fruclimadapt (version 0.4.5)

GDH_asymcur: Calculates growing degree hours (GDH) using ASYMCUR method

Description

The function calculates the daily heat unit accumulation (GDH) from hourly temperature data, using the ASYMCUR model proposed by Anderson et al (1986). The model is a refinement of the linear model proposed by Anderson and Seeley (1992) defined by a base, optimum and critical temperature. Heat accumulation begins when temperatures are above a minimum (base temperature, Tb), and growth increases with temperature up to a point (optimum temperature, Topt) at which there is no longer an increase. The critical temperature (Tcrit) is the temperature above which growth ceases. The difference of ASYMCUR model with the linear by Anderson and Seeley (1992)is that the former uses an asymmetric curvilinear relationship to model GDH accumulation. The function allows the user to define Tb, Topt and Tcrit, and uses as default the values set by Anderson et al (1986) for fruit trees: Tb=4ºC, Topt=25ºC and Tcrit=36ºC.

Usage

GDH_asymcur(Hourdata, Tb = 4, Topt = 25, Tcrit = 36)

Value

dataframe with daily data. It contains the columns Date, Year, Month, Day, DOY (day of the year), and GDH

Arguments

Hourdata

a dataframe of hourly temperatures. This data frame must have a column for Year, Month, Day, DOY (day of year), Hour, Temp (hourly temperature).

Tb

the base temperatures to calculate GDH

Topt

the optimal temperatures to calculate GDH

Tcrit

the critical temperature

Author

Carlos Miranda,

References

Anderson JL, Richardson EA and Kesner CD, 1986. Validation of chill unit and flower bud phenology models for 'Montmorency' sour cherry. Acta Horticulturae 184, 71-75. Anderson JL and Seeley SD, 1992. Modelling strategy in pomology: Development of the Utah models. Acta Horticulturae 313, 297-306.

Examples

# Generate hourly temperatures for the example dataset
library(magrittr)
library(dplyr)
library(lubridate)
Weather <- Tudela_DW %>%
   filter (Tudela_DW$Year==2003)
Tudela_HT <- hourly_temps(Weather,42.13132)
# Calculate GDH using default threshold temperatures
GDH_default <- GDH_asymcur(Tudela_HT)
# Calculate GDH using as custom set temperature thresholds
# Tb=4.5, Topt=22 and Tcrit=32
GDH_custom <- GDH_asymcur(Tudela_HT, 4.5, 22, 32)