Madagascar succulent woodlands

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Ecoregions (main)


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Berenty Wildlife Preserve, Madagascar. Source: WWF-Canon / Luc Deslarzes

The Madagascar succulent woodlands ecoregion comprises a mosaic of succulent xeric adapted plants and deciduous forests that represent critical habitats for many species of animals and plants restricted to the western region of Madagascar. Some of the remarkable fauna and flora found in this ecoregion include the Giant jumping rat (Hypogeomys antimena), the Flat-tailed tortoise (Pyxis planicauda), two species of baobabs and several species of primates. The Madagascar succulent woodlands is classified within the Desert and Xeric Shrublands Biome, and is part of the Afrotropics Realm.

Location and general description

Screenshot-2014-04-15-12.41.59.png Source: World Wildlife Fund

These succulent woodlands are situated in southwestern Madagascar extending northward to the central western part of the island. Its southern limit is the start of the Madagascar spiny thicket and northern limit the lower end of the dry deciduous forest. The southern portion of the succulent woodland ecoregion is inland from the spiny thicket and further north this ecoregion meets the Mozambique Channel near Belo-Tsiribihina. The eastern extent of the ecoregion, at the 600 metres (m) to 800 m contour, is contiguous with the sub-humid forests ecoregion, and to a large extent coincides with the southwestern limit of the central highlands. The fauna and flora of the succulent woodlands show some overlap and similarities with the spiny thickets and dry deciduous forests. Previous descriptions of phytogeographical regions of Madagascar had grouped the succulent woodlands with the dry deciduous forests as a "western domain", but here this domain is separated to better differentiate between the spiny thicket and the dry deciduous woodlands. In many ways the succulent woodland ecoregion is a transitional habitat type between these two other neighbouring ecoregions.

The succulent woodland ecoregion exhibits a tropical dry climate with a distinct dry season between May and October. During the wet season, November to April, rainfall may reach 750 millimetres (mm), within a yearly range of 575 mm to 1330 mm. The annual average daily temperature for the region is between 25°C and 31°C.

The geology of the western part of the ecoregion comprises unconsolidated sands on the coast and Tertiary limestones and sandstones inland. In the southern part of the ecoregion, there are also metamorphic and igneous basement rocks. The soils are generally sandy with richer alluvial soils around river areas. The terrain is relatively flat but there are some notable rock outcrop]s and deep precipitous valleys (e.g., in the Makay region). The vegetation of the region is similar to dry deciduous woodland but is characterized by more xerophytic species. These species often have water storage adaptations, stem photosynthesis, and remain without leaves for long periods. Forests of the ecoregion may reach 15 m in height, with the endemic baobabs (Bombaceae family) Adansonia za and A. grandidieri as distinctive emergent species. Other canopy species belong to the families Euphorbiaceae and Leguminosae including several endemic species of Pachypodium. The shrub layer consists of the families Sapindaceae, Euphorbiaceae, Anacardiaceae, and Burseraceae.

In the southwest the coastal Mikea Forest between Manombo and Morombe have some species characteristic of southern spiny thickets, such as Didierea madagascariensis of Madagascar's endemic family, Didiereaceae. These forests grow on sandy soils and in a semi-arid climate with annual precipitation as low as 350 mm. The canopy, which rarely exceeds twelve m in height, is less tall than that of the forests inland and of those further north. The plant families forming the canopy include Leguminosae, Euphorbiacae, Burseraceae, and Bombaceae. The shrub layer is comprised mainly of Croton sp. (Euphorbiaceae), Aloe vaombe (Aloaceae) and lianas such as Dioscorea sp. (Dioscoreaceae). The ecoregion also includes headwaters of the Taheza, Fiheranana, and Onilahy rivers.

Biodiversity features

230px-Redtailed lemur.jpg Red-tailed sportive lemur (Lepilemur ruficaudatus), Madagascar. Source: Karl Lehmann

The forests of the ecoregion represent important habitats for eight species of lemurs and 60 to 90 species of birds. There is an overlap of species between the succulent woodlands and the spiny thicket to the south as well as the dry deciduous forests to the north. Within the succulent woodland ecoregion there are several areas of high local endemicity (e.g., the forests between the Tsiribihina and Mangoky rivers and around the National Park of Zombitse-Vohibasia. There are a total of 260 vertebrate taxa recorded within the Madagascar succulent woodlands.

Mammals

Five mammals are endemic to this ecoregion: narrow striped mongoose (Mungotictis decemlineata decemlineata), pale fork-marked lemur (Phaner furcifer pallescens), the giant jumping rat, Berthe's mouse lemur (Microcebus berthae) and the red-tailed sportive lemur (Lepilemur ruficaudatus). Near-endemics include the large-eared tenrec (Geogale aurita), the lesser hedgehog tenrec (Echinops telfairi), and Coquerel's dwarf lemur (Mirza coquerli). Verreaux's sifaka (Propithecus verreauxi verreauxi), and the red-fronted brown lemur (Eulemur fulvus rufus) are both found in this ecoregion. Several animal species have the entirety of their very localized ranges within this ecoregion.

Avifauna

Among the bird taxa, Appert's greenbul (Xanthomixis apperti) and the white-breasted mesite (Mesitornis variegata), are considered endemic to this ecoregion. The following species are near-endemic: Madagascar teal (Anas bernieri), Madagascar plover (Charadrius thoracicus), and long-tailed ground-roller (Uratelornis chimaera). Out of the above birds, one is threatened (Madagascar teal), and three are considered vulnerable (white-breasted mesite, long-tailed ground-roller, Madagascar plover). The red-capped coua (Coua ruficeps) is found throughout this ecoregion.

Reptiles

Some of the local endemic reptiles include Oplurus cuvieri, Chalarodon madagascariensis, and the gecko Phelsuma standingi. Pyxis planicauda has a narrow distribution range within the ecoregion. One gecko species, Paroedura vazimba, is only known from Zombitse-Vohibasia National Park. A least two frog species are endemic to this region: the hyperollid Heterixalus luteostriatus and the mycrohylid Dyscophus insularis. The rare snake Liophidium chabaudi occurs in this ecoregion, as well as numerous other species with limited distributions such as Mabuya tandrefana, Furcifer antimena, and Brookesia brygooi.

Goudotsbrighteyedfrogjohnsullivan.jpg Goudot's bright-eyed frog. Source: John Sullivan Amphibians

There are exactly six anuranAn amphibian that has limbs but no tail (includes all frogs and toads) species found in the Madagascar succulent woodlands: Antsouhy tomato frog (Dyscophus insularis); Brown rainfrog (Scaphiophryne brevis); Dueril's bright-eyed frog (Boophis tephraeomystax); Goudot's bright-eyed frog (Boophis goudotii); Madagascar bullfrog (Boophis tephraeomystax); and Mocquard's rainfrog (Scaphiophryne calcarata).

Ecological status

A number of protected areas fall within the succulent woodlands ecoregion, including Zombitse-Vohibasia National Park, Andranomena Special Reserve, and Kirindy-Mitea National Park. Further, the Kirindy forest, north of Marofandilia, is managed as a private reserve. These protected zones, as well as several classified forests, comprise a relatively small area of the remaining habitat within the ecoregion. The degree to which the forest and wildlife is protected varies considerably among reserves. The classified forests offer relatively little protection as deforestation by native peoples continues in these areas. Some of the most important habitats, such as the Mikea forest, have no protection.

Ecological threats

As with many of the habitats of Madagascar, the major threat to the succulent woodlands is fire - both intentional slash and burn for expansion of agricultural lands and unintentional wildfires. Further, the conversion of hardwoods into charcoal occurs in this region. Although it is not clear whether the ecoregion comprised only dry woodland, or a mosaic of woodland and grassland prior to human settlement, the increased incidence of fire in recent times has certainly led increasingly fragmented and isolated patches of native vegetation.

The Malagasy endemic tree Hazomalania voyroni is at risk of becoming extinct through traditional forest exploitation for construction wood. Some attempts have been made to propagate and replant this species. In addition to this species, there are several other endemic trees that are removed from the forests, mainly for construction purposes including Givotia madagascariense, Cedrelopsis grevei, and Commifora arofy. Various endemic species are also collected for charcoal production, which is considered a grave problem here and in the spiny thicket ecoregion.

Traditional hunting continues in the ecoregion even within protected areas. With increasing populations and greater movement of humans, these traditional activities are possibly becoming locally unsustainable. The main species threatened by hunting are the tenrec (Tenrec ecaudatus), fruit bats (Pteropus rufus and Eidolon helvum), and the red-fronted brown lemur. In many parts of the ecoregion, cattle and goat grazing are degrading the forests. Wood exploitation for charcoal production has caused massive deforestation. Honey collection, through the felling of trees, is a traditional activity that threatens the forests of the ecoregion to lesser degree.

Justification of ecoregion delineation

This ecoregion forms the northern part of the subarid bioclimate zone of Cornet. Humbert's (1955) southern vegetation domain was used to delineate the Spiny Thicket ecoregion, with the remaining extent of Cornet's sub-arid bioclimate defined as the Succulent Woodland. It shares floral affinities with both the spiny thicket and western dry-deciduous forest, yet contains distinct assemblages of plants and mammals and represents the northern limit of Didieraceae. The Madagascar succulent woodlands is accorded the ecocode AT1312 by the World Wildlife Fund.

Neighbouring ecoregions

The following ecoregions exhibit some tangency to the Madagascar succulent woodlands:

Furthermore, there are several disjunctive patches of Madagascar sub-humid forests which are totally surrounded by the Madagascar succulent woodlands.

References

  • Cornet, A. 1974. Essai de cartographie bioclimatique à Madagascar. Notice explicative No 55, ORSTOM, Paris.
  • Du Puy, D.J., and J. Moat. 1996. A refined classification of the primary vegetation of Madagascar based on the underlying geology: using GIS to map its distribution and to assess its conservation status. In W.R. Lourenço (ed.). Biogéographie de Madagascar, pp. 205--218, + 3 maps. Editions de l'ORSTOM, Paris. ISBN: 2709913240
  • Ganzhorn, J.U., B. Rakotosamimanana, L. Hannah, J. Hough, L. Iyer, S. Olivieri, S. Rajaobelina, C. Rodstrom, G. Tilkin. 1997. Priorities for Biodiversity Conservation in Madagascar. Primate Report 48-1, Germany.
  • Guillaumet, J-L. 1984. The vegetation: An extraordinary diversity in Jolly, A., Oberlé, P. & Albignac, R. eds. Key Environments: Madagascar. Pergamon Press, Oxford. ISBN: 0080280021
  • Humbert, H. 1955. Les territoires phytogéographiques de Madagascar. In. Colloques internationaux du C.N.R.S., 59: Les divisions écologique du Monde. Moyen d'expression, nomenclature, cartographie. Paris, juin-juillet 1954. Année biologique, 3e série, 31: 439-448.
  • Langrand, O. 1990. Guide to the Birds of Madagascar. Yale University Press, New Haven. ISBN: 0300043104
  • Lowry, P.P. II, G. E. Schatz, and P.B. Phillipson. 1997. The classification of natural and anthropogenic vegetation in Madagascar. pp. 93-123 in: S.M. Goodman and B. D. Patterson (eds.). Natural change and human impact in Madagascar. Smithsonian Institution. Press, Washington, D.C. ISBN: 1560986832
  • Nicoll, M.E., and O. Langrand. 1989. Madagascar: Revue de la conservation et des Aires protégées. World Wide Fund for Nature, Gland, Switzerland.
  • Randrianasolo, J., Rakotovao, P., Deleporte, P., Rarivoson, C., Sorg, J.-P., & Rohner, U. 1996. Local tree species in the tree nursery. pp. 117-132 in J. U. Ganzhorn and J.-P. Sorg (eds.). Ecology and economy of a tropical dry forest in Madagascar. Primate Report 46-1, Germany.
  • White, F. 1983. The vegetation of Africa, a descriptive memoir to accompany UNESCO/AETFAT Vegetation map of Africa. UNESCO, Paris. ISBN: 9231019554
Disclaimer: This article contains some information that was originally published by the World Wildlife Fund. Topic editors and authors for the Encyclopedia of Earth have edited that content and added new information. The use of information from the World Wildlife Fund should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.

Citation

World Wildlife Fund, C. Michael Hogan (July 1, 2015) Madagascar succulent woodlands. Encyclopedia of Earth. National Council for Science and Environment. Washington DC. ed. M. McGinley Retrieved from http://editors.eol.org/eoearth/wiki/Madagascar_succulent_woodlands