Lauren Yamane talked about Andersen et al. (2004) in our Ecological Stoichiometry course today. Here are her slides, and below, my rough notes on the paper:

Notes on the Paper

  • Stoichiometry is a way of representing food quality - there is evidence that consumers have preference for high quality (e.g., low C:N) food.
  • There is often a mismatch between composition of prey (autotrophs) and needs of consumers. Autotrophs have variable C:N ratios, consumers are more constrained.
    • This mismatch affects carbon transfer efficiency
  • Food quality can drive population fluctuations

Biological Basis

  • N and P driven by needs of protein and RNA
  • The growth rate hypothesis states that high P-content in organisms that are
  • Among plants there is much more flexibility, but also lower relative N and P requirements
  • Heterotrophs have CNP ratios an order of magnitude below autotrophs
  • Differences between autotrophs and heterotrophs are limiting but also drive nutrient cycling and release
  • Threshold element ratio (TER) is the critical ratio where limitation shifts from C/energy to another element. However above this, transfer efficiency decreases as consumers need to excrete extra nutrients.
  • Nutrient requirements vary throughout development. Some stages may be more limiting.

Density Dependence

  • Density dependence of food quality could be positive or negative
    • Grazing of plants may lead to density dependence via quality reduction due to either selective grazing of choice nutrients or induced plant defenses.
    • Alternatively, grazers can mobilize nutrients otherwise difficult for other organisms to acquire, speed up cycling due to lower plant biomass under same nutrient inputs
    • Chemostat experiments with Daphnia have confirmed the latter effect
  • In elaborations on L-V models1, including nutrient limitation bounds the possible regions of predator-prey phase space. The constraint stabilizes the system.
  • Nutrient limitation implies that growth is limited by populations of all species in the system
  • The effect of nutrient on dynamics is limited to nutrient-constrained systems.

Idea - stoichiometry is a great mechanism for looking at seasonal and transient effects


Andersen, T., J. J. Elser, and D. O. Hessen. 2004. Stoichiometry and population dynamics. Ecology Letters 7:884–900.

  1. Alan points out that Lotka himself actually talked quite a bit about stoichiometry.

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