Temperate rain forests are rain forests with coniferous or broadleaf forests that occur in the temperate zone and receive heavy rain.
Temperate rain forests occur in oceanic moist regions around the world: the Pacific temperate rain forests of the North American Pacific Northwest as well as the Appalachian temperate rain forest in the Appalachian region of the United States; the Valdivian temperate rain forests of southwestern South America; the rain forests of New Zealand and southeastern Australia; northwest Europe (small pockets in Great Britain and larger areas in Ireland, southern Norway, northern Iberia and Brittany); the Eastern Korea-Manchuria continuum; Japan; the Black Sea–Caspian Sea region from the southeasternmost coastal zone of the Bulgarian coast, through Turkey, to Georgia, and northern Iran.
The moist conditions of temperate rain forests generally have an understory of mosses, ferns and some shrubs and berries. Temperate rain forests can be temperate coniferous forests or temperate broadleaf and mixed forests.
Definition
For temperate rainforests of North America, Alaback's definition is widely recognized: Annual precipitation over (KJ) Mean annual temperature is between . However, required annual precipitation depends on factors such as distribution of rain over the year, temperatures over the year and fog presence, and definitions in other regions of the world differ considerably. For example, Australian definitions are ecological-structural rather than climatic: Closed canopy of trees excludes at least 69% of the sky. Forest is composed mainly of tree species which do not require fire for regeneration, but with seedlings able to regenerate under shade and in natural openings.Floyd, A. (1990) Australian Rainforests in New South Wales, Vol. 1. Surrey Beatty & Sons Pty Ltd, Chipping Norton, NSW, . Australian definitions would exclude some temperate rainforests of western North America that are Coast Douglas-fir dominant, such as parts of the Klamath Mountains in southern Oregon and northern California, the Puget Lowlands of western Washington and the Georgia Depression in British Columbia,Reilly, Matthew & Spies, Thomas. (2015). Regional variation in stand structure and development in forests of Oregon, Washington, and inland Northern California. Ecosphere. 6. art192. 10.1890/ES14-00469.1. as their dominant tree species, the Coast Douglas-fir, requires stand-destroying disturbance to initiate a new cohort of seedlings. The North American definition would in turn exclude a part of temperate rainforests under definitions used elsewhere.
Canopy level
For forests, canopy refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms (epiphytes, lianas, arboreal animals, etc.). The canopy level is the third level of the temperate rainforest. The trees forming the canopy, conifers, can stand as tall as 100 metres or more. A variety of species survive in the canopy. The tops of these trees collect most of the rain, moisture, and photosynthesis that the rainforest takes in. They form a canopy over the forest, covering about 95% of the floor during the summer.
The canopy's coverage affects the shade tolerance levels of forest floor plants. When the canopy is in full bloom, covering about 95% of the floor, plant survival decreases. Some plant species have become shade tolerant in order to survive. The treetops take in the heavy amount of rain and keep the lower levels of the forest damp.
The canopy survives through photosynthesis. The leaves provide energy and nutrients for the trees, which provide homes and food for the forest. Through satellite data, the radiation use efficiency (RUE) calculates the annual amount of photosynthesis that occurs in temperate rainforests. A diverse amount of photosynthesis occurs based on the location and microclimates of the forest. Distribution
North America
Pacific temperate rainforests
A portion of the temperate rain forest region of North America, the largest area of temperate zone rainforests on the planet, is the Pacific temperate rain forests ecoregion, 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 realm. In the different system established by the Commission for Environmental Cooperation, this same general region is classed as the Pacific Maritime Ecozone by Environment Canada and as the Marine West Coast Forest Level II ecoregion by the United States Environmental Protection Agency. In terms of the floristic province system used by botany, the bulk of the region is the Rocky Mountain Floristic Region but a small southern portion is part of the California Floristic Province.
Sub-ecoregions of the Pacific temperate rainforest ecoregion as defined by the WWF include the Northern Pacific coastal forests, Haida Gwaii ecoregion, Vancouver Island ecoregion, British Columbia mainland coastal forests, Central Pacific coastal forests, Cascades forests, Klamath-Siskiyou coastal 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. Most of the precipitation occurs in winter, similar to Mediterranean climates, but in summer, fog moisture is extracted by the trees and produces a fog drip keeping the forest moist.Franklin, J.F. & Dyrness C.T. (1988) Natural Vegetation of Oregon and Washington. Oregon State University Press, . 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 rainforests of North America is the Nurse log, a fallen tree which as it decays, provides ecological facilitation to seedlings. Trees such as the Coast Douglas-fir, Western Hemlock, Western Red Cedar, Pacific Yew, and Vine Maple are more closely related to coniferous and deciduous trees in the temperate forests of East Asia.
Some of the largest expanses of old growth are found in Olympic National Park, Mount Rainier National Park, Mount Hood National Forest, Crater Lake 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 containing the largest expanses of old growth 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 US), which include the Selkirk Mountains, Monashee Mountains, and the Purcell Mountains, have the largest stretch of interior temperate coniferous rainforests.Northern Wetbelt – University of Northern British Columbia http://wetbelt.unbc.ca/ 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 rainforests are found in Mount Revelstoke National Park and Glacier National Park (Canada) in the Columbia Mountains.
Appalachian temperate rainforests
Temperate rainforests are located in the southern Appalachian Mountains where orographic precipitation increases precipitation of weather systems coming from the west and from the Gulf of Mexico. Temperate rainforest extends through the Appalachian areas of western North Carolina, southeastern Kentucky, southwest Virginia, eastern Tennessee, northern South Carolina, and northern Georgia.
Red spruce and Fraser fir are dominant canopy trees in high mountain areas. In higher elevation (over ), Fraser fir is dominant, in middle elevation () red spruce and Fraser fir grow together, and in lower elevation () red spruce is dominant. Yellow birch, mountain ash, and mountain maple grow in the understory. Younger spruce and fir and shrubs like raspberry, blackberry, hobblebush, southern mountain cranberries, red elderberry, minniebush, southern bush honeysuckle are understory vegetation. Below the spruce-fir forest, at around , are forests of American beech, yellow birch, maple birch, and oak. Skunk cabbage and ground juniper are northern species that were pushed into the areas from the north.
The mild and wet environment supports the high diversity of fungi. Over 2,000 species live in this area and scientists estimate many unidentified fungi may be there.
South America
Valdivian and Magellanic temperate rainforests
The temperate rainforests 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 Western Argentina down to the southern tip of South America, and are part of the Neotropical realm. Temperate rainforests occur in the Valdivian temperate rain forests and Magellanic subpolar forests ecoregions. The Valdivian rainforests are home to 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 and Magellanic temperate rainforests are the only temperate rainforests in South America. Together they are the second largest in the world, after the Pacific temperate rainforests of North America. The Valdivian forests are a refuge for the Antarctic flora, and share many plant families and genera with the temperate rainforests of Australia and New Zealand. 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 , while during winter the temperature can drop below .Di Castri, F and Hajek, E. (1976) "Bioclimatología de Chile", 163 pages with English summary, Catholic University of Chile.
Africa
Knysna-Amatole coastal rainforests (South Africa)
The temperate rainforests of South Africa are part of the Knysna-Amatole forests that are located along South Africa's Garden Route between Cape Town and Port Elizabeth 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 rainforests 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.
Macaronesia Azores
The rainforests of the Azores (also known as cloud forests, due to the constant cloud coverage caused by orographic lift) are found in the more humid, montane areas that transition from the lower altitude laurissilva. They are generally found at altitudes ranging from , and receive of average annual rainfall.