Equations of the phenology models compared in the present study.

y: date of leafing; xt: daily mean air temperature in degrees Celsius; Rf(xt): forcing rate function; Rc(xt): chilling rate function; Sf: state of forcing; Sc: state of chilling; Km: minimum potential of unchilled buds to respond to forcing temperature; C*: critical value of state of chilling for the transition from rest to quiescence; F*: temperature sum critical threshold; t0: starting day of the heat sum calculation or date of onset of rest; t1: date of onset of quiescence; Tb: base temperature; To: optimal temperature of the rate of chilling; Tlow: the lowest temperature of the rate of chilling; Thigh: the highest temperature of the rate of chilling; a, b, va, vb and vc: constants; iTmin: daily indicator for minimum temperature; Tmin: observed daily minimum temperature in degrees Celsius; iVPD: daily indicator for vapor pressure deficit; VPD: observed daily vapor pressure deficit in Pascals; iPhoto: daily photoperiod indicator; Photo: daily photoperiod in seconds; iGSI: daily growing season index.