BISC 121 - Ecosystem Ecology - Midterm 4

What do nutrient circuits in ecosystems involve?

Biotic and abiotic components.

What are nutrient circuits often called?

Biogeochemical cycles.

What elements cycle globally?

Gaseous carbon, oxygen, sulfur, and nitrogen.

What elements cycle more locally?

Less mobile elements such as phosphorus, potassium, and calcium.

What does a model of nutrient cycling include?

Main reservoirs of elements and processes that transfer elements between reservoirs.

What do all elements cycle between?

Organic and inorganic reservoirs.

What four factors do ecologists focus on when studying cycling of water, carbon, nitrogen, and phosphorus?

Each chemical’s biological importance.

What is the second factor ecologists focus on?

Forms in which each chemical is available or used by organisms.

What is the third factor ecologists focus on?

Major reservoirs for each chemical.

What is the fourth factor ecologists focus on?

Key processes driving movement of each chemical through its cycle.

What is water essential to?

All organisms.

Where is 97% of the biosphere’s water contained?

The oceans.

Where is 2% of Earth’s water found?

Glaciers and polar ice caps.

Where is 1% of Earth’s water found?

Lakes, rivers, and groundwater.

By what processes does water move?

Evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater.

What are carbon-based organic molecules essential to?

All organisms.

What are major carbon reservoirs?

Fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, and the atmosphere.

How is CO₂ taken up and released?

Through photosynthesis and respiration.

What human activities contribute CO₂ to the atmosphere?

Burning of fossil fuels and deforestation.

What is nitrogen a component of?

Amino acids, proteins, and nucleic acids.

What is the main reservoir of nitrogen?

The atmosphere (N₂).

In what forms must atmospheric nitrogen be converted for uptake by plants?

NH₄⁺ or NO₃⁻.

What process converts N₂ to usable nitrogen forms?

Nitrogen fixation by bacteria.

What happens to organic nitrogen during decomposition?

It is converted to NH₄⁺ by ammonification (by heterotrophs).

What process converts NH₄⁺ to NO₃⁻?

Nitrification (by autotrophs).

What process converts NO₃⁻ back to N₂?

Denitrification.

How do denitrifying organisms use NO₃⁻?

As an electron acceptor the way we use oxygen.

What has greatly changed global nitrogen supply?

Huge input from industrial production of fertilizers.

What reactive nitrogen gases are important for atmospheric chemistry and greenhouse effects?

NO and N₂O.

What important nitrogen process is missing from the text?

Anammox (anaerobic oxidation of NH₄⁺ with NO₂⁻ to make N₂ gas).

What is phosphorus a major constituent of?

Nucleic acids, phospholipids, and ATP.

What is the most important inorganic form of phosphorus?

Phosphate (PO₄³⁻).

What are the largest reservoirs of phosphorus?

Sedimentary rocks of marine origin, the oceans, and organisms.

What does phosphate bind with?

Soil particles.

What is the effect of phosphate binding to soil particles?

Movement is often localized.

What role do decomposers play in ecosystems?

They play a key role in the general pattern of chemical cycling.

What varies greatly among ecosystems in relation to nutrient cycling?

Rates at which nutrients cycle.

What mostly causes variation in nutrient cycling rates across ecosystems?

Differing rates of decomposition.

What controls the rate of decomposition?

Temperature, moisture, and nutrient availability.

What is the result of rapid decomposition?

Relatively low levels of nutrients in the soil.

What strongly regulates nutrient cycling?

Vegetation.

What do research projects monitor over long periods?

Ecosystem dynamics.

What site has been used to study nutrient cycling since 1963?

The Hubbard Brook Experimental Forest.

What did researchers construct at Hubbard Brook to monitor losses?

A dam to monitor loss of water and minerals.

What was done to trees in one of the valleys in an experiment?

The trees were cut down.

What was the valley sprayed with after trees were cut?

Herbicides.

What was found when nitrogen and water losses were studied in the deforested area?

They were greater than in an undisturbed area.

What did these results show?

How human activity can affect ecosystems.

What can biological communities do given enough time?

Recover from many types of disturbances.

What does restoration ecology seek to do?

Initiate or speed up the recovery of degraded ecosystems.

What basic assumption does restoration ecology make?

Most environmental damage is reversible.

What are the two key strategies of restoration ecology?

Bioremediation and augmentation of ecosystem processes.

What is bioremediation?

The use of living organisms to detoxify ecosystems.

What organisms are most often used in bioremediation?

Prokaryotes, fungi, or plants.

What can bioremediation organisms do to toxic molecules?

Take up and sometimes metabolize them.

What encourages growth and desirable outcomes in bioremediation?

Selectively “fertilizing” the right kind of naturally-occurring organisms.

What is biological augmentation?

Using organisms to add essential materials to a degraded ecosystem.

What is an example of biological augmentation?

Nitrogen-fixing plants increasing the available nitrogen in soil.

What must ecologists consider in restoration ecology?

Alternative solutions.

What must ecologists adjust in restoration ecology?

Approaches based on experience.

What does the gravel and clay mine in New Jersey show in 1991?

A degraded ecosystem before restoration.

What does the gravel and clay mine in New Jersey show in 2000?

Near the completion of restoration.

What does the Oak Ridge National Laboratory example show?

Unlined pits filled with wastes containing uranium leaking to groundwater.

What happened after adding ethanol to the uranium-contaminated site?

The concentration of soluble uranium decreased over days.

What does biological augmentation use?

Organisms to add essential materials to a degraded ecosystem.

What example is given of biological augmentation?

Nitrogen-fixing plants increasing the available nitrogen in soil.

What does the Truckee River, Nevada example show?

Controlled release of water from a dam.

What does the Kissimmee River, Florida example show?

A restored meandering river that had once been redirected to a straight canal.

What does the tropical dry forest in Costa Rica example show?

Land that had been converted to agriculture.

What does the Rhine River, Europe example show?

A river that was over-dredged and straightened.

What does the Succulent Karoo, South Africa example show?

Land that was overgrazed.

What does the Maungatautari, New Zealand example show?

Invasive species kept out.

What does the coastal Japan example show?

Degraded seaweed beds restored.

What does the Strassburg et al. 2020 estimate show?

Restoring 15% of converted lands in priority areas could avoid 60% of expected extinctions while sequestering 299 gigatonnes of CO₂.