rangr (version 1.0.6)

growth: Population Growth Functions

Description

Population growth functions are used during simulation conducted by the sim function. The user is required to specify the name of a growth function while initialising the sim_data object using initialise.

Usage

exponential(x, r, ...)
ricker(x, r, K, A = NA)
gompertz(x, r, K, A = NA)

Value

Object of the same dimensions as x that contains expected number of individuals in the next time step.

Arguments

x

number of individuals

r

intrinsic population growth rate

...

not used, added for compatibility reasons

K

carrying capacity

A

coefficient of Allee effect (A <= 0: weak, A > 0: strong, NA: none)

Details

x can be a vector, matrix, SpatRaster or any other R object for which basic arithmetic operations produce valid results. These functions are intended to be used in the sim function, where x is a matrix of the same dimensions as the SpatRaster object specified in n1_map parameter.

References

Boukal, D. S., & Berec, L. (2002). Single-species models of the Allee effect: extinction boundaries, sex ratios and mate encounters. Journal of Theoretical Biology, 218(3), 375-394. tools:::Rd_expr_doi("10.1006/jtbi.2002.3084")

Gompertz, B. (1825) On the Nature of the Function Expressive of the Law of Human Mortality, and on a New Mode of Determining the Value of Life Contigencies. Philosophical Transactions of the Royal Society of London, 115, 513-583. tools:::Rd_expr_doi("10.1098/rstl.1825.0026")

Ricker, W.E. (1954) Stock and Recruitment. Journal of the Fisheries Research Board of Canada, 11, 559-623. tools:::Rd_expr_doi("10.1139/f54-039")

Hostetler, J.A. and Chandler, R.B. (2015), Improved state-space models for inference about spatial and temporal variation in abundance from count data. Ecology, 96: 1713-1723. tools:::Rd_expr_doi("10.1890/14-1487.1")

Courchamp, F., L. Berec and J. Gascoigne. 2008. Allee Effects in Ecology and Conservation. Oxford University Press, New York. 256 pp. ISBN 978-0-19-857030-1

Examples

x <- 1:10
exponential(x, r = 0.4)

ricker(x, r = 2, K = 5)
ricker(x, r = 2, K = 5, A = -5)

gompertz(x, r = 1.2, K = 5)
gompertz(x, r = 1.2, K = 5, A = 5)