Title: Woodland Habitat

What is a woodland? That might seem a rather obvious and easy to answer question and I suspect many would say a woodland is an area of land covered by trees. That is an accurate but possibly inadequate definition.  

How big an area do the trees have to cover to be a woodland? How many trees constitute a woodland? Does the area have to be totally covered in trees or can there be open spaces too? Does it matter what sort of trees are present to be a woodland? Does it matter how long the trees have been present? 

There is a further question too; when does a woodland become a copse or a plantation or even a forest? 

That obvious question I asked at the outset is, perhaps, more complicated than you may have thought and we have to be a bit more precise in our answer perhaps. 

To help make some sense of this I will use the “Handbook for Phase 1 habitat surveys”. Surveying sites and classifying the habitat types present is an accepted practice in conservation circles and this field guide was developed in 1990 by the Nature Conservancy Council to standardise classification and to provide consistency. It is not the only system used but it is widely used.

The definition for woodland gives us a precise understanding of the features that are necessary for a formal classification. Woodland is defined as being and I quote from the handbook “vegetation dominated by trees more than five metres high when mature, forming a distinct, although sometimes open, canopy”. 

From that we can conclude that there is no size limitation, no specific number of trees or type of trees and no minimum requirement for density of trees. It seems our initial broad brush definition of a woodland being an area of land covered by trees is basically correct.

Having accepted a broad definition of woodland we have to understand that there are, of course, various types of woodland which prompted those follow up questions.

The first consideration is whether trees are broadleaf or conifer. If ninety percent of the canopy or more is broadleaf we would classify it as being a broadleaf woodland. If the canopy is ninety percent or more conifer then it is obviously coniferous woodland. Where neither type is dominant the classification becomes mixed woodland and the surveyor is required to estimate the percentage of each present. 

The second consideration is the density of the trees and it is interesting that at a covering of less than thirty percent is still considered woodland but would be described as scattered trees. This means a woodland does not have to be formed of dense trees and can be quite open in structure.

Moving on we then need to consider whether the woodland is natural or planted. The age of the woodland is not an issue in deciding this and some woodland can be quite new but natural although, in reality, this sort of woodland is very scarce. Just for clarification, natural woodland means, as implied, that the trees were self seeded and grew naturally and apart from some ancient woods that are over 500 years old most woodland is plantation. Where a woodland has both natural and planted trees it would have to have at least thirty percent or more natural trees to be deemed semi-natural. If there is less than thirty percent it is a plantation.

Establishing whether trees are natural or not can be tricky if the wood has established trees and plantations are not always conifers, species like beech, sycamore, sweet chestnut and horse-chestnut have all been used in plantation and their presence would lead one to conclude that the woodland is plantation. The other guide is to look and see if the trees have been planted in rows or are scattered across the landscape.

We are making progress with our survey but we are not done yet! We need to look for specific subtypes that occur. The obvious one is an arboretum or estate garden where exotic and ornamental trees have been planted. Others include orchards where there are a number of fruit trees, parkland where the trees are well scattered, woodland that has historically been coppiced or possibly pollarded, and young plantation where the trees are less than five metres tall.

Hopefully you are still with me as we come to the last general classification of woodland based mainly on species present. We might encounter lowland mixed oak and ash woodland which is likely to be well established and possibly ancient. In some areas, mainly around the heathland areas, one will find lowland dry oak and birch woods. Where the ground is water-logged one will find carr, formed mainly of alder, willow and birch. Finally there are then open areas known as wood pasture, often associated with deer parks where the trees were planted for the deer to feed on and finally the common woodland conifer plantation.

There you have it, a guide to classifying woodland habitat. Why should you be interested in this? Well, once you have established the type of woodland you are in it will give you a pretty good idea of the various other types of nature you might encounter as a woodland is much more than just trees; it is animals, insects, flowers, fungi and more besides. Understanding the habitat you are in is a step towards understanding the ecological activity of where you are and should massively increase your enjoyment of your surroundings.

Scrub:

Any area of open ground will, if left to nature, gradually turn into woodland. This is a natural regeneration process (called succession) and it is happening around us all the time and largely goes unnoticed. First bare ground loving plants like poppies and daisies will appear and then the grasses take over. Amongst the grasses shrubs start to take hold and then, over a much longer period of time, the trees grow and develop and the woodland is formed. It can take a hundred years or more but it will happen!

At the point when the shrubs are at their peak the resulting habitat is generally called scrub. In some places where there is regular livestock grazing the animals will browse and keep the scrub at bay. In other areas, often where grazing is not practical, the scrub takes a firm hold. If the soil or terrain is such that the development of trees is impaired then scrub habitat becomes almost the norm.

Scrub is an important habitat in its own right and is essential for the survival of some bird species. The nightingale, for example, thrives in scrub but nowhere else.  Scrub is formed mainly of shrubs from the rose family; bramble and dog-rose, hawthorn and blackthorn being the most common. On acid soils gorse becomes the dominant species and bracken often occurs too.

It is easy to overlook the importance of scrub. We tend to think mixed scrub is untidy and indicates neglect and that hedges need to be annually manicured to keep them tidy as well as functional. Nature reserves often have mixed scrub which is controlled to ensure the benefits of scrub are retained without losing the underlying grassland or heathland habitat that it is invading.  Thank heavens for the conservation volunteers!

In the Sidmouth area there is some mixed scrub which is a naturally generated collection of bushes that are not managed but are developing on their own in conditions that suit them. The most common is what we know as hedgerow scrub; hedges are shrubs (and trees) that are managed and form boundaries between fields. 

Phase 1 Habitat Surveys Description

The "Handbook for Phase 1 Habitat Surveys" describes woodland as an area where the vegetation is dominated by trees more than five metres high when mature forming a distinct, although sometimes open, canopy. Woodlands are amongst our most complex and diverse habitat systems and there is no such thing as typical woodland (my observation!). Many factors influence what a particular woodland will be like and what wildlife one might find there. The influences that readily come to my mind are (in no particular order if significance): 

• The type of tree that forms the canopy; broad-leaf deciduous trees, evergreen conifers or a mix of the two
• The density of the trees and how close together they are; whether there are clearings, glades and rides between them
• The foundation soil underlying the woodland; variations between acid/alkaline and dry/wet soil can produce significant differences
• The area covered by the woodland; larger woodlands are likely (but not necessarily) to be more diverse
• The age of the woodland; obviously older woods will have more mature trees than a recent plantation
• The management of the woodland; this plays a major role and may be harvesting for timber, copicing for hurdles, cover for pheasant rearing and so on 

A woodland typically has four layers: 

• The canopy formed by the upper branches of the trees
• The under-storey formed by shrubs that can grow and prosper in shade under the canopy
• The floor which is profoundly affected by the amount of light reaching it through the canopy and the leaf mix that falls from the trees
• The soil layer where the trees and flora draw nutrients and moisture but also a home for a myriad of invertebrates that live within it 

Put all this together and you quickly see why woodlands can be so diverse; there are so many factors at work. In simple terms though there are five main types of woodland you might encounter in this area.

• Broad-leaf: a woodland where the canopy is formed almost exclusively by deciduous broad-leaf trees like ash and oak
• Acid: a woodland where the acid soil means that the tree mix is often oak, birch and possibly some Scots pine
• Mixed: a woodland where conifers have been planted amongst deciduous trees, often pines amongst beech
• Plantation: a woodland almost exclusively pine or spruce planted for a timber crop
• Amenity: A woodland planted for a specific purpose for the benefit of human beings; orchards, arboretum, shelter belts, parkland, etc 

Walk into any woodland and look at the main trees present and you can easily decide which of these environments you are in. Each is quite distinctive and has a unique feel and a unique flora and fauna. Look for evidence of the trees being in straight rows, this indicates a recent plantation. There are no 'natural' woodlands locally but there are some that have flora that indicates the origins may be ancient and these tend to be where the wildlife is most diverse and well established.