Lecture 9

• Connection between nuclear weapons and ecological research:
• Aspects of selected biogeochemical cycles

  • Carbon cycle
  • Nitrogen cycle
  • Phosphorus cycle
• Manhattan Project was the classic model for collaborative "Big Science," a model that ecologists tried to follow with limited success
• C, N, & P cycles

  • All tied to hydrologic cycle
  • Carbon cycle subsumes trophic webs
  • N and P are the two elements most likely to limit plant productivity
• Chemical elements aren't created or destroyed, but they do move around and change oxidation states, forming cycles
• Flux is basically from one pool in the ground to the air
• Radioactive tracers

  • Allowed following fates of chemicals in natural communities
• Effects of Radionuclide fallout on food chains

  1. Where the compounds go

  2. How they affect organisms
• Large organic molecules are constantly being synthesized, consumed, and broken down in the chemistry of the natural world
• The sequencing of the human genome is another example of the whole community and the government
• Phase change between ice water and gas is important in the cycles
• Stable, long-lived compounds like water and some pollutants can persist much as elements do, but phase changes may be important
• Human interventions in the C cycle include combustion of fossil fuels and land conversion
• Pinkish figures from Begon et al.

  • Solid black lines = strong natural fluxes
  • Solid red lines = strong human fluxes
  • Dashed black lines = weaker natural fluxes
• Roughly 1/3 of the world's forests have been lost, mostly in the recent century, primarily for agriculture
• The carbon cycle subsumes trophic webs
• There has been a long and steady rate of forest loss, with areas of revegetation
• Deforestation has accelerated in modern times, with poor soil for agriculture and logging of California redwoods
• More deforestation occurs in tropical environments compared to temperate regions, with some tropical clearing for subsistence agriculture involving burning and adding nitrogen and phosphorus to the soil
• Agricultural impacts on carbon include deforestation for hunting, agriculture, and waste removal
• All cycles are tied to the hydrologic cycle
• CO2 is the gaseous phase in the C cycle, with much carbon in organisms (food chains) and an inactive sedimentary pool of carbonates
• Nitrogen (N) and Phosphorus (P) are the two elements most likely to limit plant productivity
• Recovery in some places like Rhode Island contrasts with continued harvest in others like coniferous forests cut for paper pulp in Maine and the maritimes
• The interpretation of the lake core least likely to be true is that woodland species pollen is more common in ancient times
• Current deforestation is mostly in the tropics, with some tropical clearing for subsistence "slash and burn" agriculture
• Burn and then nitrogen and phosphorus added and it becomes arable for planting
• Oil palm plantation


  • Oil for food
  • Biodiesel
• Cattle uses the most land out of all the animals and especially Brazilian beef is the driver of tropical deforestation
• John Stinchcombe: 'More deforestation in the tropical environment and then temperate not so much deforestation anymore'
• Tropical forests have great pools of carbon and contain a lot of carbon in the soil and bound in organic matter and vegetation
• High energy society burned coal
• If the forest burns, the peat burns, too
• Current annual rates of CO2 release: Fossil fuel burning ~ 6 billion tonnes, Deforestation ~ 1.6 billion tonnes
• Lake Superior is superior for eutrophication
• Ecosystems being enriched with nitrate buildup in groundwater and eutrophication of coastal waters
• Human intervention in nitrogen cycle: Combustion of fuels, use of energy to make synthetic fertilizers
• Monoculture of oil palm is different and is pretty bad
• Industrial revolution

  Powered by fossil fuel combustion
• Some tropical clearing is subsistence “slash and burn” for garden plots