Some soils become extremely dry because of evaporation and form laterite layers. Tropical Rainforest Tropical rainforests occur in a broad zone outside the equator . Annual rainfall, which exceeds 2000 to 2250 millimeters, is generally evenly distributed throughout the year. Temperature and humidity are relatively high through the year. Some other common plants include ferns and palms.
Most plants are evergreen with large, dark green, leathery leaves.
Tropical trees often have buttressed bases to help support their heavy above-ground biomass. Decomposition is rapid in the tropicals because high temperatures and an abundance of moisture. Because of the frequent and heavy rains, tropical soils are subject to extreme chemical weathering and leaching . These environmental conditions also make tropical soils acidic and nutrient poor.