Nowadays, both spontaneous and cultivated Pinus forests occur throughout the Mediterranean basin, especially along coastal areas. Stone pine (Pinus pinea, hereafter ‘Pinus’) is a xeric and thermophilic tree native to the Mediterranean region, which preferably colonises deep, loose, sandy and siliceous soils. The high landscape and historical value of these forests motivated its consideration as priority habitats (code 2270) by the European Council Directive 92/43/EEC. However, Pinus plantations outside their original forest areas may involve negative effects on pre-existing habitats such as over-exploitation of water, the reduction of light inside the forest mass, the accumulation of needles, an increased flammability or the decrease in seed germination.

 Felling and forwarding of Pinus in the present work aimed at recovering the number and abundance of species characteristic to the original ecosystems. However, Pinus forests are also recognised as a priority habitat and in the Doñana Natural Area overlap other priority habitats such as the Dorset heath (code 4020), Atlantic decalcified fixed dunes (Calluno-Ulicetea) (code 2150) and Malcolmietalia dune grasslands (code 2230). The coincidence in space of four priority habitats posed a challenge during the planning stage that requested to define conservation priorities. The sharp decrease of the Dorset heath observed in the study area since the XVII century tipped the balance towards the conservation of this habitat and fixed dunes over high cover Pinus plantations.

The high dissimilarity (90.8%) between ‘Pinus plots’ and ‘open, well-preserved plots’ suggests that Pinus plantations may outcompete the Mediterranean xerophytic scrub when Pinus trees reach a high cover (100%). Results agree with the diversity loss reported in plantations replacing natural shrub lands. Also, a high canopy cover in Pinus spp. forests from coastal Italy was associated with generalist and alien species, whereas lower canopy cover supported herbaceous and shrub species typical of natural dunal succession. The significant decrease of woody species richness and overall shrub cover reported in heathlands of the Strait of Gibraltar invaded by maritime pine (Pinus pinaster) is seen. Therefore, felling and forwarding of high cover Pinus patches is proposed as a general recommendation to improve the biodiversity of the native shrubland, particularly in coastal sand dunes.

The forwarder mainly affected the areas with a percentage of bare soil>20%. The impact of the forwarder on the xerophytic plant community typical of stabilised dunes showed promising signs of reversibility in areas in which the forwarder caused deep disturbance compared with others with a shallower disturbance but with a high Pinus cover. Results suggest that a high cover of Pinus have a more lasting effect than the mere physical disturbance caused by the passing of the forwarder in areas without any pines. Findings may serve as a guide for future management and planning of old, disused Pinus plantations in natural areas aimed at prioritising biodiversity conservation.

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