Modeling phenology of the Central European apple: The seasonal forecast application perspective

Tree phenology dynamic is the direct response of the plant to seasonal environmental conditions. Therefore, most trees have been strongly impacted by the increasing frequency of extreme weather events caused by global warming. In the past decade, fruit production in Europe has suffered a catastrophic failure of the yield because of the extreme and adverse weather events occurring (mostly frost) during winter dormancy and tree flowering. Therefore, forecasting the phenological development on the seasonal time scale can help in the organization of the prevention measures in the upcoming production season.

The Central European apple orchards' phenology dynamics are analyzed using the first bloom data and meteorological measurements collected during the COMBIRISK project. Projection to Latent Structures regression analysis (PLSR) from the ChillR package (https://cran.r-project.org/web/packages/chillR/index.html) is used to analyze two dormancy stages in the phonological development: endodormancy (chilling period) and ecodormancy (forcing period) in order to determine the changes in the phenological development patterns. Flowering is modeled considering chilling and forcing plant requirements and focusing on the temperature stresses impact through the stress factor calibration.

ECMWFs seasonal forecasts (SEAS5) are statistically downscaled by the Austrian national weather service (ZAMG) to a 1 km horizontal grid. These seasonal forecasts are used as input meteorological data for the apple phenology dynamic model in the AGROFORECAST project. Obtained results are compared with the observed timing of flowering to test the efficacy of available seasonal forecast for this application. This study is supported by the Ministry of education, science and technological development of the Republic of Serbia (agreement 451-03-9/2021-14/200117).