The natural diversity of species in old oak trees is greater than previously thought. This is the conclusion of research led by a Dutch botanist in a British forest with the highest density of ancient oaks in Europe.
Wim Eikelboom2 July 2023, 22:00
“Here in this tribe, we made an exciting discovery.” Aljos Farjon gingerly leans forward to peer into the fallen hollow tree. “In the brown rot of the old oak we found a very rare pseudo-scorpion (Dendrochernes cyrneus), a spider-like animal with the appearance of a scorpion. The bug lives in the fungal brown wood rot of the oak tree, just like many other insects.”
Farjon takes a handful of wood chips. “Look, this is the work of the brown tree ant who digs tunnels in the brown rot. The ant colony lives in the oak tree. You rarely get to see them, because they don’t like daylight. An oak-own ant.”
Nowhere in Europe are so many monumental oak trees clustered together as in the closed part of Blenheim Park near the British Woodstock, called High Park. Farjon mapped 275 old oaks here with a trunk circumference of more than five metres. All of them veteran trees with an age of four hundred to eight hundred years. “This is unprecedented. There is no place in Europe where so many old oaks are together,” says Farjon. By way of comparison: There are approximately 170 oak trees with a trunk circumference of more than five meters throughout the Netherlands.
Strict conditions
The secret to Blenheim Park’s high density of veteran trees is that the site has been off limits to the public for centuries. Scientists are only allowed to roam around here under strict conditions.
The history of the unique oak forest about 100 kilometers northwest of London goes back to the Middle Ages. King Henry 1 of England used this forest for deer hunting as early as 1100. After the park came into the possession of Winston Churchill’s ancestors in 1764, a landscape designer decided to leave 150 hectares of forest alone. The unique monumental oak forest on the edge of Blenheim Park is due to this. Between the trees on the rolling hills, Blenheim Palace can be seen in the distance, the birthplace of the famous British Prime Minister with a round-neck.
Aljos Farjon near an old oak tree in High Park. Image Wim Eikelboom
Farjon brought the existence of the exceptional oak forest to light in 2016 when writing an overview book about the oldest oaks in England: Ancient Oaks in the English Landscape. He then made the national news. “I was amazed at the amount of giants I found here. That is when I came up with the idea of working with scientists to make an inventory of the biodiversity in this unique place.”
77-year-old Farjon (born in Hilversum) is a leading conifer expert by training. To his name is a scientific standard work in which all 615 species of conifers in the world are described. After his retirement from the renowned Royal Botanic Gardens Kew in London, he devoted himself to research into ancient oak trees.
National tree
The oak is the national British tree. Pedunculate oaks are not called English Oaks for nothing. The national nature and culture conservation organization National Trust has the oak leaf as its emblem. Farjon: “You can tell from everything that old oaks hold a special place in British culture, history and the hearts of the people.”
The enclosed oak forest of Blenheim Park is a Valhalla for lovers of very old oaks. Virtually no maintenance takes place here. Thick trees that fall over remain lying there, just like broken branches. The alternation of living and dead oak wood makes it a paradise of species diversity, says Farjon.
“The longer wood remains, the more valuable it becomes as a habitat for beetles and fungi. Many insects are specialized and associated with a particular stage of oak decay. It also applies to mushrooms and fungi.” Moments later, Farjon sticks his head into a large hollow of a fallen giant oak. “In it, a mycologist discovered an extraordinarily rare bright orange fungus. It was the second find in Britain.”
Hollow inside
Live ancient oaks are all hollow inside. That says nothing about their vitality, Farjon emphasizes over a saggy lad. “This tree is said to be perhaps a thousand years old. The tree is still in leaf and probably also produces acorns. As long as cambium is in contact with part of the root system, the tree is alive. To properly understand a tree, you must realize that it is a completely different organism than an animal. If an animal loses a leg, it is doomed. A tree is compartmentalised. So if a tree loses a branch, it regenerates itself somewhere else in the tree.”
Nowhere in Europe are so many monumental oak trees clustered together as in the closed part of Blenheim Park near Woodstock.Image Wim Eikelboom
Aged oaks are known to rank highly as hosts for hundreds of species of insects, fungi and plants. Five years of ecological fieldwork in Blenheim Park has revealed astonishing figures. Figures that exceed the previously known biodiversity value of oak trees.
Led by Aljos Farjon, a team of fifty ecological experts studied the monumental oak forest. Traps were set on and around the trunks to catch insects. With magnifying glasses, connoisseurs studied the ancient bark of oaks on lichens.
ice age
“The lichen connoisseurs in particular were lyrical,” says Farjon, walking among the giant oaks. “The lichen researchers were amazed at the number of species they found on live and dead old oaks. They even found two species that are new to Britain.” Researchers came up with 231 species of lichen and 480 species of fungi.
Aljos Farjon peeks into the fallen hollow tree. ‘In the brown rot of the old oak we found a very rare pseudo-scorpion, a spider-like animal with the appearance of a scorpion.’Image Wim Eikelboom
The abundance of insects also amazed researchers. “A total of 930 species of beetles, 684 species of moths and almost 700 species of flies have been found on and around the oaks. Among them are several rarities associated with old oaks. This also applies to butterflies such as the large reflection butterfly and oak page.”
What is the reason why oaks in particular score so high in biodiversity? That is a matter of evolution, explains Farjon. “The longer in time a tree has a place in the ecosystem, the greater the number of species that enter into a relationship with this tree. The oak has been growing in England since the last ice age, over ten thousand years ago. We are still learning about the value of this tree for biodiversity.”
cry along
The sum of five years of ecological field research on and around the ancient oak trees of Blenheim Park was overwhelming for Farjon. He is working on a book with the results. “We found nearly 4,100 species of organisms on a 130-hectare site.”
Many of the ancient oaks in Britain’s High Park are rich in insects. ‘The longer in time a tree has a place in the ecosystem, the greater the number of species that enter into a relationship with this tree,’ says Farjon.Image Wim Eikelboom
High Park Blenheim is now in the top three sites with the highest biodiversity in the UK, along with New Forest and Windsor Great Park. “But the other two are places where research into biodiversity has been going on for decades. So I suspect that Blenheim Park will score even higher in the long term.”
The demonstrated enormous diversity of species in the old British oak forest is hopeful evidence for the Dutch scientist that nature is more powerful than we think. “There is a lot of talk in our time about how bad things are with nature. Concerns about climate change and species extinction dominate the news.”
“I find it regrettable that many conservationists cry along with this story. Our research in Blenheim Park proves that biodiversity is immensely rich if you do proper research. The old untouched oaks here tell the story that not everything in nature deteriorates.”
IVF with jerks
Although the species richness of the oldest oak forest in Europe is unprecedentedly high, the reproduction of the trees continues to be a problem. Due to the presence of fallow deer, only a few acorns manage to grow into a tree. Fallow deer find young eggs tasty. The wandering red deer thus puts a stop to the natural rejuvenation of the forest.
Something has been found. With the cultivation of three thousand collected acorns, the British Blenheim Park safeguards the legacy for the ancient oaks. The young oaks are raised in pots in greenhouses and will eventually be replanted on the estate. “The saplings are all direct descendants of the original medieval oaks. It is hoped that the new growth will ensure that the legacy of Blenheim’s ancient oaks lives on for centuries to come,” said Rachel Brodie of the Blenheim Park forestry team.
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2023-07-02 20:00:00
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