fruclimadapt (version 0.4.5)

chill_portions: Calculation of chill portions from hourly temperature data (Dynamic model)

Description

The function calculates chill portions according to the Dynamic model proposed by Fishman et al. (1987a,b), using the formulas extracted by Luedeling et al (2009) from functions produced by Erez and Fishman (1990), available at the University of California, Agriculture and Natural Resources (UC ANR) website http://ucanr.edu/sites/fruittree/files/49319.xls. To date, chill portions is the best existing model for most growing regions, so chill fulfilment should be calculated preferably using this method, especially when transferring varieties from one region to another, or in studies on climate change.

Usage

chill_portions(climdata, Start)

Value

dataframe with the chill accumulated for all the seasons in the dataset. Seasons begin at the start date and end the day before the start date of the following year. It contains the columns Year, Month, Day, DOY, Chill

Arguments

climdata

a dataframe with hourly temperature data. It must contain the columns Year, Month, Day, DOY, Temp.

Start

parameter indicating the day of the year when chill accumulation is supposed to start.

Author

Carlos Miranda,

References

Erez A, Fishman S, Linsley-Noakes GC and Allan P, 1990. The dynamic model for rest completion in peach buds. Acta Horticulturae 276, 165-174.

Fishman S, Erez A and Couvillon GA, 1987a. The temperature dependence of dormancy breaking in plants - computer simulation of processes studied under controlled temperatures. Journal of Theoretical Biology 126, 309-321.

Fishman S, Erez A and Couvillon GA, 1987b. The temperature dependence of dormancy breaking in plants - mathematical analysis of a two-step model involving a cooperative transition. Journal of Theoretical Biology 124, 473-483.

Luedeling E, Zhang M, Luedeling V and Girvetz EH, 2009. Sensitivity of winter chill models for fruit and nut trees to climatic changes expected in California's Central Valley. Agriculture, Ecosystems and Environment 133, 23-31.

Examples

# Generate hourly temperatures
library(magrittr)
library(dplyr)
library(lubridate)
Weather <- Tudela_DW %>%
   filter (Tudela_DW$Year<=2002)
Tudela_HT <- hourly_temps(Weather,42.13132)
# Calculate chill as chill portions, starting on DOY 305
Chill_p <- chill_portions(Tudela_HT,305)