Autumnal phenology integrated to frost hardiness modelling of walnut and apple trees
2018
Baffoin, Romain | Charrier, Guillaume | Serre, Christophe | Lacointe, André | Ameglio, Thierry
Frost is one of the first causes in the fruit crops yield loss, mostly in autumn and spring. To protect themselves against low temperatures, trees adopt different strategies. Studying tree’s responses to frost events in autumn and spring is important to understand those strategies. To detect trees responses to frost events, we put sensors on four varieties of walnut fruit trees, one variety of wood walnut tree and one variety of apple tree. Data acquired with PépiPIAF sensors show us micro-variations of tree’s trunks or stems and highlight reactions of to freezing events and the decreasing of foliar transpiration until the end of leaf fall. Those data were linked to field observations of leaf senescence and records of temperature variations. Leaf fall is an autumnal phenological event marking the beginning of dormancy and often occurs during the firsts freezing events. In spring, budburst occurs when high temperature comeback and make the trees vulnerable to late frosts. Therefore, mechanistic models were developed to predict the end of dormancy with budburst in spring but were calibrated mostly on one variety of walnut Juglans regia cv Franquette. Data obtained with PépiPIAF and field observations of leaf senescence were linked to dormancy assessment. Thus, the goal was to identify trees reactions to autumnal frosts as phenological markers of dormancy entry and to take it into account to improve models predicting budburst. Firsts results show differences in tree reactions, leaf fall and dormancy induction between the studied species. Differences and similarities between experimental data and model’s predictions may indicate mechanisms involved in frost hardiness of trees.
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