The monsoon rain forest ecoregion encompasses the interior mountain range, surrounded by the coastal plains.

The forest canopy is generally sparse, and sufficient light reaches the ground to support a grass under-story.

Evergreen trees also occur in this area, especially on shaded slopes that have more retentive soils, and at slightly higher elevation.

Tropical montane forests at the middle elevations include chinquapin (Castanopsis), stone oaks (Lithocarpus), and laurels (Lauraceae).

More savanna-like vegetation is found higher and drier areas of the interior, with brush and silk trees (Albizia procera).