GRPsi_models function

Hydro-time models based on the germination rate

These models describe the response of germination rate to water potential in the substrate.

GRPsiLin()
GRPsiPol()
GRPsiPol2()
GRPsi.Lin()
GRPsi.Pol()
GRPsi.Pol2()
GRPsiLin.fun(Psi, Psib, thetaH)
GRPsiPol.fun(Psi, Psib, thetaH)
GRPsiPol2.fun(Psi, Psib, thetaH)

Arguments

The functions 'GRPsiLin()', 'GRPsiPol()', 'GRPsiPol2()', GRPsi.Lin(), GRPsi.Pol(), GRPsi.Pol2() have no arguments. The functions 'GRPsiLin.fun()', 'GRPsiPol.fun()' and 'GRPsiPol2.fun()' have the following arguments:

• Psi: Water potential in the substrate
• Psib: Base water potential within the population
• thetaH: Hydro-time parameter

Details

The functions 'GRPsiLin()', 'GRPsiPol()', 'GRPsiPol2()', GRPsi.Lin(), GRPsi.Pol(), GRPsi.Pol2() are meant to be used with the 'drm()' function in the 'drc' package ('GRPsiLin()' and 'GRPsi.Lin()', 'GRPsiPol()' and 'GRPsi.Pol()', 'GRPsiPol2()' and 'GRPsiPol2()' are totally equivalent, apart from the names). The functions 'GRPsiLin.fun()', 'GRPsiPol.fun()' and 'GRPsiPol2.fun()' are used for general purposes (plotting and other uses). Details about these functions and the meaning of parameters are described in Bradford (2002) and in the package ducumentation (see references below).

Returns

The 'GRPsiLin.fun()', 'GRPsiPol.fun()' and 'GRPsiPol2.fun()' functions return the germination rate for any given values of water potential in the substrate. The 'GRPsiLin()', 'GRPsiPol()' and 'GRPsiPol2()' (and 'GRPsi.Lin()', 'GRPsi.Pol()' and 'GRPsi.Pol2()') functions return a list containing the nonlinear function, the self starter function, the parameter names and other items which are internally used by the 'drc()' function.

References

See package documentation at: https://www.statforbiology.com/_seedtutorial/

Author(s)

Andrea Onofri

Examples

library(drcte)
# Observed data
Psi <- c(-2, -1.5, -1.2, -1, -0.8, -0.6, -0.4, -0.25,
         -0.12, -0.06, -0.03, 0)
GR <- c(0, 0, 0, 0, 0.0585, 0.094, 0.1231, 0.1351,
        0.1418, 0.1453, 0.1458, 0.1459)
Psi2 <- c(-0.5, -0.6, -0.7, -0.8, -0.9, -1, -1.1, -1.2,
          -1.5)
GR2 <- c(1.4018, 1.0071, 0.5614, 0.3546, 0.2293, 0, 0,
         0, 0)

# Model fitting
modHT1 <- drm(GR ~ Psi, fct = GRPsiLin())
modHT2 <- drm(GR ~ Psi, fct = GRPsiPol())
modHT3 <- drm(GR2 ~ Psi2, fct = GRPsiPol2())

summary(modHT1)
summary(modHT2)
summary(modHT2)