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Understanding Matter Flows in Ecosystems

Feb 24, 2025

Lecture Notes: Flows of Matter in Ecosystems

Overview

  • Main Topic: IBESS Topic 2, Ecosystems and Ecology
  • Subtopic: 2.3 Part 2, Flows of Matter (Part 1 covers Flows of Energy)
  • Significant Idea: Ecosystems are linked by energy and matter flows.

Matter Flow in Ecosystems

  • Includes nutrients and approximately 40 elements that cycle through ecosystems (some in trace amounts).
  • Key Elements: Oxygen, carbon dioxide, water.
  • Difference from Energy Flow:
    • Energy flows one-way (solar radiation to heat via respiration).
    • Matter cycles and is absorbed, circulated, and released back (biogeochemical cycles).
    • Matter identified as inputs and outputs in organisms; changes form but doesn't degrade.

Carbon Cycle

  • Storages (Sinks):
    • Organic: Land/water organisms, plants, forests, fossilized life forms, fossil fuels.
    • Inorganic: Fossil fuels replaced by inorganic molecules, sedimentary rocks, oceans (dissolved or carbonates).
  • Flows:
    • Carbon fixation during photosynthesis.
    • Release via respiration and combustion.
    • Human impacts: Fossil fuel burning, cement making, deforestation increasing atmospheric CO2.
    • Offsets by photosynthesis and ocean absorption, but net increase in atmospheric CO2.
  • Human Impact:
    • Changes in land use and burning fossil fuels increase atmospheric carbon.
    • Positive feedback mechanism exacerbated by decreased plant and forest biota.

Nitrogen Cycle

  • Importance: Essential for proteins, DNA, regulates primary productivity and species diversity.
  • Sinks: Organisms, soil, fossil fuels, atmosphere, water.
  • Flows and Processes:
    • Nitrogen Fixation: Biological (bacteria in soil/root nodules, cyanobacteria), lightning/volcanic activity, Haber process.
    • Nitrification: Conversion of ammonia to nitrite and then to nitrate by bacteria.
    • Assimilation: Incorporation into complex molecules (amino acids, proteins, DNA).
    • Ammonification: Decomposition releases ammonia/ammonium ions.
    • Denitrification: Conversion back to nitrogen gas.
  • Human Impact:
    • Burning fossil fuels, fertilizer application increasing nitrogen availability.
    • Disruption leads to eutrophication, forest health changes, biodiversity loss, and carbon storage changes.

Human Impact on Biogeochemical Cycles

  • Local and Global: Human activities alter flows of carbon and nitrogen cycles.
  • Agriculture: Use of fertilizers and leguminous crops alter nitrogen availability.
  • Eutrophication: Excess nitrogen leaches into water bodies causing oxygen depletion and biodiversity changes.

Role of Sun’s Energy

  • Drives photosynthesis, which influences both carbon and nitrogen cycles.
  • Photosynthesis affects plant growth, health, and capacity to incorporate nitrogen.
  • Oxygen produced is crucial for aerobic nitrifying bacteria.

Conclusion

  • Summary Points: Understanding of flows of matter and energy in ecosystems, human impacts, and the biogeochemical cycles.
  • Additional Resources: IBESS textbook, online resources like Cognity.
  • Presented by: Dr. Nina Markham, images via Creative Commons unless noted otherwise.

Note: This lecture is a continuation of Part 1 that covered Flows of Energy.

Full transcript