La savina turífera (Juniperus thurifera L.) als Pirineus catalans : distribució, població i conservació

Thuriferous Juniper (Juniperus thurifera L.) is a Western Mediterranean endemic tree with a fragmented area. Only three populations are known ont the Pyrenees, at the northern border of its range. In this paper we present the results of a field study on the Pallars county population (Catalonia, Central Pyrenees), which is the most large pyrenean population and the only one in the southern slope of this mountain range. This species is found in the three main valleys of the Pallars (Ferrera, Cardós and Noguera Pallaresa). They probably constitute three different populations, one for the whole Ferrera and Cardós valleys, and two other in Noguera Pallaresa valley. The area of occupancy has been estimated in 356 ha (460 ha if a correction for the slopes is applied), 84% of which is in Ferrera valley. The typical habitat are rocky slopes with SW or SE orientation, in altitudes of (860)1100-1450(1600) m, covered with a mosaic of vegetation dominated by plants of rocky habitats and xerophilous meadows. The population has been estimated at 3585-4724 individuals (approximately 50% are adults), 95% of which can be founs in Ferrera valley. Structure of local populations shows important differences in fuction of central or peripheral situation and the density of individuals. In central and dense local population it can be observed a continuous recruitment, a balanced sex ratio with a positive bias for females and a clear dominance of single-stemmed trees. In subcentral and middle density population we found a weaker and discontinuous recruitment, a sligth predominance of male individuals and an equilibrated proportion of single-stemmed and multi-stemmed trees. In a peripheral local population with very low density the recruitment in the last two decades has been null, sex ratio is highly female-biased and show a dominance of multi-stemmed trees. These differences could be attributed to the quality of local habitats and denso-dependent factors that affect seed dispersion. No differences in the average number of seeds per cone (3.09) are observed in the studied local populations. All the local populations show signs of a recent increase —from 40-30 years ago until present— thanks to the colonization of abandoned meadows and fields. According the data obtained the IUCN category for the species in Catalonia is VU D2.