Vegetation Layers in an English Woodland

The different layers within a woodland are one of those classic illustrations from ecology textbooks – usually a cartoon graphic showing how the structure changes as you move from the ground up to the canopy. The distinctions are indicative – there is often plenty of overlap between the layers – but these are a useful way of thinking about the woodland in terms of its ecological function beyond what simply meets the eye. Helping you to see the wood for the trees, if you will!

We undertake tree climb and inspect surveys for bats in a variety of settings – from individual trees in gardens to well-spaced parklands and dense woodlands. Each of these gives a different insight into vertical variation but a recent climb in an oak and ash woodland gave a nice opportunity to illustrate how this changes in a typical ancient woodland habitat.

English Oak Woodland Structure
Photographs taken at 2m (bottom), 6m (middle) and 12m (top) in an English oak and ash woodland to illustrate the variation in spatial structure.

The number of ‘layers’ and their distinctions vary between sources and across countries – I’ve seen three defined layers, nine defined layers and every number in between delineated in various graphics. I’m going to keep this simple and focus on the three broad categories which are shown in these photos:

Field Layer – taken at 2m height

Ground Layer
Photograph taken at 2m showing the field or ground layer in an English oak and ash woodland


This photograph encapsulates what could be considered the field layer, the ground layer or the forest floor depending on which divisions you use. Broadly, this is the view from the ground – the most apparent vista for most visitors to the woodlands but the scene varies greatly as the year progresses. In secondary woodland or more botanically diminished sites, this can be a mass of ruderals such as nettles, cow parsley and bramble whilst some plantation woodlands can be head-high in bracken. In ancient woodland – such as this – springtime sees a flush of ancient woodland species which time their flowering early in the season before the canopy closes overhead. As May arrives and the trees and shrubs come into leaf, the main event on the forest floor is already coming to an end. Some species flourish later in the season but in September, the vegetation has largely died back often leaving a relatively bare floor. The dominant vegetation remaining is therefore the trunks of the trees and the shrubs which rise above the field layer to leaf and flower higher.

Scrub Layer – taken at 6m height

Shrub Layer
Photograph taken at 6m showing the hazel-dominated shrub layer in an English oak and ash woodland

This could be described as the under-canopy, the scrub layer, the shrub layer or the under-storey layer. This is the level at which the shrubs flourish – those smaller woody species which often include hawthorn, blackthorn, hazel, holly, dogwood and elder, amongst others. These shrubs can often form such a dense canopy that the view to the treetops above can be quite obscured – something of an issue when you’re searching for bat roosts! In this instance, hazel and hawthorn dominate and as the photograph shows, they form a dense and highly cluttered environment some 6m above the ground.

Canopy Layer – taken at 12m height

Canopy Layer
Photograph taken at 12m showing the space between the shrub layer and the woodland canopy in an English oak and ash woodland

This is up at the top of the trees, where the taller trees branch and close their canopies to claim first use of the sunlight available. I’m not right in the canopy in this photograph – the trees did not require us to climb to the peaks – but this nicely illustrates the shrub layer below with the high canopy of the oak and ash above. In some forests, the species composition includes a sub-canopy of smaller trees – such as rowan, silver birch and field maple – which form a layer between the lower shrubs and the taller climax species. This photograph nicely illustrates how much of a space can open up between distinct layers within the higher reaches of the forest structure.

Why does it matter?

An appreciation of how the character and conditions of a woodland change on a vertical plane are just as important, although a little harder to appreciate, than the variation on the ground. The illustrations above are for just one section of just one woodland and each type of species composition but they help to give a visual idea of how this works.

One example of how this type of variation is important is when considering how bats might use a habitat. Different species of bat have different hunting characteristics and habitat preferences, and this often relates to how open or cluttered a habitat is. Species such as brown long-eared are highly maneuverable and will glean insects from leaves so a reasonably cluttered woodland environment suits them perfectly. At the other end of the spectrum, a noctule hawks in open space, often flying over fields and catching its prey on the wing. Species such as pipistrelle are typically characterised as edge specialists which forage along woodland edges, hedgerows and other similar environments.

Pipistrelle bats are typically described as ‘edge’ species which forage along the edges of vertical features, such as a woodland edge

The field layer of the woodland looks ideal for a species such as brown long-eared but you might think that it would be too cluttered and enclosed for other species. However an insight into the structure above the shrub layer reveals a mosaic of open space and leaf cover which provides perfect ‘edge’ habitat for a hunting pipistrelle, and the voids between the trees would be perfectly navigable for a noctule in search of a roost. This was the subject of a talk by Ian Davidson-Watts at a recent BCT Bats and Woodland conference which you can read more about in this blog post here.

If you’re looking for tree climb and inspect surveys for bats, do check out this page for further details!


What did the faeries ever do for us?

I picked up a copy of a little Shire Classics book called ‘Discovering the folklore of plants’ when I was caught out with nothing to read a few weeks ago. The historical beliefs associated with our native flora and their uses can be fascinating, as can a good guide to botanical epiphets which explains the latin parts of species names to somebody like me who didn’t have the benefit/torture of latin lessons at school. This additional context can add to the understanding of a plant, its habits, uses and historical connections which often have a bearing on the patterns still present in the landscape today. I suddenly saw significance, after reading this book, in the grouping of mature holly, bay and elder outside the doorstep of our rented cottage.

As I read through the book, I began to make a note of the superstitions and supernatural beliefs which frequently seem to result in an ecological or environmental benefit. In the same way that religion historically safeguarded moral behaviour by providing an all-seeing deity to watch over our deeds, the belief in the spirits within plants often seemed to ensure good environmental practise.

Many of these beliefs seem to have been prevalent up until the earlier parts of the 20th century. It was in 1917 that the five photographs of faeries in Cottingley were published to mixed public reaction, however many people believed them to be genuine, including none other than Arthur Conan Doyle.

Incidentally, I am aware that this is rather like a topic which an under-occupied vicar may have written a pamphlet on in the 19th centurary to be read by only 3 other people. Fortunately, blogging opens up such exercises in futility to the busier masses!

Leave some fruit for the birds

Many conservation charities and wildlife organisations advise gardeners to leave some of their windfall fruits, such as apples and pears, to provide a food source for garden birds. Many bird species, particularly the blackbirds including the native blackbird and song thrush as well as the migratory redwing and field fare, rely upon fruits and berries especially when the weather turns colder and their preferred food of invertebrates is in short supply.

Before social media and gardening magazines promoted the message on behalf of the birds, appeasement of the faeries performed a similar role:

Stray fruits were left at the end of picking for the faeries, in a custom variously called ‘pixy-hoarding’, ‘cull-pixying’ or ‘griggling’”

Blackberries are stripped from the brambles today, as can be seen from their absence below 2m along most public footpaths. However, an old superstition drew a line under the feasting which would ensure provision of fruit for birds and mammals as the weather turned wintery:

‘In many English counties, blackberries are never picked after Michaelmas Day (29th September) when the devil curses them.’


A presumption against tree-felling

Woodland once covered the vast majority of Britain but now represents only 12% of land cover. Unsurprisingly, considering that they evolved within this vast woodland habitat, the majority of our native fauna also relies upon trees for food or shelter, from tiny invertebrates up to birds and mammals as well as fungi, lichens and mosses. It follows that every tree is sacred in terms of ecological benefit.

It was historically considered unlucky to fell a number of tree species, including ash, hawthorn, holly and elder.

 Elder was one of the most unlucky species to fell of all, as the elder mother dwelt within and guarded the tree. Her permission must be sought before the tree could be cut.

We also have these beliefs to thank for some of the standard trees present in hedgerows even to this day.

‘The ban on cutting holly means that the handsome, dark green trees stand high above farm hedges, giving visual emphasis to the landscape’

Hawthorn stands out in particular in the folklore as a faery tree which could bring some serious ill luck upon those who cut it.

‘In Ireland, a ‘sentry thorn’ or ‘lone bush’ was a faery trysting place demanding the greatest respect and especially dangerous at May Day, midsummer of Halloween when faery power was at its strongest. Farmers laboriously cultivated round these thorns in fields. Felling must be carried out for ritualistic or healing purposes only, never just to tidy the farm.’

In the modern world, trees and shrubs stand little chance of holding up a housing development or major infrastructure project unless they are home to a protected species rather more real than the faeries, such as bats or breeding birds. But even into the 1900’s, hawthorns could hold sway over the designs of developers.

When one thorn lay in the path of a railway, the track was elaborately carried over it to avoid felling. To fell a hawthorn in preparing a house site means misfortune or even death for those who will live in the house.’

Garden for wildlife

Our gardens are one of the most ubiquitous areas of potential habitat within the landscape. If only properly planted and managed, they would create green corridors which would snake through our towns and cities and turn a village into an oasis of trees and shrubs within an arable landscape. This importance to make each garden count is recognised by many wildlife charities; the RSPB, the Butterfly Conservation Trust, the Bat Conservation Trust and Buglife will all advise on species to include within the planting. The Nottingham Wildlife Trust has an ongoing campaign to create mini meadows within gardens, providing free species-rich seed mixes to help establish these little patches of biodiversity across the county.

Yet the draw of the nice, neat paving or that lovely sheet of tarmac is too much for many. Almost 1/3 of the 20 million homes with front gardens have turned them into hardstanding for cars, a 2012 report showed, whilst lazy insurance assessors require the removal of larger trees growing close to houses – often without justification – and discourage their inclusion in new developments.

Trees were traditionally viewed as protective entities and were specifically planted at the doorstep to houses in order to ward off harm.

‘Aspen would keep thieves away;

Bay with its pungent smelling leaves would keep the plague away;

Elder, with the protective elder mother dwelling within, would keep away witchcraft, lightening and evil;

Holly would also protect against lightening, as well as fire and the evil eye’

‘Rowan; the cardinal keeper of the northern cottage door keeps witches away’

‘A rosemary bush near the doorstep purges the house, and a pot on the doorstep keeps thieves and witches away.’

Similarly, the greening of inert brick walls would help to protect the house.

Honeysuckle is a mighty barrier to the witch and, growing over the door, keeps out fever and the ill intentioned’.

Ivy if it grew vigorously on a house its occupants would be safe from witchcraft and the evil eye.’

Both of these species are fantastic nectar sources for insects during their respective flowering periods, the late flowering of ivy making it particularly important in the cycle of nectar sources for our pollinators.

Don’t pick wild flowers

As everybody knows now, the mantra of the countryside is ‘take nothing but photographs, leave nothing but footprints’, a message which encourages visitors to enjoy nature without taking it home. Whilst many of the remedies and uses of plants within the book talk of their picking for decoration, for cures, for rituals, there are some which are protected by the faeries.

‘Anyone picking stitchwort is likely to be pixy-led’

‘Anyone who stepped on St John’s Wort would be carried off by a faery horse which rose from beneath him and took him for a wild ride, then in the morning dropped him off at the wayside miles from home’

‘Willowherb and cow parsley would bring death the mother of any child who picks it’


Let nature take its course

Weeds are often defined as any plant in the wrong place. Personally, I love seeing any vegetation greening up an otherwise inert area of concrete or pavement; I am not a fan of the Best Kept Village competition which seems to see such natural opportunism as the antithesis of a suitable village. So although this aversion to weeding doesn’t seem to be supported by the folklore in general, the note below caught my eye:

‘A self-set elder is lucky and should be given space to grow’