2.1. Site description
The quarries where the experimental restoration was carried out are at the eastern border of Sierra de Gádor, 36o55´20´´N, 2o30´29´´W (Fig 1), 20 km NW of Almeria city, about 370 m a.s.l.
Climate is near the boundary between arid and semiarid, i.e, where the aridity index (P/PET) is slightly below 0.2 (UNESCO, 1977). The data from the Alhama de Almería station (AL003, Junta de Andalucía) show an average annual precipitation, since the hydrological year 2002, of 241 mm, with a minimum annual of 106 mm and a maximum of 466 mm. The hydrologic years just two years after the start of the experiment were wetter than average (466 mm and 304 mm respectively), and the three following years were much drier than average (167 mm, 202 mm and 165 mm, respectively). Summers are particularly dry and temperatures are quite high (averages 27°C in August with mean daily maximum above 35°C).
The natural soils around the quarries are either Calcaric Regosols or Eutric Regosols (IUSS Working Group WRB 2015) which have formed over the lithology of the area (marls and calcareous sandstones) and over mixed slope deposits.
The vegetation around the quarries is essentially an alpha-grass community, clearly dominated by Macrochloa tenacissima (L.) Kunth, with some species of grasses, shrubs or dwarf shrubs such asDactylis hispanica Roth, Rhamnus lycioides L., Maytenus senegalensis Lam., Anthyllis cytisoides L., Anthyllis terniflora (Lag.) Pau, Thymus hyemalis Lange,Artemisia barrelieri Besser, Thymelaea hirsuta(L.) Endl., and Launaea lanifera Pau. Some stands of Pinus halepensis Mill. are found on favorable run-on locations and near a natural spring located not far from the quarried area.