes
stable, long-lived compounds (water, pollutants, etc.)
C, N, P cycles are all tied to ___ cycle
hydrologic
C cycle is tied with…
trophic webs
what are the 2 elements most likely to limit plant productivity?
N, P
limiting steps of C cycle
- creation by photosynthesis
- respiration/combustion of organic matter
human intervention in C cycle
combustion & extraction of fossil fuel, land conversion (deforestation)
why do humans deforest?
- easier for hunting
- land for agriculture
- remove agricultural waste
C sequestered in trees is released by…
fire
transient effect of burning cut trees
add NPK to soil: short-term enrichment of soil
Evidence that Neolithic humans cleared forests
pollen in lake sediments
in the past, most of the pollen was found in ___. now, mostly found in ___. This is because…
woodland species;
open-country species;
woodland cleared to grasslands
People always deforested. Why is it a problem now?
we have the technology & labour power to do it faster.
What is 1 place where forests were restored?
Eastern North America (Rhode Island)
- poor farm land
- Sugar maples grew back
____ forests were cut for paper pulp in Maine, maritimes
coniferous
current deforestation is mostly in the ___
tropics (South America)
slash and burn
involves the cutting and burning of trees and plants in forests or woodlands to create fields
- release N & microelements
reasons for clearing tropical forests
- slash & burn
- lumber, pulp, plantation clearning
oil palm plantation provides…
oil for food, biodiesel
Tropical forests contain great stores of…
Example?
carbon (~1000 tons/hectare in Indonesian Kalimantan swamp forest, including both alive & dead plants)
usually, tropical forests are too wet to burn, but ___ causes drying. Why?
Logging;
less cover, so sun & wind dry soil
Peat
- brown, soil-like material
- very smoky when burnt
Tropical forests are reservoirs for __ diversity
species
most recent example of tropical forest deforestation
Asian Fires (1997-1998): affected 5 million hectares
Effect of logging on C
- remove plants which can photosynthesize C out of atm
- dry out soil -> more easy to burn -> release stored C to atm
Industrial revolution was powered by…
fossil fuel combustion
Fossil fuel moves C from ___, burn it, and release…
stores (soil, bedrock, fossils);
CO2 & smoke into atm
Cars are very efficient at…
fossil fuel -> atm CO2
Human activities that release CO2 into atm
- Fossil fuel burning - 6 billion tons
2. Deforestation - 1.6 billion tons
Is N soluble?
Yes
There are ___ sedimentary pools for N
minimal
Limiting step of N cycle
convert atm N2 -> nitrate or ammonium
What usually converts atm N2?
- Legume: Rhizobium
- eubacteria
- cyanobacteria
- lightning
N fixation
reduce N2 -> NH3
Nitrification
NH4+ -> NO3- (nitrate)
Denitrification
NO3- -> N2
How do make N fertilizers?
fix N2 using electricity/natural gas
N cycle is ___, meaning it cycles very fast
atmospheric
Combustion of fuels releases which form of N into the atm?
NO2
Humans are accelerating the N cycle so much that…
combustion exceeds natural production rates
- in some areas, rainwater is dilute fertilizer
consequences of N found in rainwater
- remove limiting nutrient for plants
- reduce biodiversity
- some plants favoured (weeds)
- nitrate buildup in groundwater (hazard in agricultural areas)
- eutrophication of costal waters -> anoxia
P is mostly found in…
sedimentary pools (ocean sediments)
Limiting step in P cycle
- weathering of rocks in soil (mycorrhizae)
- geological uplift
mycorrhizae helps…
plants take up phosphorus from soil (makes it soluble)
P has no __ forms
gaseous
___ is sometimes an important input of P
atm dust from Saharan Africa
Phosphate
PO4^-3
is phosphate soluble?
technically yes, but bound by soil components
P is a ___ cycle, so it is slow
sedimentary
sources of P for humans
- mining
- guano
P is lost from terrestrial systems by…
- run-off
- erosion
- over-application of fertilizers
- eutrophication of rivers & lakes
Ends up back in marine sediments
Biggest P reserves
Morocco > USA > South Africa
Liquid peruvian guano has higher ___% than bat guano
P
What areas are best sources of guano? Why?
islands off the coast of Peru
- lots of seabirds, no predators
- fish best in areas with cold-water upwelling
- which brings P up to surface
- bird eat P-rich fish
- dry climate: P is not washed by rain back to ocean
