Broadleaved forests

Closed moist forests have a high degree of endemism (nearly 90%); this is especially true of those on ultrabasic (eruptive) rock, which are very different from those on other types of rock. Typical families are Podocarpaceae, Cunioniaceae and Araucariaceae. The upper storey is usually high (up to 40 m) and the lower storey consists mainly of Araliaceae and Myrtaceae. Shrubs grow to 1.5 m, totalling over 400 species belonging to 50 families. Lianas and epiphytes are plentiful. When forests on this type of subsoil are destroyed, they are replaced by "mining brushland", while the degraded forms on sedimentary and metamorphic rock are mainly savannah and thickets.

Closed moist forests take different forms, depending on altitude and local conditions:

    coastal forests, located directly beside the sea on sedimentary and metamorphic rock, are mainly climax formations consisting of low-altitude pan-tropical species. These are mature forests of medium height, with a well-developed undergrowth; the main species include the famous column pine (Araucaria columnaris), Alexandrian laurel (Calophyllum inophyllum) and of course coconut (Cocos nucifera), plus lianas and shrubs;

    coastal forests on ultrabasic rock are practically identical with those on other types of subsoil, with a high concentration of conifers (especially Araucaria spp.);

    valley or low-altitude forests (below 300 m) on sedimentary and metamorphic rock are composed of such species as Archidendropsis granulosa, candleberry (Aleurites moluccana) and ironwood (Casuarina collina). This type of forest survives only in relic form as a result of heavy human pressure as well as frequent bushfires; when destroyed, it is replaced by savannah;

    forests on ultrabasic rock at the same altitude have a high rate of endemism when they are intact. The many species found here include Agathis lanceolata, Macaranga alchorneoides and Neoguillauminia cleopatra. These formations can take on different forms, depending on soil conditions and human pressure. For example, ironwood stands are relatively low formations (reaching a height of 10 m), dominated by Casuarina deplancheana; Syzygium forests, found at low altitudes, are closed formations dominated by what is known as "mine-prop wood". The flora is rich and the canopy may be 5 or 6 m high. The structure of these formations is identical with that of riparian formations on ultrabasic rock (see below);

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      slope or medium-altitude forests are found at between 300 and 1 000 m, mostly in the centre of Grande Terre. On sedimentary and metamorphic rock, the many trees can grow very large, reaching heights of 30 or 40 m. The most common species include Agathis corbassonii, A. moorei, Montrouziera cauliflora, Calophyllum caledonicum and Kermadecia leptophylla;

      on ultrabasic terrain, these forests form high stands rich in pteridophytes and especially gymnosperms (15 genres present) and with a very high rate of endemism. They are distinguished by a high canopy (20-30 m), with some emergent species, in particular Agathis spp. and Araucaria spp., which can reach 40 m. These formations are rich in good timber species, but are now found mainly in relatively inaccessible regions (the centre and east coast of Grande Terre); the undergrowth is very dense;

      there is a special type of closed moist forest on ultrabasic rock, forest on ironstone, which grows on soil of this type in the southeast of New Caledonia at altitudes of up to 600 m. This is a climax forest of medium height and contains many uncommon species such as Cicerone spp., Agathis spp. and Calophyllum spp.;

      summit or high-altitude forests (at over 750 m) on sedimentary and metamorphic rock are made up of smaller trees. There are also fewer trees, and they have small crowns that do not touch. These forests thus seem to be dotted with gaps containing low vegetation resembling brushland in appearance, especially on eastern slopes which are more exposed to the wind. Antholma spp., Apodytes clusiifolia and Nyemeyera balansae are among the common forest species in such formations, and palms and tree ferns (Cyathea spp.) are also found;

      Agathis montana forest is found at the same altitudes and is made up of a pure layer of A. montana, sometimes together with Araucaria schmidii and Freycinetia spp.; the undergrowth is very open;

      summit or high-altitude forests on ultrabasic rock vary in form, depending on exposure, soil and rainfall (brushland, low forest, with or without Araucaria, etc.). They are lower (5 m maximum) than closed forests at lower altitudes, the trees are more numerous, and new species, particularly Araucaria (A. humboldtensis, A. montana, A. muellerii, etc.), appear here.

    Sclerophyllous forest, once covered the whole of the western coast between sea-level and 300 m on varying substrata (mainly sedimentary rock, more rarely basalt), but is now confined to a few protected sites, having shrunk as a result of fires and clearing. It is a closed formation, with cover that lets only a little light filter through. The tree storey is thinner than that of closed moist forest, but the undergrowth is generally thicker. Trees in the upper storey tend not to exceed 15 m in height, and the floristic composition of this storey varies from region to region, with, for example, Arytera chartacea, Diospyros fasciculosa and Planchonella cinerea. Shrubs are not clearly stratified, although they are on the whole between 3 and 10 m tall; the commonest shrub species belong to the Eugenia, Austomyrtus and Cleidion genres. Lianas are plentiful. After degradation, these forests have often given way to niaouli formations.

    Mangroves are located on the western coast and along the banks of the lower courses of rivers (where these become tidal). They are more limited on the eastern coast, which is very steep, so that it is hard for this type of vegetation to become established. The flora is relatively poor, with no endemic species. Rhizophora mangrove is found along the sea coast; reaching a height of 2 to 5 m, it forms almost pure stands. Another type of mangrove forest, which is more diverse and taller (8 m), is found along the tidal reaches of rivers and consists mainly of Bruguiera gymnorhiza, Rhizophora spp., Lumnitzera racemosa and Sonneratia alba.

    Riparian forests are found upstream of mangroves, reaching into the valleys. In the alluvial plains they are usually very degraded. Cordia dichotoma, Casuarina collina, Trema orientalis, etc., are found in combination in these stands. The most boxed-in valleys contain forests of Pandanus macrocarpus and Elaeocarpus angustifolius, reaching a height of 15 to 20 m.

    Forests with a predominance of Nothofagus are found in regions around springs and along rivers at over 650 m. Nothofagus is sometimes mixed with Araucaria, and the undergrowth is very dense.

    Along rivers in mountain massifs of ultrabasic rock, when the slope is gentler, formations are lower (reaching a maximum height of 5-10 m), thick and rich in species.

last updated: Monday, January 12, 2004