Flora del Pirineo navarro

Abstract

This study gathers together and critically analyses data about the flora of the Navarrese Pyrenees. This data was collected from our own field studies, arround 12,000 specimens, from a review of the information contained in herbaria and bibliographical references about the territory. The area studied, situated in the north-east of Navarre and included in the westem Pyrenees, borders with the French Basque Country in the north, with the sinuous line that follows the alignments of Gongolatz, Idokorri and Illón in the south, with the valley of the river Urrobi in the west and, to the east, with the valley of the river Esca, which is the limit with the Autonomous Community of Aragón. The Navarrese Pyrenees, which cover an area of 1,525 square kilometres, form an area of high relief with altitude varing fi·om 245 metres in Valcarlos to 2,428 metres at the Mesa de los Tres Reyes, which is the highest point ofthe Foral Community. The climatic gradient ranges from a strong Atlantic influence in the west to an appreciable Mediterranean influence in the south-east, faithfully reflected by the vegetation cover. Basic substraía (limestone, marl and flysch) are predominant, with acid rocks (schist, slate, quartzite and sandstone) being restricted to small islands such as mount Lakora or the paleozoic massifs of Oroz­-Betelu and Quinto Real, which adds a touch of originality to the regional flora. The land area includes both the Eurosiberian Region and the Mediterranean Region, and in the former we find the alpine zone, above an altitude of 2,200 to 2,300 metres, covering a small area, and in which basophilous pastures of Carici­ Elynetum myosuroidis predominate. Below this is the subalpine zone -above an altitude of 1,600 to 1,700 metres- which includes the highest mountain chains and is marked by the presence ofblack pine woods and, principally, by moorland and pastures of different types (Nardion, Festucion gautieri and Festucion eskiae, among others). The montane zone, above an altitude of 600 to 650 metres, covers a large area where beech, oak and pine woods and fir forests predominate (in this zone the livestock and forestry sectors have gained a firm foothold). Finally, in the lowest-lying zone of this region, below 600 to 650 metres, the presence of trees is generally limited to oak groves, greatly reduced in extension by livestock farming and agriculture. In the Mediterranean Region, the supramediterranean zone contains residual pyrenean oak groves, holm-oak groves and gall oak groves, all pushed into retreat by livestock farming, agriculture and forestry re­ plantations.

Of the 2,071 taxa studied, 1,822 constitute the floral catalogue of the  Navarrese Pyrenees, ofwhich 98.30% are spontaneous, 0.77% are accidental and 0.93% are cultivated. We have not included in the catalogue those species which are close to the territory (12% of the taxa studied) nor erroneous references (3.2%). More than 600 distribution maps, with a UTM grid of 10 by 10 kilometres, represent about 700 of the most significant species of the flora. The predominant species belong to the Compositae (12%), Gramineae (8.24%), Leguminosae (7.02%) and Rosaceae (6.70%) families, which together make up a third of the existing flora. As in the case of other mountainous regions, almost 50% of the flora can be considered rare or very rare, with only 17 of the taxa being very common. In terms of chorological groups, the dominant group is formed by the Eurosiberian element (29.2% of the flora), followed by the Mediterranean one (19.46%), the endemic (10.32%), European orophytes (8.24%) and pluriregional elements (7.28%).

Related to vegetation zones, the montane zone includes 89.84% ofthe flora, followed by the coline zone (61.28%), the subalpine zone (36.24%) and the alpine zone (6.15%). Eight taxa are present in all the vegetation zones and only three are found exclusively in the alpine zone: Draba dubia subsp. laevipes, Carex capillaris and Salix retusa.

As a feature of the peculiarity of the territory, and a consequence of the varied climate, topography, lithology and a gradual descent in altitude towards the west, 116 taxa have their known limits of distribution within the territory.

As regards protection of the flora, 20 taxa are included in the Catologue of Threatened Flora of Navarre, of which 32.07% are found totally or partially in protected areas. Seven taxa, according to the cataloguing of the UICN, are included in the Red List of Spanish Vascular Flora, either as species in danger (EN) or as vulnerable (VU), and for 6 the evaluation insufficient data is assigned (DD). We propose the inclusion of at least 8 taxa in the cited Catalogue of Threatened Flora of Navarra.