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Madagascar Subhumid Forests
This ecoregion contains a large number of endemic species, found in the remaining forest patches and also in some wetland areas, but the remaining habitats are highly fragmented and surrounded by a sea of anthropogenic grasslands and agricultural areas that have almost no biological value. This ecoregion is the site of some of the major extinctions of recent times, including that of the world’s largest flightless bird (Aepyornis maximus), and a number of large lemurs. With only small fragmented areas of habitat left within most areas of this ecoregion, there is a high risk of further species extinction in the near future.
This ecoregion is an important part of the Madagascar and the Indian Ocean Islands biodiversity hotspot. Dominated by the nation of Madagascar, the fourth largest island on Earth, the hotspot also includes the independent nations of Seychelles (including Aldabra), the Comoros, Mauritius (including Rodrigues), and the French overseas departments of Réunion, Mayotte (one of the Comoros) and the Iles Esparses around Madagascar in the Indian Ocean.
Location and General Description
The Madagascar Subhumid Forests are scattered in several "islands" of montane humid forest throughout the central highlands of Madagascar, the zone generally defined as above the coastal plain and escarpment starting at 900 meters. The remaining large areas of the forest habitat are in the Sambirano region in the northwest, portions of Amber Mountain (Montagne d’Ambre) in the north, significant areas of the northern highlands, and the middle elevational portions of certain massifs in the central highlands (e.g., Ankaratra and Andringitra). Also included are some wetlands and lakes (e.g., Lake Alaotra) and the "tapia" forest of the central highlands between 800-1600 m and in the dry southwest portion of the ecoregion. Also, a few remnant regions of forest, isolated and highly fragmented, remain scattered across the central highlands (e.g., Ambohitantely, Ambohijanahary, Isalo). In the extreme southwest of the island, the isolated mountain of Analavelona retains in the summital area (1000-1300 m) a remnant subhumid forest surrounded by much drier vegetation. Degraded forests, huge expanses of secondary grasslands and exotic tree plantations surround these habitats. This secondary vegetation is the result of human activity.
The subhumid forest ecoregion has been previously mapped as part of the eastern Madagascar regional center of endemism. To the east, these subhumid forests meet moist forests, in the lowland forest ecoregion around 800 m elevation, and to the west they merge into the dry deciduous forest ecoregion around 600 m elevation. At higher elevations (generally above 1,800 to 2,000 m) these habitats are replaced by ericoid thickets.
The rainfall is approximately 1,500 mm per year, although it may total as much as 2,000 mm in the Sambirano area in the northwest and as little as 600 mm in the southwest. The temperatures at higher elevations are mainly moderate, between 15° and 25°C. There is a cool, dry season between July and September and a warmer wet season during the rest of the year.
The underlying geology of the ecoregion is mainly ancient Precambrian basement rocks that have been deformed and uplifted over millions of years. There are a few areas of more recent lava flows, and some alluvial deposits associated with wetlands.
Vast grasslands now cover the central highlands at elevations ranging from 1,000 to 1,500 meters. There is some debate regarding the degree to which this upland area was formerly forested and the degrees to which humans have affected the fauna and flora. However, it is clear there have been very significant anthropogenic (human-caused) changes in the ecoregion. The central highlands was once home to a remarkable array of endemic species. These included several species of elephant birds (Aepyornithidae), including the world’s largest bird species (Aepyornis maximus), a giant tortoise, and several species of lemurs most of which were large bodied species, some larger than female gorillas today. All of these species have become extinct since the arrival of humans on the island around 2,000 years ago.
The secondary grasslands that cover most of the high, central highlands are composed of alien or pantropical grass and tree species. There are only 3 or 4 species of grass over vast areas, resulting in a virtually sterile landscape with extremely low species diversity and endemism. The dominant grasses are Aristida similis and A. rufescens, interspersed with a few herbaceaous species. Several species of Eucalyptus and Acacia trees have been introduced and are now the most common trees in the highlands. Some native, fire-resistant trees persist in areas of the central highlands, including the endemic palms Bismarckia nobilis and Ravenala madagscariensis and the tapia tree (Uapaca bojeri). Other native trees of the genera Sarcolaena, Tambourissa and Weinmannia are also found.
The Sambirano region in the northwest is a center of endemism and a transition zone between the species compositions (both plant and animal) of the western and the eastern regions of Madagascar. The montane forests of the Sambirano, starting at between 600 and 1000 meters, are very similar in structure to more eastern subhumid forests. Relatively little remains of the lowland forest between sea level and about 800 m, the zone that was separated as the Sambirano Domain. There are subhumid forests up to 1,800 m. This habitat changes to a more sclerophyllous forest at higher elevations. This higher ground, above 2000 m, including the Tsaratanana Massif, is included in the ericold thicket ecoregion.
There are few remaining patches of subhumid forest on the central highlands. Small patches are found on Ankaratra Massif, and some larger forest blocks are on the slopes of Andringitra and Tsaratanana massifs. At the higher elevations, the subhumid forest, also referred to as sclerophyllous montane forest, holds canopy trees that are 10 to 12 m in height, including species from the families Rubiaceae, Lauraceae, Verbenaceae and Ericaceae. At lower elevations, from 1,400 to 1,600 m, the forest has a 15 m canopy and includes species in the families Cunoniaceae, Araliaceae, Cornaceae, Celestraceae, Anacardiaceae, Burseraceae, Euphorbiaceae, Lauraceae and Ebenaceae.
Amber Mountain (Montagne D’Ambre) contains a significant area of humid forest. An isolated basaltic mountain with a humid microclimate above 1000 m, it is surrounded by dry deciduous forests. At sea level, the annual precipitation is approximately 980 mm, while at the peak of Amber Mountain the precipitation averages 2,378 mm. The humid forest on the mountain slopes has a canopy 40 meters high, dominated by plants from the families Sapotaceae, Burseraceae, Monimiaceae, Lauraceae, Flacourtiaceae, Sterculiaceae, Myrtaceae, Annonaceae, Apocynaceae, Potaliaceae and Elaeocarpaceae. In addition to the floral diversity of the forest, the faunal diversity is high with 8 species of primates and nearly 80 species of birds, including the endemic species the Ambre Mountain Rock Thrush (Monticola erythronotus). As the natural habitats of this ecoregion experienced numerous vegetational shifts associated with Pleistocene climatic vicissitudes, many species are endemic and have very narrow altitudinal or isolated distributions.
The remaining "tapia" woodlands, in the southwest of the ecoregion are restricted in distribution. The largest intact areas of this habitat are found in the Isalo and Itremo massifs on sandstone and quartzite. They are characterized by a relatively open canopy dominated by members of the family Sarcolaenaceae and Euphorbiaceae, including the fire-resistant Uapaca bojeri and the genus Sarcolaena. The shrub layer consists of Asteraceae, Rubiaceae, and Leguminosae. There are also some endemic Kalanchoe and Aloe species.
Madagascar Subhumid Forests
This ecoregion contains a large number of endemic species, found in the remaining forest patches and also in some wetland areas, but the remaining habitats are highly fragmented and surrounded by a sea of anthropogenic grasslands and agricultural areas that have almost no biological value. This ecoregion is the site of some of the major extinctions of recent times, including that of the world’s largest flightless bird (Aepyornis maximus), and a number of large lemurs. With only small fragmented areas of habitat left within most areas of this ecoregion, there is a high risk of further species extinction in the near future.
This ecoregion is an important part of the Madagascar and the Indian Ocean Islands biodiversity hotspot. Dominated by the nation of Madagascar, the fourth largest island on Earth, the hotspot also includes the independent nations of Seychelles (including Aldabra), the Comoros, Mauritius (including Rodrigues), and the French overseas departments of Réunion, Mayotte (one of the Comoros) and the Iles Esparses around Madagascar in the Indian Ocean.
Location and General Description
The Madagascar Subhumid Forests are scattered in several "islands" of montane humid forest throughout the central highlands of Madagascar, the zone generally defined as above the coastal plain and escarpment starting at 900 meters. The remaining large areas of the forest habitat are in the Sambirano region in the northwest, portions of Amber Mountain (Montagne d’Ambre) in the north, significant areas of the northern highlands, and the middle elevational portions of certain massifs in the central highlands (e.g., Ankaratra and Andringitra). Also included are some wetlands and lakes (e.g., Lake Alaotra) and the "tapia" forest of the central highlands between 800-1600 m and in the dry southwest portion of the ecoregion. Also, a few remnant regions of forest, isolated and highly fragmented, remain scattered across the central highlands (e.g., Ambohitantely, Ambohijanahary, Isalo). In the extreme southwest of the island, the isolated mountain of Analavelona retains in the summital area (1000-1300 m) a remnant subhumid forest surrounded by much drier vegetation. Degraded forests, huge expanses of secondary grasslands and exotic tree plantations surround these habitats. This secondary vegetation is the result of human activity.
The subhumid forest ecoregion has been previously mapped as part of the eastern Madagascar regional center of endemism. To the east, these subhumid forests meet moist forests, in the lowland forest ecoregion around 800 m elevation, and to the west they merge into the dry deciduous forest ecoregion around 600 m elevation. At higher elevations (generally above 1,800 to 2,000 m) these habitats are replaced by ericoid thickets.
The rainfall is approximately 1,500 mm per year, although it may total as much as 2,000 mm in the Sambirano area in the northwest and as little as 600 mm in the southwest. The temperatures at higher elevations are mainly moderate, between 15° and 25°C. There is a cool, dry season between July and September and a warmer wet season during the rest of the year.
The underlying geology of the ecoregion is mainly ancient Precambrian basement rocks that have been deformed and uplifted over millions of years. There are a few areas of more recent lava flows, and some alluvial deposits associated with wetlands.
Vast grasslands now cover the central highlands at elevations ranging from 1,000 to 1,500 meters. There is some debate regarding the degree to which this upland area was formerly forested and the degrees to which humans have affected the fauna and flora. However, it is clear there have been very significant anthropogenic (human-caused) changes in the ecoregion. The central highlands was once home to a remarkable array of endemic species. These included several species of elephant birds (Aepyornithidae), including the world’s largest bird species (Aepyornis maximus), a giant tortoise, and several species of lemurs most of which were large bodied species, some larger than female gorillas today. All of these species have become extinct since the arrival of humans on the island around 2,000 years ago.
The secondary grasslands that cover most of the high, central highlands are composed of alien or pantropical grass and tree species. There are only 3 or 4 species of grass over vast areas, resulting in a virtually sterile landscape with extremely low species diversity and endemism. The dominant grasses are Aristida similis and A. rufescens, interspersed with a few herbaceaous species. Several species of Eucalyptus and Acacia trees have been introduced and are now the most common trees in the highlands. Some native, fire-resistant trees persist in areas of the central highlands, including the endemic palms Bismarckia nobilis and Ravenala madagscariensis and the tapia tree (Uapaca bojeri). Other native trees of the genera Sarcolaena, Tambourissa and Weinmannia are also found.
The Sambirano region in the northwest is a center of endemism and a transition zone between the species compositions (both plant and animal) of the western and the eastern regions of Madagascar. The montane forests of the Sambirano, starting at between 600 and 1000 meters, are very similar in structure to more eastern subhumid forests. Relatively little remains of the lowland forest between sea level and about 800 m, the zone that was separated as the Sambirano Domain. There are subhumid forests up to 1,800 m. This habitat changes to a more sclerophyllous forest at higher elevations. This higher ground, above 2000 m, including the Tsaratanana Massif, is included in the ericold thicket ecoregion.
There are few remaining patches of subhumid forest on the central highlands. Small patches are found on Ankaratra Massif, and some larger forest blocks are on the slopes of Andringitra and Tsaratanana massifs. At the higher elevations, the subhumid forest, also referred to as sclerophyllous montane forest, holds canopy trees that are 10 to 12 m in height, including species from the families Rubiaceae, Lauraceae, Verbenaceae and Ericaceae. At lower elevations, from 1,400 to 1,600 m, the forest has a 15 m canopy and includes species in the families Cunoniaceae, Araliaceae, Cornaceae, Celestraceae, Anacardiaceae, Burseraceae, Euphorbiaceae, Lauraceae and Ebenaceae.
Amber Mountain (Montagne D’Ambre) contains a significant area of humid forest. An isolated basaltic mountain with a humid microclimate above 1000 m, it is surrounded by dry deciduous forests. At sea level, the annual precipitation is approximately 980 mm, while at the peak of Amber Mountain the precipitation averages 2,378 mm. The humid forest on the mountain slopes has a canopy 40 meters high, dominated by plants from the families Sapotaceae, Burseraceae, Monimiaceae, Lauraceae, Flacourtiaceae, Sterculiaceae, Myrtaceae, Annonaceae, Apocynaceae, Potaliaceae and Elaeocarpaceae. In addition to the floral diversity of the forest, the faunal diversity is high with 8 species of primates and nearly 80 species of birds, including the endemic species the Ambre Mountain Rock Thrush (Monticola erythronotus). As the natural habitats of this ecoregion experienced numerous vegetational shifts associated with Pleistocene climatic vicissitudes, many species are endemic and have very narrow altitudinal or isolated distributions.
The remaining "tapia" woodlands, in the southwest of the ecoregion are restricted in distribution. The largest intact areas of this habitat are found in the Isalo and Itremo massifs on sandstone and quartzite. They are characterized by a relatively open canopy dominated by members of the family Sarcolaenaceae and Euphorbiaceae, including the fire-resistant Uapaca bojeri and the genus Sarcolaena. The shrub layer consists of Asteraceae, Rubiaceae, and Leguminosae. There are also some endemic Kalanchoe and Aloe species.
Madagascar Subhumid Forests
Madagascar Subhumid Forests
Madagascar Subhumid Forests
Madagascar Subhumid Forests
Madagascar Subhumid Forests
Madagascar Subhumid Forests
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