La transición mediterráneo-eurosiberiana en Navarra: caracterización de los tomillares y aliagares su mediterráneos ( Thymelaeo-Aphyllanthetum monspeliensis )

Structure, flora, ecology and dynamics of submediterranean Thymus vulgaris garrigues ( Thymelaeo-Aphyllanthetum monspeliensis ) are analysed and compared with two groups of calcicolous scrubs, based upon 391 releves from Navarre (NE Spain). Those submediterranean Thymus vulgaris garrigues are more diverse, have higher proportion of hemicryptophytes than cushion heaths of Genista occidentalis ( Genistion occidentalis ) and show wide ecological differences, as they thrive at lower altitudes, on less inclined slopes with preference for southward exposures. They are distinguished from the more xerophillous somontano-aragones Thymus vulgaris garrigues ( Aphyllanthion ) by their higher frequency of Atlantic and Eurosiberian taxa, lower proportion of nano-phanerophytes and affinity for more humid climates. There is a gradual change in the flora and structure of those three scrub groups related with the Eurosiberian-mediterranean climatic transition. Thymelaeo-Aphyllanthetum floristic composition has higher frequency of character taxa of Rosmarinetea and Rosmarinetalia than those of Festuco-Ononidetea striatae and Ononidetalia striatae , and this feature together with its structure justify the inclusion of this community in Aphyllanthion alliance, pointing out their relationship with somontano-aragones Thymus vulgaris garrigues.