Contribució al coneixement geobotànic de les comunitats de Juniperus sabina i de Juniperus communis (Cupressaceae) als Pirineus catalans

Abstract

Here we study the plant communities formed by Juniperus sabina, J. communis var. intermedia and J. communis subsp. nana in the Pyrenees. These three taxa may be found as detached shrubs within grassland or rocky areas, or forming low scrubs, or in the forest understorey. As such, these scrub communities have low singularity. Indeed, they play a noticeable role in mountain landscapes and most of them are recognized as Habitats of Community Interest, thus they should be characterized and typified as phytosociological units. On the basis of thirty relevés, we describe two new plant associations and a new subassociation. Roso siculae-Juniperetum sabinae ass. nova is scarce and mostly concentred in the montane and low subalpine belts of Espot and Jou valleys, on rocky slopes and in old fields and pastures. The Juniperus communis formations are much more distributed through the Catalan Pyrenees. Those of J. communis var. intermedia (Helleboro occidentalis-Juniperetum intermediae ass. nova) are found in the high montane and low subalpine belts, within grassland landscapes; and the scrubs of J. communis subsp. nana (Cytiso oromediterranei-Arctostaphyletum uvae-ursi juniperetosum nanae subass. nova) thrive on south-facing rocky slopes of the subalpine and low alpine belts. The ongoing decrease of the traditional extensive grazing in mountain areas enhances the expansion of all these scrubs through varying encroachment dynamics. However, the spontaneous afforestation by Pinus uncinata and P. sylvestris keeps the scrubland in a dynamic status, which is more apparent in the communities of J. communis var. intermedia.