Phenological models for blooming of apple in a mountainous region

Abstract

Six phenological series were available for 'Golden Delicious' apple blooming at six sites in Trentino, an alpine fruit-growing region. Several models were tested to predict flowering dates, all involving a "chilling and forcing" approach. In many cases, application of the models to different climatic conditions results in low accuracy of prediction of flowering date. The aim of this work is to develop a model with more general validity, starting from the six available series, and to test it against five other phenological series outside the original area of model development. A modified version of the "Utah" model was the approach that performed best. In fact, an algorithm using "chill units" for rest completion and a thermal sum for growing-degree-hours (GDH), whose efficiency changes over time depending on the fraction of forcing attained, yielded a very good prediction of flowering. Results were good even if hourly temperatures were reconstructed from daily minimum and maximum values. Errors resulting from prediction of flowering data were relatively small, and root mean square errors were in the range of 1-6 days, being <2 days for the longest phenological series. In the most general form of the model, the summation of GDH required for flowering is not a fixed value, but a function of topoclimatic variables for a particular site: slope, aspect and spring mean temperature. This approach allows extension of application of the model to sites with different climatic features outside the test area.

Risk of spring frost to apple production under future climate scenarios: the role of phenological acclimation

“…Parallel models do not explain how chill accumulation can compensate for heat during bud development, but they introduce the concept that a higher accumulation of chilling during the winter results in a lower heat requirement during the forcing stage. This approach, implemented also in the "Modified Utah" model, was considered suitable by Rea and Eccel (2006), and is used in the present study.…”

Climate change effects on winter chill for tree crops with chilling requirements on the Arabian Peninsula

“…Trees and shrubs that require winter chill rely on the occurrence of cold conditions during the winter, in order to break their dormancy and initiate fructification. In spite of the importance of this phenomenon for horticultural production, the physiological details of this process are still relatively unknown, and the existence of several competing models to quantify winter chill suggests that the climatic conditions required to break a tree's dormancy are as yet relatively poorly understood and possibly vary between species (Kozlowski and Pallardy 2002;Rea and Eccel 2006). This is also reflected by the fairly elaborate structure of some existing models and by their specificity to a certain species or even variety (Richardson et al 1974;Shaltout and Unrath 1983).…”

Modelling flower production of kiwifruit (Actinidia deliciosa) from winter chilling

“…= 5.7-0.3(T aN ); r 2 = 1.00). other authors (Rea & eccel 2006) have also found that long-term mean temperatures are useful for constructing specific site-dependent variables.…”

“…latitude may be an effective parameter because the three research orchards used are located at similar altitudes, and so latitude may be acting as a surrogate measure of mean annual temperature. If orchards at greater range of altitudes are compared (Rea & eccel 2006) then latitude alone may not adequately characterise the sites. The similarity of the location-dependent models implies that the site factors are closely linked to some aspect of climate, and regression analysis reveals that, for the three sites used, the site offset and the long-term mean annual temperature are linearly correlated (site offset Table 4 Coefficients of determination (r 2 ) for regressions of flower production (Flowers WB ) against individual mean monthly temperatures and hydrogen cyanamide usage, using flowering and temperature data for research orchards 1996-98 (n = 18).…”