The oak woods of Mousehold Heath are one of the glories of Norwich. Towering trunks and branches expand into fine canopies. In some places they have had over a century to grow undisturbed. The best place to visit them is up on the northern side of the Heath.
Oaks have a long history on Mousehold. In early mediaeval times Thorpe Great Wood extended over the area and was “covered with oaks”. By the 16th century, open heathland had expanded and woodland had become very patchy. A map of 1585 shows trees surviving tound St William’s Chapel – probably old Oaks.
Oaks are found almost everywhere on the Heath, often with an understorey of Bramble. They are players in a drama of natural plant succession.
Heathland will turn into woodland, unless some intervention happens. If left to itself, the heathland will quickly be colonised by light-loving Birch and Bracken which will over-shade and suppress young Oaks.
So how does the Oak manage to form such lofty woodland - has it been planted?
Jays are regularly seen on the Heath, and they are one way that Oak can spread. They collect acorns in Autumn then bury them in the topsoil, sometimes on open ground. If an acorn is not recovered then a seedling may result.
Oaks are slow-growing, and their seedlings are sensitive to shade and browsing by deer. However they can survive if surrounded by Holly and Bramble and other spiny bushes which act as ‘nurses’. Oak saplings can grow here and eventually may live to tower up and over-shade their neighbours. Holly can survive in these conditions because its evergreen leaves can make energy even in Winter.
Spongey ‘oak apples’ are obvious evidence of the Oak Apple Gall Wasp Biorhiza pallida at work.
Berry-like ‘currant galls’ are the larval chambers of the tiny Neuroterus quercusbaccarum gall wasp.
Chewed leaves with a curled over margin are evidence of the Winter Moth. Its caterpillars are favoured spring-time food for blue tits.
Mosses and lichens grow readily on damp, shaded trunk and branches of Oak.
The grey lobes of Powdered Ruffle Lichen contrast with the feathery stalks of Cypress-leaved Plait-moss on a tree near Vinegar Pond.
Tawny Owls are more often heard than seen, the females with their keewik call or the males with a warbling hoot. They spend the day roosting in the secluded nook of a tree, often an ivy-shrouded Oak.
[Image courtesy Hans Watson]
The Sulphur Polypore fungus forms fleshy yellow brackets on hardwood trees such as Oak. It is sometimes known as Chicken-of-the-Woods. As it ages it becomes breeding ground for specialised gnats and flies.
Purple Hairstreak butterflies spend much of their lives in the canopy of Oak trees, where they sip the honeydew exuded by aphids – you will probaby need binoculars to see them. The females have pearly grey under-wings and can be most easily seen when they descend to lower branches to lay eggs.
[Image courtesy Will Stewart]
Text by Tim Holt-Wilson.
All images courtesy the author, unless otherwise indicated.
