Social:Hassell model

Short description: Framework in population ecology

Template:Only primary sources The Hassell model (or Hassell equation) is a classic discrete-time population model which gives the estimates for a single species the number of individuals in the population in a given discrete time step as a function of the number of individuals in the preceding time step. It is a generalization of the Beverton-Holt model and historically descends from the Ricker model.

$N_{t+1}=\frac{R_0{N}_t}{(1+a{N}_t{)}^b}.$

The equation was written by Michael Hassell in 1975. Here $R_0$ is to be understood as the competition-free growth rate, $b$ as a value that parameterizes the kind of competition ranging from scramble competition to contest competition, and while $a$ lacks a clear and distinct biological meaning, simple algebra reveals that if $b=1$, then $a=1/K$, where $K$ denotes the long-run carrying capacity.