Analyse structurale et floristique de la végétation selon les différents types de gestion sur le Plateau Calcaire Mahafaly.

International audienceLe parc national de Tsimanampesotse a connu son extension vers le Sud. Le principe adopté a été d'entourer ce parc des zones de transfert de gestion gérées par les VOI (Vondron'olona Ifotony). La présente étude a été réalisée dans le Plateau Calcaire Mahafaly, situé dans la partie Sud-Ouest de Madagascar. Notre objectif est de voir la pertinence ou non d'un transfert de gestion à travers l'analyse structurale de la végétation dans différents types de gestion. Trois zones ont été étudiées dont la zone Aire Protégée (AP), la zone Transfert de Gestion (TG) et la zone à Droit d'Usage (DU). Trois parcelles de 1 ha chacun subdivisées en plusieurs placettes de 20 m x 50 m ont été installées dans chaque site. La structure des formations étudiées a été évaluée selon la méthode de Gautier (1994). Les résultats de cette étude ont montré une grande différence au niveau de la structure de la végétation dans les trois zones d'études surtout entre la zone à DU et les deux autres zones à savoir la zone AP et la zone TG. Les différences sont surtout observées au niveau de l'ouverture de la formation et de la densité des individus par ha dans chaque zone d'étude. La formation végétale dans la zone à DU est la plus ouverte avec 60% de degré d'ouverture contre 50% pour la zone TG et 27 à 33% pour la zone AP. La densité des individus dans la zone à DU est très faible avec 1023 à 1356 ind/ha contre 2876 à 3149 ind/ha pour la zone TG et 2986 à 3478 ind/ha pour la zone AP. Nous constatons que le contrôle des prélèvements a des impacts sur la santé de la forêt bien que l'idée d'appropriation est encore embryonnaire

Bulbostylis itremoensis (Abildgaardieae, Cyperaceae), a new sedge species from Madagascar

An endemic species of Bulbostylis (Abildgaardieae, Cyperaceae) from Madagascar is described as new to science. Bulbostylis itremoensis is only known from two localities: the Itremo and Isalo massifs in the province of Fianarantsoa. The species can be recognised by its habit with numerous crowded culms, leaves and thick, soft roots with an outer mycorrhizal layer. Its culm is hairy, angular with about 10 rounded longitudinal ridges without conspicuous surface cells. The leaf sheaths are light brown to straw-coloured with numerous longitudinal nerves, densely short-hairy on the nerves but with numerous flexuose whitish hairs at their oblique orifices. Its inflorescence is a dense hemispherical head of c. 15 crowded spikelets with many erect or spreading involucral bracts. Its glumes are ovate, densely scabrid of which medium-reddish brown with a prominent 1 – 3-nerved green midrib ending below the obtuse apex or excurrent into a short mucro. This species is described, illustrated and compared to the other species of Bulbostylis that occur in the Itremo Massif Protected Area

Bark Essential Oil of Cedrelopsis grevei from Madagascar: Investigation of Steam-Distillation Conditions.

International audienceThe effect of the distillation time on the yield and chemical composition of the bark essential oil of Cedrelopsis grevei Baill. was investigated. Distillation kinetics were determined for three batches of bark sampled from two sites, i.e., Itampolo (batches IT1 and IT2) and Salary (SAL), located in a region in the south of Madagascar with characteristically large populations of C. grevei. The bark samples were subjected to steam distillation, and the essential oil was collected at 3-h intervals. The total yield (calculated after 14 h of distillation) varied from 0.9 to 1.7%, according to the batch tested. Moreover, the essential oils obtained were characterized by GC-FID and GC/MS analyses. During the course of the distillation, the relative percentages of the most volatile components (monoterpenes and sesquiterpene hydrocarbons) diminished progressively, whereas the least volatile ones (oxygenated derivatives) increased at a consistent rate. Principal component analysis (PCA) and agglomerative hierarchical clustering analysis (AHC) of the results, performed on 13 principal components, allowed distinguishing three chemical groups, corresponding to the three batches, irrespective of the distillation time. This indicated that the chemical variability currently observed with commercial samples is not mainly linked to the experimental conditions of the extraction process, as the distillation time did not significantly alter the chemical composition of the essential oils

Clove based cropping systems on the east coast of Madagascar: how history leaves its mark on the landscape

International audienceClove farming developed on the east coast of Madagascar a little over a century ago. The species is largely cultivated and farmed by communities of smallholders. This study aims to characterize clove based cropping systems. There are three types of coexisting clove systems: monoculture where clove is the sole crop with inter-rows covered by wild grasses, agricultural parklands where clove is associated with annual crops (rain fed rice, sugar cane, cassava) and finally complex agroforestry systems where clove is associated with other crops (vanilla), fruit trees (lychees, breadfruit, jackfruit) and pepper vines, as well as some forest trees. The study also shows that the majority of existing clove trees in the various cropping systems are over 50–60 years old. Our study aims to characterise the different clove based cropping systems with the intention of establishing a typology by measuring biometric criteria associated with clove trees, by determining the accompanying species and by characterising the horizontal and vertical structuration of plots. From these observations, we suggest some evolutionary hypotheses of clove systems in an attempt to resituate this typology in a historical dynamic implicating the agricultural history of the east coast of Madagascar and the evolution of the smallholders’ strategies