Material Cycles

• Specific supply of nutrients is required for optimal performance
• Plant uptake of nutrients starts the flow of elements through the ecosystem
• Materials are recycled
• Macronutrients are elements that make up the bulk of an organism: C, H, O, N, S, P
• Micronutrients are elements that form important components of molecules or enzymes: Ca, K, Mg, Na, Cl, Fe, Cu, Zn, I, Bo, Co, Mo, Mn, Se
• Essential nutrients are materials in the environment required for performance, such as mineral elements, CO2, H2O, O2
• Limiting nutrients are nutrients that, if supplied in greater amounts, cause the organism to perform better, often N and P
• Law of the Minimum states that the growth of a plant is limited by the element present in least supply
• Redfield Ratio states that organisms require specific balances or ratios of nutrients, e.g. 106C:16N:1P for phytoplankton
• Ratio in the environment against organism's ratio of nutrient requirement:

  • Ocean = 800C:16N:1P
  • Phytoplankton = 106C:16N:1P
• Differences in stoichiometric ratios among organisms relate to how each organism is built:

  • Organisms with lots of muscles, enzymes, skin have high N requirement
  • Organisms that are growing or reproducing, or with skeleton have high demand of P
  • Woody plants have high demand of C
• Greater the difference in C:N:P ratios between trophic levels, the fewer individuals in higher trophic levels
• Nutrients are stored in organic and inorganic "reservoirs" in the ecosystem:

  • Organic materials available as nutrients (organisms, detritus)
  • Organic materials unavailable as nutrients (coal, oil, peat)
  • Inorganic materials available as nutrients (atmosphere, soil, H2O)
  • Inorganic materials unavailable as nutrients (minerals in rocks)
• Factors affecting nutrient availability:

  • Weathering of rocks
  • Plant uptake (immobilization)
  • Decomposition (mineralization)
  • Soil acidity
  • Quality of plants
• Decomposition is the breakdown of chemical bonds formed during the construction of plant or animal tissues, leading to the release of energy, carbon dioxide, water, and conversion of organic compounds into inorganic nutrients
• Processes involved in decomposition:

  • Decomposition
  • Leaching
  • Ingestion
  • Excretion of waste
  • Fragmentation
• Factors affecting decomposition:

  • Quality of plant litter as substrate for microorganisms
  • Type and quantity of carbon compounds present
  • Soil properties
  • pH
  • Texture
  • Climate
  • Temperature
  • Precipitation
• If element ratio of food ≠ organism's element ratio  nutrient deficiency  limited performance