Location and General Description
The northwestern Iberian Mountains extend from the Mediterranean southern slopes of the Cantabric Mountains to the central Iberian high mountain range. The ecoregion is characterized by low to medium elevations, which occasionally exceed 2,000 m (Teleño, 2,188 m; Peña Trevinca, 2,124 m). These mountains are part of the western Iberian old Hercynian system, which constitutes medium elevations with a smooth relief, scarcely influenced by the Alpine orogeny. From the geological point of view, ancient Paleozoic rock (granite, slate, schist, conglomerates, quartzite, and sandstone) predominates.
Climatically, the ecoregion is characterized by mild Mediterraneo-Atlantic conditions (average annual temperatures between 7-13º C, average rainfall between 500-1,000 mm), with cold winters (average temperature of the coldest month between 0-5º C) and a moderately intense summer drought period.
The Northwestern Iberian forests show some variation in accordance with altitude. Lower elevations and river canyons, such as the central Duero Basin on the border of Spain and Portugal, are characterized by sclerophyllous broadleaf species (Quercus ilex ballota, Olea europaea, and Pistacia terebinthus). The river canyons harbor refugees of a number of relict broadleaf species, for example, Celtis australis. Juniper (Juniperus oxycedrus) woodlands also occupy certain rocky plateaus. Medium and high elevations are dominated by deciduous oak forests of Quercus pyrenaica and Q. faginea. Relict pine (Pinus pinaster) forest stands occur on rocky and dry slopes, where they compose mixed pine/oak formations.
From a biogeographic point of view, emphasis should be placed on some very valuable relict conifer forests of Pinus sylvestris and Juniperus thurifera, which are found scattered on rocky sites of the Cantabrian southern slopes. These juniper and pine forest types currently predominate on cold and continental mountain areas of other Mediterranean ecoregions, such as the Iberian Mountain Conifer and Mixed Broadleaf Forests ecoregion.
The Northwestern Iberian forests do not host a very rich indigenous flora. The ecoregion has some endemics, but the endemism rate is less that 10% of the total flora. Examples are Angelica angelicastrum, Aquilegia dichroa, Armeria humilis, Centaurea micrantha subsp. herminii, C. rothmalerana, Dianthus planellae, Isatis platyloba, Jasione crispa serpentinica, Linaria coutinhoi, and Murbeckiella sousae.
Large carnivores are primarily represented by the wolf (Canis lupus). The wolf population is currently increasing in the ecoregion and represents the largest Iberian population, focused in the Culebra Mountains. The Cantabric brown bear (Ursus arctos) populations range into this ecoregion, in the bordering part of the Cantabric southern slopes. Other Cantabric species that seasonally spread into this ecoregion are the Cantabrian chamois (Rupicapra parva) and the highly endangered capercaillie (Tetrao urogallus).
Large herbivores, such as red deer (Cervus elaphus elaphus) and roe deer (Capreolus capreolus), are generally largely distributed. Other significant mammals distributed widely in the ecoregion are wild cat (Felis sylvestris), Eurasian badger (Meles meles), beech marten (Martes foina), and small-spotted genet (Genetta genetta). Otter (lutra lutra) is still well represented in the mountain rivers and canyons.
Among the most prominent bird species to be mentioned are griffon vulture (Gyps fulvus), golden eagle (Aquila chrysaetos), short-toed eagle (Circaetus gallicus), and Egyptian vulture (Neophron percnopterus). Some noteworthy reptiles are Mauremys caspica, Lacerta schreiberi, Anguis fragilis, and Macroprotodon cucullatus.
The ecoregion’s forests have been intensively converted to grassland for use by livestock and for agricultural land. The remaining forests are almost entirely transformed into coppice woodlands, due to intense firewood collection during the last centuries. The rural abandonment trend of the last five decades has contributed to the expansion of secondary forests and dense shrublands. Pines (Pinus pinaster) were frequently planted during the 60’s and 70’s.
Types and Severity of Threats
Due to the high density of flammable resinous pine species, these secondary forests are very vulnerable to forest fires, which are generally started by man. Very remote and wild areas are still to be found along the border of Spain and Portugal, due to the low human population that has historically characterized this area (i.e. the Arribes del Duero international river canyons). Nevertheless, overly intense and poorly regulated hunting is threatening many faunal species, especially in Portugal.
Justification of Ecoregion Delineation
This ecoregion is equivalent to the DMEER (2000) unit of the same name. It comprises the Iberian supra- and meso-Mediterranean Quercus forests of the northwestern Iberian peninsula (Bohn et al. 2000).
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Prepared by: Pedro Regato
Reviewed by: In process