The typical structure of these forests includes four layers.[1]
The uppermost layer is thecanopy composed of tall mature trees ranging from 30 to 61 m (100 to 200 ft) high. Below the canopy is the three-layered,shade-tolerantunderstory 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 theshrub layer, composed of low growing woody plants.
In the Northern Hemisphere, characteristic dominantbroadleaf trees in this biome include oaks (Quercus spp.), beeches (Fagus spp.), maples (Acer spp.), or birches (Betula spp.).[1] 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, theconifers may be a more important canopy species than the broadleaf species. In the Southern Hemisphere, endemic genera such asNothofagus andEucalyptus occupy this biome, and most coniferous trees (members of theAraucariaceae andPodocarpaceae) occur in mixtures with broadleaf species, and are classed as broadleaf and mixed forests.
Temperatebroadleaf and mixed forests occur in areas with distinct warm and cool seasons, including climates such ashumid continental,humid subtropical, andoceanic, 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 distinctdry season. A dry season occurs in the winter in East Asia and in summer on the wet fringe of theMediterranean 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 asUssuriland, or theUpper Midwest, where temperate forests can occur despite very harsh conditions with very cold winters.
^Zhao, Ji; Zheng, Guangmei; Wang, Huadong; Xu, Jialin, eds. (1990).The natural history of China. New York: McGraw-Hill Publishing Company.
^Martin, WH; Boyce, SG; Echternacht, AC, eds. (1993).Biodiversity of the southeastern United States: Lowland terrestrial communities. New York: John Wiley and Sons.
This article incorporates text available under theCC BY-SA 3.0 license.World Wide Fund for Nature."Temperate Broadleaf and Mixed Forest Ecoregions". Archived fromthe original on 1 April 2011. Retrieved29 May 2019.
