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Temperate rain forest
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Temperate rainforests are coniferous or broadleaf forests that occur in the temperate zone and receive high rainfall.
temperate rain forests of North America, Alaback's definition is widely recognized:
- Annual precipitation over 1400 mm.
- Mean annual temperature between 4 and 12 degrees Celsius. (39 and 54 degrees Fahrenheit)
However, required annual precipitation depends on factors such as distribution of rainfall over the year, temperatures over the year and fog presence, and definitions in another countries differ considerably.
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Temperate rainforests are coniferous or broadleaf forests that occur in the temperate zone and receive high rainfall.
Definition
For temperate rain forests of North America, Alaback's definition is widely recognized:
- Annual precipitation over 1400 mm.
- Mean annual temperature between 4 and 12 degrees Celsius. (39 and 54 degrees Fahrenheit)
However, required annual precipitation depends on factors such as distribution of rainfall over the year, temperatures over the year and fog presence, and definitions in another countries differ considerably. For example, Australian definitions are ecological-structural rather than climatic:
- Closed canopy of trees excludes at least 70% of the sky.
- Forest is composed mainly of tree species, which do not require fire for regeneration but their seedlings are able to regenerate under shade and in natural openings.
The latter would, for example, exclude a part of the temperate rain forests of western North America, as Coast Douglas-fir, one of its dominant tree species, requires stand-destroying disturbance to initiate a new cohort of seedlings. The strictly applied North American definition would in turn exclude a part of temperate rain forests in other countries.
Characteristics
Temperate rain forests have following characteristics:
- Relative proximity to the ocean, usually coastal mountains. Temperate rain forests depend on the proximity to the ocean to moderate seasonal variations in temperature, creating milder winters and cooler summers than continental-climate areas. Many temperate rain forests have summer fogs that keep the forests cool and moist in the hottest months. Coastal mountains increase rainfall on the ocean-facing slopes.
- Wildfires are uncommon because of constant high moisture content in forest.
- Epiphytes, including mosses, are abundant. They are dependent on rainfall and high atmospheric moisture levels, as they have no access to soil water.
Temperate rain forests may be predominantly coniferous, broadleaf deciduous, broadleaf evergreen, or mixed forests, and occur in Temperate broadleaf and mixed forests and Temperate coniferous forests ecoregions.
The temperate coniferous rain forests sustain the highest levels of biomass in any terrestrial ecosystem and are notable for trees of massive proportions, including Coast Redwood (Sequoia sempervirens), Coast Douglas-fir (Pseudotsuga menziesii var. menziesii), Sitka Spruce (Picea sitchensis), Alerce (Fitzroya cupressoides), Formosan Cypress (Chamaecyparis formosensis), Taiwania (Taiwania cryptomerioides), Japanese Cedar (Cryptomeria japonica) and Kauri (Agathis australis).
Global distribution
Temperate forests cover a large part of the globe, but temperate rain forests only occur in few regions around the world. Most of these occur in Oceanic-Moist Climates: the Pacific temperate rain forests in Western North America (Southeastern Alaska to Central California), the Valdivian and Magellanic temperate rain forests of southwestern South America (Southern Chile and adjacent Argentina), pockets of rain forest in northwest Europe (southern Norway to northern Spain), temperate rain forests of southeastern Australia (Tasmania and Victoria) and the New Zealand temperate rain forests (South Island's west coast).
Others occur in Subtropical-Moist Climates: South Africa's Knysna-Amatole coastal forests, the Colchian rain forests of the eastern Black Sea region (Turkey and Georgia), the Caspian temperate rain forests of Iran (Jungles of Iran), the mountain temperate rain forests along eastern Taiwan's Pacific Coast, southwest Japan's Taiheiyo forests, Australia's coastal NSW and New Zealand's North Island.
Some areas, however, such as the Rocky Mountains of British Columbia, northern Idaho and nortwestern Montana, Rocky Mountain Trench of BC's and Montana's interior and the Russian Far East (Ussuri, Manchuria, Sakhalin) in Asia have more of continental climate but get enough precipitation in both rain and snow to harbor significant pockets of temperate rain forest.
Scattered small pockets of temperate rain forest also exist along the Appalachian Mountains from northern Georgia to New England. The mountainous coniferous forests of the Changbai Mountains bordering China and North Korea are a good example contain some of the richest high-elevation coniferous evergreen forests in East Asia.
Temperate rain forest regions
Pacific temperate rain forests of western North America
A portion of the temperate rain forest region of North America, the largest area of temperate zone rain forests on the planet, are the Pacific temperate rain forests which occur on west-facing coastal mountains along the Pacific coast of North America, from Kodiak Island in Alaska to northern California, and are part of the Nearctic ecozone.
Pacific temperate rain forests can be found in the Northern Pacific coastal forests, Queen Charlotte Islands, Vancouver Island, British Columbia mainland coastal forests, Central Pacific coastal forests, Central and Southern Cascades forests, Klamath-Siskiyou forests, and Northern California coastal forests ecoregions. They vary in their species composition, but are all predominantly coniferous, sometimes with an understory of broadleaved trees and shrubs. The conifer dominance is a consequence of two climatic factors: Although the region has high total precipitation, most occurs during the winter, and summers are relatively dry. During summer, moisture stress reduces the amount of photosynthesis possible especially for broadleaved trees. However, winters are very mild, and coniferous species are capable to carry on substantial amounts of their yearly photosynthesis during fall, winter and spring. The Northern California coastal forests are home to the Coast Redwood (Sequoia sempervirens), the world's tallest tree. In the other ecoregions, Coast Douglas-fir (Pseudotsuga menziesii var. menziesii), Sitka Spruce (Picea sitchensis), Western Hemlock (Tsuga heterophylla) and Western redcedar (Thuja plicata) are the most important tree species. A common feature of Pacific temperate rain forests of North America is the Nurse log, a fallen tree which as it decays, provides ecological facilitation to seedlings.
Some of the best forests are found in Olympic National Park, Mount Rainier National Park, Tongass National Forest, Mount St. Helens National Monument, Redwood National Park, and throughout British Columbia (including British Columbia's Coastal Mountain Ranges) with the coastal Great Bear Rainforest being the largest temperate rainforest found in the world.
British Columbia's Rocky Mountains, Cariboo Mountains, Rocky Mountain Trench (east of Prince George) and the Columbia Mountains of Southeastern British Columbia (west of the Canadian Rocky Mountains that extend into parts of Idaho and Northwestern Montana in the USA), which encompass the Selkirk Mountains, Monashee Mountains, and the Purcell Mountains, have the largest stretch of interior temperate coniferous rain forests. These inland rainforests have more continental climate with a large proportion of the precipitation falling as snow. Being closer to the Rocky Mountains, there is more of a diverse mammalian fauna. Some of the best interior rain forests are found in Mount Revelstoke National Park and Glacier National Park (Canada) in the Columbia Mountains.
Appalachian temperate rain forests of the eastern USA
Temperate rain forests in the eastern USA are limited to areas in the southern Appalachian Mountains where orographic precipitation causes weather systems coming from the west and from the Gulf of Mexico to drop more precipitation than in surrounding areas. The largest of these forest blocks are located in western North Carolina, northern Georgia, and far eastern Tennessee, largely in the Pisgah, Nantahala, Chattahoochee National Forests and nearby Gorges State Park. In addition, small areas in the highest elevations of the Great Smoky Mountains also receive substantial rainfall, with Clingmans Dome, for example, collecting about 2000 mm of precipitation per year. Although the highest summits of the Green Mountains of Vermont, the White Mountains of New Hampshire, and Mount Katahdin in Maine receive over 2000 mm of precipitation per year, some of these locations have alpine environments and whether or not temperate rain forests exist in these regions is subject to debate. It is possible for small blocks of temperate rainforest to exist along the slopes of these mountain ranges below the tree line where annual precipitation is sufficient for such forests to thrive.
Valdivian and Magellanic temperate rainforests of South America
The temperate rain forests of South America are located on the Pacific coast of southern Chile, on the west-facing slopes of the southern Chilean coast range, and the Andes Mountains in both Chile and Argentina down to the southern tip of South America, and are part of the Neotropic ecozone. The Valdivian rainforests are dominated by a variety of broadleaf evergreen trees, like Aextoxicon punctatum, Eucryphia cordifolia, and southern beech (Nothofagus), but include many conifers as well, notably Alerce (Fitzroya cupressoides), one of the largest tree species of the world. The Valdivian rainforests occur in the Valdivian temperate rain forests and Magellanic subpolar forests ecoregions.
The Valdivian and Magellanic temperate rainforest's are the only temperate rain forests in South America. Together they are the second largest in the world, after the Pacific temperate rain forests of North America. The Valdivian forests are a refuge for the Antarctic flora, and share many plant families and genera with the temperate rainforest's of New Zealand, Tasmania, and Australia. Fully half the species of woody plants are endemic to this ecoregion.
In the Valdivian region the Andean Cordillera intercepts moist westerly winds along the Pacific coast during winter and summer months; these winds cool as they ascend the mountains, creating heavy rainfall on the mountains' west-facing slopes. 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 62 degrees Fahrenheit (16.5 °C), while during winter the temperature can drop below 45 °F (7 °C).
South Africa's Knysna-Amatole coastal rain forests
The temperate rain forests of South Africa are part of the Knysna-Amatole forests that are located along South Africa's Garden Route between Cape Town and Durban on the south-facing slopes of South Africa's Drakensberg Mountains facing the Indian Ocean. There are several coniferous podocarps that grow here. This forest receives a lot of moisture as fog from the Indian Ocean, and resembles not only other temperate rain forests worldwide, but also the montane evergreen Afromontane forests that occur at higher elevations in southern and eastern Africa. A fine example of this forest is in South Africa's Tsitsikamma National Park.
Northwest Europe
Temperate rainforest occurs in fragments across the west of Britain, Ireland, Brittany, southern Norway and northern Spain. They mainly consist of oak species, typically Quercus petraea and have been managed by people for thousands of years. The woodlands are variously referred to in Britain as Upland Oakwoods, Atlantic Oakwoods, Western Oakwoods or Temperate Rainforest. They are also listed in the British National Vegetation Classification as British NVC community W11 and British NVC community W17 depending on the ground flora. In England many steep sided valleys in Devon and Cornwall harbour the rainforest with notable examples being the Fowey valley in Cornwall and the valley of the river Dart which, flowing off Dartmoor, has rainfall in excess of 2 metres per year.
Colchian rain forests of Turkey and Georgia
The Colchian rainforests are found around the southeast corner of the Black Sea in Turkey and Georgia and are part of the Euxine-Colchic deciduous forests ecoregion, together with the drier Euxine forests further west. The Colchian rain forests are mixed, with deciduous Black Alder (Alnus glutinosa), hornbeam (Carpinus betulus and C. orientalis), Oriental Beech (Fagus orientalis), and Sweet Chestnut (Castanea sativa) together with evergreen Nordmann Fir (Abies nordmanniana, the tallest tree in Europe at 78m), Caucasian Spruce (Picea orientalis) and Scots Pine (Pinus sylvestris).
Iran rain forests and jungles
The Caspian Hyrcanian mixed forests ecoregion in northern Iran contains a jungle in the form of a rain forest which stretches from the east in the Khorasan province to the west in the Ardebil province, covering the other provinces of Gilan, Mazandaran, and Golestan. The Elburz or Alborz mountain range is the highest mountain range in the Middle East which captures the moisture of the Caspian Sea to its north and forms subtropical and temperate rain forests in the northern part of Iran. The Iranians call this forest and region Shomal which means north in Persian.
They are deciduous forests containing tree species such as Black Alder (Alnus glutinosa subsp. barbata), hornbeam (Carpinus betulus and C. orientalis), Caucasian wingnut (Pterocarya fraxinifolia), chestnut-leaved oak (Quercus castaneifolia), Caucasian oak (Quercus macranthera), oriental beech (Fagus orientalis), Persian ironwood (Parrotia persica) and Persian silk tree (Albizia julibrissin).
Taiwan's mountain rain forests
These forests are found in eastern Taiwan and Taiwan's Central Mountain Ranges, part of the Taiwan subtropical evergreen forest region covering the higher elevations. Most of the lower elevations are covered by subtropical broadleaf evergreen forests, dominated by Chinese Cryptocarya (Cryptocarya chinensis), Castanopsis hystrix and Japanese Blue Oak (Quercus glauca). Higher elevations give way to temperate forests with large stands of old growth Taiwan Cypress (Chamaecyparis taiwanensis), Camphor tree (Cinnamomum camphora), maple (Acer spp.), Chinese yew (Taxus chinensis), Taiwan Hemlock (Tsuga chinensis), and Taiwan Douglas-fir (Pseudotsuga sinensis var. wilsoniana). These higher elevation forests include also giant conifers Formosan Cypress (Chamaecyparis formosensis) and Taiwania (Taiwania cryptomerioides) Some fine examples of forests are found in Yushan (Jade Mountain) National Park and Alishan.
Japan's Taiheiyo (Pacific) rain forests
Southwestern Japan's Taiheiyo evergreen forests region covers much of Shikoku and Kyushu Islands, and the Southern/Pacific Ocean-facing side of Honshu ("Taiheiyo" is the Pacific Ocean, in Japanese). Here the natural forests are mainly broadleaf evergreen in lower elevations and deciduous in higher elevations. The limit occurs at 500-1000 metres depending on latitude. The main tree species are members of beech family (Fagaceae). In lower altitudes these include evergreen oaks (Quercus spp.), Japanese Chinquapin (Castanopsis cuspidata) and Japanese Stone Oak (Lithocarpus edulis), and in higher altitudes Japanese Blue Beech (Fagus japonica) and Siebold's beech (Fagus crenata).
Some of the best preserved examples of forest are found in Kirishima-Yaku National Park on the Island of Yakushima off of Kyushu in a very wet climate (the annual rainfall is 4,000 to 10,000 mm depending on altitude). Because of relatively infertile soils on granite, Yakushima's forests in higher elevations are dominated by a giant conifer species, Japanese Cedar (Cryptomeria japonica), rather than deciduous forests typical of the mainland. Other areas include Mount Kirishima near Kagoshima in southern Kyushu. On Southern Honshu, there is a splendid forest with the beautiful Nachi Falls located in Yoshino-Kumano National Park. This particular area of Honshu has been described as one of the rainiest spots in Japan.
Australian temperate and subtropical rain forests
In Australia rainforests occur near the mainland east coast and in Tasmania. Australian non-tropical rainforests are divided principally into subtropical, warm-temperate and cool-temperate rainforests. They are broadleaf evergreen forests with the exception of montane rainforests of Tasmania. Eucalypt forests are not classified as rainforests although some eucalypt forest types receive high annual rainfall (to over 2000 mm in Tasmania), and in the absence of fire they may develop to rainforest. If these widespread wet sclerophyll forests were considered rainforests, the total area of rainforest in Australia would be much larger.
Subtropical rainforests can be found from NSW and Queensland, in the north they occur with increasing altitude. They are floristically very rich, up to 100 tree species per 10 hectares including booyongs (Argyrodendron spp.), Yellow Carabeen (Sloanea woollsii), Rosewood (Dysoxylum fraserianum), figs (Ficus spp.) and (Syzygium spp.).
Warm-temperate rainforest replaces subtropical rainforest on poorer soils or with increasing altitude and latitude in NSW and Victoria. They are dominated by Coachwood (Ceratopetalum apetalum), Australian Sassafras (Doryphora sassafras), and in the south by Lilly Pilly (Syzygium smithii).
Cool-temperate rainforests are widespread in Tasmania (Tasmanian temperate rain forests ecoregion) and they can be found scattered from the World Heritage listed Border Ranges National Park and Lamington National Park on the NSW/Queensland border to Otway Ranges, Strzelecki Ranges, Dandenong Ranges and East Gippsland in Victoria. In the northern NSW they are usually dominated by Antarctic Beech (Nothofagus moorei), in the southern NSW by Pinkwood (Eucryphia moorei) and in Victoria and Tasmania by Myrtle Beech (Nothofagus cunninghamii). The montane rainforests of Tasmania are dominated by tasmanian endemic conifers (mainly Athrotaxis spp.).
New Zealand temperate rain forests
The temperate rain forests of New Zealand occur on the western shore of New Zealand's South Island and on New Zealand's North Island. The forests are made up of coniferous podocarps and broadleaf evergreen trees; the podocarps are dominant at lower elevations, while southern beech (Nothofagus) becomes dominant on higher slopes and in the cooler southernmost rain forests. Ecoregions include the Fiordland temperate forests and Westland temperate forests.
Southern ocean island temperate rain forests
The islands of the Tristan da Cunha group and New Zealand's southern outlying islands of the Antipodes Islands, Auckland Islands, and Campbell Island group all host temperate rain forests. Annual rainfall totals are high due to the lack of landmass in their latitudes. Some areas of these islands are too windy for forests, but those areas that are not as windy are capable of growing temperate rain forests. The only thing preventing the Falkland Islands from having temperate rain forest is the proximity of the very high Andes Mountains to the west.
Images
External links
- - preserving rainforests in Southeast Alaska
- - preserving rainforests in coastal British Columbia's Great Bear Rainforest
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