Distinct forest types also occur within each of these broad groups. Tropical forests are characterized by the greatest diversity of species. The length of daylight is 12 hours and varies little. Precipitation is evenly distributed throughout the year, with annual rainfall exceeding 2000 mm. Soil is nutrient-poor and acidic.
Decomposition is rapid and soils are subject to heavy leaching.
Canopy in tropical forests is multilayered and continuous, allowing little light penetration. Trees are 25-35 m tall, with buttressed trunks and shallow roots, mostly evergreen, with large dark green leaves. Fauna include numerous birds, bats, small mammals, and insects. Temperate forests occur in eastern North America, northeastern Asia, and western and central Europe. Well-defined seasons with a distinct winter characterize this forest biome.