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The mighty English oak tree is the king of the woods, supporting more life than any other native tree species in Britain. Even leaves that have fallen from the boughs in autumn support biodiversity. According to the Woodland Trust, the oak tree supports 31 different species of mammals, with acorns being one of the main attractions. In fact, the oak supports a staggering 2,300 wildlife species in total when you include plant life too. Offering shelter, food and a breeding ground for animals and birds, they are one of the greatest supporters of biodiversity in the world. More than 200 species supported by the oak are rarely found on other trees and 326 species depend solely on it for their survival. Even more amazing is the fact that an oak tree can live for 1,000 years, so it can sustain wildlife for many generations. According to research by the UK Centre for Ecology and Hydrology, the oak's significance may be even greater than we think, as the current figures don't include micro-organisms.   How do you recognise an oak tree? You are most likely to find an English oak in deciduous woodlands in central and southern Britain. A common tree, it has assumed the status of a national emblem. This large, deciduous tree can grow up to 40 metres tall. When it matures, it forms a wide crown, with sturdy branches below. Its distinctive leaves are around 10cm long, with four or five deep lobes and smooth edges. In mid-May the leaf burst occurs, when the leaves have almost no stem. They grow in bunches and have short leaf stalks or petioles. The flowers are long, hanging, yellow catkins that distribute pollen into the air. The fruit of the oak tree, the acorn, is around 2.5 cm long and has a cup-shaped base, known as a cupule. When ripe, acorns fall onto the canopy below and sprout the following spring. In autumn and winter, the oak tree sports rounded buds in clusters.   Which species does the oak support? Oak trees are host to hundreds of insect species, which in turn supply birds with a source of food. Mammals including badgers, squirrels and deer eat the acorns in autumn. The leaf buds and flowers are a source of food for purple hairstreak butterfly caterpillars. A solitary oak tree can support a whole colony of butterflies. When the oak leaves fall in autumn, they break down easily to form a rich leaf mould underneath the tree. This will provide a source of food for invertebrates such as stag beetles. It also supports fungi, such as the oakbug milkcap mushroom. Crevices and holes in the tree bark provide nesting spots for birds such as the marsh tit, pied flycatcher and redstart. Old woodpecker holes provide roosts for bats, which will also nest under loose bark and feed on the vast supply of insects in the tree's canopy.   Mythology and symbolism In mythology, the oak tree was sacred to various gods including Jupiter, Zeus and the Celtic Dagda. The gods were said to be the rulers of thunder and lightning. Oak trees are often hit by lightning during storms because they are the tallest feature on the landscape. This furthered the myth of being sacred to the gods. The ancient Druids would practice rituals in oak forests. They cherished the mistletoe that could be found in oak trees' branches. The mighty oak is also linked to royalty, as Roman emperors and ancient kings traditionally wore crowns made of oak leaves. The oak is a symbol of strength in England. In Oliver Cromwell's time in the 17th century, couples were married under ancient oak trees. Today, the oak is the emblem of environmental groups, such as the Woodland Trust. It is also associated with the legendary outlaw, Robin Hood, who "robbed from the rich to give to the poor". In Sherwood Forest, where Robin and his band of Merry Men hid, according to legend, the iconic, ancient Major Oak tree can't be missed. Standing a 15-minute walk from the visitor centre, the tree is an estimated 800 to 1,100 years old! It has been in existence since the time of the Vikings and has stood tall through famous battles such as Hastings in 1066, Agincourt in 1415 and Waterloo in 1815. It has lived through the births and deaths of William Shakespeare, Charles Dickens, Charles Darwin, Isaac Newton, Geoffrey Chaucer and Oliver Cromwell; and has survived two world wars and outlived at least 50 monarchs. If only it could talk!   Threats and conservation Although still plentiful, the English oak tree is under threat. Diseases such as acute oak decline and chronic oak decline first caused concern in the 1920s, when mature oaks began to fail. It was blamed on the oak leaf roller moth caterpillars that defoliated the trees. In 1924, alarming numbers of oaks were dying, but the diseases appeared to disappear for around 30 years and some of the weak trees recovered. Then, in 1958, young oak trees started to die in woods near the Norfolk coast. Scientists say there is no one factor responsible for acute and chronic oak decline. They cite drought, exposure, mildew and the effects of defoliating insects as contributory factors. Cases today occur mainly in southern, central and eastern England. The oak processionary moth is also threatening oak trees' survival. This non-native pest has been found in London, Berkshire and Surrey. It damages the trees' foliage and increases their susceptibility to diseases. Vital to our planet's future survival, the oak and other trees are protected. As well as providing a home and food source to mammals, birds and insects, trees fight climate change. Without them, the earth's future would be at risk. Aside from their importance in this respect, there is nothing more pleasant than to go for a walk through a forest of oaks. An autumn stroll, listening to the birdsong and soaking up the atmosphere, is a tranquil and relaxing experience away from the hustle and bustle of everyday life.