Modeling spring phenology and chilling requirements using the chill overlap framework

K.S. Pope, T.M. DeJong
The timing of bloom and leaf-out has important implications for orchard systems. As temperatures continue to shift under climate change, it is important to be able to accurately model the impact of these changes on the timing of spring phenological events. Changing temperatures may impact cultivars differently, and interfere with pollinizer variety bloom overlap. Bloom windows may shift later or earlier, potentially increasing the risk of exposure to frost or to warm conditions that can interfere with ovule fertilization. Recent work modeling the bloom timing of multiple cultivars of Prunus dulcis (almond) in California predicted bloom reasonably well based on a chill overlap or 'optimal' framework. This approach uses non-linear regression to integrate the well-documented compensatory relationship between chill and heat accumulation, by which greater chill accumulation requires less heat accumulation for bloom and vice versa. However, this approach used chilling requirements estimated from work in other climates or with other chill accumulation models. The present work extends the chill overlap framework to estimate chilling requirements and the relationship between chill and heat accumulation that results in bloom based on historic records of bloom timing. This approach has the potential to estimate bloom prediction curves for numerous cultivars and crops in silico without the effort and expense of forcing experiments, which have proven difficult for many crops.
Pope, K.S. and DeJong, T.M. (2017). Modeling spring phenology and chilling requirements using the chill overlap framework. Acta Hortic. 1160, 179-184
DOI: 10.17660/ActaHortic.2017.1160.26
chilling requirement, heat requirement, bloom, bud break, Prunus dulcis

Acta Horticulturae