Evaluation du rôle des feux de brousse sur la composition, la structure, la phénologie, et la résistance de la végétation des bois de tapia (Uapaca bojeri) du massif d'Ibity, Nouvelle Aire Protégée, en vue de sa gestion durable

Aujourd'hui la perte et la transformation des habitats sont les principales menaces qui causent la diminution de la diversité biologique. A Madagascar, 90% des espèces végétales sont endémiques de l île et la plupart des formations végétales sont actuellement fortement dégradées ou remplacées par des formations secondaires résultant des activités humaines. Le bois de tapia, dominé par l espèce endémique de Madagascar Uapaca bojeri, est une formation végétale sclérophylle limitée aux Hautes Terres de l île. Cette formation, adaptée et résistante au régime de feu naturel de la région, est aujourd'hui fragmentée, couvrant une surface équivalente à 132 255 ha au total. Afin d augmenter la protection du bois de tapia, une nouvelle aire protégée (NAP) a été établie sur le Massif d Ibity. L état actuel de la végétation de bois de tapia est le résultat de l interaction de facteurs comme le type de sol, le climat, les pratiques humaines traditionnelles et le feu. Bien que le feu soit un des phénomènes qui fasse partie de la dynamique de cette végétation, le régime de feu actuel est également une des causes de sa dégradation. L objectif de cette thèse est donc d étudier le rôle du feu sur le cycle démographique et certains processus importants pour l installation et le recrutement. Ainsi, la germination, la phénologie et la résistance des plantules au feu ont été étudiées. Cette recherche montre que le problème actuel du bois de tapia est 1) la réduction de la floraison et de la fructification par les fréquences de feu élevées ; 2) la réduction du pourcentage de germination après l exposition des graines à de hautes températures, et 3) la mortalité élevée des plantules après le passage d un feu, en particulier quand la quantité de combustible est élevée. Ainsi l installation et le recrutement des espèces ligneuses sont limités par le feu, qui a un effet négatif sur la régénération naturelle. La gestion du feu autour de l aire protégée est ainsi nécessaire pour sa conservationCurrently loss and transformation of habitats are the main threats which cause the decrease of biological diversity. In Madagascar, 90% of plants species are endemic of the island and most of the plant formations types are at present strongly degraded or replaced by secondary formations resulting from human activities. Tapia woodland, dominated by the endemic tree Uapaca bojeri, is a sclerophyllous vegetation type limited in the Malagasy highlands. This vegetation type, adapted and resistant to the natural fire regime, is very fragmented today, covering a surface equivalent to 132 255ha on the island. In order to increase the protection of tapia woodland, a new protected area was established on Ibity massif. The current state of the woody vegetation is the result of the interaction of some factors as soil type, climate, human traditional practices and fire. Although fire is one of the phenomena that determine the dynamics of this vegetation, the current fire regime is also one of the main causes of degradation. The objective of this thesis is to study the role of fire on the demographic cycle and on some main processes for installation and recruitment. Thus, germination, plant phenology and seedlings resistance after burnt were studied. This research shows that the current problem of tapia woodland are 1) the reduction of flowering and fruiting by high fire frequencies; 2) the reduction of germination percent after seed exposure with high temperatures, and 3) high seedlings mortality after burnt, in particular when the quantity of fuel is raised. Installation and recruitment of woody species are limited by fire, which has a negative effect on natural regeneration. Fire management around the protected area is thus necessary for its conservationAVIGNON-Bib. numérique (840079901) / SudocSudocFranceF

Fire and the reproductive phenology of endangered Madagascar sclerophyllous tapia woodlands

AbstractTapia woodland vegetation is a remnant of Madagascar sclerophyllous forest that has developed under the selective pressure of fire and is dominated by the endemic tree Uapaca bojeri (Phyllanthaceae), locally named tapia. We carried out a 2-year study in tapia woodland at Ibity mountain, a new protected area in central highlands of Madagascar. We aimed to describe the reproductive phenology of this vegetation type and to determine whether it is affected by fire. We addressed two main questions: 1) does fire frequency affect the proportion of reproducing individuals and the intensity of each flowering and fruiting event?; and 2) does fire frequency influence the reproductive synchrony of species across the landscape? Thirteen woody species (373 individuals) were sampled at six sites selected across the Ibity mountain, where three that were burned three times between 2000 and 2010 and three burned just once during the decade. We found that (1) fire reduced the percentage of individuals that participate in each phenophase, and flower and fruit production was lower at the more frequently burned sites; and (2) increased fire frequency reduced the reproductive synchronization of species throughout the landscape. Fire is recognized as one of the major disturbances affecting mortality and recruitment of trees in tapia woodland. Our study indicates that fire also impacts the timing of plant reproduction at community and landscape levels

Influences des formations vegetales malgaches et des principaux facteurs climatiques dans la composition des flux polliniques atmospheriques de la region de Tananarive (Madagascar) au cours des 3 cycles annuels (1979, 1980, et 1981)

SIGLECNRS TD 11992 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Effects of heat on the germination of sclerophyllous forest species in the highlands of Madagascar

International audienceThe effects of fire on germination have been extensively studied in many ecosystems. Several studies have shown that plant species in ecosystems frequently exposed to fire can survive through two main mechanisms: vegetative regeneration (re-sprouts) and recruitment of new individuals from a fire-resistant seed bank. In Africa, an increase in temperature can break seed dormancy and stimulate germination of some herbaceous and woody species. In Madagascar, the once widespread highland ecosystems dominated by woody species are now highly fragmented and dominated by anthropic grasslands and fields, with a significantly reduced area occupied by sclerophyllous forests referred to as ‘tapia woodlands’. Six species of this endemic vegetation type were studied: Abrahamia ibityensis (Anacardiaceae), Aphloia theiformis (Aphloiaceae), Carissa edulis (Apocynaceae), Pentachlaena latifolia (Sarcolaenaceae), Uapaca bojeri (Phyllanthaceae) and Vaccinium secundiflorum (Ericaceae). Germination tests were conducted (i) by soaking seeds in water for 24 h (imbibition) or (ii) by exposing the seeds to dry heat. Four different temperatures (40, 60, 80 and 120°C) were applied, and seeds were exposed for 10, 30, 60 and 90 min. To simulate hotter faster-burning fires, two higher temperatures (100 and 120°C) were also used by exposing seeds to dry heat for 5 min. The results did not reveal any significant effect of 24-h water imbibition on germination. For most species, germination decreased with increasing temperature of treatment using dry heat. Uapaca bojeri did not germinate under any treatment. Further studies on the biological and ecological characteristics of tapia woodland species in response to fire are needed to help guide conservation, management and restoration activities focusing on this endemic vegetation type

Comparison of plant communities on the Ibity and Itremo massifs, Madagascar, with contrasting conservation histories and current status

<div><p><b><i>Background:</i></b> Deforestation processes and species extinction on islands have made them the focus of substantial efforts to create and strengthen local environmental organisations, establish new protected areas and improve natural resource management. In Madagascar, despite promising new policies, the flora and fauna are under serious threat. More than 80% of the island shows a significant loss of natural plant cover. Current levels of diversity reflect natural disturbance regimes, with fire representing one of the more important factors.</p><p><b><i>Aims:</i></b> We compared two new protected areas (Ibity and Itremo) with different environmental and management contexts to identify the roles and impacts of the environmental conditions and the different types of management applied by their respective local communities on vegetation. Both areas have extensive stands of tapia (<i>Uapaca bojeri</i>) woodland.</p><p><b><i>Methods:</i></b> Herbaceous vegetation surveys were carried out enumerating 16 1-m² quadrats in each of 10 sites on Ibity and seven on Itremo to characterise plant community composition and structure, complemented by tree and shrub surveys within three 40 × 40 m quadrats at each site.</p><p><b><i>Results:</i></b> Floristic richness was higher at Ibity. Populations of <i>U. bojeri</i> were better conserved at Itremo.</p><p><b><i>Conclusions:</i></b> While the total exclusion of fire is impracticable, careful management should enable the maintenance of natural conditions and at least lead to a reduction in the impacts on the structure of tapia woodland vegetation.</p></div

Achieving sustainable conservation in Madagascar: The case of the newly established Ibity Mountain Protected Area

International audienceGlobally, the number of protected areas (PAs) has increased exponentially during the last 25 years, particularly in biodiversity-rich developing countries. Many recent initiatives have integrated local-scale socioeconomic development into both design and management. Because the rates of deforestation and species extinction are increasing in most parts of the world, substantial efforts have been made to build and strengthen local environmental organizations, to establish new protected areas (NPAs), and to improve natural resource management. An NPA was recently established at Ibity Massif in central Madagascar, where a community-based conservation project is being coordinated by the Missouri Botanical Garden (MBG). In December 2008, a temporary protection order was issued, and definitive establishment of the NPA, which falls under Category V of the IUCN PA system, is expected before the end of 2015. This initiative has involved significant outreach and community education programs to raise awareness of Ibity's conservation and economic importance and the threats to its biodiversity, along with ongoing efforts to reduce fire frequency and implement ecological restoration projects with significant local community participation. In order to ensure the sustainability of this NPA, a co-management plan has been implemented involving MBG, local authorities, and the local population. This study describes the diagnostic process undertaken at Ibity in order to: 1) disseminate the data gathered to inform establishment of the NPA; and 2) summarize the initial state of the environment on the massif prior to the implementation of a management plan, as a baseline for assessing the NPA's effectiveness.Globalement, le nombre d'aires protégées (AP) a augmenté de façon exponentielle au cours des 25 dernières années, en particulier dans les pays en développement plus riches en biodiversité. De nombreuses initiatives récentes ont intégré le développement socio-économique à l'échelle locale dans sa conception et gestion. Etant donné que les taux de déforestation et d'extinction des espèces sont en augmentation dans la plupart des régions du monde, des efforts considérables ont été faits pour construire et renforcer les organisations locales de l'environnement, pour créer de nouvelles aires protégées, et pour améliorer la gestion des ressources naturelles. Une nouvelle AP est actuellement mise en place dans le massif d'Ibity, dans les haut-plateaux au centre de Madagascar, où un projet de conservation basé dans la participation communautaire est coordonné par le Missouri Botanical Garden (MBG). En Décembre 2008, un arrêté temporaire de protection a été délivré et la mise en place définitive de la nouvelle AP qui est classé dans la catégorie V selon le système des aires protégées de l'UICN est attendue avant la fin de 2015. Cette initiative a impliqué un programme de vulgarisation et d'éducation à la communauté centré sur la sensibilisation de la conservation de la diversité d'Ibity et de l'importance économique, les menaces qui pèsent sur la biodiversité, et les efforts en cours pour réduire la fréquence des feux et la mise en oeuvre des projets de restauration écologique avec une importante participation de la communauté locale. Afin d'assurer la durabilité de cet AP, un plan de co-gestion a été mis en place impliquant MBG, les autorités locales et la population locale. Cette étude documente et synthétise le processus de diagnostic entrepris à Ibity afin de: 1) faciliter la diffusion des données recueillies afin d'informer l'établissement de la nouvelle AP; 2) résumer l'état initial de l'environnement sur le massif avant la mise en oeuvre d'un plan de gestion et d'établir ainsi une base de référence qui peut être utilisée pour évaluer l'efficacité des nouvelles AP