Lec 27 (Nutrient cycle part 2) Flashcards
Nutrients and Organisms… talk about them.
Organisms can modify the distribution and
cycling of nutrients in ecosystems.
Although same ecological processes occur in
terrestrial and aquatic habitats, there are
consistent differences
Aquatics vs Terrestrial when it comes to organisms and nutrients
Aquatic systems tend to have greater proportion
of autotrophs consumed by herbivores compared
to terrestrial system, where autotrophs consumed
by detritivores
Even if aquatic and terrestrial NPP are the same…?
Aquatic tends to have…
lower autotroph biomass
more herbivore and herbivory
Fewer detritivores, detritus, and decomposers
than terrestrial systems
Aquatic life has less autotroph biomass (less detritus) and more herbivore (less detritus) which results in?
Overall quicker cycling of nutrients
Terrestrial life has more autotroph biomass (More detritus) and fewer herbivores (More detritus)
Overall slower cycling of nutrients
Streams and vertebrate move nutrients across systems are examples of?
Aquatic nutrient cycling
Water in streams
moves…..
As a result, nutrient cycling doesn’t occur in
a single stationary location, leading to nutrient spiraling
Spiraling Length?
Nutrient Retentiveness?
The length of stream required for
an atom of a nutrient to complete a cycle from
release into the water column to re-entry into the
benthic environment
The inverse of spiraling
length, or the tendency of a stream to retain
nutrients.
Longer spiraling length?
Short spiraling length?
Longer spiraling length = low nutrient retentiveness
Short spiraling length = high nutrient retentiveness
Where spiralling lengths are short, a particular nutrient atom may be used only once before it is washed out of a stream system.
True or False
False… a particular nutrient atom may be used MANY times before it is washed out of a stream system.
If there is a photo of a lake or stream with red and purple lines… What does the red line indicate? What about the purple line?
Red = short spiraling length, long nutrient retentiveness (nutrients stay close to where they started)
Purple = long spiraling length, short nutrient retentiveness (nutrients moved further from where they started)
How does nutrient cycling work in streams?
Nutrients move up the food web, then down as organisms decompose, all the while being pushed forever downstream!
_______ only contain 10% of the retained aquatic nitrogen but consumes a large
proportion of available nitrogen.
Macroinvertebrates
-What all contributes to nitrogen retention in creeks and streams?
Increase in biomass combined with rapid flux of nitrogen between consumers and primary producers contribute to nitrogen retention.
High abundances of macroinvertebrates can?
speed up the nutrient cycling in streams
Faster nutrient cycling = Greater primary production
Nutrient Cycling in Aquatic Ecosystems:
Vertebrate move nutrients across systems… What’s an example?
- Salmon migration from ocean → freshwater to spawn
- Transfer huge amounts of
nutrients (e.g. nitrogen) from the
ocean to forest ecosystems
Nutrient Cycling in Terrestrial Ecosystems:
Grasslands… What’s an example?
Pocket Gophers can…
• Increased light penetration to high nitrogen soil
• Bring up nitrogen rich soil to the
surface, where soil is usually poor in nitrogen
Why are grasses growing on prairie dog colonies containing more nitrogen?
Gophers burrow/build mounds which increase heterogeneity in soil nitrogen and light penetration.
What effect do large grazers have on nutrient availability in terrestrial ecosystems?
- Large grazers, like deer, may increase primary productivity of ecosystem through increased rates of nutrient cycling.
- On top of this nutrient cycling shift, heavy grazing shifts composition of plants (east more palatable species, leaving behind seedlings of less palatable species!)
Without large grazers…?
nutrient cycling occurs more slowly
(by decomposition and feeding of
small grazers)
How have humans messed up the nitrogen cycle?
We have converted massive amounts of nitrogen from
the atmosphere reservoir to terrestrial reservoirs through the use of fertilizers.
Haber Process?
artificial nitrogen fixation. Combines N gas and H gas using a metal catalyst under high heat and pressure to form NH3
Nitrogen fixation by humans has now exceeded non-human nitrogen fixation.
True or False
True
-What are some consequences for the effect of human on the nitrogen cycle? (too much nitrogen)
Acid rain (NOx)
Methemoglobinemia (“Blue baby syndrome”)
Shift from grasslands to forests
-What is Acid rain (NOx) and Methemoglobinemia (“Blue baby syndrome”)?
Acid rain (NOx): Nitrogen oxides, produced by internal combustion engines, when combined with water vapor form acid (= why cars have catalytic converters)
Methemoglobinemia (“Blue baby syndrome”): nitrates in drinking water (usually from agricultural runoff) can cause hemoglobin in blood to oxidize, reducing its capacity to carry O2
-Why is there a shift from grasslands to forests?
• Increases in nitrogen (from both combustion engines and agriculture runoff) allows trees to competitively exclude many grasses
• Increased N deposition across the prairies is causing
expansion of forests into areas historically covered by prairie habitats.
History of atmospheric composition of CO2 has been
recreated by studying?
studying air bubbles that get trapped in ice. Ice cores allows estimates going back 160,000 years.
-When we see population size increase we usually see?
-Forest areas increase due to nitrogen increase (grasslands was an exception… might be due to a limited effect by humans)
-What were the findings from air bubbles
in Vostok ice core?
CO2 oscillated between 190 – 280
ppm (parts per million) over past 160,000 years.
Temperature has change has directly mirrored CO2 change.
True or False
True
-What trends/patterns have we seen human impact have on the carbon cycle?
Atmospheric CO2 Over The Past 1,000 years shows rapid increase in starting in 1800s (Industrial revolution)
Atmospheric CO2 concentrations were 413 ppm in April 2019 – an unprecedented 100 ppm increase.
*300ppm highest CO2 level ever recorded in previous 160,000 yrs
-How are humans causing this effect on the carbon cycle?
Industrial activities…
Human industrial activities center on burning fossil fuels
→ combustion reaction that releases CO2
What are some past interruptions of global economic activity (and fossil fuel burning) related deviations fromCO2
increase.
WW1 and WW2
Great depression
Corona Virus most likely
What are the three human Influence on Carbon Cycles
Takeaways…
- CO2 in the atmosphere has varied widely during the last 160,000 years and closely parallels global temperature. High CO2 → high temperatures.
- Atmospheric CO2 has increased substantially in the past two centuries, exceeding all levels reached during the past 160,000 years.
- Present levels of CO2 in the atmosphere are strongly
influenced by the burning of fossil fuels (i.e. activities of us humans).
How does deforestation affect nitrogen levels?
Clear cutting causes more nitrogen to be tied up in the soil. (Soil erosion)
What is a way to combat forest cutting such as forest fires or logging?
Work by Turner and colleagues (2003) has shown that young, rapidly growing understory vegetation can act as a NUTRIENT SINK after a disturbance such as
logging or forest fire.
How does flooding effect nutrient cycles?
-This effects Phosphorus Movement
• Inputs (inputting phosphorus into the stream)
– Geological (weathering of rocks causes the release of phosphorous into the water)
– Meteorological (precipitation into the stream)
• Exports (export of phosphorus out of the stream)
– Geological (phosphorous dissolved into the stream)
-When is most phosphorus lost? Gained?
Lost: During storms and spring (melting of snow)
Gain: During fall/autumn when leaves are falling
