The Mysterious Universe Of The Oak
The fascinating world of the oak tree (and its inhabitants)
It can live for centuries, gives shelter to thousands of different animal species and provides us with the oxygen we need to live. Oak trees are one of the most incredible miracles of nature
rom one second to the next the gnarled branch of the old oak tree is transformed into an arena: as the sun sets on the horizon, two male stag beetles get ready for a treetop duel – their antler-like mandibles directed threateningly in the other’s direction. Usually, this would be the cue for them to storm towards each other and attempt to throw the other onto its back with their three-centimetre-long jaws, or to push their opponent from the branch. But this time things are rather different: one of the beetles begins to teeter precariously and shortly afterwards tumbles to the ground below.
The duel is over before it has begun – because the beetle made a fatal mistake: before the battle it slurped away on a sugary juice found dripping from a crack in the oak. What the insect didn’t realise was the oak’s sweet sap had been fermented into alcohol by bacteria. The beetle’s opponent doesn’t look in the least bit worried by this: he’s excited about picking up the spoils of his victory, a female, and lets off a triumphant buzzing to celebrate. This is just one of many fascinating storylines that play out daily in the universe of the oak, and which have done for millions of years.
WHERE IS THE OLDEST OAK TREE IN THE WORLD?
The Pechanga Great Oak Tree in Temecula, California, is around 2,000 years old. And Standing in a field in Manthorpe in the UK is a tree believed to be about 1,000 years old. Known as the Bowthorpe Oak, the tree’s trunk is now hollow but its staggering 15-metre circumference is so cavernous it’s claimed that 39 people once managed to stand inside it.
These two giant trees have observed the lives and deaths of several generations of people. They’ve seen wars and natural disasters, and been witness to exciting new eras – almost in a time lapse, as if they have lived life in slow motion. Oaks grow just four centimetres in height every year while a spruce manages 37 centimetres per year. An oak grows for half a century before it carries its first blossoms. And yet every oak forges its own individual history as a microcosm for thousands of living organisms. The tree is a mysterious continent on which the greatest miracle of nature is waiting to be discovered.
HOW MANY TONS OF DUST DOES AN OAK FILTER FROM THE AIR?
In spring, once the cold weather has gone and temperatures are finally rising, the oak wakes up from its winter sleep. The buds start to open pretty much immediately and the first green leaves soon become visible. Shortly afterwards, the characteristic lobed leaves begin to shoot everywhere on the oak’s branches and twigs. The first blossoms appear. On every male flower or catkin there are up to 40,000 pollens, which are carried to the female flowers by the wind.
The leaves of the oak are true miracles of nature: not only do they act as a source of nutrients and a nesting place for countless animal species, they also serve as umbrellas, climate control units, air filters and oxygen factories combined.
“Using its 150,000 leaves, a 100-year-old oak tree converts around 6,000kg of carbon dioxide per year into 45,000 kg of oxygen,” explains biologist Mario Ludwig. That’s equivalent to the annual requirement of 11 people. The tree also functions as an active F
“There is something to discover in every oak. If you are quiet and patient, the tree will reveal its secret.” SOLVIN ZANKL, PHOTOGRAPHER
air filter: with a leaf surface area of up to 1,600 square metres, it filters up to a ton of pollution-containing dust a year.
Above all, the silent giants are a complex ecosystem that offer a habitat to more than 1,000 species of animal – no other tree provides as much shelter. Over the course of evolution each one has adapted to the unique living conditions of the oak tree and developed strategies to survive.
WHICH ANIMALS NEED DYING OAKS TO SURVIVE?
Many creatures benefit from eating the carbohydrate-rich, fatty fruits of the oak: the acorns. Unlike wild boar or dormice, at least the Eurasian jay makes itself useful while doing so by contributing – albeit unintentionally – to the dispersal of the tree. In autumn it buries acorn reserves under the soil that it can often not find again so that, in some spots, new oak saplings are already sprouting by the next year.
Many insects have also discovered the nutrient-rich tree fruits for themselves – both as a hiding place for their offspring and as a source of nourishment. The acorn weevil deposits its eggs in acorn shells, which helps protect them from hungry predators as well as meaning the larvae will be greeted with an opulent feast when they hatch. Their close relation, the oak leaf-rolling weevil, folds artful nests from the oak leaves by cutting through the leaf, rolling up the sides and curling it up from the tip. It then lays a single egg inside.
Even inside the oak leaves and deep in the tree bark there exists a wealth of hidden riches unique to the oak tree: here the leaf miners are in charge – the tiny larvae of flies, butterflies and beetles which eat straight through the oak and leave behind empty corridors, known as mines, in the process. Some of them, like the oak bark beetle, can quickly become a real nuisance to the giant trees thanks to their insatiable hunger. Trees infested by the pest exhibit general symptoms of decline including reduced growth, wilted foliage and