The forest types of Saint Lucia

The Classificaton of the Vegetation of Saint Lucia was based on a combination of field studies and satellite image analysis. Some two hundred plots were surveyed, each 20 metres in radius, covering a wide range of elevations in all parts of the country. Both floristic and biophysical data were recorded within every plot.

The lead investiagtor was Roger Graveon, supported by a team that included Melvin Smith, Field Assistant, Jennifer Daltry, Conservation Biologist, Bob Tennent, Project Leader, Vijay Datadin, GIS & Data Management Specialist, Matthew Morton, Critical Habitats Specialist and Rebecca Rock, GIS Management Specialist with the Forestry Department.

In the windiest spots on the Mount Gimie/ Troumassée ridges and peaks, at an elevation above 700 metres, a shrubland vegetation class dominates. The canopy is up to 2m tall, but often less, with an occasional slightly taller Prestoea acuminata palms. Cloud and mist cover, with heavy rainfall, is predominant with occasional short periods of sunshine. Relatively few species are found in this vegetation type: mainly a mixture of bromeliads, sedges and grasses and shrubs, with many Lesser Antillean endemics.

This vegetation class is found on the high summits of the Mount Gimie range, including Piton Troumassée (although not in the most windy spots), at an elevation of 700m or higher and possibly the eastern interior end of Mount Tabac ridge and a small area on the western end of the La Sorciere ridge. The canopy is about 8m high with occasional much taller trees of Freziera undulata. Terrestrial ferns, anthuriums, bromeliads, and epiphytes are very common; moss cover is often several centimetres thick. Cloud and mist cover, with heavy rainfall, is predominant, with only occasional and short periods of sunshine. Some species found in Montane and Lower Montane Rainforest are also found here, e.g. Byrsonima trinitatis (bwa tan wouj) and Micropholis guyanensis (fey dowé). However, other species appear almost unique, e.g. Podocarpus coriaceus (lowyé woz), Freziera undulata, Schleffera attenuata (fijé di mon), Miconia globulifera and Guettarda crispiflora. The steeper slopes are often covered in monotypic stands of small, stocky Prestoea montana (palmis).

Montane Rainforest is on the western side and sheltered eastern slopes of the Mount Gimie Range, including Piton Troumassée, above 650m. Slopes are extremely steep, rainfall is very heavy, there is little wind and landslides are very common. The steepest areas are covered with tree ferns and palms, with canopy height of about 4-6m, with some scattered taller trees on slightly less steep areas. The dominant species are Prestoea montana (palmis) and Alsophila and Cnemidaria tree ferns. The spiny Alsophila imrayana is a good indicator of this forest class. On slightly less steep slopes, trees typical of higher elevation Lower Montane Rainforest such as Byrsonima trinitensis (bwa tan wouj) and Micropholis guyanensis (fey dowé) can reach 8m tall. Terrestrial ferns, anthuriums and bromeliads are very common and there is a large quantity of slowly rotting organic material.

Lower Montane Rainforest is a suite of many different types of forest where the canopy height can vary from 4m to more than 45m; canopy cover is often quite complete on gentler slopes, but broken on steep slopes; ferns, mosses, ground anthuriums, vines, and epiphytes vary from absent to abundant; trees with buttresses and prop roots are present in some areas and absent in others. At ground level, it varies from humid, quite dark and still, to rather breezy and bright.Trees are evergreen because there is no water deficit most years in any month. In general, trees of all heights are found, without clear divisions into separate canopy layers. Lauraceae, particularly Ocotea eggersiana (lowyé ti fey) and Ocotea leucoxylon (lowyé mabwé) are common, along with Ormosia monosperma (dédéfouden) and with smaller trees such as Faramea occidentalis (ti kafé) Gymnanthes hypoleuca (bwa sadinn) and Eugenia coffeifolia. Also common are trees such as Myrcia deflexa (bwa kwéyòl) and Guapira fragrans (mapou) which are also found in other vegetation classes. Sterculia caribaea (maho kochon) is often the most common tree. Away from the edge of the forest, on comparatively gentle slopes without much wind, occasional very tall trees, reaching 45m, are found among the main 30-m canopy. This distinctive forest is often called the Dacryodes excelsa (gonnmyé)–Sloanea caribaea (chatannyé) alliance. Higher slopes, which are usually steeper, tend to have a more vines, moss, ground ferns, ground anthuriums and epiphytes.

Semi-evergreen Seasonal Forest occupies the zone between Deciduous Seasonal Forest and Lower Montane Rainforest. It is characterized by upper canopy trees with rather thin, often broad, and quite often compound leaves, which may lose some, but not all, of their leaves during a dry spell. There are no, or very few, epiphytes, ground ferns and mosses. Elevation ranges from almost sea-level in ravines to the summit of Gros Piton. In comparison with Deciduous Seasonal Forest, this forest class has a higher canopy and greater canopy cover and trunks with a greater girth. It occurs in less windy areas, and generally at a higher elevation. This rare forest has almost been completely destroyed for agriculture: most of the areas currently occupied by banana plantations would have had Semi-evergreen Seasonal Forest. Semi-evergreen Seasonal Forest is now mainly found in small pockets among fields, by roads and as a thin line along rivers, and is virtually all secondary, with the possible exception of the upper third of Gros Piton, Mount Parasol and the northern slope of Mount Souf. Typical species of Semi-evergreen Seasonal Forest include Cordia sulcata (sip blan), Guazuma ulmifolia (bwa lonm), Inga ingoides (kakoli), Daphnopsis americana (maho pimen), Lonchocarpus heptaphyllus (Savonnèt gwan fey).

This vegetation class covers large areas in Saint Lucia from the coast to the summit of Petit Piton, although it is virtually all secondary and much of it degraded. This class is defined as deciduous because the taller trees tend to lose all their leaves in most dry seasons, although the smaller trees and shrubs are evergreen. Its overall appearance during a normal dry season is of a more or less leafless canopy. The main canopy of dominant trees such as Bursera simaruba and Lonchocarpus punctatus are deciduous and give these slopes a barren appearance during the dry season. However, the understory trees and shrubs, such as Myrtaceae and Celastraceae, keep their leaves. The largest area of Deciduous Seasonal Forest is found in the north-east of the island, between Cas en Bas and Dennery. It is virtually all secondary and much of it shows signs of recent disturbance. Large areas of Deciduous Seasonal Forest are also found on the Caribbean coast, particularly from Anse La Raye to the Bouton area, Soufriere. In general, they are moderately to severely degraded, with only the ravines holding a more natural forest. Anse La Liberté is now a protected area and the forest is slowly recovering.

This vegetation class, like mangrove, is independent of direct rainfall and more dependant on edaphic (soil) water and occurs in flat areas close to sea-level, with a permanent or seasonal freshwater flow and no inflow of salt water. Trees are evergreen and there is a tendency for more or less monotypic (single-species) stands to form. This class varies from the permanently muddy and occasionally inundated swamp redwood forest beside rivers with a permanent flow of water, to forest on flat areas behind beaches that rely on seasonal creeks to maintain the water table. The classic Freshwater Swamp Forest is swamp redwood forest. The magnificent Pterocarpus officinalis, with its sinuous plank buttresses, forms monotypic stands. Formerly, this forest would have covered large areas in the flood plains of large rivers, such as Cul de Sac, Roseau and Fond D‟Or, but much of it has been destroyed and replaced by banana plantations or Herbaceous Swamps. Relics remain at Fond d’Or (north end) and Cul de Sac (beside an old rubbish dump). A more pristine area remains at Ger River, Micoud, between the bridge on the highway and the sea. Small stands can sometimes be seen along estuaries of smaller rivers.

Mangroves contain four tree species and are mainly on the Atlantic coast. Rhizophora mangle (manng wouj, red mangrove) is found usually in standing brackish water and sends out prop roots from its trunk and branches which arch down to the ground. Avicennia germinans (manng salé, black mangrove), is found in muddy areas or shallow surface brackish water, often in quite extensive stands (A. schaueriana is much rarer, but occupies a similar habitat). The ground beneath Avicennia trees has clusters of upward-pointing aerial roots (pneumatophores). Laguncularia racemosa (manng blan, paltivyé, white mangrove) also forms extensive stands, usually further inland than Avicennia germinans. On the edge of the mangrove, several mangrove-associated species are found. The most important are Conocarpus erectus (paltivyé wouj, button wood) and the shrubby vine Dalbergia ecastaphyllum. Much of Saint Lucia’s mangroves have disappeared and the rest are still being damaged, sometimes by clearing, more often by drainage changes.

Behind sandy beaches, rocky cliffs and pavements, an evergreen forest or shrubland is found, especially on the Atlantic coast. The harsh conditions caused by wind, salt-spray, often a thin soil and a water deficit even during most of the wet season, favour an evergreen arborescent flora with thick leathery leaves. This vegetation class takes the form of wind-sculptured low shrubland, sometimes reaching 100 metres inland. Although often one metre tall or less, it may contains dwarfed trees with substantial trunks. Typical species include Tabebuia pallida / heterophylla (white cedar, poyé). Coccoloba uvifera (wézen, siwiz, sea grape) is commonly present in this vegetation class.

Seasonally or permanently muddy or flooded areas with a mainly herbaceous cover, along with some shrubs, and possibly an occasional tree. Most Herbaceous Swamps are not natural, but result from the clearing of forest in flat areas. The biggest areas are in the Cul de Sac and Fond D’Or river valleys, where swamp redwood forest has been cleared. Grasses and sedges dominate, often with Acrostichum danaeifolium ferns. Neglected ditches and ponds can become small Herbaceous Swamps.

This class includes Marine Herbaceous Vegetation, that occurs in coastal waters. Sea-grasses are not true grasses, but rooted, submerged flowering plants. They form ecologically important beds in shallow marine waters. The other group is Freshwater Herbaceous Vegetation, that comprises several species that float on freshwater including the alien invasive water hyacinth.

Mainly herbaceous, often succulent, low vegetation found on coastal cliffs and the flatter rocky areas behind them. More common on the Atlantic coast, where conditions are extreme with strong winds, long periods of drought, fierce sunshine and very little or no soil. These areas are home to a quite varied, special flora of low herbs, often interspersed with the Turk’s Cap cactus (Melocactus intortus).

Mainly herbaceous, salt-tolerant vegetation, growing on loose sand on beaches and adjacent low dunes. The pioneer species are trailing rooting herbs, with succulent species slightly further inland. In some locations, shrubs appear on low sand dunes a few metres inland of high tide. Sporobulus virginicus and Ipomoea pescaprae are the most common of the pioneer plants. Shrubs may develop a few metres above the high tide mark, where the sand is still more or less loose or slightly consolidated in small dunes. This is best observed on the southern half of Anse des Sables, Vieux Fort Some rare species, such as Corchorus hirsutus and Sophora tomentosa, are also found here.

This type of vegetation is found in a narrow zone between littoral rock and cliff vegetation and Deciduous Seasonal Forest or Littoral Evergreen Forest. It consists of shrubs, cacti and sometimes grassy spaces.

Open grassy areas are probably not a natural vegetation class in Saint Lucia, except perhaps as small patches in rocky coastal cliffs and pavement. These are generally open areas covered mostly by grasses or sedges, but other herbs and low shrubs are also present. Individual trees or small clumps of trees and taller shrubs may also be present. This vegetation class is most common near areas of Deciduous Seasonal Forest and is usually a result of extreme disturbance to that forest class. Fires and other continual disturbance of Deciduous Seasonal Forest produces degraded “grassy‟ areas (including sedges) with some shrubs and trees. Abandoned gardens in wetter areas can temporarily take on this form, but quickly develop into secondary forest. The Choiseul to La Pointe area also has extensive tracts of Grassland on what was originally Deciduous Seasonal Forest. This has in some cases been caused by clearance for farming and subsequent abandonment.

This is a rare acid-tolerant class confined to the Sulphur Springs, especially on the slope of Mount Souf. It is dominated by ferns about 2m tall and a bromeliad, with widely-spaced trees. Only plants that can tolerate very acidic conditions can survive here. The most tolerant is Pitcairnia angustifolia. This, and two fern species, Blechnum serrulatum and Pteridium arachnoideum, dominates the hillside along with planted, and now self-seeding, Caribbean pines and Clusia plukenetii (awali).

This class has mature trees that have been planted in an organized manner, mainly in and around the forest reserve, with smaller wild trees and shrubs growing between them. Substantial areas of the rainforest reserves have been replanted with Talipariti elatum (blue maho), Swietenia macrophylla (Honduras mahogany), Eucalyptus, Gmelina arborea and Pinus caribaea (Caribbean pine). The natural forest has been allowed to grow through.