Climate relationships of growth and establishment across the altitudinal range of Fagus sylvatica in the Montseny Mountains, northeast Spain

A rise in elevation of the temperate biome has been reported in the mountains of northeast Spain. We aimed to determine the principal climatic factors limiting growth and establishment of the dominant temperate tree, Fagus sylvatica, across its altitudinal range and how its climate-response has varied over time. We determined the climate-response of the growth of adult trees and the establishment of juveniles using dendroecological methods at 3 sites along an elevational gradient spanning this species' full altitudinal distribution of approximately 1000–1650 m above sea level. We found strong altitudinal variation in growth and establishment responses to climate. The most common growth response was to high spring and summer temperature (April–July), which promoted growth and establishment at the upper treeline but had the opposite effect at low altitudes. Precipitation was strongly limiting for adult growth at the lower limit of F. sylvatica and declined in importance with increasing altitude. Sensitivity of growth to summer temperature increased over the second half of the 20th century. Future increases in summer temperature are likely to have negative consequences for growth and establishment at this species' low altitude, low latitude range-edge, particularly if temperature increase is not matched by increasing precipitation.