Eastern Madagascan Lowland Rain Forest
Below an altitude of about 800 m this unique tropical rain forest once extended along the entire east coast of Madagascar. Compared to its counterpart in the Guineo-Congolian BioProvince the canopy of these forests are generally lower and the foliage is much more coriaceous and xeromorphic. They are extremely species-rich and show great variation in species composition. The upper canopy is mainly characterized by endemic species of the Lauraceae (Anthostema madagascariensis, Ocotia, Ravensara), Monimiaceae (Tambourisa), Proteaceae (Dilobeia), Fabaceae (Dalbergia), Burseraceae (Canarium), Euphorbiaceae, Sapindaceae, Anacardiaceae, Elaeocarpaceae (Echinocarpus), Myrtaceae, Malpighiaceae, Flacourtiaceae, Loganiaceae, Hypericaceae (Mammea, Symphonia) and Ebenaceae (Diospyros). The giant endemic monocot Ravenula madagascariensis (Arecaceae) and several Dracaena species also contribute to the upper canopy. The lower tiers include small trees and shrubs frequently represented by Euphorbiaceae, Rubiaceae, Ochnaceae, Erythroxylaceae, Myrsinaceae, Celastraceae, Violaceae (Rinorea), Flacourtiaceae and Tiliaceae. Characteristic secondary forest species include endemics such as Harungana madagascariensis (Clusiaceae) and Psiadia altissima (Asteraceae), but these areas also comprise many introduced species.
Eastern Madagascan Moist Montane Forest
These forests are scattered in several areas of the central highlands chiefly between altitudes of 800-1300 m. They tend to be lower in statue than the lowland forests and the trees usually have an uneven, knarled appearance. They also support more epiphytes, especially mosses. Some of the largest remaining stands are on Amber Mountain (Montagne d’ Ambre). The canopy is usually characterized by members of the endemic genera Cuphocarpus (Araliaceae), Dilobeia (Proteaceae), Tambourissa (Monimiaceae), or mainly endemic species of Brachylaena (Asteraceae), Canarium (Burseraceae), Dalbergia (Fabaceae), Diospyros (Ebenaceae), Dombeya (Malvaceae), Eugenia (Myrtaceae), Grewia (Malvaceae), Protorhus (Anacardiaceae), Schefflera (Araliaceae), Symphonia (Clusiaceae), Vernonia (Asteraceae) and Weinmannia (Cunoniaceae). Although not confined to these formations, the endemic Podocarpus madagascariensis (Podocarpaceae) also occurs, while the two endemic genera (Ephippiandra and Hedycaryopsis) of the Monimiaceae are confined to these montane forests. Among the shrub layer are many endemic members of the Asteraceae, Myrsinaceae and Rubiaceae, while the herb layer is remarkable for the occurrence of species belonging to several temperate genera including Ajuga, Alchemilla, Cardamine, Cerastium, Hydrocotyle, Plantago, Ranunculus, Sanicula, Vaccinium and Viola.
Eastern Madagascan Sclerophyllous Forest
Usually at higher altitudes than the moist montane forests, mostly between 1300-2300m, these forests are exposed to lower temperatures with greater daily and seasonal variation, and stronger winds. Consequently the canopy tends to be lower (10-12m) and less well differentiated from the lower tiers. In fact, their structure is intermediate between forest and thicket. The trees are richly branched and typically have leaves that are small and zeromorphic in structure. Characteristic canopy species include various endemic members of the Asteraceae (such as Psiadia, Senecio, Vernonia and the endemic genera Apodocephala and Centauropsis), Ericaceae (Agauria), Lauraceae (Ocotea), and Rubiaceae (Clerodendrum). Epiphytic bryophytes and lichens are also well represented with many of the trees festooned with Usnea, while the ground layer is often composed of a dense carpet of mosses including mounds of Sphagnum. Other characteristic components include various members of the endemic genera Dicoryphe (Dicoryphe viticoides), Ocostemum, Tina (Tina isoneura), and Ascarinopsis (Ascarinopsis coursii) the only member of the Chloranthaceae found on Madagascar, and the endemic palm genera Chrysalidocarpus and Neodypsis.
Eastern Madagascan ‘Tapia’ Forest
On the western slopes of the central massif between about 800-1600 m the forests are dominated by Uapaca bojeri. These gnarled fire resistant trees, known locally as tapia, have evergreen coriaceous leaves and look similar in appearance to cork oak. The most frequent associates include Leptolaena bojereran, L. pauciflora, Sarcolaena oblongata (of the endemic family Sarcolaenaceae), while less frequent endemics include Asteropeia densiflora (Asteropeiaceae), Brachylaena microphylla (Asteraceae), Dicoma incana (Asteraceae) and Dodonaea madagascariensis (Sapindaceae). The shrub layer is mainly composed of Philippa species of the Ericaceae, together with various endemic Asteraceae (Conyza, Helichrysum, Psiada, Senecio, Vernonia), Fabaceae and Rubiaceae. Tree ferns, however, are lacking and the only palm present is the endemic Chrysalidocarpus decipiens (Arecaceae). Epiphytes are also rare, being composed of a few small ferns, various orchids of the genus Bulbophyllum and lichens. Ground layer species are also sparse and usually devoid of bryophytes.
Eastern Madagascan Ericoid Thicket
At high altitude above about 1800 m the montane sclerophyllous forest gives way to a thickets dominated by ericaceous species, which has only recently been explored biologically. They have a single, often impenetrable, stratum of woody plants growing to no more than about 6 m tall, and virtually all of the species are evergreen, ericoid types. In fact, the genus Erica (heather) has undergone massive speciation here. The chief components include mainly endemic species of Ericaceae (principally Philippa and Vaccinium), Asteraceae (principally Helichrysum, Psiadia, Senecio, Stenocline, Stoebe, Vernonia) and Rubiaceae. Somewhat less common are various endemic species of the Gentianaceae, Lamiaceae and Melastomataceae, but all have the ericoid habit. Scattered throughout the thicket are a few bushy trees emerging slightly above the general canopy including endemic trees such as Dodonaea madagascariensis (Sapindaceae) and Tambourissa gracilis (Monimiaceae), while on the massif of Manongariva the endemic palm Chrysalidocarpus acuminum (Arecaceae) occurs. Lianas and vascular epiphytes are absent except for a few small orchids, but epiphytic bryophytes and lichens are plentiful. The ground layer is also poorly developed, but includes a few endemic species of Impatiens (Balsaminaceae), and of the families Cyperaceae and Poaceae. Other endemic species occur in damp, peat filled depressions, while on the dryer outcrops draught tolerant endemics of Aloe, Kalanchoe and Helichrysum occur. One endemic species of particular interest is Sedum madagascariense (Crassulaceae) since this is the only Malagasy representative of this largely northern latitude genus.
Eastern Madagascan Rupicolous Shrublands
These areas are analogous to the bushlands of rock outcrops in Africa, but because of their lower stature, usually less than 2 m; the Malagasy versions are more accurately described as shrublands. The plants are usually rooted in crevices between rocks or on mats of thin soil, but because the soils tend to dry out rapidly between rain most of the species are draught resistant. The most frequent shrubs include several endemic members of the succulent genus Aloe including A. helenae and A. suzannae (Asphodelaceae). Other shrubs likely to be encountered are Cyanotis nodiflora, three species of Xerophyta of which X. dasylirioides is the most widespread, and the endemic Myrothamnus moschatus (Myrothamnaceae). The associated grasses include several endemic species mainly of the genera Aristida, Heterpogon, Hyparrhenia and Loudetia, while four grasses, Redfieldia hitchcockii and three species of Isalus are confined to inselbergs. Other herbaceous species in the ground layer include orchids of the genera Anagraecum and Cynorkis, many endemic species of Kalanchoe, and the endemic legume Mundulea phylloxylon (Fabaceae).
Further information required.
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