Plant life

From Mgias

Contents 1 Introduction 2 Relationships with African and Asian species 3 Vegetation types within the 5 Regions 3.1 Northern Region 3.2 Central Region 3.3 Western Region 3.4 Southern Region 3.5 Eastern Region

Introduction

Madagascar was once covered in virgin primary vegetation. It also once had a more humid climate. It was named” the green island" by the first inhabitants who arrived in the country around the 6th to 9th century.

Its original forests were very rich holding an abundance of wildlife consisting of some extinct megafauna which was related to native vegetation.

Madagascar has since been subjected to Quaternary climate changes which followed the vegetation change. This has had profound impact on the distribution of fauna and flora throughout Madagascar. Since the arrival of humans in Madagascar, this natural change has been followed by an increase in the number of bush fires. In the last few decades with rapid population growth rate, fires have raged. Now, 80% of Madagascar's original virgin forest is are gone forever. This has caused the degradation of the environment from soil erosion, silting, and declining soil fertility.

However,the remaining Malagasy flora has one of the world ‘s most fascinating plant diversity with 191 families being represented, 8 of which are totally endemic. In fact 85% of Madagascar's 12,000 plants are endemic. Of these, 75% are used in herbal medecine and in pharmacology.

This astonishing biodiversity is the result of Madagascar’s prolonged isolation from the African mainland following the break-up of Gondwanaland around 165 million years ago. So native species have evolved on their own on a micro-continent with different climatic zones. Of particular interest is the primitive flowering plant Takhtajania perrieri which belongs to Winteraceae family and existed around the same period as the dinosaurs. It is endemic to Madagascar and has been discovered in Manongarivo massif and Anjanaharibe in the far north.

Relationships with African and Asian species

The dry deciduous vegetation of the western ‘s Madagascar has close affinities with those of Africa , while the moist forest of the eastern part of the island has strong relationship with flora of Asia. Madagascar possesses only 25% of Africa’s plants including some orchids and dry-adapted plants such as euphorbias and baobabs. 7 of Madagascar's baobab species are endemic and only one is also found in Africa. On the other hand, the carnivorous plant genus, found in the coastal areas of eastern Madagascar, is related to those of South-east Asia.

Vegetation types within the 5 Regions

Northern Region

The Northern Region is a leeward region like the western coast of the country. Here there are three distict forest types

1. A Dry deciduous forest,caused by a dry tropical climate with mean annual rainfall over 900mm. The trees of the forest canopy here shed their leaves during the prolonged dry season.
2. A Rainforest with an annual rainfall is averaging 2500 mm. This is caused by the presence of Tsaratanana massif and the volcanic Montagne d’Ambre massif which creates micro-climate to the surrounding areas.
3. A Transition forest between dry and wet areas which can be seen near Daraina

Central Region

The Central Region is composed of highlands with rainfall exceeding 2000 to 3000mm, and plains. It also has three vegetation types:

1. Secondary grassland, where much of the area is degraded, and remainder of virgin primary vegetation is confined to inaccessible areas. The central highlands lie on elevations
2. High montain vegetation lying above 1500m in elevation. Here the plants are characterised by cold adapted heathland(Phillipia, Erica...), rupicolous shrubland,(Psydia, Helichrysome), and lichen and moss forests.
3. Middle elevation rainforest which lies about 800m to 1475m. This is on the rainforest corridor of the eastern escarpment, and is dominated by emergent trees such Dalbergia family, (rosewood),Tambourissa , wild fig and Weinmania, and several compositae. A multitude of endemic Symphonia species are found in mountainous regions, in contrast to Africa and South America have just one species each. Orchids ,epiphytes, bamboos , treeferns, lichens and palms are also present.

It is also home to rare endemic plants that have adapted to harsh thirst-land conditions. These include

1. The succulents Pachipodium rosulatum rosulatum,
2. Aloe isaloensis,
3. Euphorbia duvani and
4. Kalanchoe sp. These cling to rocky hillsides.

Western Region

The Western Region has an annual rainfall ranging from 500 to 2000 mm. There is a marked dry season of 7 to 8 months, during which most of the trees shed their leaves. The dry deciduous forest canopy is generally low, ranging only from 12 to 20 meters high. Obviously there is a predominance drought resistant plants whose stems, trunks or roots store water. Leguminous trees such as dalbergia, cassia, commiphora, hildegardia are also common. Additionally, 5 species of Madagascar's 7 baobab trees, such as Adansonia grandidieri or fan shape baobab (Morondava) are present in this area.

Southern Region

The plant life of the Southern Region is characterised by a striking dry thorny thicket forest or spiny forest which has a capacity to survive in drought conditions. This is composed mainly of Didiereacae, an endemic plant family with various Euphorbia species, which live in an area below 400m altitude, 50km inland from the coast. However, situated along permanent rivers the dry deciduous vegetation or gallery forest reaches an altitude of 800m, composed of large trees such as rosewood, wild fig and tamarind trees.

For those who wish to experience unique desert game drive with an abundance of spiny forests of varieties of Didiera plants growing among 2 baobab species, including the Adansonia Fony which grows in the middle of sisal plantation in the South, we recommend:

1. Berenty private reserve(near Fort-dauphin)
2. Ifaty forest(north of Toliara)
3. Anakao forest(south of Toliara)
4. Beza Mahafaly reserve(south)

Eastern Region

The Eastern Region extends along the narrow band of the east coast from sea level to 800meters altitude. This area receives perpetual annual rainfall ranging from 2000 to 3000mm with high constant temperature. This area hosts the largest concentration of wildlife and plant species with high rate of endemicity. It is among the world’s highest priority for conservation because much of this forest cover is threatened by slash and burn agriculture known locally as “Tavy” which is common in the east. The eastern region is open grassland with stand of Traveller’s palm, the remnant of original rainforest are concentrated on the eastern escarpment, holding a large varieties of endemic plants including the country’s 600 endemic orchid species.

The height of the forest canopy averaging 25 to 30 meters, with some hardwood trees such as rosewood. Palms, lianas, bamboos, epiphytes , tree-ferns and lichens are also present in the rainforest.