Temperature rather than individual growing period length determines radial growth of sessile oak in the Pyrenees

• Oak growing period decreases by 70 days along an elevational gradient of 1500 m. Growing extends in warmer years within population at a given elevation. Phenological ranks between individuals remain mostly stable over years. Radial growth benefits from temperatures only higher elevations. There is no link radial and length population. Tree leaf phenology are both affected global warming. Mountain ecosystems paramount importance for studying phenological responses trees to the gradual variation temperature. However, relationship season tree has been little studied level individual trees. Here, we investigated relationships phenology, degree-days sessile oaks nine populations m French Pyrenees. In each population, unfolding spring coloration autumn were monitored 2005 2015 on 25-30 having contrasting ( i.e. early vs. late flushing trees). These cored 2013 analyse annual tree-ring widths. While displayed consistent their years, decreased with increasing elevation, about 210 lowest elevation (131 a.s.l.) 140 highest (1630 a.s.l.). For year, dates correlated positively lower elevations, but negatively was likely because often associated severe droughts lowlands this region. No clear found This indicates that climatic conditions during have more important impact secondary than length. Our findings suggest lengthening response warming does not necessarily lead productivity.