Temperate broadleaf and mixed forest is a temperate climate terrestrial habitat type defined by the World Wide Fund for Nature, including temperate forest, mixed coniferous forest, and temperate rainforest ecoregions. These forests are richest and most distinctive in central China and eastern North America, with some other globally distinctive ecoregions in the Himalayas, Western and Central Europe, the southern coast of the Black Sea, Australasia, Southwestern South America and the Russian Far East.
Ecology The typical structure of these forests includes four layers.
The uppermost layer is the canopy, composed of tall mature trees ranging from 30 to 61 m (100 to 200 ft) high. Below the canopy is the three-layered, shade-tolerant understory that is roughly 9 to 15 m (30 to 50 ft) shorter than the canopy. The top layer of the understory is the sub-canopy composed of smaller mature trees, saplings, and suppressed juvenile canopy layer trees awaiting an opening in the canopy. Below the sub-canopy is the shrub layer, composed of low growing woody plants. Typically the lowest growing (and most diverse) layer is the ground cover or herbaceous layer.
Trees In the Northern Hemisphere, characteristic dominant broadleaf trees in this biome include oaks (Quercus spp.), beeches (Fagus spp.), maples (Acer spp.), or birches (Betula spp.). The term "mixed forest" comes from the inclusion of coniferous trees as a canopy component of some of these forests. Typical coniferous trees include pines (Pinus spp.), firs (Abies spp.), and spruces (Picea spp.). In some areas of this biome, the conifers may be a more important canopy species than the broadleaf species. In the Southern Hemisphere, endemic genera such as Nothofagus and Eucalyptus occupy this biome, and most coniferous trees (members of the Araucariaceae and Podocarpaceae) occur in mixtures with broadleaf species, and are classed as broadleaf and mixed forests.
Climate Temperate broadleaf and mixed forests occur in areas with distinct warm and cool seasons, including climates such as humid continental, humid subtropical, and oceanic, that give them moderate annual average temperatures: 3 to 23 °C (37 to 73 °F). These forests occur in relatively warm and rainy climates, sometimes also with a distinct dry season. A dry season occurs in the winter in East Asia and in summer on the wet fringe of the Mediterranean climate zones. Other areas, such as central eastern North America, have a fairly even distribution of rainfall; annual rainfall is typically over 600 mm (24 in) and often over 1,500 mm (59 in), though it can go as low as 300 mm (12 in) in some parts of the Middle East and close to 6,000 mm (240 in) in the mountains of New Zealand and the Azores. Temperatures are typically moderate except in parts of Asia such as Ussuriland, or the Upper Midwest, where temperate forests can occur despite very harsh conditions with very cold winters. The climates are typically humid for much of the year, usually appearing in the humid subtropical climate and in the humid continental climate zones to the south of tundra and the generally subarctic taiga. In the Köppen climate classification they are represented respectively by Cfa, Dfa/Dfb southern range and Cfb, and more rarely, Csb, BSk and Csa.
Ecoregions
Australasia
Eurasia
Americas
See also Mixed coniferous forest Kuchler plant association system Mediterranean forests, woodlands, and scrub Temperate deciduous forest Trees of the world
References
External links
World Wildlife Fund−WWF Biomes: Temperate broadleaf and mixed forests biome Temperate forest Bioimages.vanderbilt.edu: Index of North American Temperate Broadleaf & Mixed Forests ecoregions Terraformers Canadian Forest Conservation Foundation
