Biodiversity and ecosystem functioning: A complex adaptive systems approach

Jon Norberg

2004

Introduction

Introduction

  • how species richness relates to trait distribution in communities in general?
  • what the processes relating regional to local species abundances are, and species area relationships?
  • how species sorting processes affect local trait distribution?
  • how trait distributions in the community relate to ecosystem functioning?

Complex adaptive systems

Complex adaptive systems

  • A complete picture (of ecosystems) MUST involve the environment affecting ecosystem functioning both directly (the individual species response to the environmental factor) and via changes in the trait distribution in the community

  • Species richness is more a result of the selection processes acting on traits tha a causal variable affecting ecosystem functioning

  • Given similar environmental constraints, similar emergent structures and patterns may develop, even though the components (the species) may differ

Complex adaptive systems

Complex adaptive systems components

  • Sustained diversity and individuality of components
  • Localized interactions among those components
  • An autonumous process that selects from among those components, based in the result of local interactions

Complex adaptive systems components

  • The net result is that the assemblage of species continously changes toward a dominance of those best suited to deal with the selective forces in the environment
  • Does not imply group selection or optimization at the ecosystem level, but rather focuses on the consequences of sorting processes
  • Similar structures and patterns arise on different parts of earth even though the components (species) are not the same
    • Traits

Traits

Traits

  • Two types:
    • Related to the range if substitutable resources
    • Related to efficency of uptake of essential resources
  • Species richness will not matter (for ecosystem functioning) unless species differ in their propierties (traits)

Trait tradeoffs

Trait tradeoffs

  • If a set of species compete, species with the most competitive set of traits will shape the average properties of the community due succesion
  • there are traits that are not relevant for the sorting process (but potentially colud be relevant for ecosystem functioning)

Modellation

Modellation

\(f_{Temp}(Z,T,w) = [1-\frac{(T-Z)^2}{w}]\cdot0.59 e^{0.0633T}\)

  • Z[°C] temperature where growth rate is equal to maximum determinated by the envelope

  • T[°C] environmental temperature

  • w[°C] width of the temperature response function

Modellation

\(f_{RU}(Z,Q) = r\cdot\frac{Q}{k(Z)+Q}-(bm + cZ)-d\)

  • If Q (resources) is constant

  • There is only one optimal trait, \(Z_{opt}\), for any value of the environmental constrain

\(\frac{dẐ}{dt} = f'V+\frac{M}{C_T}(Ẑ_M-Ẑ)\)

  • The rate at wich average trait in the community moves towards the optimal trait is proportional to trait variance

Modellation

\(f_{RU}(Z,Q) = r\cdot\frac{Q}{k(Z)+Q}-(bm + cZ)-d\)

  • If cZ (metabolic investment) is constant

Traits based models

  • Powerful concept: based on physical principles of conservation of mass and energy / Thermodynamics > - Any use of energy for some porpouse other than reproduction and growth WILL decrease the intrinsic growth rate of the species

  • Evolution

  • H’ vs average and the variance of traits

Conclusion

Conclusion

  • The effect of sorting proccesses driven by the environmental variable(s) represents the link between the environment and the trait distribution in the community

  • Species traits and trait diversity are of more importance than species numbers or taxonomic identity for ecosystem functioning

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