The riparian forests in north Algeria : attempting to draw up a synsystematic synthesis in the western Mediterranean area. In Northern Africa, in recent decades, damage due to population increase, urbanisation and river management has resulted in a sharp decline in both area and quality of the forests in general, and riparian forests in particular. A regional study of the North Algerian riparian forests has been undertaken. Numerical analysis of the data revealed 3 main types of riparian forest communities, the plain alders of eastern Algeria, a biome unique to North Africa, riveraine forests of white poplar, the most important in their distribution and amount of surface cover, and high-altitude riparian forests, of which several new types have been described. This contribution aims mainly at comparing riparian forests from North Africa, which up till now had been poorly known and were not taken into account in a global system, with their homologue in the north-western Mediterranean sector. It submits a synsystematic diagram that does not only offer a new approach for all theses formations at the scale of the Western Mediterranean, but also shows the uniqueness of the riparian communities in the Maghreb (Clematido cirrhosae-Populion albae all. nov.) compared to the northerly Populion albae Br.-Bl. 1931.

Research on the habitats protected by the European Union's Habitats Directive (HD) has increased rapidly since its adoption in 1992. However, the methods and tools used to assess their conservation status are varied. In this context, we reviewed and summarized the scientific literature related to the coastal Natura 2000 habitats to list and sort parameters used to assess and map their conservation status. We found 225 papers that specifically focused on the assessment of conservation status of coastal habitats. An analysis of the papers was conducted based on the four parameters (range, area, structure and functions, future prospects) specified in the guidelines.Results highlight knowledge gaps regarding the availability of data and methods that measure the range, area, structure and functions and trends. Most of the papers focused on coastal dunes and were located in the Mediterranean biogeographic region. Therefore, the process of assessing the conservation status of coastal habitats remains complicated to implement because methodological approaches are mainly dominated by expert statements and all the procedures of the Habitats Directive are carried out within each member country and the final assessments are often the synthesis of these partial assessments. However, the multiscalar approach and the use of innovative technologies (databases, remote sensing) can be particularly relevant to develop replicable approaches and facilitate monitoring and the implementation of management measures.

The main concepts and definitions related to dynamic-catenal phytosociology are presented and discussed, in order to share common definitions within the French national program CarHAB dedicated to serial and catenal vegetation typology and mapping. Symphytosociology is based on serial approach and on the vegetation series concept, while Geosymphytosociology is based on catenal approach and on the geoseries concept.

Depuis une vingtaine d’années, l’évaluation de l’état de conservation des habitats est devenue un élément important des plans de gestion d’espaces naturels. La transposition de la Directive Habitats-Faune-Flore (92/43/CEE) (DHFF) dans le code de l’environnement fournit un cadre réglementaire pour l’évaluer à l’échelle d’un site Natura 2000. Le Muséum national d’Histoire naturelle (MNHN) a été chargé de proposer des méthodes à l’intention des gestionnaires afin de standardiser les évaluations et produire un diagnostic utile à la gestion. En se centrant sur la notion d’habitat (terrestre et marin) et sur son évaluation, nous proposons dans cet article des définitions afin de combler certaines lacunes identifiées et de préciser le concept d’état de conservation. La nécessité de se situer dans le cadre d’une typologie est évoquée avec ses avantages et ses limites. En considérant l’habitat comme un système complexe selon les théories générales des systèmes, son état de conservation traduit l’état de ses composantes ainsi que de leurs interactions, entre elles et avec l’environnement. Évaluer l’état de conservation implique ainsi d’évaluer la structure, la composition et les fonctions d’un habitat, qui sont interdépendantes. La nécessité d’évaluer amène à faire des choix, il s’agit de définir «l’état optimal souhaité» comme objectif théorique à long terme, et «l’état favorable choisi» comme proposition de cible opérationnelle pour les gestionnaires. Ces choix de seuils doivent être éclairés par des éléments scientifiques, tout en s’insérant dans le contexte socio-économique et culturel pris en compte par la DHFF. Nous discutons également de l’influence de la dynamique des habitats sur la définition des états de conservation. Enfin, certains choix méthodologiques clés sont présentés, notamment la place des espèces dans l’évaluation des habitats et les liens possibles entre diagnostic et gestion.

Based on the main landscape phytosociology works (symphytosociology and geosymphytosociology), elements of methods to carry out sigmarelevés and geosigmarelevés are brought through with the analysis of various concrete cases.These methodological elements follow an inductive approach for the characterization of sigmassociations and geosigmassociations (series and geoseries of vegetation).