Ecology Exam 4

What is the black box approach?

a way to measure the total activity of an ecosystem without having to measure all parts and exchanges within the ecosystem; puts a "box" around an ecosystem and measure what comes in and what comes out

What is mass balance?

uses all living and non-living objects in a specified space to follow the movement and fate of materials and estimate unknown fluxes by difference

How do we determine where we set the boundaries of a box?

you can set the boundaries to match the question of interest or find the places where fluxes are the easiest to measure

What do ecosystem scientists use to classify and compare ecosystems?

structure, function, control, and temporal dynamics

How do we determine if an ecosystem is a sink or a source of a given material?

by measuring the net flux of that material

What is the first law of thermodynamics?

matter and energy cannot be created or destroyed

T or F: There is a small atmospheric pool of nonreactive N

False, there is a large atmospheric pool of nonreactive N

What is nitrogen fixation?

converts atmospheric nitrogen (N2) to ammonium (NH4+)

What is nitrification?

converts ammonium (NH4+) to nitrate (NO3-)

What forms of nitrogen are most easily assimilated by plants?

ammonium (NH4+) and nitrate (NO3-)

What is mineralization?

organic N is converted to ammonium (NH4+)

What is denitrification?

converts nitrate (NO3-) to atmospheric nitrogen (N2) which is lost to the atmosphere

T or F: Humans have intensely manipulated the N cycle

True

What plants are really good at nitrogen fixing?

legumes and beans

What does lightning do in the nitrogen cycle?

fixes atmospheric nitrogen into ammonium (NH4+)

What carries out nitrogen cycling?

aerobic and anaerobic bacteria

What environment does nitrification occur under?

oxic conditions (oxygen present)

What environment does denitrification occur under?

anoxic conditions (no oxygen)

What environment does mineralization occur under?

oxic and anoxic conditions

What is the Haber-Bosch process?

uses high temperature and pressure to combine atmospheric N2 with H to produce NH3, which is a major component of fertilizers

How much global food production uses ammonia from the Haber-Bosch process?

about 2/3 of global food production uses ammonia from this, supporting almost half the world's population

What is Haber known for?

the Haber-Bosch process, "father of chemical warfare" for work developing and weaponizing chlorine and other gasses during WW1

What are nitrogen oxides (NOx)?

NO2, NO, and N2O

produced through combustion of fossil fuels, contributors to acid rain, smog, and affect tropospheric ozone (greenhouse gas)

How is nitrous oxide (N2O) created?

during denitrification

NO3 -> NO2 -> NO -> N2O -> N2

T or F: N2O is a much stronger greenhouse gas than CO2

True, N2O is 300x stronger than CO2

Where do the majority of nitrogen emissions come from?

fertilized soil and animal waste

What is the main difference between the nitrogen and phosphorous cycles?

there is no atmospheric pool in the phosphorous cycle

Where does phosphorus come from?

geological weathering of rocks

Why is phosphorus relatively scarce?

it has low solubility in water and is easily bound by sediments

What biological roles does phosphorus have?

major roles in metabolism; included in enzymes, DNA, RNA, etc.; key component of bones and teeth

What determines phosphorous content in soil?

soil age

What did Chadwicks study on rock-derived and atmosphere-derived elements show?

since phosphorous does not have an atmospheric source, it becomes the master regulator of biological activity in the oldest sites

When does dust from Central Asia become a dominant source of phosphorous?

on a million year scale

What did Yu et al.'s study show about phosphorus deposits?

dust from the Sahara dessert is deposited in the Amazon, allowing phosphorus from depleting in this area

What kind of soil do we see in the tropics?

old, highly-weathered, nutrient-poor soils

What kind of soil do we see in temperate regions?

younger, more nutrient-rich soils

Why is guano important in the phosphorus cycle?

guano is used as phosphorus fertilizer and is still harvested to this day

How have human activities influenced the phosphorous cycle?

human alterations have tripled the global P mobilization at land-water interfaces and increased P accumulation in soil

How do internal fluxes compare to external fluxes in the N and P cycles?

within the biosphere internal cycling fluxes are often much larger than external inputs and outputs

What are internal cycling fluxes?

plant uptake, litter fall, mineralization, etc.

What is the key input and output of the nitrogen cycle in unpolluted, unfertilized systems?

input: fixation of N2

output: denitrification, leaching of dissolved organic material and nitrate, erosion of organic matter

What is the key input and output of the phosphorous cycle in unpolluted, unfertilized systems?

input: rock weathering

output: erosion of organic matter

What is eutrophication?

excessive richness of nutrients in water, frequently due to runoff from the land, which causes a dense growth of plant life and death of animal life from lack of oxygen

What did Schindler's experiment on algal blooms show?

phosphorous, not nitrogen, is what causes eutrophication

What does Justus von Liebig's Law of Minimum say?

production is limited by the least abundant mineral

What are trace elements?

elements necessary for life in small amounts

Who showed that trace elements were limiting resources?

Kaspari

What is a pool?

a compartment with the capacity to hold matter

What are some examples of carbon pools?

soil carbon, leaf litter, wood biomass

What is stock?

the amount of matter in a pool

How is stock measured?

mass per area or mass per volume

What is flux?

flow of movement from one pool to another

What unit is flux measured in?

per time

What is the slow carbon cycle?

carbon stored in rocks, soil, ocean, and atmosphere takes 100-200 million years to cycle

How much moves through the slow carbon cycle per year?

10^13-10^14 grams (10-100 million metric tons)

How does tectonic activity affect the carbon cycle?

can release CO2 which is returned into the atmosphere through volcanoes

What happens when calcium ions mix with bicarbonate ions?

they make calcium carbonate which is made by shell-building organisms

What is the fast carbon cycle?

carbon circulating between life forms on earth

When do autographs and heterotrophs release carbon?

through respiration, decomposition, and combustion

When do plants and phytoplankton absorb carbon?

through photosynthesis

How much carbon moves through the fast carbon cycle per year?

10^15 to 10^17 grams (1,000 to 100,000 metric tons)

What is the gross primary production of the carbon cycle?

GPP= photosynthesis

What are the carbon fluxes from the ecosystem to the atmosphere?

autotrophic respiration (Ra) and heterotrophic respiration (Rh) add up to equal ecosystem respiration (Re)

Re= Ra + Rh

What is net primary production in the carbon cycle?

NPP= GPP - Ra

Net primary production = Gross primary production (photosynthesis) - autotrophic respiration

What is net ecosystem production in the carbon cycle?

NEP = GPP - Ra - Rh = GPP - Re

What is the net ecosystem carbon balance?

all fluxes in and out of the ecosystem

What does net primary production represent in the carbon cycle?

the rate at which biomass is produced

What did the study of atmospheric CO2 at Mauna Loa show?

carbon dioxide levels in the atmosphere are ultimately increasing but fluctuate slightly throughout the year

What greenhouse gas is more directly influenced by human activity?

carbon dioxide

What is the most important greenhouse gas?

water

What is the most potent greenhouse gas?

methane (CH4)

T or F: Carbon dioxide levels and temperature are positively correlated

true

T or F: the rate of warming is lower now than any time in the last thousand years

false, it is higher

T or F: Without the land and ocean sinks, carbon dioxide would be rising twice as fast

True

Why do the carbon land and ocean sinks exist?

in response to increases in atmospheric greenhouse gas concentrations

What percent of human CO2 emissions are left in the atmosphere, absorbed by the land, and absorbed by the oceans?

50 stays in atmosphere

25 in land

25 in oceans

How do we measure the global carbon land sink?

Atmospheric Increase = Emissions - Ocean Sink - Land Sink

What causes the global carbon land sink?

forest regrowth, CO2 fertilization, increased growing season length at high latitudes

How does CO2 fertilization affects the carbon land sink?

Elevated atmospheric CO2 causes plants to acquire more CO2 per unit of time while stomata are open, stomata can be closed more often too prevent water loss, higher rates of photosynthesis can occur

How are Amazon forests turning into carbon sources rather than sinks?

Loss of C through combustions during fires combined with deforestation

T or F: Soil carbon sticks are a big stock of C and a large potential sink

True

How could increasing temperatures affect soil carbon stocks?

could increase microbial respiration of the soil and net flux to the atmosphere

What did the Harvard soil warming experiment show?

there was a significant increase in respiration resulting in a 31% reduction of carbon storage

T or F: the ocean carbon sink is due to diffusion of CO2 down a concretion gradient

true, its caused by high levels ini the atmosphere diffusing down to low levels in the ocean

How does carbon diffusion lead to ocean acidification?

addition of CO2 leads to bicarbonate and free H+ ions

What happens to shells under low pH conditions?

they degrade

T or F: ALL groups are sensitive to ocean acidification

false, some groups are positively/negatively affected and some are not affected at all

T or F: Coral reefs are in decline

True

What is bottom up control?

the lower trophic level in the ecosystem affects the community structure of higher trophic levels by means of resource availability/restriction

What is top down control?

the higher trophic level influences the community structure of the lower tropic level through consumption

T or F: Class ecosystem ecology has a bottom-up view

True

What is the green world hypothesis?

plants don't go extinct because the presence of the top predator has a positive impact on the plant by controlling the populations of the herbivores