Chilling and heat requirements for leaf unfolding in European beech and sessile oak populations at the southern limit of their distribution range

摘要: With global warming, an advance in spring leaf phenology has been reported worldwide. However, it is difficult to forecast for a given species, due lack of knowledge about chilling requirements. We quantified and heat requirements unfolding two European tree species investigated their relative contributions phenological variations between within populations. used extensive database containing information the 14 oak 10 beech populations monitored over elevation gradients since 2005. In parallel, we studied various bud dormancy phases, controlled conditions, by regularly sampling low- high-elevation during fall winter. Oak was 2.3 times more sensitive temperature gradient had lower requirement release than beech. found that currently insufficient full dormancy, both at lowest elevations area studied. Genetic variation timing probably differences rather requirement. Our results demonstrate importance forest trees indicate with increasing will be less pronounced forecasted. This highlights urgent need determine experimentally interactions improve our understanding modeling changes under warming.