135-531: Aspen is a common name for certain tree species; some, but not all, are classified by botanists in the section Populus , of the Populus genus . These species are called aspens: Aspen trees are all native to cold regions with cool summers, in the north of the northern hemisphere , extending south at high-altitude areas such as mountains or high plains. They are all medium-sized deciduous trees reaching 15–30 m (50–100 ft) tall. In North America,
270-1014: A keystone species , as it helps to support the ecosystem which it inhabits. It creates wetlands, which provide habitat for European water vole , Eurasian otter and Eurasian water shrew . By coppicing waterside trees and shrubs it facilitates their regrowth as dense shrubs, thus providing cover for birds and other animals. Beavers build dams that trap sediment, improve water quality , recharge groundwater tables and increase cover and forage for trout and salmon . Also, abundance and diversity of vespertilionid bats increase, apparently because of gaps created in forests, making it easier for bats to navigate. Eurasian beavers have one litter per year, coming into oestrus for only 12 to 24 hours, between late December and May, but peaking in January. Unlike most other rodents, beaver pairs are monogamous, staying together for multiple breeding seasons. Gestation averages 107 days and they average three kits per litter with
405-409: A symbiotic relationship with Frankia species, a filamentous bacterium that can fix nitrogen from the air, converting it into ammonia . They have actinorhizal root nodules on their roots in which the bacteria live. This process enables the tree to live in low nitrogen habitats where they would otherwise be unable to thrive. The plant hormones called cytokinins initiate root nodule formation, in
540-519: A Belarusian fisherman who "tried to grab" a beaver died after it bit him several times, severing an artery in his leg, which caused him to bleed to death. In Denmark , the beaver appears to have gone extinct 2,000–2,500 years ago, though a small population might have survived into the 1st millennium AD. In 1999, 18 beavers were reintroduced to the river Flynder in Klosterhede Plantage state forest in west-central Jutland , brought from
675-692: A beaver pair was reintroduced in East Anglia for the first time. A four-hectare beaver enclosure on a farm in North Essex is part of a flood risk reduction project designed to reduce property flooding. The impact on flooding, wildlife and rural tourism is monitored by a private landowner. The places in England where beavers now live include the following (date first present): In 2022, beavers became legally protected in England, "making it illegal to capture, kill, injure or disturb them." In Wales
810-416: A classic example of parallel evolution . With an estimated 60,000-100,000 species, the number of trees worldwide might total twenty-five per cent of all living plant species. The greatest number of these grow in tropical regions; many of these areas have not yet been fully surveyed by botanists , making tree diversity and ranges poorly known. The majority of tree species are angiosperms or hardwoods. Of
945-503: A drier savanna climate and insufficient rainfall to support dense forests, the canopy is not closed, and plenty of sunshine reaches the ground which is covered with grass and scrub. Acacia and baobab are well adapted to living in such areas. The roots of a tree serve to anchor it to the ground and gather water and nutrients to transfer to all parts of the tree. They are also used for reproduction, defence, survival, energy storage and many other purposes. The radicle or embryonic root
1080-624: A family of beavers has lived since 2021 in the Cors Dyfi nature reserve in Powys . Fossils of C. fiber have been discovered in the famous Denisova Cave . In Iraq , Iran , Syria , and Turkey , subfossil evidence of beavers extends down to the floodplains of the Tigris - Euphrates basin, and a carved stone stela dating between 1,000 and 800 BC in the Tell Halaf archaeological site along
1215-518: A few hundred beavers live in the basin of the Ulungur River near the international border with Mongolia. The Bulgan Beaver Nature Reserve ( Chinese : 布尔根河河狸自然保护区 ; 46°12′00″N 90°45′00″E / 46.20000°N 90.75000°E / 46.20000; 90.75000 ) was established in 1980 to protect the creatures. Fossils found in the Spanish region around Atapuerca show that
1350-465: A five-year research project to assess the effects of beaver reintroduction. Over the course of the trial, 16 individual beavers were released in total, with the goal of establishing four breeding pairs. 14 beaver kits were born; by the end of the trial in 2014, eight of the reintroduced beavers had survived and one or two of the wild-born beavers were estimated to be alive in the Knapdale area. In 2016,
1485-418: A hundred litres are required to make one litre of birch syrup. Various parts of trees are used as spices. These include cinnamon , made from the bark of the cinnamon tree ( Cinnamomum zeylanicum ) and allspice , the dried small fruits of the pimento tree ( Pimenta dioica ). Nutmeg is a seed found in the fleshy fruit of the nutmeg tree ( Myristica fragrans ) and cloves are the unopened flower buds of
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#17327652942781620-473: A larger, less rounded head; a longer, narrower muzzle. The Eurasian beaver also has longer nasal bones, with the widest point being at the end of the snout; in the case of the North American beaver, the widest point is at the middle of the snout. The Eurasian beaver has a triangular nasal opening, unlike those of the North American beavers, which are square. Furthermore, the foramen magnum is rounded in
1755-509: A process closely related to mycorrhizal association. It has been demonstrated that some trees are interconnected through their root system, forming a colony. The interconnections are made by the inosculation process, a kind of natural grafting or welding of vegetal tissues. The tests to demonstrate this networking are performed by injecting chemicals, sometimes radioactive , into a tree, and then checking for its presence in neighbouring trees. The roots are, generally, an underground part of
1890-404: A process known as cladoptosis . The crown is the spreading top of a tree including the branches and leaves, while the uppermost layer in a forest, formed by the crowns of the trees, is known as the canopy . A sapling is a young tree. Many tall palms are herbaceous monocots, which do not undergo secondary growth and never produce wood. In many tall palms, the terminal bud on the main stem
2025-454: A range of two to six kits. Most beavers do not reproduce until they are three years of age, but about 20% of two-year-old females reproduce. European beavers are herbivorous, eating "water and river bank plants", including tubers, "rootstocks of myrtles, cattails , water lilies", and also trees, including softwood tree bark. Their long appendices and the microorganisms within make possible the digestion of bark cellulose. Their daily food intake
2160-422: A second spurt of growth, a Lammas growth may occur which is believed to be a strategy to compensate for loss of early foliage to insect predators. Primary growth is the elongation of the stems and roots. Secondary growth consists of a progressive thickening and strengthening of the tissues as the outer layer of the epidermis is converted into bark and the cambium layer creates new phloem and xylem cells. The bark
2295-489: A significant role in reducing erosion and moderating the climate . They remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues. Trees and forests provide a habitat for many species of animals and plants. Tropical rainforests are among the most biodiverse habitats in the world. Trees provide shade and shelter , timber for construction, fuel for cooking and heating, and fruit for food as well as having many other uses. In much of
2430-424: A similar growth form, by usually growing larger and having a single main stem; but there is no consistent distinction between a tree and a shrub, made more confusing by the fact that trees may be reduced in size under harsher environmental conditions such as on mountains and subarctic areas. The tree form has evolved separately in unrelated classes of plants in response to similar environmental challenges, making it
2565-467: A single tree species, which will not flourish in the absence of its mycorrhizal associate. Others are generalists and associate with many species. The tree acquires minerals such as phosphorus from the fungus, while the fungus obtains the carbohydrate products of photosynthesis from the tree. The hyphae of the fungus can link different trees and a network is formed, transferring nutrients and signals from one place to another. The fungus promotes growth of
2700-640: A slightly looser definition; while the Joshua tree , bamboos and palms do not have secondary growth and never produce true wood with growth rings, they may produce "pseudo-wood" by lignifying cells formed by primary growth. Tree species in the genus Dracaena , despite also being monocots, do have secondary growth caused by meristem in their trunk, but it is different from the thickening meristem found in dicotyledonous trees. Aside from structural definitions, trees are commonly defined by use; for instance, as those plants which yield lumber. The tree growth habit
2835-629: A subspecific distinction. In 2005, analysis of mitochondrial DNA of Eurasian beaver samples showed that only two evolutionarily significant units exist: a western phylogroup in Western and Central Europe , and an eastern phylogroup in the region east of the Oder and Vistula rivers. The eastern phylogroup is genetically more diverse, but still at a degree below thresholds considered sufficient for subspecific differentiation. The Eurasian beaver's fur colour varies between regions. Light, chestnut-rust
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#17327652942782970-484: A tree is any plant with the general form of an elongated stem, or trunk, which supports the photosynthetic leaves or branches at some distance above the ground. Trees are also typically defined by height, with smaller plants from 0.5 to 10 m (1.6 to 32.8 ft) being called shrubs , so the minimum height of a tree is only loosely defined. Large herbaceous plants such as papaya and bananas are trees in this broad sense. A commonly applied narrower definition
3105-436: A wide range of edible fruits are found in the tropics. Other commercially important fruit include dates, figs and olives. Palm oil is obtained from the fruits of the oil palm ( Elaeis guineensis ). The fruits of the cocoa tree ( Theobroma cacao ) are used to make cocoa and chocolate and the berries of coffee trees, Coffea arabica and Coffea canephora , are processed to extract the coffee beans. In many rural areas of
3240-416: A wide range of shapes and sizes, in response to environmental pressures including climate and predation. They can be broad or needle-like, simple or compound, lobed or entire, smooth or hairy, delicate or tough, deciduous or evergreen. The needles of coniferous trees are compact but are structurally similar to those of broad-leaved trees. They are adapted for life in environments where resources are low or water
3375-552: A widespread diverse group of which the only survivor is the maidenhair tree Ginkgo biloba . This is considered to be a living fossil because it is virtually unchanged from the fossilised specimens found in Triassic deposits. During the Mesozoic (245 to 66 million years ago) the conifers flourished and became adapted to live in all the major terrestrial habitats. Subsequently, the tree forms of flowering plants evolved during
3510-478: Is base-rich , meaning aspens are important hosts for bryophytes and act as food plants for the larvae of butterfly ( Lepidoptera ) species—see List of Lepidoptera that feed on poplars. Young aspen bark is an important seasonal forage for the European hare and other animals in early spring. Aspen is also a preferred food of the European beaver . Elk , deer , and moose not only eat the leaves but also strip
3645-533: Is a species of beaver widespread across Eurasia , with a rapidly increasing population of at least 1.5 million in 2020. The Eurasian beaver was hunted to near-extinction for both its fur and castoreum , with only about 1,200 beavers in eight relict populations from France to Mongolia in the early 20th century. It has since been reintroduced into much of its former range and now lives from Western , Southern , Central and Eastern Europe , Scandinavia , Russia through China and Mongolia, with about half
3780-557: Is a flavouring obtained from distilling bark from the roots of the sassafras tree ( Sassafras albidum ). The leaves of trees are widely gathered as fodder for livestock and some can be eaten by humans but they tend to be high in tannins which makes them bitter. Leaves of the curry tree ( Murraya koenigii ) are eaten, those of kaffir lime ( Citrus × hystrix ) (in Thai food ) and Ailanthus (in Korean dishes such as bugak ) and those of
3915-516: Is a rudimentary stalk and neatly folded miniature leaves, ready to expand when the next growing season arrives. Buds also form in the axils of the leaves ready to produce new side shoots. A few trees, such as the eucalyptus , have "naked buds" with no protective scales and some conifers, such as the Lawson's cypress , have no buds but instead have little pockets of meristem concealed among the scale-like leaves. When growing conditions improve, such as
4050-416: Is a sudden movement of sap at the end of the winter as trees prepare to burst into growth. In North America, the sap of the sugar maple ( Acer saccharum ) is used in the production of maple syrup . About 90% of the sap is water, the remaining 10% being a mixture of various sugars and certain minerals. The sap is harvested by drilling holes in the trunks of the trees and collecting the liquid that flows out of
4185-466: Is also a popular animal bedding, since it lacks the phenols associated with pine and juniper , which are thought to cause respiratory system ailments in some animals. Heat-treated aspen is a popular material for the interiors of saunas . While standing trees sometimes tend to rot from the heart outward, the dry timber weathers very well, becoming silvery-grey and resistant to rotting and warping, and has traditionally been used for rural construction in
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4320-557: Is also found in the southern hemisphere, as for example in the Eastern Australia temperate forest, characterised by Eucalyptus forest and open acacia woodland. In tropical regions with a monsoon or monsoon-like climate, where a drier part of the year alternates with a wet period as in the Amazon rainforest , different species of broad-leaved trees dominate the forest, some of them being deciduous. In tropical regions with
4455-528: Is an evolutionary adaptation found in different groups of plants: by growing taller, trees are able to compete better for sunlight. Trees tend to be tall and long-lived, some reaching several thousand years old. Several trees are among the oldest organisms now living. Trees have modified structures such as thicker stems composed of specialised cells that add structural strength and durability, allowing them to grow taller than many other plants and to spread out their foliage. They differ from shrubs , which have
4590-516: Is approximately 20% of their body weight. The Eurasian beaver is recovering from near extinction, after depredation by humans for its fur and for castoreum , a secretion of its scent gland believed to have medicinal properties . The estimated population was only 1,200 by the early 20th century. In many European nations, the Eurasian beaver became extinct, but reintroduction and protection programmes led to gradual recovery so that by 2020,
4725-418: Is continually replaced by a living layer of cells called the cork cambium or phellogen. The London plane ( Platanus × hispanica ) periodically sheds its bark in large flakes. Similarly, the bark of the silver birch ( Betula pendula ) peels off in strips. As the tree's girth expands, newer layers of bark are larger in circumference, and the older layers develop fissures in many species. In some trees such as
4860-503: Is developed by the Indian banyan . Many large trees have buttress roots which flare out from the lower part of the trunk. These brace the tree rather like angle brackets and provide stability, reducing sway in high winds. They are particularly prevalent in tropical rainforests where the soil is poor and the roots are close to the surface. Some tree species have developed root extensions that pop out of soil, in order to get oxygen, when it
4995-414: Is estimated that there are around three trillion mature trees in the world currently. A tree typically has many secondary branches supported clear of the ground by the trunk, which typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another. For most trees the trunk is surrounded by a layer of bark which serves as a protective barrier. Below
5130-486: Is inelastic. Eventually the growth of a tree slows down and stops and it gets no taller. If damage occurs the tree may in time become hollow. Leaves are structures specialised for photosynthesis and are arranged on the tree in such a way as to maximise their exposure to light without shading each other. They are an important investment by the tree and may be thorny or contain phytoliths , lignins , tannins or poisons to discourage herbivory. Trees have evolved leaves in
5265-623: Is long-lived. In some cases, this is for thousands of years, sending up new trunks as the older trunks die off above ground. For this reason, it is considered to be an indicator of ancient woodlands. One such colony in Utah, given the nickname of " Pando ", has been estimated to be as old as 80,000 years, if validated, this would be making it possibly the oldest living colony of aspens. Some aspen colonies become very large with time, spreading about 1 m (3 ft) per year, eventually covering many hectares. They are able to survive forest fires , because
5400-424: Is not available in the soil because of excess water. These root extensions are called pneumatophores , and are present, among others, in black mangrove and pond cypress. The main purpose of the trunk is to raise the leaves above the ground, enabling the tree to overtop other plants and outcompete them for light. It also transports water and nutrients from the roots to the aerial parts of the tree, and distributes
5535-458: Is ready to eat when the process is complete, having been tenderised and flavoured by the smoke it has absorbed. In the cold process, the temperature is not allowed to rise above 100 °F (38 °C). The flavour of the food is enhanced but raw food requires further cooking. If it is to be preserved, meat should be cured before cold smoking. Wood has traditionally been used for fuel, especially in rural areas. In less developed nations it may be
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5670-428: Is related to climatic conditions; growth normally ceases when conditions are either too cold or too dry. In readiness for the inactive period, trees form buds to protect the meristem , the zone of active growth. Before the period of dormancy, the last few leaves produced at the tip of a twig form scales. These are thick, small and closely wrapped and enclose the growing point in a waterproof sheath. Inside this bud there
5805-407: Is scarce. Frozen ground may limit water availability and conifers are often found in colder places at higher altitudes and higher latitudes than broad leaved trees. In conifers such as fir trees, the branches hang down at an angle to the trunk, enabling them to shed snow. In contrast, broad leaved trees in temperate regions deal with winter weather by shedding their leaves. When the days get shorter and
5940-510: Is scattered, and there's often only room for one territory in a habitat patch. The beavers spread slowly from watershed to watershed in the hilly terrain. Some spread could only be plausibly explained by assuming travel through sheltered sea water in fjords . In Sweden , the Eurasian beaver had been hunted to extinction around 1870. Between 1922 and 1939, some 80 individuals were imported from Norway and introduced to 19 sites in Sweden. In 1995,
6075-402: Is that a tree has a woody trunk formed by secondary growth , meaning that the trunk thickens each year by growing outwards, in addition to the primary upwards growth from the growing tip . Under such a definition, herbaceous plants such as palms , bananas and papayas are not considered trees regardless of their height, growth form or stem girth. Certain monocots may be considered trees under
6210-595: Is the dominant colour in Belarus . In Russia 's Sozh River basin, it is predominantly blackish brown, while in the Voronezh Nature Reserve beavers are both brown and blackish-brown. The Eurasian beaver is one of the largest living rodent species and the largest rodent native to Eurasia. Its head-to-body length is 80–100 cm (31–39 in) with a 25–50 cm (9.8–19.7 in) long tail length. It weighs around 11–30 kg (24–66 lb). By
6345-471: Is the first part of a seedling to emerge from the seed during the process of germination . This develops into a taproot which goes straight downwards. Within a few weeks lateral roots branch out of the side of this and grow horizontally through the upper layers of the soil. In most trees, the taproot eventually withers away and the wide-spreading laterals remain. Near the tip of the finer roots are single cell root hairs . These are in immediate contact with
6480-465: Is the flattened leaf petiole, which reduces aerodynamic drag during high winds and decreases the likelihood of trunk or branch damage. Dropping leaves in the winter (like most but not all other deciduous plants) also helps to prevent damage from heavy winter snow. Additionally, the bark is photosynthetic, meaning that growth is still possible after the leaves have been dropped. The bark also contains lenticels that serve as pores for gas exchange (similar to
6615-452: Is the only one to develop, so they have unbranched trunks with large spirally arranged leaves. Some of the tree ferns, order Cyatheales , have tall straight trunks, growing up to 20 metres (66 ft), but these are composed not of wood but of rhizomes which grow vertically and are covered by numerous adventitious roots . The number of trees in the world, according to a 2015 estimate, is 3.04 trillion, of which 1.39 trillion (46%) are in
6750-587: The South-West . A population of unknown origin has been present on the River Otter, Devon since 2008. An additional pair was released to increase genetic diversity in 2016. As part of a scientific study, a pair of Eurasian beaver was released in 2011 into a three-hectare fenced enclosure near Dartmoor in southern Devon . The 13 beaver ponds now in place impacted flooding to the extent of releasing precipitation over days to weeks instead of hours. In 2019,
6885-578: The 4th century BC , Aristotle described this species under the name λάταξ/ (latax). He wrote that it is wider than the otter, with strong teeth, and at night it often uses these teeth to cut down trees on riverbanks. Ιt's not clear when beavers vanished from Kastoria (which may have been named after the beaver – κάστορας in Greek), but as late as the 18th century they were still hunted for fur. Buffon wrote that they were very rare in Greece at that time. In
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#17327652942787020-913: The Baltic States and Kazakhstan . In Greece , the Eurasian beaver was present in the Last Glacial Period ; remains have been found in Epirus . Beaver remains from the Neolithic have been found in coastal Evros and Argura ; from the Neolithic to Bronze Age transition period in the Ptolemaida basin and in Sitagroi ; and beaver remains from the Early Helladic II have been found in northeastern Peloponnese. In
7155-515: The Cretaceous period. These began to displace the conifers during the Tertiary era (66 to 2 million years ago) when forests covered the globe. When the climate cooled 1.5 million years ago and the first of four glacial periods occurred, the forests retreated as the ice advanced. In the interglacials , trees recolonised the land that had been covered by ice, only to be driven back again in
7290-865: The Dnieper basin; in the Don basin; in the northern Urals and in the upper reaches of the Yenisei along the Azas river. The total number of beavers did not exceed 900 heads. Beaver hunting was banned in 1922. In 1923, a hunting reserve was organised in the Voronezh region along the Usman river, which in 1927 was transformed into the Voronezh State Reserve . At the same time, two more such reserves were created: Berezinsky and Kondo-Sosvinsky. 1927 also included
7425-620: The Elbe river in Germany. At Arresø in northern Zealand , 23 beavers were reintroduced between 2009 and 2011. By 2019, it was estimated that the Jutland population had increased to 240–270 individuals, and had spread far, from Hanstholm in the north to Varde and Kolding in the south. The population in northern Zealand, which had yet to significantly expand its geographic range, had increased to 50–60 individuals in 2019. In Norway , there
7560-798: The Khabur River in northeastern Syria depicts a beaver. Although accounts of 19th-century European visitors to the Middle East appear to confuse beavers with otters, a 20th-century report of beavers by Hans Kummerlöwe in the Ceyhan River drainage of southern Turkey includes the diagnostic red incisor teeth, flat, scaly tail, and presence of gnawed willow stems. According to the Encyclopaedia Iranica , early Iranian Avestan and Pahlavi , and later Islamic literature, all had different words for otter and beaver, and castoreum
7695-682: The Netherlands , beavers were completely extirpated by 1826. Due to official reintroductions since 1988, beavers are now found in most parts of the country, in particular the south, centre and north-west. The population was around 3500 in 2019. In Belgium the beaver was extirpated in 1848. Current populations are descendants of animals released in the Ardennes in 1998–2000 and in Flanders in 2003. Some beavers also arrived in Flanders from
7830-614: The North American beaver , there are several important differences, chief among these being that the North American beaver has 40 chromosomes , while the Eurasian beaver has 48. The two species are not genetically compatible: the result of over 27 attempts in Russia to hybridise the two species was just one stillborn kit, bred from the pairing of a male North American beaver and a female Eurasian beaver. The difference in chromosome count makes interspecific breeding unlikely in areas where
7965-692: The River Tay and Knapdale areas. The Knapdale population, sourced from Norway, was released by the Scottish Wildlife Trust and the Royal Zoological Society of Scotland , while the other populations are of unknown origin. Sixteen beavers were released between 2009 and 2014 in Knapdale forest, Argyll . A 2009 release of three beaver families of 11 individuals was the start of the Scottish Beaver Trial,
8100-709: The Sava - Danube system ( Drina , Jadar , Great Morava , Tamnava , Tisza , Bega , Timiș , the canal system in Vojvodina ), they were found in the capital Belgrade , and had spread to neighbouring Bosnia and Herzegovina . In Italy , beavers returned in 2018 after an absence of almost 500 years, when they were spotted in the Friuli-Venezia Giulia region. The beaver resurgence in Eurasia has brought an increase in human-beaver encounters. In May 2013,
8235-755: The Swiss plateau and the Swiss Alps (with the exception of Ticino ). In Poland , as of 2014, the beaver population had grown to 100,000 individuals. In Romania , beavers became extinct in 1824, but were reintroduced in 1998 along the Olt River , spreading to other rivers in Covasna County . In 2014, the animals were confirmed to have reached the Danube Delta . In Russia , by 1917, beaver populations remained in four isolated territories: in
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#17327652942788370-729: The Zadorra river up to Vitoria-Gasteiz , the Arga river up to Pamplona , the Huerva river up to Mezalocha , and the Jalón river into the province of Soria . In November 2021, a young beaver was photographed for the first time outside the Ebro basin, in the upper Douro river in Soria . In 2020, the population was estimated to be more than 1,000. In Portugal , the beaver was distributed mostly in
8505-414: The annual growth rings There may also be rays running at right angles to growth rings. These are vascular rays which are thin sheets of living tissue permeating the wood. Many older trees may become hollow but may still stand upright for many years. Trees do not usually grow continuously throughout the year but mostly have spurts of active expansion followed by periods of rest. This pattern of growth
8640-552: The pine ( Pinus species) the bark exudes sticky resin which deters attackers whereas in rubber trees ( Hevea brasiliensis ) it is a milky latex that oozes out. The quinine bark tree ( Cinchona officinalis ) contains bitter substances to make the bark unpalatable. Large tree-like plants with lignified trunks in the Pteridophyta , Arecales , Cycadophyta and Poales such as the tree ferns, palms, cycads and bamboos have different structures and outer coverings. Although
8775-409: The stomata on leaves). Aspens are also aided by the rhizomatic nature of their root systems. Most aspens grow in large clonal colonies , derived from a single seedling, and spread by means of root suckers ; new stems in the colony may appear at up to 30–40 m (100–130 ft) from the parent tree. Each individual tree can live for 40–150 years above ground, but the root system of the colony
8910-540: The 12,000 years since the start of human agriculture, the number of trees worldwide has decreased by 46%. There are approximately 64,100 known tree species in the world. With 43% of all tree species, South America has the highest biodiversity, followed by Eurasia (22%), Africa (16%), North America (15%), and Oceania (11%). In suitable environments, such as the Daintree Rainforest in Queensland , or
9045-726: The 1870s, with the last specimens being seen around 1900–1902. In 2004, 31 beavers were reintroduced in the Zasavica reserve by the Biology Faculty of the Belgrade University in collaboration with the Bavarian Science Society, and 45 beavers were released in the Obedska bara reserve. They spread quickly. By 2020, they had spread 150 km (93 mi) north, west and east, inhabiting rivers in
9180-640: The 19th century, beavers could still be found in the Alfeios river and in Mesolongi . In Bulgaria , fossil, subfossil and subrecent remains have been found in 43 localities along 28 lowland rivers, from Struma and Maritsa in the south till the Danube in the north, while the last finds from Nicopolis ad Istrum date to the 1750–1850 period. In 2021, the Eurasian beaver was confirmed to have returned to Bulgaria. In Serbia , beavers were mostly extinct by
9315-620: The English oak ( Quercus robur ) and 306 species of invertebrate on the Tasmanian oak ( Eucalyptus obliqua ). Non-native tree species provide a less biodiverse community, for example in the United Kingdom the sycamore ( Acer pseudoplatanus ), which originates from southern Europe, has few associated invertebrate species, though its bark supports a wide range of lichens, bryophytes and other epiphytes. Trees differ ecologically in
9450-707: The Eurasian beaver was present in the Early Pleistocene but not in the Middle Pleistocene despite apparently favourable environmental conditions. It reappeared in the region during the Late Pleistocene and Holocene. The Eurasian beaver Castor fiber was once widespread in Europe and Asia but by the beginning of the 20th century both the numbers and range of the species had been drastically diminished, mainly due to hunting. At this time,
9585-401: The Eurasian beaver, but triangular in the North American beaver. The Eurasian beaver has shorter shin bones than the North American species and a narrower, less oval-shaped tail, making it less capable of bipedal locomotion. The anal glands of the Eurasian beaver are larger, and thin-walled, with a large internal volume, relative to that of the North American beaver. The Eurasian beaver is
9720-546: The European bay tree ( Laurus nobilis ) and the California bay tree ( Umbellularia californica ) are used for flavouring food. Camellia sinensis , the source of tea, is a small tree but seldom reaches its full height, being heavily pruned to make picking the leaves easier. Wood smoke can be used to preserve food. In the hot smoking process the food is exposed to smoke and heat in a controlled environment. The food
9855-649: The Netherlands in 2003. In 2018, the population was 2,200–2,400, with Flanders having around 400 beavers and Wallonia 1,800–2,000 beavers. In Switzerland , the Eurasian beaver was hunted to extirpation in the early 19th century. Between 1956 and 1977, 141 individuals from France, Russia and Norway were reintroduced to 30 sites in the Rhône and Rhine catchment areas. As of 2019, Switzerland had an estimated 3,500 beavers (a sharp increase from 1,600 beavers in 2008), with permanent beaver presence along most larger rivers of
9990-531: The Rhône river and its tributaries, including the Saône , and other river systems such as Loire , Moselle , Tarn and Seine . In 2011, the French beaver population was estimated at 14,000 individuals living along 10,500 km (6,500 mi) of watercourses. In 2022, its range was estimated to have increased to 17,000 km (11,000 mi) of watercourses. In Germany , around 200 Eurasian beavers survived at
10125-555: The Scottish government declared that the beaver populations in Knapdale and Tayside could remain and naturally expand. Beaver translocations now occur throughout many catchments in Scotland. In England , wild beavers are now present in all nine regions, with a population exceeding 1,000 (2024 estimate). Most sites are recent authorised introductions in large enclosures, but there are established completely free-living populations in
10260-599: The Southern Balkans: Albania , Kosovo , Northern Macedonia , Greece and European Turkey . It is also not known to be present in the microstates of Andorra , Monaco , San Marino and Vatican City . In Spain , the beaver was extirpated in the 17th century. In 2003, 18 beavers were unofficially released. Current range includes the Ebro river in La Rioja , Navarre , and province of Zaragoza ;
10395-584: The Swedish beaver population was estimated at 100,000. In Finland , there are some Eurasian beavers that have been re-introduced or spread from Sweden, but most of the Finnish population is a released North American beaver population. This population is controlled to prevent it from spreading into areas inhabited by the Eurasian beaver. The Eurasian beaver was well-established in Great Britain, but
10530-496: The arrival of warmer weather and the longer days associated with spring in temperate regions, growth starts again. The expanding shoot pushes its way out, shedding the scales in the process. These leave behind scars on the surface of the twig. The whole year's growth may take place in just a few weeks. The new stem is unlignified at first and may be green and downy. The Arecaceae (palms) have their leaves spirally arranged on an unbranched trunk. In some tree species in temperate climates,
10665-465: The aspen is referred to as quaking aspen or trembling aspen because the leaves "quake" or tremble in the wind. This is due to their flattened petioles which reduce aerodynamic drag on the trunk and branches. Aspens typically grow in environments that are otherwise dominated by coniferous tree species, and which are often lacking other large deciduous tree species. Aspens have evolved several adaptations that aid their survival in such environments. One
10800-407: The average weights known, it appears to be the world's second heaviest rodent after the capybara , and is slightly larger and heavier than the North American beaver. One exceptionally large recorded specimen weighed 31.7 kg (70 lb), but it is reportedly possible for the species to exceptionally exceed 40 kg (88 lb). Although the Eurasian beaver appears superficially similar to
10935-437: The bark functions as a protective barrier, it is itself attacked by boring insects such as beetles. These lay their eggs in crevices and the larvae chew their way through the cellulose tissues leaving a gallery of tunnels. This may allow fungal spores to gain admittance and attack the tree. Dutch elm disease is caused by a fungus ( Ophiostoma species) carried from one elm tree to another by various beetles. The tree reacts to
11070-434: The bark with their front teeth. Aspen wood is white and soft, but fairly strong, and has low flammability. It has a number of uses, notably for making matches and paper where its low flammability makes it safer to use than most other woods. Shredded aspen wood is used for packing and stuffing, sometimes called excelsior (wood wool) . Aspen flakes are the most common species of wood used to make oriented strand boards . It
11205-440: The clove tree ( Syzygium aromaticum ). Many trees have flowers rich in nectar which are attractive to bees. The production of forest honey is an important industry in rural areas of the developing world where it is undertaken by small-scale beekeepers using traditional methods. The flowers of the elder ( Sambucus ) are used to make elderflower cordial and petals of the plum ( Prunus spp. ) can be candied. Sassafras oil
11340-465: The cone for years waiting for a trigger event to liberate it. Fire stimulates release and germination of seeds of the jack pine , and also enriches the forest floor with wood ash and removes competing vegetation. Similarly, a number of angiosperms including Acacia cyclops and Acacia mangium have seeds that germinate better after exposure to high temperatures. The single extant species of Ginkgophyta ( Ginkgo biloba ) has fleshy seeds produced at
11475-424: The ease with which they can be found by herbivores. Tree apparency varies with a tree's size and semiochemical content, and with the extent to which it is concealed by nonhost neighbours from its insect pests . In ecosystems such as mangrove swamps, trees play a role in developing the habitat, since the roots of the mangrove trees reduce the speed of flow of tidal currents and trap water-borne sediment, reducing
11610-521: The end of the 19th century in the Elbe river system in Saxony , Saxony-Anhalt and Brandenburg . Official reintroduction programs, in particular in Bavaria, resulted in major population growth and beavers are now found throughout most of eastern and southern Germany, with strongly established disjunct populations in the west. By 2019, beavers numbered above 40,000, and appear in many urban areas. In
11745-664: The ends of short branches on female trees, and Gnetum , a tropical and subtropical group of gymnosperms produce seeds at the tip of a shoot axis. The earliest trees were tree ferns , horsetails and lycophytes , which grew in forests in the Carboniferous period. The first tree may have been Wattieza , fossils of which were found in New York state in 2007 dating back to the Middle Devonian (about 385 million years ago). Prior to this discovery, Archaeopteris
11880-461: The far north of the northern hemisphere is moist taiga or northern coniferous forest (also called boreal forest). Taiga is the world's largest land biome , forming 29% of the world's forest cover. The long cold winter of the far north is unsuitable for plant growth and trees must grow rapidly in the short summer season when the temperature rises and the days are long. Light is very limited under their dense cover and there may be little plant life on
12015-621: The first attempts to reintroduce beavers in other areas. As a result, by the end of the 1960s, the beaver's range in the Soviet Union was almost as large as in the 17th century. The beavers’ growing numbers made commercial capture possible again. In 2016, there were an estimated 661,000 beavers in Russia; in 2019, the estimate was 774,600. In the lands that made up the Soviet Union, almost 17,000 beavers were translocated from 1927 to 2004. Some 5,000 of these went to Ukraine , Belarus ,
12150-480: The food produced by the leaves to all other parts, including the roots. In the case of angiosperms and gymnosperms, the outermost layer of the trunk is the bark , mostly composed of dead cells of phellem (cork). It provides a thick, waterproof covering to the living inner tissue. It protects the trunk against the elements, disease, animal attack and fire. It is perforated by a large number of fine breathing pores called lenticels , through which oxygen diffuses. Bark
12285-401: The forest floor, although fungi may abound. Similar woodland is found on mountains where the altitude causes the average temperature to be lower thus reducing the length of the growing season. Where rainfall is relatively evenly spread across the seasons in temperate regions, temperate broadleaf and mixed forest typified by species like oak, beech, birch and maple is found. Temperate forest
12420-768: The former Soviet Union due to reintroductions. The Eurasian beaver lives in almost all countries in Continental Europe, from Spain , France and the United Kingdom in the West, to Russia and Moldova in the East, and Montenegro , Serbia and Bulgaria in the South-East. In 2022, beaver signs were found in Portugal , near the border with Spain. The only significant areas where it has no known population are
12555-425: The fruits and either discard the seeds, or swallow them so they pass through the gut to be deposited in the animal's droppings well away from the parent tree. The germination of some seeds is improved when they are processed in this way. Nuts may be gathered by animals such as squirrels that cache any not immediately consumed. Many of these caches are never revisited; the nut-casing softens with rain and frost, and
12690-436: The global population was estimated to be around 1,200 individuals, living in eight separate sub-populations. Conservation of the Eurasian beaver began in 1923 in the Soviet Union , with the establishment of the Voronezh Nature Reserve . From 1934 to 1977, approximately 3,000 Eurasian beavers from Voronezh were reintroduced to 52 regions from Poland to Mongolia. In 2008, the Eurasian beaver was categorized as least concern on
12825-480: The ground underneath trees there is shade, and often there is undergrowth, leaf litter , and decaying wood that provide other habitat. Trees stabilise the soil, prevent rapid run-off of rain water, help prevent desertification, have a role in climate control and help in the maintenance of biodiversity and ecosystem balance. Many species of tree support their own specialised invertebrates . In their natural habitats, 284 different species of insect have been found on
12960-557: The ground, the roots branch and spread out widely; they serve to anchor the tree and extract moisture and nutrients from the soil . Above ground, the branches divide into smaller branches and shoots. The shoots typically bear leaves, which capture light energy and convert it into sugars by photosynthesis , providing the food for the tree's growth and development. Trees usually reproduce using seeds . Flowering plants have their seeds inside fruits, while conifers carry their seeds in cones, and tree ferns produce spores instead. Trees play
13095-421: The ground. Trees use a variety of methods of seed dispersal . Some rely on wind, with winged or plumed seeds. Others rely on animals, for example with edible fruits. Others again eject their seeds (ballistic dispersal), or use gravity so that seeds fall and sometimes roll. Seeds are the primary way that trees reproduce and their seeds vary greatly in size and shape. Some of the largest seeds come from trees, but
13230-413: The growth of the fungus by blocking off the xylem tissue carrying sap upwards and the branch above, and eventually the whole tree, is deprived of nourishment and dies. In Britain in the 1990s, 25 million elm trees were killed by this disease. The innermost layer of bark is known as the phloem and this is involved in the transport of the sap containing the sugars made by photosynthesis to other parts of
13365-447: The heartwood are blocked in some species. Heartwood is usually darker in colour than the sapwood. It is the dense central core of the trunk giving it rigidity. Three quarters of the dry mass of the xylem is cellulose , a polysaccharide , and most of the remainder is lignin, a complex polymer . A transverse section through a tree trunk or a horizontal core will show concentric circles of lighter or darker wood – tree rings. These rings are
13500-411: The inserted spigots; the sap is then heated to concentrate the flavour. Similarly in northern Europe the spring rise in the sap of the silver birch ( Betula pendula ) is tapped and collected, either to be drunk fresh or fermented into an alcoholic drink. In Alaska, the sap of the sweet birch ( Betula lenta ) is made into a syrup with a sugar content of 67%. Sweet birch sap is more dilute than maple sap;
13635-400: The inside. The newly created xylem is the sapwood . It is composed of water-conducting cells and associated cells which are often living, and is usually pale in colour. It transports water and minerals from the roots to the upper parts of the tree. The oldest, inner part of the sapwood is progressively converted into heartwood as new sapwood is formed at the cambium. The conductive cells of
13770-528: The largest tree, Sequoiadendron giganteum , produces one of the smallest tree seeds. The great diversity in tree fruits and seeds reflects the many different ways that tree species have evolved to disperse their offspring. For a tree seedling to grow into an adult tree it needs light. If seeds only fell straight to the ground, competition among the concentrated saplings and the shade of the parent would likely prevent it from flourishing. Many seeds such as birch are small and have papery wings to aid dispersal by
13905-562: The main river basins north of the Tagus River , until it was extirpated around 1450. In 2023, signs of beaver activity were found on the Douro river about 5 km from the Spanish border. In France , the Eurasian beaver was almost extirpated by the late 19th century, with only a small population of about 100 individuals surviving in the lower Rhône valley. Following protection measures in 1968 and 26 reintroduction projects, it re-colonised
14040-409: The mixed podocarp and broadleaf forest of Ulva Island, New Zealand , forest is the more-or-less stable climatic climax community at the end of a plant succession, where open areas such as grassland are colonised by taller plants, which in turn give way to trees that eventually form a forest canopy. In cool temperate regions, conifers often predominate; a widely distributed climax community in
14175-519: The next glacial period. Trees are an important part of the terrestrial ecosystem , providing essential habitats including many kinds of forest for communities of organisms. Epiphytic plants such as ferns , some mosses, liverworts, orchids and some species of parasitic plants (e.g., mistletoe ) hang from branches; these along with arboreal lichens, algae, and fungi provide micro-habitats for themselves and for other organisms, including animals. Leaves, flowers and fruits are seasonally available. On
14310-431: The northwestern regions of Russia (especially for roofing, in the form of thin slats). Tree In botany , a tree is a perennial plant with an elongated stem , or trunk , usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth , plants that are usable as lumber or plants above a specified height. In wider definitions,
14445-420: The old lineages of flowering plants called basal angiosperms or paleodicots ; these include Amborella , Magnolia , nutmeg and avocado , while trees such as bamboo, palms and bananas are monocots . Wood gives structural strength to the trunk of most types of tree; this supports the plant as it grows larger. The vascular system of trees allows water, nutrients and other chemicals to be distributed around
14580-527: The only fuel available and collecting firewood is often a time-consuming task as it becomes necessary to travel further and further afield in the search for fuel. It is often burned inefficiently on an open fire. In more developed countries other fuels are available and burning wood is a choice rather than a necessity. Modern wood-burning stoves are very fuel efficient and new products such as wood pellets are available to burn. European beaver The Eurasian beaver ( Castor fiber ) or European beaver
14715-585: The plant and reduce water loss. Both the production of wood and the production of cork are forms of secondary growth. Trees are either evergreen , having foliage that persists and remains green throughout the year, or deciduous , shedding their leaves at the end of the growing season and then having a dormant period without foliage. Most conifers are evergreens, but larches ( Larix and Pseudolarix ) are deciduous, dropping their needles each autumn, and some species of cypress ( Glyptostrobus , Metasequoia and Taxodium ) shed small leafy shoots annually in
14850-409: The plant, and without it trees would not be able to grow as large as they do. Trees need to draw water high up the stem through the xylem from the roots by capillary action , as water continually evaporates from the leaves in the process of transpiration . If insufficient water is available the leaves will die. The three main parts of trees include the root, stem, and leaves; they are integral parts of
14985-536: The population in Russia. It is listed as least concern on the IUCN Red List . Castor fiber was the scientific name used by Carl Linnaeus in 1758, who described the beaver in his work Systema Naturae . Between 1792 and 1997, several Eurasian beaver zoological specimens were described and proposed as subspecies , including: These descriptions were largely based on very small differences in fur colour and cranial morphology , none of which warrant
15120-503: The population was at least 1.5 million. It likely survived east of the Ural Mountains from a 19th-century population as low as 300 animals. Factors contributing to their survival include their ability to maintain sufficient genetic diversity to recover from a population as low as three individuals, and that beavers are monogamous and select mates that are genetically different from themselves. About 83% of Eurasian beavers live in
15255-437: The rest, many are gymnosperms or softwood trees; these include conifers , cycads , ginkgophytes and gnetales , which produce seeds which are not enclosed in fruits, but in open structures such as pine cones , and many have tough waxy leaves, such as pine needles. Most angiosperm trees are eudicots , the "true dicotyledons", so named because the seeds contain two cotyledons or seed leaves. There are also some trees among
15390-428: The roots and helps protect the trees against predators and pathogens. It can also limit damage done to a tree by pollution as the fungus accumulate heavy metals within its tissues. Fossil evidence shows that roots have been associated with mycorrhizal fungi since the early Paleozoic , four hundred million years ago, when the first vascular plants colonised dry land. Some trees such as Alder ( Alnus species) have
15525-445: The roots are below the heat of the fire, and new sprouts appear after the fire burns out. The high stem turnover rate combined with the clonal growth leads to proliferation in aspen colonies. The high stem turnover regime supports a diverse herbaceous understory. Aspen seedlings do not thrive in the shade, and it is difficult for seedlings to establish in an already mature aspen stand. Fire indirectly benefits aspen trees, since it allows
15660-900: The saplings to flourish in open sunlight in the burned landscape, devoid of other competing tree species. Aspens have increased in popularity as a forestry cultivation species, mostly because of their fast growth rate and ability to regenerate from sprouts. This lowers the cost of reforestation after harvesting since no planting or sowing is required. Recently, aspen populations have been declining in some areas ("Sudden Aspen Death"). This has been attributed to several different factors, such as climate change , which exacerbates drought and modifies precipitation patterns. Recruitment failure from herbivory or grazing prevents new trees from coming up after old trees die. Additionally, successional replacement by conifers due to fire suppression alters forest diversity and creates conditions where aspen may be at less of an advantage. In contrast with many trees, aspen bark
15795-464: The seeds on the surface of water. Mangroves often grow in water and some species have buoyant fruits with seeds that start germinating before they detach from the parent tree. These float on the water and may become lodged on emerging mudbanks and successfully take root. Other seeds, such as apple pips and plum stones, have fleshy receptacles and smaller fruits like hawthorns have seeds enclosed in edible tissue; animals including mammals and birds eat
15930-434: The soil particles and can absorb water and nutrients such as potassium in solution. The roots require oxygen to respire and only a few species such as mangroves and the pond cypress ( Taxodium ascendens ) can live in permanently waterlogged soil. In the soil, the roots encounter the hyphae of fungi. Many of these are known as mycorrhiza and form a mutualistic relationship with the tree roots. Some are specific to
16065-471: The start of the dry season. Many deciduous trees flower before the new leaves emerge. A few trees do not have true leaves but instead have structures with similar external appearance such as Phylloclades – modified stem structures – as seen in the genus Phyllocladus . Trees can be pollinated either by wind or by animals, mostly insects. Many angiosperm trees are insect pollinated. Wind pollination may take advantage of increased wind speeds high above
16200-413: The surviving seeds germinate in the spring. Pine cones may similarly be hoarded by red squirrels , and grizzly bears may help to disperse the seed by raiding squirrel caches. The seeds of conifers, the largest group of gymnosperms, are enclosed in a cone and most species have seeds that are light and papery that can be blown considerable distances once free from the cone. Sometimes the seed remains in
16335-521: The taller palms , tree ferns , bananas , and bamboos are also trees. Trees are not a monophyletic taxonomic group but consist of a wide variety of plant species that have independently evolved a trunk and branches as a way to tower above other plants to compete for sunlight. The majority of tree species are angiosperms or hardwoods; of the rest, many are gymnosperms or softwoods. Trees tend to be long-lived, some reaching several thousand years old. Trees evolved around 370 million years ago, and it
16470-661: The temperature begins to decrease, the leaves no longer make new chlorophyll and the red and yellow pigments already present in the blades become apparent. Synthesis in the leaf of a plant hormone called auxin also ceases. This causes the cells at the junction of the petiole and the twig to weaken until the joint breaks and the leaf floats to the ground. In tropical and subtropical regions, many trees keep their leaves all year round. Individual leaves may fall intermittently and be replaced by new growth but most leaves remain intact for some time. Other tropical species and those in arid regions may shed all their leaves annually, such as at
16605-408: The tree, but some tree species have evolved roots that are aerial . The common purposes for aerial roots may be of two kinds, to contribute to the mechanical stability of the tree, and to obtain oxygen from air. An instance of mechanical stability enhancement is the red mangrove that develops prop roots that loop out of the trunk and branches and descend vertically into the mud. A similar structure
16740-432: The tree. It is a soft spongy layer of living cells, some of which are arranged end to end to form tubes. These are supported by parenchyma cells which provide padding and include fibres for strengthening the tissue. Inside the phloem is a layer of undifferentiated cells one cell thick called the vascular cambium layer. The cells are continually dividing, creating phloem cells on the outside and wood cells known as xylem on
16875-492: The tropics or sub-tropics , 0.61 trillion (20%) in the temperate zones , and 0.74 trillion (24%) in the coniferous boreal forests . The estimate is about eight times higher than previous estimates, and is based on tree densities measured on over 400,000 plots. It remains subject to a wide margin of error, not least because the samples are mainly from Europe and North America. The estimate suggests that about 15 billion trees are cut down annually and about 5 billion are planted. In
17010-458: The two species' ranges overlap. The guard hairs of the Eurasian beaver have longer hollow medullae at their tips. There is also a difference in the frequency of fur colours: 66% of Eurasian beavers overall have beige or pale brown fur, 20% have reddish brown, nearly 8% are brown, and only 4% have blackish coats; among North American beavers, 50% have pale brown fur, 25% are reddish brown, 20% are brown, and 6% are blackish. The Eurasian beaver has
17145-403: The vascular system which interconnects all the living cells. In trees and other plants that develop wood, the vascular cambium allows the expansion of vascular tissue that produces woody growth. Because this growth ruptures the epidermis of the stem, woody plants also have a cork cambium that develops among the phloem. The cork cambium gives rise to thickened cork cells to protect the surface of
17280-429: The water depth and creating suitable conditions for further mangrove colonisation. Thus mangrove swamps tend to extend seawards in suitable locations. Mangrove swamps also provide an effective buffer against the more damaging effects of cyclones and tsunamis. Trees are the source of many of the world's best known fleshy fruits. Apples, pears, plums, cherries and citrus are all grown commercially in temperate climates and
17415-437: The wind. Ash trees and maples have larger seeds with blade shaped wings which spiral down to the ground when released. The kapok tree has cottony threads to catch the breeze. The flame tree Delonix regia shoots its seeds through the air when the two sides of its long pods crack apart explosively on drying. The miniature cone-like catkins of alder trees produce seeds that contain small droplets of oil that help disperse
17550-465: The world, forests are shrinking as trees are cleared to increase the amount of land available for agriculture. Because of their longevity and usefulness, trees have always been revered, with sacred groves in various cultures, and they play a role in many of the world's mythologies . Although "tree" is a common word, there is no universally recognised precise definition of what a tree is, either botanically or in common language. In its broadest sense,
17685-769: The world, fruit is gathered from forest trees for consumption. Many trees bear edible nuts which can loosely be described as being large, oily kernels found inside a hard shell. These include coconuts ( Cocos nucifera ), Brazil nuts ( Bertholletia excelsa ), pecans ( Carya illinoinensis ), hazel nuts ( Corylus ), almonds ( Prunus dulcis ), walnuts ( Juglans regia ), pistachios ( Pistacia vera ) and many others. They are high in nutritive value and contain high-quality protein, vitamins and minerals as well as dietary fibre. A variety of nut oils are extracted by pressing for culinary use; some such as walnut, pistachio and hazelnut oils are prized for their distinctive flavours, but they tend to spoil quickly. In temperate climates there
17820-534: Was driven extinct there by humans in the 16th century, with the last known historical reference in England in 1526. It is unclear whether beavers ever existed in Ireland. In the early 21st century, the beaver became the first mammal to be successfully reintroduced in the United Kingdom, after unofficial and official reintroductions to Scotland and England. In Scotland , free-living beaver populations occur around
17955-876: Was highly valued in the region. Johannes Ludwijk Schlimmer, a noted Dutch physician in 19th-century Iran, reported small numbers of beavers below the confluence of the Tigris and the Euphrates, along the bank of the Shatt al-Arab in the provinces of Shushtar and Dezful . Austen Layard reported finding beavers during his visit to the Kabur River in Syria in the 1850s, but noted they were being rapidly hunted for said castoreum to extirpation. Beavers were specifically sacred to Zoroastrianism (which also revered otters), and there were laws against killing these animals. In China,
18090-644: Was still a beaver population in the early 1900s, one of the few surviving in Europe at that time. Following protection, the Norwegian range of the species has expanded. The surviving population was in southern Norway; beavers were reintroduced to central Norway's Ingdalselva River watershed on the Agdenes peninsula in Sør-Trøndelag in 1968–1969. The area is hilly to mountainous, with many small watersheds. Rivers are often too steep for beavers, so their habitat
18225-455: Was the earliest known tree. Both of these reproduced by spores rather than seeds and are considered to be links between ferns and the gymnosperms which evolved in the Triassic period. The gymnosperms include conifers, cycads, gnetales and ginkgos and these may have appeared as a result of a whole genome duplication event which took place about 319 million years ago. Ginkgophyta was once
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