The Rainforest mesocosm, at the north end of Biosphere 2, was created to simulate several tropical Rainforest habitats. The biome can be divided into the following habitats:
- Lowland rainforest includes most of the eastern part of the biome. It is dominated by large trees with a ground layer of aroids.
- Terraces surround the east, west and north sides of the central "mountain." Small trees including papaya, coffee, and palms are in these areas.
- Ginger belts contain fast-growing large monocots such as banana, gingers, and bird-of-paradise to reduce lateral radiation from outside.
- Bamboo belt of dense bamboo species was intended to screen the biome from airborne salt that might be entrained from the ocean biome.
- Varzea, intended to simulate an Amazonian seasonal floodplain, is located in the southwest corner of the biome.
- Tepui (Cloud forest) was designed to simulate a highland cloud forest. Due to high temperatures vegetation evolved into a marsh dominated by umbrella sedge and morning glory vines.
Initially, about 300 species of plants were introduced with an emphasis on neotropical species and plants used by indigenous people. Dominants among the surviving plant species (less than 100), include Clitoria racemosa, Ceiba pentandra, Musa spp., Arenga pinnata, Epipremnum pinnatum, Syngonium podophyllum, and Cissus sicyoides. The dominant species have changed since initial assembly due to both managerial and ecological factors. One managerial influence occurred in the early years; Leucaena leucocephala, a fast growing legume tree species, was planted throughout the biome to shade the newly planted seedlings. This species was removed in early 1994 to give room for other tree species.
The soils in the biome are synthesized from local material with textures ranging from sandy loam to clayey loam. In profile, the soils contain a top soil layer which is usually less than one meter thick and subsoil which consists of gravelly granite material.
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