Secret World Below The Canopy

Unbowed by time, the long-lived oak has a vital role to play in the lifecycle of hundreds of plants, animals and insects

Tom Mason

AS THE WARMTH begins to fade on another English summer, an oak tree stands proud on the edge of a green field. The thick mature trunk supports a wide crown of branches which spread out above, as well as one or two dead ones, a sign of its age. The change in season has triggered the inevitable; the oak’s leaves start to brown, and the acorns ripen and fall from their cupules. They drop to carpet the land below with a rich source of food, perfect for the jay that is hurriedly jumping between a grazing herd of red deer, which are also making the most of the feeding opportunity.

As the sun starts to fall, a little owl finds its position among the branches. It peers down at the ground to spy a meal of the last large insects of the year or a bank vole feeding on the fresh acorn platter. With the onset of winter inevitable, a female stag beetle makes her way through the fallen leaves and acorns to where she emerged in a decaying limb of the oak.

The English oak, Quercus robur, is a large deciduous tree that is one of the most important, owing to its support of such a large amount of biodiversity. With single trees being able to sustain in excess of 300 species, they are one of the pillars of the English countryside. Growing rapidly for the first 120 years of their life, they slow down in the later years.

Reaching from 65ft to 130ft (20-40m) in height, oaks have a large crown, with study branches beneath. Their original smooth silvery-brown bark becomes fissured and rugged with age.

Dead branches at the top are not signs of weakness. Instead, they are indicators of times the tree has passed through hardship, pulling water from its extremities to preserve life. Oaks can even become shorter with age, stopping the flow of nutrients to their outer branches. This slows or even stops growth, but extends their lifespans. This extension is vastly important for the entire ecosystem. The oaks’ longevity, sometimes in excess of 400 years, provides a stable habitat in the landscape. Mature trees have complex relationships with bacteria, fungi, birds and mammals, allowing the support of a vast and healthy food web.

A feast for many

In autumn, the ground below the tree is the stage for the annual rut. Red deer stags position themselves, squaring up to rivals and fighting with the clash of antlers below the branches. They defend their right to keep their hard-fought-for harems. The does, meanwhile, are busy feeding up on the acorns littering the floor. The 1in (2.5cm) long acorns, born of lengthy stalks, are the fruit of the oak.i

The tiny bank vole eats both nuts and insects below the oak. They grow to approximately 4in (10cm) in body length with a 2in (6cm) long tail.

They provide food for a variety of life, but are not produced until a tree reaches after maturity at 40 years. Peak acorn production comes at 80-120 years, before declining as the tree moves into old age from 250-350 years.