Significant delays in Aleppo pine phenology induced by a rain-exclusion experiment to emulate climate of 2100
Des retards significatifs dans la phénologie du pin d'Alep induit par une expérimentation d'exclusion de pluie simulant le climat de 2100
Girard, F. ; Vennetier, M. ; Buissart, F.
Type de document
Communication scientifique sans actes
Affiliation de l'auteur
UNIVERSITE DE MONTREAL CAN ; IRSTEA AIX EN PROVENCE UR RECOVER FRA ; IRSTEA AIX EN PROVENCE UR RECOVER FRA
Résumé / Abstract
Introduction: Global climate models agree in predicting a faster warming in the Mediterranean than in most of other continental regions, along with a reduction of spring and summer precipitations. By increasing drought stress and changing phenology patterns, global warming and its corollaries, as heat waves and extensive droughts, are direct threats to forest productivity, health and survival. Expected stress-related changes in phenology are delays in flowering, fruiting, dormancy and needle growth. The objective of this research was to assess tree phenological responses in a 2100 rainfall context. Methods: We used an experimental forest site were 30% of rainfalls are excluded using gutters, along with a control. Scaffoldings were built up to the forest canopy to monitor tree phenology and crown development on 16 trees. Phenological surveys were performed monthly between 2009 and 2015. Evaluations of budburst, shoot and needle elongation and fruiting were made on five to eight branches on the whole crown of each tree. Results: A significant delay in fruiting, needle extension and shoot growth was observed in the rain exclusion plot. Delays can be as long as two months for frail branches in opposition to vigorous branches in the control plot. Some years, bud burst never occurred for some frail branches. The most significant result is that some trees never reached dormancy in the top crown, as a result of mild winters allowing a continuous growth, exposing the active shoots to frost damages. Discussion: A warmer climate is supposed to lengthen the growth season, what was observed for some trees. But drought stress may offset this gain by opposite effects, significantly delaying bud burst, shoot growth and needle development. We also expect severe damages in the future for trees growing yearlong in case of unusual low temperature during winter, such as in 2012 in our case.
ECOSUMMIT, 29/08/2016 - 01/09/2016, Montpellier, FRA