Spatio-temporal variability of faunal and floral assemblages in Mediterranean temporary wetlands.

Six temporary wetlands in the region of Sejenane (Mogods, NW Tunisia) were studied in order to characterize the aquatic flora and fauna and to quantify their spatio-temporal variability. Samplings of aquatic fauna, phytosociological relevés, and measurements of the physicochemical parameters of water were taken during four different field visits carried out during the four seasons of the year (November 2009-July 2010). Despite the strong anthropic pressures on them, these temporary wetlands are home to rich and diversified biodiversity, including rare and endangered species. Spatial and temporal variations affect fauna and flora differently, as temporal variability influences the fauna rather more than the plants, which are relatively more dependent on spatial factors. These results demonstrate the interest of small water bodies for maintaining biodiversity at the regional level, and thus underscore the conservation issues of Mediterranean temporary wetlands that are declining on an ongoing basis currently.

High genetic diversity and distinctiveness of rear-edge climate relicts maintained by ancient tetraploidisation for Alnus glutinosa.

Populations located at the rear-edge of a species' distribution may have disproportionate ecological and evolutionary importance for biodiversity conservation in a changing global environment. Yet genetic studies of such populations remain rare. This study investigates the evolutionary history of North-African low latitude marginal populations of Alnus glutinosa Gaertn., a European tree species that plays a significant ecological role as a keystone of riparian ecosystems. We genotyped 551 adults from 19 populations located across North Africa at 12 microsatellite loci and applied a coalescent-based simulation approach to reconstruct the demographic and evolutionary history of these populations. Surprisingly, Moroccan trees were tetraploids demonstrating a strong distinctiveness of these populations within a species otherwise known as diploid. Best-fitting models of demographic reconstruction revealed the relict nature of Moroccan populations that were found to have withstood past climate change events and to be much older than Algerian and Tunisian populations. This study highlights the complex demographic history that can be encountered in rear-edge distribution margins that here consist of both old stable climate relict and more recent populations, distinctively diverse genetically both quantitatively and qualitatively. We emphasize the high evolutionary and conservation value of marginal rear-edge populations of a keystone riparian species in the context of on-going climate change in the Mediterranean region.

Conservation of Mediterranean wetlands: interest of historical approach.

The wetlands of North Africa are an endangered and invaluable ecological heritage. Some of these wetlands are now protected by various conservation statutes; which actual impact has not yet been reliably evaluated. This article aims to assess the conservation management (Nature Reserve and Ramsar site) of a protected Tunisian lake, Majen Chitane, by using palaeoecological, historical and modern data, and by comparing it with the unprotected lake Majen Choucha. While located in similar environments, these lakes are today home to very different flora. Baseline conditions reconstructed from literature indicate that both lakes were very similar until the 1950s, and comparable to the current state of Majen Choucha, housing rich oligotrophic plant communities. In the 1960s, at the time that cultivation of the adjacent peatland began, Majen Chitane underwent strong ecological changes as the initial oligotrophic plant, diatom and zooplankton communities were replaced by eutrophication-tolerant ones. Eutrophication led to the local extinction of 40-55% of the hydrophytic and temporary-pool plant species, including those characteristic of the Isoetion. Given the damages and despite the recent conservation status of the site, it's unlikely that Majen Chitane will undergo any natural regeneration. Restoring it would start with completely protecting the complex lake-peatland and re-introducing the locally extinct species from Majen Choucha. This work exemplifies the usefulness of connecting palaeoecological, historical and modern data for the conservation of Mediterranean wetlands.

[Threats to and conservation of North African wetlands: the case of the Ramsar site of Beni-Belaid (NE Algeria)]. / Menaces et conservation des zones humides d'Afrique du Nord : le cas du site Ramsar de Beni-Belaid (NE algérien).

Because of their biogeographical and geomorphological context, the northeastern Algeria wetlands present high species and community richness. The vegetation study of the Ramsar site of Beni-Belaid (Kabylia) showed the existence of four main communities, distributed along gradients of hydrology and disturbance. The obtained results reveal worrying threats on short term: overgrazing results in the lake invasion by the sand eroded from the coastal dune; agriculture induces illegal cutting, water pollution and excessive groundwater pumping; finally, hunting and fishing are illegally practiced into the Ramsar site. The awareness of public authorities is needed in order: (1) to completely protect the wetland with the aim of restoring a riparian forest belt; and (2) to initiate a campaign for increasing the local population awareness, and its involvement in conservation programs.

[Alder forests of Numidia (N.E. Algeria): floristic biodiversity, vulnerability and conservation]. / Les aulnaies de Numidie (N.E. algérien) : biodiversité floristique, vulnérabilité et conservation.

The phytoecological study of the alder forests of north-east Algeria shows that these habitats with boreal affinities harbour very high species richness (> 400 species) and complex structures, which suggest their ancient origin. They correspond phytosociologically to two syntaxa, the Campanulo alatae-Alnenion glutinosae (riparian alder forests) and the Rusco hypophylli-Alnetum glutinosae (peat-forming alder carrs), respectively. Their degraded state and their regressive dynamics, observed during the 14 years of the study, reveal their precarious situation and their rapid ongoing decline under the influence of human-induced uncontroled disturbances (cutting, burning, draining, dumping…). With regard to their ecological, historical and patrimonial importance, the alder forests of Algerian Numidia should be urgently protected, with the aim of assuring the perennity of their exceptional floristic corteges.

Impact of grazing on the species richness of plant communities in Mediterranean temporary pools (western Morocco).

The impact of grazing on the vegetation of Moroccan temporary pools has been studied at 2 scales: regional (inter-pools) and local (intra-pools). Half of the 16 forest pools studied is located in a reserve and ungrazed. The other half, located within public forest, is grazed. Vegetation relevés coupled to water-depths measurements were carried out in each pool. The results showed a significant effect of grazing on both scales of analysis. This effect was found in the species composition of the vegetation, which differed between the 2 types of pools, and in the lower species richness and abundance of plant species in the grazed pools. These differences are interpreted as resulting from the selection by herbivores and the differential tolerance of species to disturbance. These impacts are likely to expose certain species to local extinction by reducing their populations.

[Vegetation structures and conservation of Mediterranean temporary wetlands: Mogods region (northern Tunisia)]. / Structures de végétation et conservation des zones humides temporaires méditerranéennes : la région des Mogods (Tunisie septentrionale).

Floristic surveys and phytoecological relevés were conducted on 36 temporary wetlands of Mogods region. Multivariate analyses (CA, AHC) performed on these data reveal the high specific and biocoenotic diversity of Mogods wetlands, which appear controlled by substrate nature and hydrology. Among the 128 hydrophytic species inventoried, 38 are presently in precarious status and 6 are presumed extinct. The Mogods region harbours, moreover, very rare habitats (peatlands and semi-permanent lakes), and a vast plain so-called Garâa Sejenane, exceptionally rich in temporary wetlands. These results underline the urgency of an adapted conservatory management, based on the development of scientific studies dealing with structure and functioning of hydrophytic communities of the region.

Recent discovery of the small pillwort (Pilularia minuta Durieu, Marsileaceae) in Tunisia: hope for an endangered emblematic species of Mediterranean temporary pools?

This article presents a synthesis of all localities where Pilularia minuta, an endangered Pteridophyte endemic of acidic Mediterranean temporary pools, was observed since its discovery in 1835. It aims at analysing the implications of its recent discovery in Tunisia, based on the comparison between new and previously published floristic surveys. The obtained data confirm the heliophilous pioneer character of P. minuta and reveal a disturbance-favoured behaviour in Tunisia. The small pillwort, which occurs in 16 locations around the Mediterranean basin, could be characterised by a good dispersion. However, it experienced the extinction of a quarter of its known populations over the last century. This decline seems to have affected only small populations (Maritime-Alps, France; Lazio, Italy) and highly disturbed areas (Algeria), while large ones (Sardinia, Italy; Corsica and Hérault, France; Andalusia, Spain; western Morocco), presumably more stable, survived. In a context of metapopulation, these large populations could be considered as 'source populations', and should be taken more especially in account in conservation strategies. Further investigations are needed for improving the conservation of the rare plants of Mediterranean temporary pools as well as contributing to a better knowledge of the mechanisms controlling their distribution and their present-day status.

Past context and dynamics of the development of a Mediterranean peatland (Mont Aigoual, France).

A minerotrophic peatland (fen) located on Mont Aigoual (southern France) is investigated for both modern vegetation and fossil pollen. The site is shown to originate around 2300 cal. BP and to have been strongly influenced by agro-pastoral activities. The spread of nitrophilous and not-grazed plant communities, at the expense of hydrophilous ones, characterized the evolution of the site, even during the recent decline of agricultural activities. This study highlights the role of disturbance on the development of the Aigoual peatlands, and their present-day degradation status, and underlines the need of a well-adapted conservatory management.

[Palaeostructures of vegetation at the upper limit of forests in the inner French Alps]. / Paléostructures de végétation à la limite supérieure des forêts dans les Alpes françaises internes.

The comparison of six pollen diagrams from French Alps allows us to reconstruct the past changes of vegetation structure at the upper limit of Subalpine range. Dense populations of Pinus cembra developed between 6500 and 2400 cal. BP, both in the southern Alps and the northern ones. Southern Alps seem however to be characterised by higher altitudinal limits, as shown by the past development of fir forests at 2080 m a.s.l. in the Ubaye valley. This study highlights the importance of taking in account local parameters in regional or continental reviews.

[Influence of vegetation on the accumulation of peat in southern Quebec]. / Influence de la végétation sur l'accumulation de la tourbe au Québec méridional.

Mirabel bog (southern Quebec) was studied with the aim of specifying the past influence of local vegetation on peat accumulation. This influence was essentially translated by the reduction of minerotrophic inputs and peat accumulation induced by the highering of the peatland surface. Extremely rich initial conditions allow to explain the very high accumulations of the beginning of the Holocene, observed in various plant communities, among which Larix forests with ferns and Carex without modern analogues. Moreover, the structure (forest density) and the composition (dominance of Cyperaceae or Ericaceae) of these communities have locally controlled the dynamic of peat accumulation. These results point out the interest of the confrontation between palynological and macrofossil data and the spatialisation of palaeoecological studies.