Analyse de la croissance en épaisseur de Dalbergia baronii (palissandre) et de Dalbergia monticola (bois de rose) dans la forêt classée d'Ambohilero sous transfert de gestion

International audienceLa gestion durable des ressources naturelles renouvelables est recommandée actuellement car elle assure à la fois la valorisation, la régénération et la conservation de la biodiversité. Cette étude basée sur l'évaluation de la croissance en épaisseur de deux espèces de Dalbergia endémiques de la forêt classée d'Ambohilero a été entreprise dans ce même contexte. Pour atteindre les objectifs, le suivi des activités cambiales utilisé et recommandé dans de nombreux pays tropicaux a été adopté. Le suivi de l'activité cambiale a été effectué à deux niveaux complémentaires : dans un premier temps le micro-échantillonnage dans le but d'analyser la variation saisonnière de l'activité cambiale et dans un second temps le marquage cambial afin d'évaluer le taux d'accroissement annuel des espèces cibles. Les résultats du micro échantillonnage ont révélé une activité cambiale maximale pendant la saison humide représentée par plus de 8 couches de cellules et minimale avec 5 couches de cellules en saison sèche. Le taux d'accroissement annuel du cambium vasculaire est 4,5mm pour D. baronii et 5,7mm pour D. monticola. Les résultats obtenus constituent un outil de base très important pour la gestion rationnelle et durable des espèces de Dalbergia dans les forêts à transfert de gestion d'Ambohilero

Ecological Restoration and Reforestation of Fragmented Forests in Kianjavato, Madagascar

A reforestation effort in Kianjavato Commune in southeast Madagascar is presented that combines native diversity with rapidly growing introduced and native pioneer trees. This work utilizes a three-tiered corridor design that capitalizes on the region’s mountainous terrain. The process of seed selection, transplantation, and survival rate of seedlings over a 16 month period is reported. The uppermost 50% of each mountain is planted with 38 woody species and most closely approximates native forest. This tier was divided into two categories, pioneer and secondary species. Most of the pioneer species were not native; however, results showed that four fast-growing, environmentally-tolerant native species could be suitable alternatives: Streblus mauritianus, Syzygium bernieri, Treculia madagascariensis and Uapaca thouarsii. More than 70,000 seeds of secondary species were extracted from fecal samples from wild, free-ranging black and white ruffed lemurs; the majority of which germinated significantly better after gut passage. The most effective pretreatment that enhanced germination was to scarify unwashed seeds. Commercially valuable trees, belonging to the community members, were grown on the lower half of each mountain. Lastly, the various contributions of the community are described along with agroforestry development plans designed to reduce pressure on forest resources and generate supplemental income

Win-win opportunities combining high yields with high multi-taxa biodiversity in tropical agroforestry

Resolving ecological-economic trade-offs between biodiversity and yields is a key challenge when addressing the biodiversity crisis in tropical agricultural landscapes. Here, we focused on the relation between seven different taxa (trees, herbaceous plants, birds, amphibians, reptiles, butterflies, and ants) and yields in vanilla agroforests in Madagascar. Agroforests established in forests supported overall 23% fewer species and 47% fewer endemic species than old-growth forests, and 14% fewer endemic species than forest fragments. In contrast, agroforests established on fallows had overall 12% more species and 38% more endemic species than fallows. While yields increased with vanilla vine density and length, non-yield related variables largely determined biodiversity. Nonetheless, trade-offs existed between yields and butterflies as well as reptiles. Vanilla yields were generally unrelated to richness of trees, herbaceous plants, birds, amphibians, reptiles, and ants, opening up possibilities for conservation outside of protected areas and restoring degraded land to benefit farmers and biodiversity alike

The aquatic Adephaga of the Makay, central-western Madagascar, with description of two new diving beetle species (Coleoptera, Gyrinidae, Haliplidae, Noteridae, Dytiscidae)

Water beetles of the families Gyrinidae, Haliplidae, Noteridae, and Dytiscidae (aquatic Adephaga) of the Makay in central-western Madagascar were surveyed in three campaigns during the years 2016–2018. A total of 74 species was collected from 62 sampling sites, all except one being newly recorded from the Makay. Copelatus malavergnorum sp. nov. (irinus group) and C. zanabato sp. nov. (erichsonii group) (Dytiscidae, Copelatinae) are described and their habitus and male genitalia are illustrated. A systematic account is given, including description of habitat preferences for each species. Analyses of species composition and dominance, species diversity and endemism highlighted the strong singularity of the aquatic Adephaga fauna inhabiting the sandstone massif of inner Makay (notably with several local endemic dytiscids) with respect to its peripheral lowlands. These comparisons were also performed between groups of sites categorised according to vegetation context (forested, semi-forested, non-forested). Rather unexpectedly, inner Makay although well-preserved and little deforested has relatively low endemism level and low species diversity (H1 Hill number twice lower than in the geographically close and geologically similar massif of Isalo). Species diversity was higher in the deforested and man-impacted peripheral sites, which yielded a rich contingent of western Madagascar lowland species including a few undescribed or rarely observed dytiscids

Distribution, biomass and local importance of tamarind trees in south-western Madagascar

The multipurpose tamarind (Tamarindus indica L.) tree is important for people’s livelihood and considered as sacred in the Mahafaly region of south-western Madagascar. However, the ongoing overexploitation of this species has caused a decline of tamarind trees. In this study, the species distribution, changes in tamarind biomass and the role of traditional taboos for the conservation of this species were determined to identify opportunities and constraints for its conservation and appropriate land management planning. Semi-structured interviews (N=63) were conducted in 10 villages in the study region to obtain information regarding the utilization of tamarind trees. During field surveys, the diameter at breast height (DBH), height, wood volume and wood biomass were measured for already felled trees (N=25). Additionally, 318 trees were inventoried by measuring their DBH, height and GPS location. Using high resolution satellite images from 2004/2005 and 2012 the crown areas of all tamarind trees in six village areas were identified. Allometric equations were established to predict their wood biomass from DBH, crown surface and wood volume. Tamarind trees are mainly used as supplementary food, as well as for traditional ceremonies, charcoal production and medicinal purposes. Altogether, 0.06–0.35 trees ha−1 were observed. A regression analysis yielded high coefficients of determination for the relationships between DBH and wood biomass (r2=0.98), DBH and crown area (r2=0.72), and crown area and wood biomass (r2=0.71). From 2004/2005 to 2012, wood biomass losses of 12%–90% were caused by charcoal production and slash and burn agriculture. The traditionally sacred status of the tree has become insufficient to secure its conservation in the Mahafaly region

Will Dalbergia species survive climate change? Predicting the potential future distribution of threatened species in Madagascar

Many species of Dalbergia, the source of highly prized rosewood, are threatened with extinction, a situation compounded by climate change. Accurate estimates of how suitable habitat will be impacted by global change are needed to inform their sustainable management. We selected five commercially exploited species endemic to humid eastern Madagascar (D. baronii, D. louvelii, D. maritima, D. normandii, and D. orientalis) to explore the potential value of species distribution modeling for understanding factors influencing their current distributions and estimating future patterns of suitable habitat, using MaxEnt and locality information for 715 taxonomically and spatially validated occurrences. Eight bioclimatic variables were used for modeling; projections were made under three scenarios for climate change and two for CO2 emissions. The distribution of each of the five species is primarily influenced by precipitation seasonality. Their potential geographical range is predicted to decrease by 2100 (-5% to -33%) under the optimistic CO2 scenario (RCP 2.6) except for a slight expansion of D. normandii (+2%), and by -14% to -58% under the pessimistic scenario (RCP 8.5). Our results show that suitable habitat will likely decrease with climate change, even within protected areas. They provide valuable information for future application of IUCN Red List criterion A to exploited species with fragmented distributions, targeting ex-situ conservation and management, and guiding restoration, reforestation, and other actions to establish and reinforce Dalbergia populations in areas where they are more likely to persist during climate change over the present century and beyond

Multiple values of isolated and clusters of Ficus tree species protected by Betsileo farmers in rural landscapes in Madagascar. Implications for biodiversity conservation

International audienceIn Madagascar, biodiversity, local livelihoods and agroecosystems are increasingly threatened. It is critical to understand and support local social-ecological systems that sustain livelihoods and value biodiversity. This study investigates why Betsileo communities in Ambendrana and Sahabe protect isolated individuals and clusters of Ficus species in their rural landscapes. Ficus trees have multiple values and sustain webs of ecological interactions that favor biodiversity. We show that spontaneous seedlings of Ficus are protected and that people also actively propagate Ficus by stem cuttings. Their multiple values and uses and the distribution patterns of each species, are linked to social-ecological dynamics and to the historical construction of local landscapes. Both past and present uses associated with each Ficus species define how they are protected