Why are conifer trees common at higher elevations in the Pyrenees?

In the Pyrenees, the distribution of vegetation is organized into distinct altitudinal levels. At higher elevations, typically starting above 5,200 feet, broad-leaved deciduous trees are replaced by needled conifers because these species require less water and are better adapted to the colder, harsher conditions found at these altitudes.1

The prevalence of these trees is driven by several environmental factors:

• Water Efficiency: Conifers are well-suited to the higher, drier parts of the mountain slopes where they often replace deciduous trees.1
• Temperature and Growth: As elevation increases, temperatures drop, which slows biological processes and shortens the growing season. Conifers are physiologically adapted to survive these lower temperatures and the associated environmental stresses, such as high winds and potential winter desiccation.12
• Regional Variations: In the Central Pyrenees, mountain pines are particularly dominant in higher, colder, and drier areas due to their high drought resistance. Conversely, in the more oceanic Western Pyrenees, higher rainfall allows broad-leaved beeches to persist at higher altitudes alongside subalpine conifers.1