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Temperate deciduous or temperate broad-leaf forests are a variety of temperate forest dominated by trees that lose their leaves each year. They are found in areas with warm moist summers and cool winters. The six major areas of this forest type occur in the Northern Hemisphere: North America, East Asia, Central and Western Europe (except Brittany, Cornwall, Wales, Ireland and western Scotland), Denmark, southern Sweden and southern Norway. Smaller areas occur in Australasia and southern South America. Examples of typical trees in the Northern Hemisphere's deciduous forests include oak, maple, beech and elm, while in the Southern Hemisphere, trees of the genus Nothofagus dominate this type of forest. The diversity of tree species is higher in regions where the winter is milder, and also in mountainous regions that provide an array of soil types and microclimates. The largest intact temperate deciduous forest in the world is protected inside of the six-million-acre Adirondack Park in Upstate New York in the United States.
Humans have often colonized areas in the temperate deciduous forest. They have harvested wood for timber and charcoal. During the settlement of North America, potash made from tree ashes was exported back to Europe as fertilizer. This left less than one-quarter of original forests to remain. Many forests are now small fragments dissected by fields and roads; these islands of green often differ substantially from the original forests, particularly along the edges. The introduction of exotic diseases continues to be a threat to forest trees, and hence, the forest; examples include the loss of chestnut and elm. At the same time, species such as deer, which are clearing rather than true forest animals, have expanded their range and proliferated in these altered landscapes. Large deer populations have deleterious effects on tree regeneration overall, but particularly for edible species including yew, yellow birch, and hemlock. Deer grazing also has significant negative effects on the number and kind of herbaceous flowering plants. The continuing pressure to increase deer populations, and the continued killing of top carnivores, suggests that overgrazing by deer will continue to be a significant forest conservation problem. Objective criteria for the restoration of deciduous forest include large trees, coarse woody debris, spring ephemeral, and top predators.