The Guianan moist forests (NT0125) is an ecoregion in the east of Venezuela, north of Brazil and the Guyanas (Guyana, Suriname and French Guiana). It is in the Amazon biome. The climate is hot and humid, with two rainy seasons each year. As of 1996 the tropical rainforest habitat was relatively intact, although there were mounting threats from illegal logging and gold mining.
Location
The Guianan moist forests ecoregion covers most of Guyana, Suriname, and French Guiana. It covers part of eastern Venezuela and parts of the north of the Brazilian states of Pará and Amapá. It has a total area of .
Along the Atlantic coast to the east and northeast the ecoregion adjoins strips of Guianan freshwater swamp forests, Amazon-Orinoco-Southern Caribbean mangroves and Orinoco Delta swamp forests. To the northwest it adjoins the Llanos ecoregion, the Guianan piedmont and lowland moist forests and Guianan Highlands moist forest. Scattered patches of this last ecoregion are found on higher ground within the Guianan moist forests ecoregion. To the southwest and in places along its southern border it adjoins large areas of Guianan savanna. Most of the southern border adjoins the Uatuma-Trombetas moist forests.
Physical
The ecoregion lies to the east of the lower Orinoco basin and covers about 65% of the northeast part of the ancient Guiana Shield. It is bounded to the south by the line of the Acarai and Tumuk Humak mountains, which defines the rim of the Amazon basin and the northern border of Brazil. A small part of the ecoregion in the east is in the lower Amazon basin. The Essequibo, Courantyne, Maroni and Oyapock rivers run through the region to the Atlantic Ocean.
The terrain is mostly plains or low hills, with some steep slopes in river valleys and the bases of tepuis. In the west-central area the ecoregion surrounds the Pacaraima Mountains, a sandstone plateau with an average elevation of . It also surrounds tepuis, or tabletop mountains, the highest being Mount Roraima with an elevation of . The highlands and tepuis have a distinct tepui ecosystem.
Ecology
The Guianan moist forests ecoregion is in the Neotropical realm and the tropical and subtropical moist broadleaf forests biome. The ecoregion is part of the Guianan Moist Forests Global Ecoregion, which also includes the Paramaribo swamp forests and the Orinoco Delta swamp forests.
Climate
The Köppen climate classification is "Af": equatorial, fully humid. The northeastern trade winds carry humidity from the Atlantic Ocean, fluctuating annually due to the effects of the Intertropical Convergence Zone (doldrums). Annual rainfall ranges from , with two rainy seasons in December–January and May–August. At a sample location () in the Central Suriname Nature Reserve temperatures vary little throughout the year, slightly warmer in October and slightly cooler in January. Yearly average temperatures are minimum and maximum with a mean of . Annual rainfall is . Monthly rainfall varies from in October to in May.
Flora
The ecoregion is mainly covered by lowland or submontane rainforest, including marsh forest along the rivers. There are an estimated 8,000 vascular plant species, of which half may be endemic. The plant species in the forests change from east to west, with species dominant in one area completely missing from another. There are also patches of savanna, and the coastal lowlands have patches of herbaceous swamp. The flora is diverse. The upper tiers of the forest may reach a height of . The trees are mainly evergreen, but may shed leaves in the dry season. The trees hold many epiphytes and parasites, and shrubs and herbaceous plants cover the forest floor.
The main plant families are Bignoniaceae, Bombacaceae, Euphorbiaceae, Moraceae, Sterculiaceae, Lauraceae, Vochysiaceae, Sapotaceae, Lecythidaceae, Fabaceae, Combretaceae, Anacardiaceae, Rubiaceae, Meliaceae, Sapindaceae, Annonaceae and Arecaceae. Common species include Calophyllum brasiliense, Carapa guianensis, Ceiba pentandra, Couroupita guianensis, Eschweilera species, Guarea trichiloides, Luehea species, Parkia pendula, Pentaclethra macroloba, Protium species, Schwartzia species and Trichilia species. Cedrela fissilis, Coumourana punctata, Coumourana punctata and Warszewiczia coccinea are common in some areas but are not found in Suriname.