Competition for resources Z506

Model name

Competition for resources

Original author(s)

Hartmut Bossel

References and/or links for original model

Format of original model

Vensim

Converted by

Madara Gaile

Date submitted

20/04/2012

Purpose

This model allows the user to examine under what conditions of competition is permanent coexistence of competitors possible, even if some are at a distinct disadvantage.

Description

The competition between population A and population B (state variables) is considered to be for the same resource (for example, a source of food which both need for their survival).

Both populations grow in proportion to their current level with corresponding (specific) growth rate A and growth rate B. Corresponding to conditions usually prevailing, logistic growth is assumed for both populations, with capacity limits carrying capacity for A and carrying capacity for B. It is assumed that the competition effect (competition) is proportional to both population A and population B. Competition causes losses of A by competition and losses of B by competition corresponding to competition effect on A and competition effect on B. In some competitive situations, for example competition for the same food source, an additive combination (c*A + d*B) is appropriate, where c and d are the specific food uptake rates of A and B.

Model size indicators

Stocks and flows

Simile diagram

Simile equations

Parameters and initial states

initial population A = 0.02 [amount A]

initial population B = 0.02 [amount B]

growth rate A = 1 [1/Month]

growth rate B = 0.99 [1/Month]

carrying capacity for A = 2 [amount A]

carrying capacity for B = 2 [amount B]

competition effect on A = 1 [1/(amount B*Month)]

competition effect on B = 1 [1/(amount A*Month)]

Dynamics

competition = population B * population A [amount A * amount B]

growth of A = growth rate A * population A * (1 - population A/carrying capacity for A) [amount A/Month]

losses of A by competition = competition effect on A * competition [amount A/Month]

population A = INTEG (+growth of A - losses of A by competition, initial population A) [amount A]

growth of B = growth rate B * population B * (1 - population B/carrying capacity for B) [amount B/Month]

losses of B by competition = competition effect on B * competition [amount B/Month]

population B = INTEG (+growth of B - losses of B by competition, initial population B) [amount B]

Files

The model and associated files are listed at the bottom of this page.

Notes on the conversion process

Extra information on original model