ricker: Ricker's Discrete Population Growth with Time-lag

In jarioksa/ecostudy: Ecology Teaching Package

Ricker's Discrete Population Growth with Time-lag

Description

Function finds a deterministic discrete population growth model (Ricker model) and draws population size against time and a phase diagram of population size and population increase side by side.

Usage

ricker(N, R, K, b)
## S3 method for class 'ricker'
plot(x, which = c(1, 2), ...)
## S3 method for class 'ricker'
traj(x, ...)

Arguments

N	Initial population size.
R	Population growth rate.
K	Carrying capacity.
b	Time lag parameter.
x	ricker result object.
which	Kind of graph displayed: which = 1 plots population size against time using plot.traj, and which = 2 displays the phase diagram with population trajectory.
...	Other parameters passed to graphical functions.

Details

The population size N at time t+1 is given as

N[t+1] = r*N[t]/(1+(a*N[t])^b),

where

a = ((R-1)^{1/b})/K.

The current formulation follows Begon et al. (1996, p. 240–242). Krebs (2009, p. 153) uses different parametrization and discusses the model under “time lag models”.

Value

Function returns the input model parameters, the calculated new parameter a and population sizes N at each step, and the function call.

Author(s)

Jari Oksanen

References

Begon, M., Harper, J.L. & Townsend, C.R. (1996) Ecology: Individuals, Populations and Communities. Blackwell. 3 ed., 1068 p.

Krebs, C. J. (2009) Ecology. Benjamin Cummings. 6 ed., 655 p.

Examples

par(mfrow=c(2,2))
mod1 <- ricker(10, 2, 50, 1)
mod4 <- ricker(10, 2, 50, 4)
mod1
mod4
plot(mod1)
plot(mod4)
par(mfrow=c(1,1))

jarioksa/ecostudy documentation built on June 27, 2022, 6:03 a.m.