Yarner Wood: Open Air Laboratory and Conservation Gem

Natural England are linking up with external contributors in our blogs to celebrate the 70th anniversary of the declaration of Yarner Wood as a National Nature Reserve (NNR).

Yarner Wood, made ancient by the crucial relationship between trees and fungi, has seen many shifting attitudes towards it across it’s long past.

In recent centuries, up to 1952, these beautiful woodlands were owned as part of the Yarner Estate. During this time, Yarner Wood was not a place of particular conservation interest, but merely a statement - tamed wilderness with an industrial past. The main track for example, winding through the woodland, was deliberately lined with introduced beech trees so that the owner could show how extensive and beautiful his land was to visitors as they travelled through it. It was also intended as a place for small scale bird-shooting, again, occasionally performed by the past owner as a means of cementing his status as a member of the English gentry.

Introduced beech treesalongside main trackat Yarner

After the turmoil of the Second World War, it was decided that the land should be stripped of its trees, the plan being to plant conifers to generate as much profit as possible (a fate shared by many other woodlands in the country). However, the Nature Conservancy luckily found money to purchase and conserve the woodland, which was deemed too beautiful and archeologically significant to monetise. Initially, at this very early stage in the history of British woodland conservation, Yarner Wood was used almost as an experimentation ground by scientists and conservationists, with the aim of demonstrating what could and should be done to improve nature conservation interest. This has indeed been demonstrated and executed at Yarner Wood, aided by the ability to make long-term decisions based solely on the habitat, rather than seeing it through the lens of an economic and social asset.

Woodland composition

The extensive woodland (roughly 150 hectares) mostly comprises of an upper canopy layer of sessile oak, with a rowan understory, and a bilberry field, or ground layer, beneath that. However, there are also scattered areas of coppiced woodland (coppicing is the act of felling trees at the base, allowing many shoots to regrow, to provide a sustainable supply of timber). These coppiced sections are an indication of a past economic practice, the use of Yarner Wood to produce charcoal; other visible clues are small, flat plateaus of land, known as charcoal hearths, where timber would be stacked and smouldered to turn it into charcoal. This industry has now collapsed; in part, the hermit-like qualities of the producers, who effectively camped at their main base of production, led them to be ostracised by a modernising society that had left them behind. To make matters worse, the remoteness of Yarner meant that, as an expanding business, it was hardly a viable location to make charcoal on a scale necessary to keep up with rising demand, especially when utilising slow growing oak. These abandoned coppice areas have been thinned (by removing the dominant stems) and now favour a variety of wildlife features.  

Abandoned coppiced area

One of the many land-based matters which conservationists must deal with, and have dealt with, is the underlying factors that affect the surface ecology. This includes the acidity and poor growth capabilities exhibited on most of Dartmoor and reflected at Yarner. During periglacial periods, the healthy, nutrient-filled soil was gradually washed down the valley towards Bovey Tracey, leaving a poor, acidic topsoil, with very few nutrients and very few growing options (aside from various tree species, it limits the growth and diversity of flowers for example). To allow the local nutrient cycle to occur, conservationists have taken a ‘minimal intervention’ policy: for example, letting dead trees decompose (as opposed to removing them) enables all the nutrients from the tree to remain in situ, as well as providing a new habitat for many different species. The policy of minimal intervention is ideal for the woodland and, while it may not seem so, a messier woodland is a clear sign of diversity and growth, and conservationists have worked hard to only tinker and tame what needs to be changed e.g. only removing a tree if it has fallen over a path.

Another change that conservationists have applied in this woodland reflects shifting attitudes to beech trees. Originally, it was decided simply to remove beech trees from the woodland, if they had been planted prior to conservation efforts, due to their dense canopy blocking out the sunlight needed for other plants to flourish. Now, however, several beech trees that have found their own way into the woodland are left alone, thereby respecting natural change and appreciating diversification. There are also other signs amongst the trees of the current thinking and work of conservation – the upright, dead nature of the birch trees, for instance, is entirely intentional, designed to provide the perfect habitat for lesser-spotted woodpeckers. Missing bark on holly trees, that can be glimpsed as one walks around the wood, is where bark has been devoured by hungry ponies, the latter having been introduced to create structure in the system.

Baedeker raid cracks in trees

Other visible signs of human impact on the woodland arose entirely by chance: large splits made in some of the abandoned coppice trees. Surprisingly, these vertical ‘cracks’ in the trees were made by falling bombs. Nazi Germany’s prolific bombing campaign in 1942, the so-called Baedeker raids, saw intense raids on cities such as Exeter; but once the pilots had flown over their target, they would circle back towards their bases in occupied France, dropping any unused payload on seemingly empty areas. Some of these incendiary bombs (designed to fire shards of burning shrapnel when detonated) were dropped over Yarner, and these cracks are today’s visible result.

Another noticeable feature across the woodland are holly trees. These were historically never a threat; they were instantly felled by those involved in the charcoal industry but are now abundant and ubiquitous. The current question is whether to let them grow or to get rid of them, for they shadow the ground from sunlight, preventing diversity in growth, as well as consuming scarce minerals and nutrients. It is, however, an entirely natural development, and it would be expensive, difficult, and perhaps raise unforeseen consequences to deal with. Nevertheless, ride-side clearance of holly has been initiated to help lichens that occur along these liner glades to flourish.

Holly growth alongside woodland track

Another issue addressed by conservationists, this one more globally significant, is climate change. The obvious answer may seem to be to plant more trees, but in fact this could prove to be counter-productive in a place like Yarner. The acidic soil is inefficient for growth, and with the specific planting of new trees comes the large and potentially devastating risk of tree disease, which would lead to huge costs in felling those infected and end up with the removal of more trees than were planted. A more subtle form of management is to maintain the existing canopy, thereby keeping humidity at a high level, accompanied by structural variation at ride interchanges and the removal of ride-side holly.

As time progresses, further conservation efforts will be made. Perhaps most notably, it is planned that the small stream passing below the car park will be slowed by blocking it with deliberately placed fallen trees. In periods of particularly heavy rain, the consequent flooding will both help to spread nutrients more widely and maintain and increase the local humidity.

Twisted tree trunks

Yarner Wood continues to function as one of the many alveoli of the earth’s great lungs. Locally, it is connected with surrounding woodlands, including those in the Bovey Valley, which together form an important corridor linking Dartmoor with Bovey Tracey and the coastal plain beyond. This taming and protecting of the woodland, working to provide the best possible outcome for the habitat and allowing and enabling the local ecosystem to flourish, is precisely what conservationists have perfectly achieved, with many subtle yet visible signs apparent in the landscape, and what they will continue to implement in years to come. 

Written by Zachary Stone

Thanks to Zachary Stone,a15-year-old student at Torbay Boys Grammar School who lives in Bovey Tracey and is undertaking his Duke of Edinburgh Bronze Award with Bovey Tracey Heritage Centre https://www.devonmuseums.net/Bovey-Tracey-Heritage-Centre/Devon-Museums/  for contributing this blog. Zachary used a combination of heritage and conservation sources following a visit he made to Yarner Wood with his Dad where they were joined by Albert Knott, Reserve Manager, Dartmoor NNRs to write this article.