Several biological and ecological characteristics of Galium minutulum Jordan, a rare steno-mediterranean annual species, were investigated on some populations of the Hyeres islands, which are located in the north-eastern limit of the species distribution. The objectives of this study were to better document distribution, autecology and the form of rarity of this species in Provence and to propose accordingly some elements for a sustainable management of that vulnerable taxa. Galium minutulum exhibits a noteworthy polymorphism and an important ecological plasticity, which were both mostly explained by the existence of two allopatric cytotypes. Tetraploid individuals, small-sized and spindly, are located in the core-areas of the biggest islands (Porquerolles, Port-Cros, Le Levant), at the edges of the sclerophyllous matorrals or the thermophilous holm-oak forest. Hexaploids, more robust, grow on the coastal habitats directly exposed to sea sprays, notably on the smallest islands (Bagaud, Grand Ribaud). Many factors such as meiosis abnormalities, reduction of germination capacity of the tetraploid cytotype, frequent infestations of a pathogene fungus (blight), and the sensitive locations near the tracks and paths, generate several threats on this species and contribute to its rarity.

Quercus ilex sensu lato plays an important role in Western Mediterranean ecosystems, but is poorly developed in the Eastern Mediterranean where it is often replaced by Quercus calliprinos.

Les auteurs etudient la structure syntaxonomique ainsi que le valeur ecologique et dynamique, des matorrals du Maroc Oriental, entre la frontiere algerienne a l'Est, et les chaines du Rif et du Moyen Atlas. Ils appartiennent a la classe des Ononido-Rosmarinetea en milieu le plus souvent semi-aride et s'inscrivent dans diverses series constituees par Tetraclinis articulata, Pinus halepensis, Juniperus turbinata et Quercus rotundifolia (...)

We propose a terminology to distinguish from others those plant species whose natural distributions were changed by human activities (voluntary or not). Such plants may be native or non-native. We also develop a typology of the different ways by which they become integrated or not into the indigenous flora.Plants associated with man usually increase their distribution. Impressive and rapid invasions of non-native plants often occur in the circum-Mediterranean region, mainly where artificial or artificialized ecosystems prevail. Contrarily, their impact is limited where well-balanced natural ecosystems are dominant. Only when the natural balance is disturbed (e.g. by fires, overgrazing, abandonment of traditional cultivation methods, reafforestation) is the distribution of the native flora severely modified. Invading species with sexual reproduction alone must be separated from those showing asexual reproduction abilities, whether natural or linked to human activities. The importance of seed adaptation for dispersal is emphasized. These plants associated with man in the Circum-Mediterranean region originate mainly from temperate North America and Tropical Africa, but in the Western Mediterranean region the impact of Eastern Mediterranean and Irano-Touranian element is also important. The contribution of plants from the other Mediterranean climatic zones is generally very weak, with some remarkable exceptions.KeywordsMediterranean RegionNative FloraCape PeninsulaWestern Mediterranean RegionIndigenous FloraThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

The development of socio-economic activity over the past ten years in the Mediterranean region has induced severe changes in the main natural forest ecosystems.

RésuméDes indices et des méthodes de plus en plus complexes ont été, depuis plusieurs décennies, mis au point pour connaître les aptitudes à la repoduction forestière des territoires.Les auteurs analysent les bases, la spécificité et l'intérêt de ces différents indices, en illustrant leur propos par des données concernant la production de diverses essences forestières méditerranéennes.

Evidence is presented for dynamic successions in the Provence on the basis of a multivariate analysis, of a very large sample. Different phases in the Quercus suber series on silicious substrate are shown. Also the evolution of the vegetation groupings on Ventoux and Sainte-Baume mountains on calcareous substrate and at different levels in the zonation is specified.

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ResumeQuercus cerris L. (Chene chevelu) et Quercus crenata Lam., deux Chenes des etages mediterraneen superieur et submediterraneen dans le Sud-Est de l'Europe et l'Asie Mineure, atteignent la limite occidentale de leur aire spontanee dans les Alpes-Maritimes et dans leur avant-pays, ou ils sont toujours rares et infeodes a d'autres groupements mais dans les memes etages de vegetation. Leur presence renforce les affinites orientales des Alpes-Maritimes et ligures, precedemment mises en evidence par les auteurs. La distribution et l'ecologie de Quercus crenata (Qu. pseudosuber auct. plur.) paraissent exclure l'origine hybridogene longtemps admise, et cette espece a probablement ete confondue tour a tour avec les nombreux hybrides que donne Quercus suber avec des Chenes caducifolies de differentes sections.

RésuméLes auteurs étudient les associations qui s'intègrent à l'ordre des Anthyllidetalia montanae Quézel, 1971 (Ononidetalia striatae), depuis les Causses jusqu'aux Alpes ligures. Ils décrivent trois alliances nouvelles (Potentillion velutinae, Lavandulo-Genistion cinereae et Seslerion elegantissimae) ainsi que divers groupements végétaux.