The composition of these woodlands varies somewhat across Mendip, but typically consist of a mixture of ash and small leaved lime standards, with a hazel, field maple and hawthorn understory, alongside occasional hornbeam, wych elm, whitebeam and wild service trees.

Semi natural ancient woodland

Many of these woods are remnant fragments which have been woodland for a very long time; the usual definition of a “semi natural ancient woodland” is that it must have been wooded since 1600 AD. Note that these sites are referred to as “semi natural” rather than natural, as throughout history, they will have been managed for timber, firewood, and coppice products.

This produces a variety of different environments, from dense bushy undergrowth to small open glades and stands of mature trees with closed high canopies. In general, the broader the range of environments, or “ecological niches”, present within a single site, the broader the range of wildlife it can support.

Going back further in time, large animals such as woolly rhino and mammoth (going back to the ice ages), or elk (up to around 3,000 years ago), would have naturally maintained a similarly varied mix of woodland structures and environments. This very long, stable period allowed our native species to evolve to make the most of the available habitats, and today our native woodland species are still best adapted to this diverse environment.

Human management of woodlands has varied throughout history in the UK, providing materials for ship building, firewood and charcoal, and oak bark for leather tanning at various points in time. Although the early 20^th century saw large amounts of woodland felled for timber to support the war effort, from this point on traditional woodland management became increasingly irrelevant to our economy, resulting in the gradual cessation of coppicing and thinning of trees.  

The open glades and rides that were present in our woodlands began to fill in, creating a more uniform environment with continuous tree canopy cover. This allows less light to hit the woodland floor, resulting in less stimulation of wildflower and understory growth. Areas where the wood had been clear felled for timber at the beginning of the 20^th century also regenerated to give a very uniform structure, with all of the trees being the same age and typically closely spaced, without room to branch out and become large veteran specimens.

Over time, this caused the loss of the varied environments originally created by large mega-fauna, and then sustained through human history by traditional woodland management practices. This inevitably leads to a reduction in the biodiversity of the wood, and the main goal of modern wildlife conservation woodland management is to reverse this process.

Woodland wildlife

One sign of an ancient woodland site is that it will tend to have a rich ground flora. Typical Mendip species include impressive stands of bluebell, ramsons and dogs mercury, and frequent wood sorrel, wood anemone, enchanters nightshade, common madder, and toothwort, as well as less common plants such as purple gromwell and starved wood sedge. They are also often home to a wide variety of lichens, ferns, and invertebrates, from butterflies and harvestmen spiders to slugs and snails (the long, pointed, dark grey two toothed door snail is one particularly characteristic species for the area).

Ash dieback & deer browsing

Our Mendip woodlands tend to have a relatively high amount of ash in their composition, and the rapid progression of ash dieback disease in the area has had a marked impact in recent years. It is likely that a small percentage of ash trees will display enough resistance to the disease to repopulate our woodlands with new, resistant, seedlings in time, but this will be a lengthy process. On a human timescale we are now observing the loss of a large proportion of the upper canopy of our Mendip woodlands.

Bearing in mind our previous discussion on maintaining a diverse woodland structure, and the need to fell trees in order to achieve this, it’s not all bad news; the loss of the ash canopy has opened up large areas of the woodland’s canopy, and has reduced the need to manually fell trees to achieve this. However, we do not have much in the way control over what areas this occurs in, or what proportion of the wood it takes place over, so in highly ash dominant woodlands this could still lead to a uniform structure, albeit a very different one than we are used to seeing.

When large gaps in the canopy are opened, light stimulates the germination of seeds and the subsequent growth of seedlings. Where wildflower seeds are present in the seed bank, we may initially see these emerge and flourish; however typically large amounts of bramble will often encroach and smother this out.

Over time, faster growing trees such as hawthorn, lime and hazel grow up through the bramble, and as they unfurl their canopies, the bramble dies back in the lower light environment. This is the natural cycle by which our native woodlands regenerate after trees have been lost.

However, we need to be careful – if there are insufficient seedlings growing in the wood, or if all of the “natural regeneration” is eaten by browsing deer before it grows out of their reach, this process can be interrupted, leading to a longer term change in the habitat. The loss of large areas of woodland in this way, particularly over a short period of time, could have a serious negative effect on biodiversity across the landscape.

For this reason, we carry out annual monitoring of our woodland nature reserves, paying close attention to the natural regeneration of new trees, and the impact that deer browsing is having on this. One useful tool to help us do this is to create a series of “exclosures” within the wood that keep deer out of a small area. Comparing the natural regeneration inside and outside of the exclosures gives us a good idea of the impact that deer browsing is having.

In general, our preferred strategy is to rely on natural regeneration to replace our lost ash trees. The seedlings grown in this way will be perfectly adapted for local conditions, and do not carry the risk of introducing diseases, or the higher carbon footprint of buying in saplings from tree nurseries to plant. However, where natural regeneration is poor, or very few non-ash species are present, we have planted a broad range of native species to kick-start the process.

Hazel dormice

Another important woodland species is the hazel dormouse. As well as being one of the UK’s most charismatic small mammals, dormice are a good “indicator species”. This is because they require large, connected, varied habitats, ranging from mature ancient woodland to dense rotational coppice, open glades and rides, and transitional scrub or connective hedgerows around the edges of a wood. They tend not to flourish in undermanaged, unconnected woodlands dominated by a uniform structure of mature trees with a closed canopy. However, if dormice are present on a site, it is a good sign that the local ecosystem is in good shape and is likely to be supporting a broad range of native wildlife.

Dormice are not easy to spot, and in order to get an idea of how their populations are changing, it is necessary to carry out long term monitoring projects. We are lucky that this has been taking place on Mendip since the 1990s; unfortunately the observed trends in their populations have been negative on many sites in recent years.

Because of the recent rapid changes to our woodland habitats caused by ash dieback, monitoring of dormouse populations is now especially important, to see what effects this is having, and to help us decide what management we can best carry out to help them.

Because of their protected status, a special licence is required to handle dormice, and our Assistant Reserve Manager Claire Hollingsworth is currently working towards obtaining this licence so that she can help monitor dormice on Mendip.

Claire is also planning on using “footprint tunnels” to see which areas of Cheddar Wood dormice are using. These tunnels contain a special, non-toxic, ink, which the dormice walk through before leaving footprints on a piece of paper. The footprint of a dormouse is sufficiently distinctive to allow it to be distinguished from other small mammals, and the nature of the monitoring means that it is not necessary to catch a dormouse “in the act” of walking through the tunnel.

This work will help us decide what future management to carry out, so that we can connect up existing areas of habitat to the best effect.

Current dormouse project work on Mendip

We are delighted to have recently received funding from DEFRA as part of the Farming In Protected Landscapes scheme, and from Aggregate Industries, through their Partnership Fund to help Wildlife Trusts carry out important habitat management work.

The funding from Aggregate Industries allowed Claire to attend a special training course hosted by the People’s Trust for Endangered Species to work towards her dormouse handling licence, and will fund the planned monitoring work using footprint tunnels in Cheddar Wood. It is also allowing us to carry out work to improve the structure of the main ride running through Cheddar Wood.

A good ride is a very important feature within a wood. It provides both permanent open space within the wood, and a long transitional edge, or “ecotone” between open and wooded habitat, where successional scrub and coppice growth is periodically cut back and then allowed to regrow.

In Cheddar Wood, we cut and remove vegetation from alternate sides of the ride each September/October to prevent coarse grasses such as Calamagrostis epigejos from dominating over the wide range of woodland wildflowers found along the ride in Cheddar Wood, including meadow saffron, yellow pimpernel, and purple gromwell. The uncut side of the ride provides a refuge for invertebrates.

A good woodland ride should have a “V” shaped profile, with the total width roughly twice the height of the mature trees in the wood. This project has helped with the ongoing transformation from what was initially quite a narrow, “U” shaped profile, to the wider, more open ride we now have, with many areas now seeing a good amount of sunlight through the canopy.

Scalloped bays like the one pictured (which was created as part of this project), can provide additional room for wildlflowers, and create sunny enclosures that are shielded from the wind for invertebrates to use, while maximising the length of the transitional edge between open habitats and denser undergrowth.

This provides the broadest range of ecological niches for native species, including dormice, to live in. Meanwhile some pinch points have been retained, with connecting branches overhead to allow arboreal movement of dormice through the tree canopy.

A series of transient glades have also been created through the wood, with many being connected to the main woodland ride. These areas provide dense young growth of understory plants and bramble, which will be beneficial for dormice, and are of general benefit in increasing the structural diversity of the woodland and hence the variety of native species that can survive within it.

Additional work funded by Farming in Protected Landscapes and partners has also allowed us to create a new woodland ride and interpretation board in nearby Mascall's Wood, and to carry out dormouse monitoring in Harridge Woods on East Mendip, as part of the wider Habitat Management for Mendip Dormice project. This collaborative project has involved a number of motivated landowners undertaking a range of work, including coppicing to regenerate existing hazel woodland, new hedge and woodland planting within the surrounding landscape, and training days on habitat management for dormice.  A number of footprint tunnel and nest tube surveys were also undertaken by volunteers and ecologists to improve our knowledge of where populations may still be present across Mendip

While these projects have been focussed around improving woodland habitats for dormice, they will benefit many other native species, as well as promoting a structurally diverse woodland. Habitat management work of this type, together with ongoing monitoring of the state of our woodlands and the wildlife they support, is crucial if we are to retain our rich natural history, and we are very grateful for the funding that enables us to carry out this work.