Laurel forest is a subtropical or mild temperate forest, found in areas with high humidity and relatively stable and mild temperatures. They are characterized by tree species with evergreen, glossy, enlongated leaves, known as laurophyll or lauroide. The members of the Laurel family (Lauraceae) may be prominent, or in association.
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The laurel evergreen temperate forest vegetation is characteristic of a climate regime with well defined seasons, but lacking in sharp contrast. The annual temperature variation is mild, without excluding winter frost, and rainfall is abundant well-distributed throughout the year, without a defined dry season. These conditions occur in four different geographical regions:
Laurel forests are characterized by evergreen and hardwood trees, reaching up to 40 meters in height.
Some species belong to the true laurel family or Lauraceae, but many have similar foliage to the Lauraceae due to convergent evolution. As in any other rainforest, plants of the laurel forests must adapt to high rainfall and humidity. The trees adapted by developing leaves that repel water. Laurophyll or lauroide leaves are characterized by a generous layer of wax, making them glossy in appearance, and narrow, pointed oval in shape with an apical mucro, or 'drip tip', which permit the leaves to shed water despite the humidity, allowing perspiration and respiration from plant. The scientific names laurina, laurifolia, laurophylla, lauriformis, and lauroides are often used to name species of other plant families that resemble Lauraceace.[1] The term "Lucidophyll", referring to the shiny surface of the leaves, was proposed in 1977 by Tatuo Kira.[2]
Mature laurel forests typically have a dense tree canopy, and low light levels at the forest floor.[2] Some forests are characterized by an overstory of emergent trees.
Laurel forests are typically multi-species, and diverse in the number of species represented, as well as the diversity of genera and families represented.[2] In the absence of strong environmental selective pressure, the number of species sharing the arboreal stratum is high, nearly 100 tree species have been described in the laurisilva rainforest of Misiones (Argentina), about 20 in the Canary Islands, not reaching the values of tropical forests. This species diversity contrasts with other temperate forest types, which typically have a canopy dominated by one or a few species. Species diversity generally increases towards the tropics.[3] In this sense, the laurel forest is a transitional type between temperate forests and tropical rainforests.
Laurel forest is a type of rainforest or Cloud Forest. An ecosystem of great exuberance characterized by high humidity, no seasonal changes and with a wide variety of botanical and zoological species but also highly fragile against external aggressions. Characterized by evergreen and hardwood trees, reaching up to 40 meters in height.
The temperate evergreen and evergreen forests are typically multispecies. Evergreen because the mild climate allows for continuous biological activity, and multispecies for the remarkable diversity of tree species in the vault forestal. Indeed, in the absence of strong environmental selective pressure, the number of species sharing the arboreal stratum is high, nearly 100 tree species have been described in the rainforest laurisilva of Misiones (Argentina), about 20 in the Canary Islands, not reaching the values of tropical forests yet. It is precisely this multispecies what they deserve the name of rainforest, in contrast to the "forest", Mediterranean forests, temperate deciduous forests etc., which is monospecific with a canopy dominated by one or a few species. In this sense, the laurel forest or laurisilva is a formation of transition between temperate forests and tropical rainforests.
However, despite the large number of species, there is considerable morphological convergence between the different species of trees, especially in the leaves, which correspond mainly to the type "lauroide" (Sweet bay): wide, oval, leathery, glossy. Hence the Latin name given to the training: laurus.
The laurel forest is a type of cloud forest, the cloud forests, are developed preferably about mountains, where the dense moisture from the sea or ocean, is precipitated by the action of the relief. Opposing the terrain to a front of warm, moist air mass, it forces to increase the height above sea level of that body wet and warm air mass, which cools and decreases the dew point, causing it to condense part of the moisture that falls as rain or fog, creating an habitat especially cool, saturated with moisture in the air and soil.
The Mediterranean climate is the balance between dry and warm influence of the subtropical anticyclone, hot and dry summer and the polar air stream, Antarctic and Arctic, responsible for carrying rain storms, cool wet winter. As latitude increases, this increases the impact of the storms, which in its journey from west to east, swept the western coasts of continents, dumping heavy rains as carrying high humidity. Precipitation multiply if these air masses are crossing mountains in the way. The resulting climate is wetter, but with an annual oscillation of the temperature moderated by the proximity of the ocean.
These are the climatic conditions of Chile between 38° and 45° latitude. Rainfall is abundant, from 1500 to 5000 mm according to locality, and are spaced out throughout the year, but still see the influence subhumid Mediterranean with 3–4 months in summer. The temperatures are unchanging enough and mild, without any month the average fall below 5 °C, with values for the warmest month below 22 °C.
The coasts of Brazil and Argentina, between 25° and 35° latitude, are under a laurel forest typical weather patterns. This region still falls in the area of influence of the subtropical anticyclone, which this side sends warm air, moist and unstable at high latitudes. During the summer the anticyclone strengthens and increases the flow of moist air mass, which, as it rises and cools, producing heavy rainfall. In winter, remove the cyclone and strengthening the polar air inlet to the west, causing rain-bearing depressions. Overall, the average annual rainfall varies according to locality, between 1,500 and 2,000 mm. The average temperature is around 20–21 °C, with mild winters and moderately hot summers, due to the moderating effect of heavy rains. This softness does not prevent them occur frost and even snow in the higher regions, which is a limiting factor for species from lower latitudes. A climate of these characteristics is classified as humid subtropical, or warm and rainy with warm summers.
The Atlantic laurel forest covered the European continent, North Africa and Middle East Asia, during the Tertiary, when tropical weather dominated the Mediterranean. Currently its largest populations are found on the islands of Macaronesia in the North Atlantic Ocean, forming the so-called Macaronesian laurissilva.
It features deep soil and is typical of the northern midlands influenced by the mists of the trade winds, lack of frost, rainfall of 500 to 1,100 mm per year and an average annual temperature between 15 and 19 °C. It comprises a variety of trees, understory plants and species of insects and animals that live in wet conditions over 80%, usually appear on the site of heavy rain, mostly occupying favorable areas named geographically Umbrias, this is north hillsides or slopes of the mountainous areas that are oriented behind the sun in the northern hemisphere, of islands between 400 and 1500 meters, thus benefiting from the humidity provided by the trade winds to form such a sea of clouds. Macaronesian laurel forest comprises two subtypes: the laurilsilva and fayal-brezal in degradated areas. Due to the large amount of water and the terrain, it flows in the form of streams and waterfalls everywhere or stay quiet in ponds and puddles or drips, it cover and soak of the plants, rocks, soil, logs, moss etc. and the forest still remain impassable during heavy rains, the beauty of the set make it a tourist attraction.
Laurel forest formations are remarkable both by extension and biodiversity in great areas of Southeast Asia and Africa, mainland and islands, with the typical formation of Annobon, but these formations are less studied.
Laurel forests occur in small areas where their particular climatic requirements prevail, in both the northern and southern hemispheres. Inner laurel forest ecoregions, a related and distinct community of vascular plants evolved millions of years ago on the supercontinent of Gondwana, and species of this community are now found on several separate areas of the Southern Hemisphere, including southern South America, southernmost Africa, New Zealand, Australia and New Caledonia. These lauroides plant communities are twofold to tropical climate and temperate climate, having the more temperate climate their origin in the named Antarctic flora.
Laurel forests are common in warm-temperate to subtropical eastern Asia, and form the climax vegetation in southern Japan, southern Korea, Taiwan, southern China, the mountains of Indochina, and the eastern Himalayas. In southern China, laurel forest once extended throughout the Yangtze Valley and Sichuan Basin from the East China Sea to the Tibetan Plateau. The northernmost laurel forests in East Asia occur at 39° N. on the Pacific coast of Japan. Altitudinally, the forests range from sea-level up to 1000 meters in warm-temperate Japan, and up to 3000 meters elevation in the tropical mountains of Asia.[3] Some forests are dominated by Lauraceae, while in others evergreen laurophyll trees of the beech family (Fagaceae) are predominant, including ring-cupped oaks (Quercus subgenus Cyclobalanopsis), chinquapin (Castanopsis) and tanoak (Lithocarpus).[2] Other characteristic plants include Schima and Camellia, which are members of the tea family (Theaceae), as well as Magnolias, bamboo, and rhododendrons.[4] These subtropical forests lie between the temperate deciduous and conifer forests to the north, and the tropical monsoon forests of Indochina and India to the south.
In the Himalayas, Nepal, subtropical forest consists of species such as Schima wallichii, Castanopsis indica, and Castenopsis tribuloides on relatively humid areas. Some common forest types in this region include Castanopsis tribuloirdes mixed with Schima wallichi, Rhododendron spp., Lyonia ovalifolia, Eurya acuminata, and Quercus glauca; Castanopsis-Laurales forest with Symplocas spp.; Alnus nepalensis forests; Schima wallichii-Castanopsis indica hygrophile forest; Schima-Pinus forest; Pinus roxburghii forests with Phyllanthus emblica. Semicarpus anacardium, Rhododendron arboreum and Lyoma ovalifolia; Schima-Lagestromea parviflora forest, Quercus lamellosa forest with Quercus lenata and Quercus glauca; Castononpsis forests with Castononpsis hystrix and Lauraceae.
Associations of Lauraceous species are common in broadleaved forests; for example, Litsea spp., litsea cupola, Persea odoratissima, Persea duthiei, etc., along with such others as Engelhardtia spicata, Rhododendron arboreum, Lyonia ovalifolia, Pyrus pashia, Rhus spp., Acer oblongum, myrica esculenta, Michelia kisopa, and Betula alnoides. Some other common trees and large shrub species of subtropical forests are Semicarpus anacardium, Cretaeava unilocularis, Trewia nudiflora, Premna interrupta, Ulmus lancifolia, Ulmus chumlia, Glochidium velutinum, Callicarpa arborea, Toona ciliata, Ficus spp., Mahosama similicifolia, Trevesia palmate, Xylosma longifolium, Boehmeria rugulosa, Scheffera venulosa, Michelia spp., Casearia graveilens, Rhus wallichii, Actinodaphne reticulata, Sapimum insegne, Alns nepalensis, Ardisia thyrsiflora, Ilex spp, Macaranga pustulata, Trichilia cannoroides, Celtis tetranda, Wenlendia puberula, Saurauia nepalensis, Ligustrum confusum, Quercus glauca, Zizyphus incurva, Camellia kissi, Hymenodictyon flaccidum, Maytenus thomsonii, Zanthoxylum armatum, Rhus succednea, Eurya acuminata, Myrsine semiserrata, Slonea tomentosa, Hydrangea asper, Symplocus spp., Cleyrea spp. and Quercus lamellose.
In Temperate zone (cloud forest) from 2,000 to 3,000 m. This zone supports broadleaved evergreen forest dominated by plants such as Quercus lamillosa and Q. semicarpifolia in pure or mixed stands. Species such as Lindera and Litsea. Tseuga dumosa and Rhododendron spp. are also present in the upper levels of this zone. Other important species are Magnolia campbellii, Michelia doltsopa, Pieris ovalifolia, Daphnephyllum himalayanse, Acer campbellii, Acer pectinatum, and Sorbus cuspidata but these species do not extend toward the west beyond central Nepal. Alnus nepalensis, a pioneer tree species, grows gregariously and forms pure patches of forests on newly exposed slopes, gullies, moist places and on riversides.
The common forest types of this zone include Rododendraon arboreum, Rohododendron barbatum, Lyonia spp., Pieris Formosa; Tsuga dumosa forest with such deciduous species as Acer and Magnolia; deciduous mixed broadleaved forest of Acer campbellii, Acer pectinatum, Sorbus cuspidata, and Magnolia campbellii; mixed broadleaved forest of Rhododendron arboreum, Acer campbellii, Symplocos ramosissima and Lauraceae.
This zone is habitat for many other important tree and large shrub species such as Abies pindrow, Betula utilis, Buxus rugulosa, Benthamidia capitata, Corylus ferox, Deutzia staminea, Euonymus tingens, Abies spectalbilis, Acanthopanax cissifolius, Acer campbellii, Acer pectinatum, Betula alnoides, Coriaria terminalis, Fraxinus macrantha, Dodecadenia grandiflora, Eurya cerasifolia, Hydrangea heteromala, Ilex dipyrena, Ligustrum spp., Litsea elongata, Juglans regia, Lichelia doltsopa, Myrsine capitallata, Neolitsea umbrosa, Philadelphus tomentosus, Osmanthus fragrans, Prunus cornuta, Rhododendron companulatum, Sorbus cuspidate, and Vibernum continifolium.
In ancient times, laurel forests (shoyojurin) were the predominant vegetation type in the Taiheiyo evergreen forests ecoregion of Japan, which encompasses the mild temperate climate region of southeastern Japan's Pacific coast. There were three main types of evergreen broadleaf forests, in which Castanopsis, Machilus, or Quercus predominated. Most of these forests were logged or cleared for cultivation, and replanted with faster-growing conifers, like pine or hinoki, and only a few pockets remain.[5]
Laurel forests occupy the humid tropical highlands of the Malay Peninsula, Greater Sunda Islands, and Philippines above 1000 meters elevation. The flora of these forests is similar to that of the warm-temperate and subtropical laurel forests of East Asia, including oaks (Quercus), tanoak (Lithocarpus), chinquapin (Castanopsis), Lauraceae, Theaceae, and Clethraceae. Epiphytes, including orchids, ferns, moss, lichen, and liverworts, are more abundant than in either temperate laurel forests or in the adjacent lowland tropical rain forests. Myrtaceae are common at lower elevations, and conifers and rhododendrons common at higher elevations. These forests are distinct in species composition from the lowland tropical forests, which are dominated by Dipterocarps and other tropical species.[6]
The laurisilva forests are found in the islands of Macaronesia in the eastern Atlantic, in particular the Azores, Madeira Islands, and Canary Islands from 400 to 1200 meters elevation. Trees of the genera Apollonias (Lauraceae), Ocotea (Lauraceae), Persea (Lauraceae), Clethra (Clethraceae), Dracaena (Ruscaceae), and Picconia (Oleaceae) are characteristic.[7] The Madeira Islands laurel forest was designated a World Heritage Site by UNESCO in 1999.
Millions of years ago, Laurel forests were widespread around the Mediterranean Basin. The drying of the region since the Pliocene, and cooling of the region during the Ice Ages, caused these rainforest to retreat. Some relict Mediterranean laurel forest species, such as Sweet Bay (Laurus nobilis) and European Holly (Ilex aquifolium), are fairly widespread around the Mediterranean basin.
In the Mediterranean there are other areas with species adapted to the same habitat, but without forming a laurel forest, they share some species of the Macaronesian laurilva. The most important is the ivy, a climber or vine that is well represented in most of Europe, where it spread again after the glaciations. The "loro" (Prunus lusitanica), the only tree that survives in a relict in some Iberian streams, especially in the western part of the peninsula, particularly Extremadura, and a little on the Northeast. In other cases, the presence of Mediterranean laurel (Laurus nobilis), provides an indication of where was the laurel forest. This species survives native in Morocco, Italy, Greece and the Mediterranean islands. In the Iberian Peninsula appears in some Mediterranean streams, such as the Parque Natural Los Alcornocales in the province of Cádiz. Also appearing in coastal mountains especially in, Girona Province of Catalonia which keeps the best "lauredales" and some scraps in the Valencia area. Cortegada Island in Galicia, is famous for its vast forest of laurels, but this forest is not indigenous to the island, because this forest originated spontaneously from the laurels that were planted after have been destroyed the original vegetation. The myrtle spread through North Africa. Tree Heath (Erica arborea) grows in southern Spain, but without reaching the dimensions reached in the temperate evergreen or North Africa. Spanish endemics Rhododendron ponticum baeticum and Rhamnus frangula baetica, still persist in humid microclimates, such as stream valleys, in Spain's Baetic Cordillera and the Rif Mountains of Morocco.[8]
Although the Atlantic laurisilva is more abundant in the Macaronesian archipelagos, where the weather just scarcely has fluctuated since the Tertiary, there are small representations and a species contribution to the environment ecoregions oceanic and Mediterranean of Europe, Asia minor and west and north of Africa refugees in microenvironments favorable climate. That is, in the coastal mountain ranges. These 'islands' inland, in some cases were genuinely islands in the tertiary and in some cases simply ice-free areas of both Eurasia and Africa. When you close the strait once again repopulated the Iberian Peninsula to the north again distributed along with other African species itself, but the change to a drier climate and seasonal prevented their previous reexpansion. But in the atlantic Europe there are subtropical vegetation interspersed taxa from Europe and North African in bioclimatic enclaves like Monchique, Sintra or the coastal mountains from Cadiz to Algeciras. In the Mediterranean, is present in some islands of the Aegean Sea, Black Sea coast of Iran and Turkey, which hosted the laurifolia castanopsis and true laurus Forests, associated with Prunus laurocerasus, and conifers Taxus baccata, Cedrus atlantica, Abies pinsapo and so on. On the Turkish coast of the Black Sea to the East arriving at Iran.
The laurel forest has been badly damaged due to short for timber harvesting, burning both accidental and deliberate by open fields for crops, either colonial or subsistence crops in the past and exotic timber plantations in the present, the open cattle pastures, golf courses and tourist facilities and the introduction of exotic animal and plant species that have replaced the original cover. Most of the biota is in serious danger of extinction. The laurel forest vegetable species are usually strong and vigorous, so the forest is regenerated easily, the decline is due to the tremendous pressure that supports them.
Laurel forests are also prevalent in the montane rain forests of the South Western Ghats in southern India and Sri Lanka.
The Afromontane laurel forests describe the plant and animal species common to the mountains of Africa and the southern Arabian Peninsula. The afromontane regions of Africa are discontinuous, separated from each other by lowlands, their distribution is analogous to a series of islands. Patches of forest with Afromontane floristic affinities occur all along the mountain chains. Afromontane communities occur above 1500–2000 meters elevation near the equator, and as low as 300 meters elevation in the Knysna-Amatole montane forests of South Africa. Afromontane forests are cool and humid. Rainfall is generally greater than 700 mm per year, and can exceed 2000 mm in some regions, occurring throughout the year, or during winter or summer, depending on the region. Temperatures can be extreme in some of the higher altitudes where snowfalls may occasionally occur.
In Subsaharan Africa, laurel forests are found in the Cameroon Highlands forests along the border of Nigeria and Cameroon, along the East African Highlands, a long chain of mountains extending from the Ethiopian Highlands around the African Great Lakes to South Africa, in the Highlands of Madagascar, and in the montane zone of the São Tomé, Príncipe, and Annobón moist lowland forests. These scattered highland laurophyll forests of Africa are similar to one another in species composition (known as the Afromontane flora), and distinct from the flora of the surrounding lowlands.
The main species of the Afromontane forests include the broadleaf canopy trees Apodytes dimidiata, Ilex mitis, Nuxia congesta, N. floribunda, Kiggelaria africana, Prunus africana, Rapanea melanophloeos, Halleria lucida, Ocotea bullata, and Xymalos monospora, along with the emergent conifers Podocarpus latifolius and Afrocarpus falcatus. Species composition of the Subsaharan laurel forests differs from that of Eurasia. Trees of the Laurel family are less prominent, limited to Ocotea, and the members of the beech family (Fagaceae) are absent.[3]
Trees can be up to 30 m or 40 m tall and distinct strata of emergent trees, canopy trees and shrub and herb layers are present. Tree species include: Real Yeilowwood Podocarpus latifolius, Outeniqua Yeilowwood Podocarpus falcatus, White Witchhazei Trichocladus ellipticus, Rhus chirendensis, Curtisia dentata, Calodendrum capense, Apodytes dimidiata, Halleria lucida, llex mitis, Kiggelaria africana, Nuxia floribunda, Xymalos monospora and Ocotea bullata. Shrubs and climbers are common and include: Common Spikethorn Maytenus heterophylla, Cat-thorn Scutia myrtina, Numnum Carissa bispinosa, Secamone alpinii, Canthium ciliatum, Rhoicissus tridentata, Zanthoxylum capense and Burchellia bubalina. In the undergrowth grasses, herbs and ferns may be locally common: Basketgrass Oplismenus hirtellus, Bushman Grass Stipa dregeana var. elongata, Pigs-ears Centella asiatica, Cyperus albostriatus, Polypodium polypodioides, Polystichum tuctuosum, Streptocarpus rexii and Plectranthus spp. Ferns, shrubs and small trees such as Cape Beech Rapanea melanophloeos are often abundant along the forest edges.
During the Miocene, oak-laurel forests were found in Central and Southern California. Typical tree species included oaks ancestral to present-day California oaks, as well as an assemblage of trees from the Laurel family, including Nectandra, Ocotea, Persea, and Umbellularia.[9][10] Only one native species from the Laurel family, Umbellularia californica, remains in California today.
The laurel forest is the most common Central American temperate evergreen cloud forest type. They are found in mountainous areas of southern Mexico and almost all Central American countries, normally more than 1,000 m above sea level. Tree species include evergreen oaks, members of the Laurel family (Lauraceae), and species of Weinmannia, Drimys, and Magnolia.[11] The cloud forest of Sierra de las Minas, Guatemala, is the largest in Central America. In some areas of southeastern Honduras there are cloud forests, the largest located near the border with Nicaragua. In Nicaragua the cloud forests are found in border zone with Honduras, and most were cleared to grow coffee. There are still some temperate evergreen hills of the north. The only cloud forest of the Pacific coast of Central America is on the Mombacho volcano in Nicaragua. In Costa Rica there are "laurisilva" in the "Cordillera de Tilarán" and Volcán Arenal, called Monteverde, also in the Cordillera de Talamanca.
The Yungas are typically evergreen forests or jungles, and multi-species, which often contain many species of the laurel forest. Appear from Venezuela to northwestern Argentina via Brazil Bolivia, Chile, Colombia, Ecuador and Peru. Discontinuously distributed in the provinces of Salta, Jujuy, Tucumán and Catamarca, usually integrated with the Sub-Andean Sierras. Its relief is varied and in places where the Andes meet the Amazon penetrate areas with high gradient. Are characteristic of this region to bring them, they are deep channels formed by the rivers, like the way the Tarma River when down to the San Ramon Valley, or the Urubamba River as it passes through Machu Picchu. Many of the Yungas are degraded areas or tree formations in recovery who have not yet reached its climax vegetation, like the Fayal-Heath of Macaronesian laurisilva.
The coasts of Brazil and Argentina, between 25° and 35° latitude, are under a laurel forest typical weather patterns. This region still falls in the area of influence of the subtropical anticyclone, which this side sends warm air, moist and unstable at high latitudes. During the summer the anticyclone strengthens and increases the flow of moist air mass, which, as it rises and cools, producing heavy rainfall. In winter, remove the cyclone and strengthening the polar air inlet to the west, causing rain-bearing depressions. Overall, the average annual rainfall varies according to locality, between 1,500 and 2,000 mm. The average temperature is around 20–21 °C, with mild winters and moderately hot summers, due to the moderating effect of heavy rains. This softness does not prevent them occur frost and even snow in the higher regions, which is a limiting factor for species from lower latitudes. A climate of these characteristics is classified as humid subtropical, or warm and rainy with warm summers.
The laurel forests of the region are known as the "Laurisilva Misionera", after Argentina's Misiones Province. The Araucaria moist forests occupies a portion of the highlands of southern Brazil, extending into northeastern Argentina. The forest canopy includes species of Lauraceae (Ocotea pretiosa and O. catharinense), Myrtaceae (Campomanesia xanthocarpa), and Leguminosae (Parapiptadenia rigida), with an emergent layer of the conifer Brazilian Araucaria (Araucaria angustifolia) reaching up to 45 meters in height.[12] The subtropical Serra do Mar coastal forests along the southern coast of Brazil have a tree canopy of Lauraceae and Myrtaceae, with emergent trees of Leguminaceae, and rich diversity of bromeliads and trees and shrubs of family Melastomaceae.[13] The inland Alto Paraná Atlantic forests, which occupy portions of the Brazilian Highlands in southern Brazil and adjacent parts of Argentina and Paraguay, are semi-deciduous.
The Valdivian temperate rain forests, or Laurisilva Valdiviana, occupies southern Chile and Argentina from the Pacific Ocean to the Andes between 38° and 45° latitude. Rainfall is abundant, from 1500 to 5000 mm according to locality, distributed throughout the year, but with some subhumid Mediterranean climate influence in 3–4 months in summer. The temperatures are unchanging enough and mild, with no month falling below 5 °C, and the warmest month below 22 °C.
The eastern end of Malesia, including New Guinea and the Aru Islands of eastern Indonesia, is linked to Australia by a shallow continental shelf, and shares many marsupial mammal and bird taxa with Australia. New Guinea also has many additional elements of the Antarctic flora, including southern beech (Nothofagus) and Eucalypts. New Guinea has the highest mountains in Malesia, and vegetation ranges from tropical lowland forest to tundra.
The highlands of New Guinea and New Britain are home to tropical montane laurel forests, from about 1000 up to 2500 meters elevation. These forests include species typical of both Northern Hemisphere laurel forests, including Castanopsis, Lithocarpus, Ilex, and Lauraceae, and Southern Hemisphere laurel forests, including Southern Beech Nothofagus, Araucaria, Podocarps, and trees of the Myrtle family (Myrtaceae).[3][14] New Guinea and Norther Australia are closely related. Around 40 million years ago, the Indo-Australian tectonic plate began to split apart from the ancient supercontinent Gondwana. As it collided with the Pacific Plate on its northward journey, the high mountain ranges of central New Guinea emerged around 5 million years ago.[15] In the lee of this collision zone, the ancient rock formations of what is now Cape York Peninsula remained largely undisturbed.
Throughout the Pleistocene epoch Australia and New Guinea have been alternately land-linked and separated by water on a number of occasions. During periods of glaciation and resulting low sea levels, Cape York Peninsula provided a low-lying land link.[16] Another link existed between Arnhem Land and New Guinea, at times enclosing an enormous freshwater lake (Lake Carpentaria) in the centre of what is now the Gulf of Carpentaria.[17] In this way, Australia and New Guinea remained connected until the shallow Torres Strait was last flooded around 8,000 years ago.[18]
The majority of Norther Australia is covered in tropical and subtropical grasslands, savannahs, and shrublands. The flora of the Cape York peninsula includes original Gondwanan species, plants that have emerged since the breakup of Gondwana and species from Indo-Malaya and from across the Torres Strait in New Guinea with the most variety being found in the rainforest areas. Most of the Cape York Peninsula is drier than nearby New Guinea which limits the laurel forest plants of that island from migrating across to Australia.[19]
Tropical rainforests cover an area of 748,000 ha, or 5.6 percent of the total land area of Cape York Peninsula.[20] Rainforests depend on some level of rainfall throughout the long Dry season, climatic conditions that are mostly found on the eastern slopes of the Cape’s coastal ranges. Being almost exclusively untouched, old-growth forests and supporting a disproportionately high biodiversity including flora of Gondwanan and New Guinean origin, the rainforests are of high conservation significance.[21] The largest contiguous rainforest area on the Cape occurs in the McIllwraith Range-Iron Range area.[17] The Gondwanan flora of this area includes Araucariaceae and Podocarpaceae conifers and Arthrochilus, Corybas, and Calochilus orchids. In all, this rainforest contains at least 1000 different plants, including 100 rare or threatened species, and 16% of Australia's orchid species.
The WWF identifies several distinct montane laurel forest ecoregions on New Guinea, New Britain, and New Ireland.[22]
The laurifolia appears in mountains of the coastal strip of New South Wales in Australia, New Guinea, New Caledonia, Tasmania, and New Zealand. The laurel forests of Australia, Tasmania, and New Zealand are home to species related to those in the Valdivian laurel forests, including Southern Beech (Nothofagus) through the connection of the Antarctic flora. Other typical flora include Winteraceae, Myrtaceae, Southern Sassafras (Atherospermataceae), conifers of Araucariaceae, Podocarpaceae, and Cupressaceae, and tree ferns.[24]
New Caledonia was an ancient fragment of the supercontinent Gondwana. Unlike many of the Pacific Islands, which are of relatively recent volcanic origin, New Caledonia is part of Zealandia, a fragment of the ancient Gondwana super-continent. Zealandia separated from Australia 60–85 million years ago,[25] and the ridge linking New Caledonia to New Zealand has been deeply submerged for millions of years. This isolated New Caledonia from the rest of the world's landmasses, preserving a snapshot of Gondwanan forests. New Caledonia and New Zealand are separated by continental drift of Australia 85 million years ago. The islands still shelters an extraordinary diversity of endemic plants and animals of Gondwanan origin have spread to the southern continents later.
The laurel forest of Australia, New Caledonia (Adenodaphne), and New Zealand have a number of other related species of the Valdivian laurel forest, through the connection of the Antarctic flora of gymnosperms like the podocarpus and deciduous Nothofagus.Beilschmiedia tawa is often the dominant canopy species of genus Beilschmiedia in lowland Lauraceae forests in the North Island and the north east of the South Island, but will also often form the subcanopy in primary forests throughout the country in these areas, with podocarps such as Kahikatea, Matai, Miro and Rimu. Genus Beilschmiedia are trees and shrubs widespread in tropical Asia, Africa, Australia, New Zealand, Central America, the Caribbean and South America as south as Chile. Corynocarpus family, Corynocarpus laevigatus is called laurel of New Zealand, Laurelia novae-zelandiae belongs to the same genus that Laurelia sempervirens. The tree niaouli grows in Australia, New Caledonia and New Zealand.
New Caledonia lies at the northern end of the ancient continent Zealandia, while New Zealand rises at the plate boundary that bisects it. These land masses are two outposts of the Antarctic Flora, including Araucarias and Podocarps. At Curio Bay, logs of a fossilized forest closely related to modern Kauri and Norfolk Pine can be seen that grew on Zealandia about 180 million years ago during the Jurassic period, before it split from Gondwana.[26]
During glacial periods more of Zealandia becomes a terrestrial rather than a marine environment. Zealandia was originally thought to have no native land mammal fauna, but a recent discovery in 2006 of a fossil mammal jaw from the Miocene in the Otago region shows otherwise.[27]
New Guinea and Northern Australia ecoregion are closely related. Over time Australia drifted north and became drier as well; the humid Antarctic flora from Gondwana retreated to the east coast and Tasmania, while the rest of Australia became dominated by Acacia, Eucalyptus, and Casuarina, as well as xeric shrubs and grasses. Humans arrived in Australia 50-60,000 years ago, and used fire to reshape the vegetation of the continent; as a result, the Antarctic flora, also known as the Rainforest flora in Australia, retreated to a few isolated areas composing less than 2% of Australia's land area.