Valdivian Rain Forest

The Valdivian temperate forests (NT0404) is an ecoregion on the west coast of southern South America, in Chile and extending into 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 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 coastal range runs along the coast, and the north–south running Chilean Central Valley lies between the coastal range 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 covered by the Patagonian Ice Sheet and other glaciers at the peak of the last ice age, which descended from the Andes mountains, and the numerous lakes of the Chilean lakes district in the central part of the ecoregion were originally glacial valleys, while the southern part of the region has many glacier-carved fjords.

An old-grown pure stand of Aextoxicon in Punta Curiñanco at the Pacific coast.

To the north the Valdivian forests give way to the Mediterranean forests, woodlands, and scrub of the Chilean Matorral ecoregion. Some few Valdivian forests grows in northern Chile such as that one in 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 and tropical forests of northern South America by the Atacama desert north of the Matorral, the Andes mountains, and dry rain-shadow Argentine grasslands east of the Andes. As a result, the temperate forest regions have evolved in relative isolation, with a high degree of endemic species.

The forest of northwestern North America exist in similar settings but differ in not being connected to large inland forest like the boreal forest or the forest of the Rocky Mountains.^[1] Compared to the similar North American forest, the Valdivian temperate rain forest is considerably richer in species, a characteristic that is also found when comparing with similar forest in Tasmania.^[1]

Climate

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 arrive at the higher part of the windward slope of the Andes, thus creating rainfalls. At the same time, the northward-flowing oceanic Humboldt Current creates humid and foggy conditions near the coast. 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. In the summer the temperature can climb to 16.5 °C (62 °F), while during winter the temperature can drop below 7 °C (45 °F).^[2]

Average annual temperatures are fairly uniform within the area, especially at coastal locations where annual temperature differences between localities never exceed 7 °C.^[1]

Flora

Valdivian cloud forest Bosque de Fray Jorge in semi-arid Norte Chico.

The Valdivian temperate rain forests are temperate broadleaf and mixed forests. The Valdivian and Magellanic temperate rainforests are the only temperate rain forests in South America and one of a small number of temperate rain forests in the world. Together they are the second largest in the world, after the Pacific temperate rain forests of North America (which stretches from Alaska to northern California). The Valdivian forests are a refuge for the Antarctic flora, and share many plant families with the temperate rainforests of New Zealand, Tasmania, and Australia. Fully half the species of woody plants are endemic to this ecoregion.

Chusquea quila is a bamboo that grows in humid areas below 500 m, where Chusquea coleou becomes more dominant above. Chusquea quila can form pure stands called quilantales. Very few plants can grow under this species. Other notable species are the nalca or Chilean rhubarb (Gunnera tinctoria) and the ferns Lophosoria quadripinnata and Parablechnum cordatum. Chile's national flower, the copihue (Lapageria rosea) is a pioneer species that grows in disturbed areas of the Valdivian rain forest.

The maximum plant species richness is found at latitudes 40 to 43° S.

Matt Ginnow
Matthew Ginnow