THE YEW MATRIARCHIES OF THE SIERRA DE FRANCIA Dynamics and ecology of new known populations in the Iberian Central Mountain Range (“Sistema Central”)

Resumen

New yew populations (Taxus baccata L.) have been studied in the western sector of the “Sistema Central” mountain range of the Iberian Peninsula - known as “Sierra de Francia”- in a fully Mediterranean environment forming a mosaic of climatic variants (continental Mediterranean, submediterranean, subatlantic, and even moist subtropical Mediterranean microclimates). A very complete array of different Mediterranean yew forests that manifests the species dynamics and show their historical evolution in the Iberian Peninsula.

A census of the yew populations has been completed in five watersheds within the Sierra de Francia, belonging to the Duero River and Tajo River Basins, resulting in the largest group of yews known to date in the “Sistema Central”. Around 2450 specimens have been recorded and classified against three types of population dynamics that can be then typified as: regressional yew forests, naturally regenerating yew forests, and incipient yew forests that are colonizing new territories.

The ecology of the different subpopulations has been characterized in terms of its relationship to other plant formations (madrone, oak, ash, alder, birch forests, etc.), of how they occupy the territory as conditioned by the geology, topography, meteorology and orientation, and the influence of other factors such as erosion dynamics or herbivore-plant dynamics such as those caused by game species and human actions.

The notable differences observed in regeneration amongst said communities propitiates a population analysis aimed to explain the landscape connectivity relationships between the different population nuclei and the possibility of defining the metapopulation set so the essential role played by the large female trees located at the headwaters is confirmed. Given the regeneration and recruiting rates around such trees we have arrived to a model called “yew matriarchies”, an expression we hope carries the relevance of these female yew trees in population dynamics.