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Temperate forest ecoregion in Chile and Argentina

The Valdivian temperate forests (NT0404) is an ecoregion on the west coast of southern South America, in Chile and Argentina. It is part of the Neotropical realm. The forests are named after the city of Valdivia. The Valdivian temperate rainforests are characterized by their dense understories of bamboos, ferns, and for being mostly dominated by evergreen angiosperm trees with some deciduous specimens, though conifer trees are also common.

Temperate rain forests comprise a relatively narrow Chilean coastal strip, between the Pacific Ocean to the west and the southern Andes Mountains to the east, from roughly 37° to 48° south latitude. North of 42°, the Chilean Coast Range stretches on, with just the north–south running Chilean Central Valley between it and the Andes. South of 42°, the coast range continues as a chain of offshore islands (including Chiloé Island and the Chonos Archipelago), while the "Central Valley" is submerged and continues as the Gulf of Corcovado. Much of the ecoregion was once covered by the Patagonian Ice Sheet and other glaciers during the peak of the last ice age, with ice descending from the Andes mountains; numerous bodies of water within the Chilean Lake District (in the central part of the ecoregion) are the remnants of ancient glacial valleys. The southern part of the region features many glacier carved fjords. To the north, the Valdivian forests give way to the Mediterranean forests, woodlands, and scrub of the Chilean Matorral ecoregion. A few coastal enclaves of Valdivian forest grow in north central Chile (such as Bosque de Fray Jorge National Park) as remains of the last glacial maximum. To the south lies the Magellanic subpolar forests ecoregion. The temperate Valdivian, matorral, and Magellanic ecoregions are isolated from the subtropical/tropical forests that dominate northern South America by such landscapes as the Atacama desert (north of the matorral), the Andes Mountains, and the dry, rain shadow Patagonian steppe east of the Andes. As a result, the temperate forest regions have evolved in relative isolation, with a high degree of endemic species. Due to a similar location geographically and geologically (along the Pacific Plate), the coast hugging temperate rainforests of the Pacific Northwest (from Northern California to Southern Alaska, roughly 40° 60° north latitude) exist in similar settings, with the Rocky Mountains to the east and the Pacific Ocean to the west. East of the Rocky Mountains, the North American prairie grassland stretches from south central Canada to Texas, not unlike the Argentine grasslands to the east of the Andes. Similar to the Atacama region of Chile, the Baja California and Sonoran deserts in the US/Mexican states of California and Baja California act as climatic borders for the northwest’s rainforests.

Since the forest is located at around 40 degrees south, it is strongly influenced by the westerlies. The water vapour held by the westerlies condenses as they encounter the windward slope of the Chilean Coast Range and the Andes, creating orographic rainfall. Average annual precipitation varies from 1,000 mm at the northern edge of the ecoregion to more than 6,000 mm per year in the south. Winter temperatures are lower at higher elevations. The tree line is at about 2,400 m in the northern part of the ecoregion (35° S), and descends to 1,000 m in the south of the Valdivian region. Deciduous Nothofagus forests also grow along the Andes of central Chile as far north as 33º S latitude, from approximately 1,200 meters elevation up to the tree line at 2,400 meters elevation. A krummholz of Nothofagus antarctica and N. pumilio grows near the tree line. The southern limit of these forests is 38º S latitude. Tall coniferous pehuén monkey puzzle trees (Araucaria araucana) grow at the southern edge of the deciduous forests, from the coast at Nahuelbuta National Park to the Andes. Patagonian Andean forests. The third forest type is the Patagonian Andean forests, which are distributed at higher elevations along the Andes mountain front, and are dominated by evergreen conifers, including pehuén (Araucaria araucana) and alerce (Fitzroya cupressoides). The alerce looks like a giant sequoia, and is a rival in longevity to the bristlecone pine, some with growth rings recording 3,625 years of local weather cycles. Closer to the treeline, the conifers give way to Andean scrublands of deciduous Nothofagus antarctica. Northern Patagonian forests. The fourth and last type is the Northern Patagonian forests, which dominate the southern half of the ecoregion, with evergreen species such as the broadleaf Nothofagus dombeyi, Nothofagus betuloides and Drimys winteri and the coniferous podocarps, including Podocarpus nubigenus. Distribution of plants follow Rapoport's rule with plant species distribution increasing at higher latitudes and decreasing at those closer to the equator, incidents of endemism becoming more frequent as one moves equatorward.

The flora of the forests has inherited and developed its characteristics due to a variety of causes. Its Neotropical affinities reflect its current geographic connection to the remaining South America. There are a few "boreal" components in the Valdivian temperate rain forest which arrived by long distance transport. More specifically the refugia of the Valdivian temperate rain forest between latitudes 41 and 37° S were; the coastal region, the lower slopes of the Chilean Coast Range and the westernmost Chilean Central Valley all of which remained free of disturbance by the glacial, glacifluvial and periglacial disturbance through the glaciation.

Some of the threatened mammals of the Valdivian forests include the monito del monte (Dromiciops gliroides), an arboreal marsupial, the southern pudú (Pudu puda) the world's smallest deer, and the kodkod (Leopardus guigna), South America's smallest cat. Since the beginning of the 20th century, there have also been nonnative wild boars living in the Valdivian forests. The Chilean climbing mouse (Irenomys tarsalis) and Chilean shrew opossum (Rhyncholestes raphanurus) are endemic to the ecoregion. Most mammal genera in Valdivian forests are also found in semi arid parts of Patagonia. The slender billed parakeet (Enicognathus leptorhynchus) is endemic. Hummingbirds are common in the Valdivian forests because of the presence of plants like the maqui (Aristotelia chilensis) and the copihue.

The Valdivian forests include stands of huge trees, especially Nothofagus and Fitzroya, which can live to a great age. These magnificent rainforests are endangered by extensive logging and their replacement by fast growing pines and eucalyptus, which are more sought after by the pulp and paper industry. The native trees that are cleared to make way for these monocultures are often exported as woodchips to Japan. A start at conservation was made in November 2003 when a consortium of conservation groups, both local and international, bought at auction of a bankrupt logging firm 147,500 acres (600 km2) of biologically rich rainforest in the Valdivian Coastal Range. Gianni Lopez, Executive Director of CONAMA, Chile's national environmental agency remarked, "Ten years ago the existence of protected areas not owned by the government was unthinkable." Among the efforts supporting conservation, has been a growing ecotourism industry.

24.16% of the Valdivian temperate forests ecoregion is in protected areas.