Fig. 8
Schematic example of the frost variables in a year over 10 years of inventory period. All variables were calculated with respect to an inventory period which refers time from to trial establishment till trial inventory at trial age of 10 years. Inventory period different in each trial because of their establishment dates. This is demonstrated as an example of a few late frost variables as given below. Late frost months = May and June. Early frost months = July to Sep. LF1 = Number of days with late frost events in the inventory period. There are 3 days with Tmin < 0 °C, so LF1 = 3. LF3 = Absolute minimum temperature of late frost events within the inventory period. 29 May has the lowest Tmin of − 4 °C, so LF3 = − 4 °C. LF4 = Mean temperature of the day on which the absolute minimum temperature (LF3) in the inventory period occurred. Tmean on 29 May is 1 °C, therefore LF4 = 1 °C. LF5 = Maximum number of late frost events within a single year of the inventory period, e.g., if two events occurred in 1966 (− 0.7, − 1.2) and one in 1969 (− 3.4) than LF5 = 2