Plant succession in abandoned gypsum quarries in SE Spain

Gypsum outcrops harbour a considerable number of rare species the presence of which is restricted to these soils. By the rarity and richness of their flora, gypsum soils of Almeria Province (SE Spain) are the most valuable in Spain from a conservation viewpoint, whereas at the same time the territory is being intensively exploited by quarrying and holds the most important production of gypsum rocks in Europe. It was hence considered a priority to investigate the recovery patterns of gypsophilous species after quarries abandonment in order to seek for information that can help to develop restoration plans with an ecological basis. For this aim, chronosequences were established and the colonising flora (presence and abundance) in each successional state was recorded and compared to the non-disturbed communities. Data were mainly analysed by means of Frequency Diagrams and Multivariate Methods. Dendrograms resulting from the Cluster Analyses showed the existence of two well-defined groups of species that differed in their colonisation power. One of the groups harboured Gypsophila struthium subsp. struthium, the dominant gypsophyte in the early states (in quarries abandoned up to 25 years ago), which coexists with other less abundant ruderal species. The other group was characterised by the presence of the remaining gypsophytes such as the endemisms Teucrium turredanum or Helianthemum alypoides, which show a low colonisation ability and appear in the last stages (mainly in quarries abandoned more than 30-35 years ago). Ordination Analyses separated the samples taken from the unaltered scrub from the others, which indicates that although there is a clear tendency towards the recovery of gypsum soils by the gypsophytes of the area, the primary succession does not lead to the re-establishment of the relative abundances of all the original species in the interval of time considered.