Rescales an ecological gradient to a constant rate of change of community composition.

Description

Function gradscale tries to scale an ecological gradient to a constant rate of compositional change. Usually this is not strictly possible.

Usage

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gradscale(resp, grad, ...)

Arguments

resp

A data frame of fitted species response models.

grad

The gradient used for responses resp.

...

Other parameters.

Details

Function gradscale tries to rescale an ecological gradient to the constant rate of compositional change as measured by betadiversity. Usually this is not strictly possible, because the responses fitted after rescaling indicate local aberrations, although the average change is close to constant.

The function gradscale makes the distance of ordered gradient points equal to sum of change in species abundance. In most cases, this is equal to change in fitted values, but if the species has its optimum between the gradient values, gradscale will estimate the accumulated change through that optimum point.

Value

The function returns the rescaled gradient at the point given by grad.

Author(s)

Jari Oksanen.

References

Oksanen, J. & Tonteri, T. (1995). Rate of compositional turnover along gradients and total gradient length. Journal of Vegetation Science 6, 815-824.

See Also

betadiversity.

Examples

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data(mtf01)
data(mtf.alt)
attach(mtf.alt)
mod <- HOF(mtf01, Altitude, M=1)
beta <- betadiversity(mod, Altitude)
plot(beta)
Alt.s <- gradscale(mod, Altitude, M=1)
mod.s <- HOF(mtf01, Alt.s, M=1)
plot(betadiversity(mod.s, Alt.s))