Evaluation of degree-days for spring crops, considering upper temperature thresholds and cut-off techniques

Variations in temperature trends connected to climate change have considerable consequences on plants’ phenological development, being temperature its major driving force. Several modeling approaches exist, to simulate the phenological development through the calculation of GDDs, all of them having in common the consideration that the plant starts to cumulate heat units above a minimum temperature threshold (base temperature), required to develop from one stage to another, and slows down, or stops, when a maximum temperature threshold is reached. Aim of the present work was to compare different upper threshold cut-off techniques, applied to the single triangle method, in order to assess which of them could give the best results in terms of GDDs calculation for summer crops in the climate change scenario in the North of Italy. For this purpose, a historical series of phenological data was used, comparing “standard years” and years in which high temperatures conditions were recorded.