Fernández Collao, Eduardo: Dormancy in temperate fruit trees - Perspectives for farming in a changing climate. - Bonn, 2021. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-62350
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-62350,
author = {{Eduardo Fernández Collao}},
title = {Dormancy in temperate fruit trees - Perspectives for farming in a changing climate},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2021,
month = may,

note = {Deciduous fruit trees, which originated in temperate climates, exhibit an inactive period (i.e. dormancy) between late autumn and early spring. This period allows trees to endure the severe winter temperatures usually observed in their native habitat. During dormancy, trees require exposure to chilling and subsequent warm conditions to resume growth (i.e. chill and heat requirement). The exposure to chill triggers physiological modifications inside the buds, restoring the growth mechanisms that were suspended at the beginning of winter. After trees experience enough cold, warm temperatures trigger growth resumption and bloom. To quantify effective accumulation of chill and heat, scientists have developed a number of mathematical models. However, none of these approaches include up-to-date knowledge about the biology of dormancy progression. A process-based model is likely to better represent the entire dormancy phase and to help the temperate fruit industry in preparing for the impacts of climate change. In this thesis, I report on a set of field experiments and assessments of historic weather records. I studied the dormancy phase in temperate fruit trees with a view towards renewed modeling approaches, and I assessed the possible impacts of climate change on the cultivation of temperate fruit trees in a three-year project.A description of these experiments as well as the key results from each study are summarized as follows:
1. In chapter 2, I report on the relationship between chill accumulation and the concentration of non-structural carbohydrates (CHOs) in sweet cherry branches. Results show that the dynamics of starch and hexoses are closely related to dormancy progression. However, our modeling approach using CHOs as predictors of budburst moment performed differently among cherry cultivars, suggesting that other co-occurring processes (e.g. hormonal signaling, genetic expression) must be considered in future dormancy modeling.
2. In chapter 3, I present the calculation of climate-related metrics (i.e. chill availability and spring frost risk) for major agricultural zones of Chile for historic and future climate scenarios using up-to-date methods. Projections suggest that the cultivation of temperate fruit trees in northern-central Chile may face severe obstacles in the near future regarding chill accumulation. In central and southern-central Chile, strategies to ensure dormancy release and budburst may become critical for adequately cultivating deciduous fruit trees.
3. In chapter 4, I report on the comparison of outputs from 13 chill models for historic and future scenarios for nine sites around the globe. In this comparison, we found that chill model selection is the main source of variation in the assessment, more important than the site or future climate scenario. Among all the available approaches, the Dynamic model appears to be the best option for chill estimation due its more credible biological structure. Dormancy researchers, geneticists and other stakeholders should be wary of the high variability between models when working with temperate trees.
4. In chapter 5, I report on the impacts of an unusual drought period during the summer of 2018 on bud dormancy and flowering in an apple orchard in Germany. Results show that under low-chill conditions, buds on non-irrigated trees developed faster than those on irrigated trees. This suggests an impact of summer drought on bud dormancy. We conclude that accounting for the effects of summer drought and warm winters may be necessary for accurately predicting the future phenology of deciduous trees.
Overall, the results of this thesis may be useful for scientists studying the dormancy phase, plant breeders developing new cultivars, stakeholders and authorities making decisions in the fruit industry, and most importantly farmers and orchard managers cultivating deciduous fruit trees.},

url = {https://hdl.handle.net/20.500.11811/9107}

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