Yew (Taxus baccata L.) population dynamics in the Iberian Mediterranean Mountains: natural regeneration and expansion in East Central System (Spain)

Aim of study: To evaluate demographical dynamics of yew populations in the Iberian Mediterranean mountains in order to assess population trends and a hypothetical natural regeneration of the species.Area of study: Ayllón Mountain Range, Eastern end of Central Mountain Range, Spain.Material and methods: Afield survey was conducted on three yew groves, taking data of altitude, orientation, companion woody species, UTM coordinates, height, perimeter (at breast height, 120cm) and sex. Individuals were classified in four age groups, considering height and trunk perimeter: AgeGroup1, Seedling; AgeGroup2, Juvenile; AgeGroup3, Adult and AgeGroup4, Old. Finally Recruitment rate was calculated for each population.Main results: Surveyed yew populations include more than 1600 trees, showing elevated Recruitment rates, which indicates that there are more seedling and juvenile individuals (Group1 and Group2) than adult and old ones (Group3 and Group4).Research highlights: Surveyed yew populations show vigorous regeneration. These results lead us to reconsider the relictic character assigned to the species in the Iberian Mediterranean mountains.Key words: Ayllón; microclimatic; regeneration rate; relictic; survey

Yew (Taxus baccata L.) population dynamics in the Iberian Mediterranean Mountains: natural regeneration and expansion in East Central System (Spain)

Aim of study: To evaluate demographical dynamics of yew populations in the Iberian Mediterranean mountains in order to assess population trends and a hypothetical natural regeneration of the species. Area of study: Ayllón Mountain Range, Eastern end of Central Mountain Range, Spain. Material and methods: Afield survey was conducted on three yew groves, taking data of altitude, orientation, companion woody species, UTM coordinates, height, perimeter (at breast height, 120cm) and sex. Individuals were classified in four age groups, considering height and trunk perimeter: AgeGroup1, Seedling; AgeGroup2, Juvenile; AgeGroup3, Adult and AgeGroup4, Old. Finally Recruitment rate was calculated for each population. Main results: Surveyed yew populations include more than 1600 trees, showing elevated Recruitment rates, which indicates that there are more seedling and juvenile individuals (Group1 and Group2) than adult and old ones (Group3 and Group4). Research highlights: Surveyed yew populations show vigorous regeneration. These results lead us to reconsider the relictic character assigned to the species in the Iberian Mediterranean mountains

Yew matriarchies of the Sierra de Francia. Dynamics and ecology of recently identified Yew populations in the Central Iberian Mountain Range (Sistema Central)

Aim of study: Our study design presents two main objectives: 1) to create a census that details the number of yew individuals and their geographic distribution, and 2) to attempt to unravel possible reproductive relationships and their connection between true population nuclei and meta-population models.Area of study: Recently identified yew populations (Taxus baccata L.) were studied in the western sector of the Sistema Central mountain range of theIberian Peninsula, known as the Sierra de Francia. The study was carried out in five watersheds within Las Batuecas-Sierra de Francia Natural Park.Material and Methods: All yew specimens were counted and assigned to age groups. The notable differences observed in regeneration aof these communities propitiates population analysis aimed at explaining the landscape connectivity relationships between the different population nuclei and the possibility of defining the meta-population set. Ecological niche models were also created to define the main ecological characteristics of the different subpopulations studied, and to compare them.Main results: Yew in the Sierra de Francia live in an array of different Mediterranean forests, indicative of species dynamics in theIberian Peninsula. 2,450 specimens were recorded and classified into the three types of yew forest population dynamics: regressional-, naturally regenerating-, and incipient- (i.e.  colonizing new territories).Research highlights: The essential role of connectivity between populations was recognized and confirmed in this study, specifically among the large female trees located at the headwaters. Based on the role of these female trees, we have created a model called “yew matriarchies”, which serves to express the relevance of large female yew trees in population dynamics.Keywords: Taxus baccata; census; connectivity; seed dispersal.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