BIOL-208 Lecture Notes - Lecture 16: Log-Normal Distribution, Community Structure, Community Association
17 Dec 2016
School
Department
Course
Professor
Community Structure and Function
- Introduction
- Community association of interacting species inhabiting some defined area
- Community structure
- Number of species
- Relative abundance
- Diversity indices
- Guild: group of organisms that makes their living in similar way
- Animal ecologists
- Comparing carnivores in one place versus carnivores in another
- Life - growth - form, functional - group
- Plant ecologists
- Manageable portion of community
- plants: taxa and life-forms
- Take one wetland type: tree rich fen
- Survey it for plant diversity and community attributes in 3 locations at the
landscape scale
- Test for differences by taxa and life-form
- Species Abundance
- Relative abundance: one of the most fundamental aspects of community
structure
- Dominance: one or a few species are substantially more abundant than other
species
- Biomass, area occupied, number of individuals, etc
- Regularities in abundance:
- Most species are moderately abundant
- Few are abundant or rare
- Lognormal Distribution
- Abundance is relative
- One species is two times more abundant as another
- Each interval twice the one preceding
- This is the log2 scale
- Taking large samples will show more of a lognormal distribution
- Sample sizes matter because rare orchids were found once although
approximately 300 sites were sampled. If there were fewer sample sites,
might not have found the rare orchids at all
- Why is it normal?
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Document Summary
Community association of interacting species inhabiting some defined area. Guild: group of organisms that makes their living in similar way. Comparing carnivores in one place versus carnivores in another. Life - growth - form, functional - group. Take one wetland type: tree rich fen. Survey it for plant diversity and community attributes in 3 locations at the landscape scale. Test for differences by taxa and life-form. Relative abundance: one of the most fundamental aspects of community structure. Dominance: one or a few species are substantially more abundant than other species. Biomass, area occupied, number of individuals, etc. One species is two times more abundant as another. Taking large samples will show more of a lognormal distribution. Sample sizes matter because rare orchids were found once although approximately 300 sites were sampled. If there were fewer sample sites, might not have found the rare orchids at all. May (1975): random environment variation have statistical artifact.
