Parameters of leaf phenology for North American forests

Leaf phenology regulates multiple aspects of plant vital activities and provides feedback to climate change. Despite its importance, an effective parameterization method to predict continental-scale leaf phenology has been elusive. Here, we developed a new parameterization method using local climatic conditions instead of species or plant function types to calibrate the phenology parameters of forests. We provided the parameters of phenology include: the effective temperature threshold (TA) to determine spring phenology (i.e. start of the season; SOS); the critical heat threshold (SA) to determine SOS; the effective temperature threshold (TB) to determine autumn phenology (i.e. end of the season; EOS); the effective photoperiod threshold (Pstart) to determine EOS, and the critical chilling threshold (SB) to determine EOS. Methods We used the average temperature and photoperiod from the first day to the phenological date in a given year to express the climatic conditions. Using this parameterization method and the typical phenology models, we extrapolated to the continental scale using satellite-derived leaf area index product as a basis to predict the distribution and changes of forest leaf phenology.