Place et rôle de Juniperus thurifera dans les structures de vegetation des Alpes du Sud

Les formations a genévrier thurifère des Alpes françcaises du sud, présentent un intérêt biogeographique et historique de première importance. Les auteurs étudient les structures de végétation que le genevrier organise dans les étages supraméditerranéen et montagnards.

Nomenclature and syntaxonomic notes on some high-rank syntaxa of the European grassland vegetation

We present descriptions of a new order (Ranunculo cortusifolii-Geranietalia reuteri and of a new alliance (Stachyo lusitanicae-Cheirolophion sempervirentis) for the herbaceous fringe communities of Macaronesia and of the southwestern Iberian Peninsula, respectively. A new alliance, the Polygalo mediterraneae-Bromion erecti (mesophilous post-cultural grasslands), was introduced for the Peninsular Italy. We further validate and typify the Armerietalia rumelicae (perennial grasslands supported by nutrient-poor on siliceous bedrocks at altitudes characterized by the submediterranean climate of central-southern Balkan Peninsula), the Securigero-Dasypyrion villosae (lawn and fallow-land tall-grass annual vegetation of Italy), and the Cirsio vallis-demoni-Nardion (acidophilous grasslands on siliceous substrates of the Southern Italy). Nomenclatural issues (validity, legitimacy, synonymy, formal corrections) have been discussed and clarified for the following names: Brachypodio-Brometalia, Bromo pannonici-Festucion csikhegyensis, Corynephoro-Plantaginion radicatae, Heleochloion, Hieracio-Plantaginion radicatae, Nardetea strictae, Nardetalia strictae, Nardo-Callunetea, Nardo-Galion saxatilis, Oligo-Bromion, Paspalo-Heleochloetalia, Plantagini-Corynephorion and Scorzoneret alia villosae. 

Validations and descriptions of European syntaxa of vegetation dominated by lichens, bryophytes and algae

Fourty-two high-rank syntaxa and seven associations of the thallophyte system of syntaxa are either described as new or validated in this paper. Among those, there are the following nine classes: Aspicilietea candidae, Caulerpetea racemosae, Desmococcetea olivacei, Entophysalidetea deustae, Gloeocapsetea sanguineae, Mesotaenietea berggrenii, Naviculetea gregariae, Porpidietea zeoroidis, Roccelletea phycopsis. Eleven orders and ten alliances as well as three associations are described or validated: the Aspicilietalia verruculosae (incl. Aspicilion mashiginensis and Teloschistion contortuplicati), the Caulerpetalia racemosae (incl. Caulerpion racemosae), the Desmococcetalia olivacei (incl. Desmococcion olivacei), the Dirinetalia massiliensis, the Fucetalia vesiculosi (incl. Ascophyllion nodosi), the Gloeocapsetalia sanguineae, the Lecideetalia confluescentis (incl. Lecideion confluescentis), the Mesotaenietalia berggrenii (incl. Mesotaenion berggrenii, Mesotaenietum berggrenii and Chloromonadetum nivalis), the Naviculetalia gregariae (incl. Oscillatorion limosae and Oscillatorietum limosae), the Porpidietalia zeoroidis (incl. Porpidion zeoroidis), and the Roccelletalia fuciformis (incl. Paralecanographion grumulosae). Further, five orders, seven alliances and four associations, classified in known classes, were described as well. These include: the Bacidinetalia phacodis, the Agonimion octosporae and the Dendrographetalia decolorantis (all in the Arthonio radiatae-Lecidelletea elaeochromae), the Staurothelion solventis (in the Aspicilietea lacustris), the Pediastro duplicis-Scenedesmion quadricaudae and the Pediastro duplicis-Scenedesmetum quadricaudae (both in the Asterionelletea formosae), the Peccanion coralloidis and the Peltuletalia euplocae (both in the Collematetea cristati), the Laminarion hyperboreae, the Saccorhizo polyschidi-Laminarietum and the Alario esculenti-Himanthalietum elongatae (all in the Cystoseiretea crinitae), the Delesserietalia sanguinei, the Delesserion sanguinei and the Delesserietum sanguineae (all in the Lithophylletea soluti), as well as the the Rinodino confragosae-Rusavskietalia elegantis and the Rhizocarpo geographici-Rusavskion elegantis (both in the Rhizocarpetea geographici).

How simple grazing rules can lead to persistent boundaries in vegetation communities.

Natural landscape boundaries between vegetation communities are dynamically influenced by the selective grazing of herbivores. Here we show how this may be an emergent property of very simple animal decisions, without the need for any sophisticated choice rules etc., using a model based on biased diffusion. Animal grazing intensity is coupled with plant competition, resulting in reaction-diffusion dynamics, from which stable boundaries spontaneously emerge. In the model, animals affect their resources by both consumption and trampling. It is assumed that forage consists of two heterogeneously distributed competing resource species, one that is preferred (grass) over the other (heather) by the animals. The solutions to the resulting system of differential equations for three cases a) optimal foraging, b) random walk foraging and c) taxis-diffusion are presented. Optimal and random foraging gave unrealistic results, but taxis-diffusion accorded well with field observations. Persistent boundaries between patches of near-monoculture vegetation were predicted, with these boundaries drifting in response to overall grazing pressure (grass advancing with increased grazing and vice versa). The reaction-taxis-diffusion model provides the first mathematical explanation for such vegetation mosaic dynamics and the parameters of the model are open to experimental testing.

Vegetation history at the multi-period prehistoric complex at Ballynahatty, Co. Down, Northern Ireland.

Palaeoecological methods can provide an environmental context for archaeological sites, enabling the nature of past human activity to be explored from an indirect but alternative perspective. Through a palynological study of a small fen wetland located within the catchment of a multi-period prehistoric complex at Ballynahatty, Co. Down, Northern Ireland, we reconstruct the vegetation history of the area during the early prehistoric period. The pollen record reveals tentative evidence for Mesolithic activity in the area at 6410-6220 cal. BC, with woodland disturbance identified during the Mesolithic-Neolithic transitional period ca. 4430-3890 cal. BC. A more significant impact on the landscape is observed in the Early Neolithic from 3944-3702 cal. BC, with an opening up of the forests and the establishment of a mixed agricultural economy. This activity precedes and continues to be evident during the Mid-Neolithic during which megalithic tombs and related burial sites were constructed at Ballynahatty. Due to chronological uncertainties and a possible hiatus in peat accumulation in the fen, the contemporary environment of the Ballynahatty timber circle complex (constructed and used ca. 3080-2490 cal. BC) and henge (dating to the third millennium cal. BC) cannot certainly be established. Nevertheless, the pollen record suggests that the landscape remained open through to the Bronze Age, implying a long continuity of human activity in the area. These findings support the idea that the Ballynahatty prehistoric complex was the product of a gradual and repeated restructuring of the ritual and ceremonial landscape whose significance continued to be recognised throughout the early prehistoric period.

Water requirements as a bottleneck in the reintroduction of European roe deer to the southern edge of its range

Success rates of reintroduction programs are low, often owing to a lack of knowledge of site-specific ecological requirements. A reintroduction program of European roe deer (Capreolus capreolus (L., 1758)) in a dry Mediterranean region in Israel provides an opportunity to study the bottleneck effect of water requirements on a mesic-adapted species. Four does were hand-reared and released in a 10 ha site consisting of an early succession scrubland and a mature oak forest. We measured daily energy expenditure (DEE) and water turnover (WTO) using the doubly labeled water technique during summer and winter. DEE was similar in the summer and winter, but there was a significant difference in WTO and in the source of gained water. In winter, WTO was 3.3 L/day, of which 67% was obtained from vegetation. In summer, WTO dropped to 2.1 L/day, of which only 20% was obtained from the diet and 76% was gained from drinking. When the water source was moved to a nonpreferred habitat, drinking frequency dropped significantly, but water consumption remained constant. In a dry Mediterranean environment, availability of free water is both a physiological contraint and a behavioral constraint for roe deer. This study demonstrates the importance of physiological and behavioral feasibility studies for reintroduction programs.