Comparing Apple and Pear Phenology and Model Performance: What Seven Decades of Observations Reveal

Abstract

Based on observations for the beginning of the flowering stage of Malus domestica (apple) and Pyrus communis (pear) for the 1950-2018 period, phenological trends in north-eastern Belgium were investigated in function of temperatures during dormancy. Moreover, two different phenological models were adapted and evaluated. Median flowering dates of apple were on average 9.5 days earlier following warm dormancy periods, and 11.5 days for pear, but the relationship between bloom date and temperature was found not to be linear, suggesting delayed fulfilment of dormancy requirements due to increased temperatures during the chilling period. After warm chilling periods, an average delay of 5.0 and 10.6 days in the occurrence date of dormancy break was predicted by the phenological models while the PLSR reveals mixed signals regarding the beginning of flowering. Our results suggest overlapping chilling and forcing processes in a transition phase. Regarding the beginning of flowering, a dynamic chill model coupled to a growing degree days estimation yielded significantly lower prediction errors (on average 5.0 days) than a continuous chill-forcing model (6.0 days), at 99% confidence level. Model performance was sensitive to the applied parametrization method and limitations for the application of both models outside the past temperature ranges became apparent.Other weather-related hazards were several light frost nights, frequent local hailstorms, and three heatwaves in 2019, an extensive drought period for more than two months in combination with a heat wave in 2018, water excess and storms in 2016, and a devastating summer storm in 2011. The consequences of extreme weather in addition to the Russian embargo on fruit imports since 2014 led the entire Belgian fruit sector into an officially recognized crisis, to the extent that federal and regional governments are preparing policies to increase resilience in the face of more frequent extreme weather events and in the context of a changing climate in general.Therefore, a better understanding is needed of the impacts of warming on phenology in the specific case of apple and pear cultivation in Flanders. By means of adapted phenological models, variations in flowering and the related frost-sensitive stage can be estimated across temporal and spatial scales, which can support decision-making regarding (new) orchard locations and cultivar selection.Following [3], the part of the growth cycle between late summer and budburst is conceptualized as dormancy period, and can be decomposed in a sequence of paradormancy, endodormancy, and ecodormancy phases. Endodormancy, i.e., 'chilling period', is induced by lower temperatures in late fall. The moment that a species' specific exposure to cold temperatures has been fulfilled, ecodormancy is induced and the accumulation of growing degree hours becomes the determining process for further phenological development [4], i.e., 'forcing period'. From then onwards, warmer temperatures favor earlier and no longer later bloom. Insolation and tem...

Changes in Reactive Oxygen Species, Antioxidants and Carbohydrate Metabolism in Relation to Dormancy Transition and Bud Break in Apple (Malus × domestica Borkh) Cultivars

“…The fulfillment CR and HR is interrelated and crucial for homogenous budburst and flowering in spring. After dormancy release, buds lose their cold hardiness and become more sensitive to spring freezes, which are predicted to increase in the future due to global climate change [3]. Bloom delay using plant growth regulators (PGRs) and vegetable oil-based adjuvants has been suggested as an effective frost avoidance strategy, especially in grapes and stone fruits [4][5][6].…”

Assessment of Climate Change Impacts on Chilling and Forcing for the Main Fresh Fruit Regions in Portugal

“…For the case of citrus, such as oranges, these plants are usually grown in warmer climates, and exposure to cold temperatures (<5 • C) may result in chilling injuries (Yuen et al, 1995;Santos et al, 2019). When spring arrives, forcing becomes a much stronger driver of tree phenology than chilling (Luedeling et al, 2013), and a period of warm temperatures (heat accumulation) is needed for adequate blooming and fruit ripening (Arroyo et al, 2013;Drepper et al, 2020;Rodriguez et al, 2020;Cho et al, 2021).…”

Climate risk services for cereal farming

“…The temporal overlap between weather conditions and crop stages in arable cropping systems was determined using a model that couples phenology to the soil Published by Copernicus Publications. water balance and crop growth (Gobin, 2010Durgun et al, 2016). In addition to a shift in adverse temperature related events, crop development has advanced with up to 4 d per decade , which warrants a dynamic modelling approach to simulate the different processes of crop phenology and weather risk occurrence.…”