No-interaction model

To produce a humped-back response [Fig: jpeg, 89K] in species richness against biomass, you need only three assumptions:

  1. Plants have a fixed minimum size, and in non-crowded plots biomass is determined by the number of plants.
  2. When the plot is crowded, biomass is higher if plants are bigger, so that there are fewer plants in a fixed area.
  3. The number of plants has an increasing monotonic relation to the number of species.

This model means that the number of plants will vary with the biomass in sample quadrats of equal physical size. This variation in number of plants will cause variation through species-area relation [Fig: jpeg, 9K].

Maximum number of plants and maximum species richness is achieved at the crowding biomass, and both the plant number and species number decrease in lower and higher biomass, because

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Updated 29/4/97