When you start to think of what makes a good wood for conservation, ancient woodland (continuous woodland since 1600), native trees, and perhaps oak and all its insect species are things that may come to kind. But woodland structure is equally important and sometimes under-valued. I think this is especially so when thinking of commercial forestry and conifer woodlands. There the picture often painted is dense even-aged stands, with little light and poor wildlife habitat. This is indeed true in many, but not all cases; though typical of upland conifers, there are many more examples of diverse woodland structure in lowland conifer plantations.
A woodland which supports a wide range and quantity of invertebrates will in turn attract birds and mammals. Even better if the woodland also produces fruit and seeds and provides cover for nesting or hibernating. In conservation circles this is exemplified with the traditional woodland management of coppice with standards. In the south west pure stands of oak coppice are more common, but in other parts of the country many woods were managed with a long rotation of oak trees, with a maximum canopy cover of about 50%, and a dense understorey, most commonly hazel, managed on a much shorter rotation of between seven and fifteen years. Cut trees, or stools, regenerated freely, and in the first couple of years conditions are particularly good for wild flowers and butterflies. Young bushes then make excellent habitat for nesting birds, while the old mature standards remain for insects, bats and all sorts. A system designed to provide timber for construction, and hazel poles for hurdles, wattle buildings, thatching spars, or just firewood, was accidentally a fantastic wildlife habitat. Many nature reserves today have reinstated previous abandoned coppice cycles for that reason. Bradfield Woods (Suffolk Wildlife Trust), is one of the best known examples, and a site where coppicing never died out. Sweet Chestnut coppicing in the south east is not as widespread as it once was, but still supports a healthy commercial industry.
Coppice with standards (Hillcombe, Dorset). From Geograph Link
Continuous cover forestry is also, however, possible in commercial conifer woods. One well known example local to the south west is the Bradford Hutt system, developed and implemented on the Tavistock Woodlands Estate. The 6th Earl of Bradford (he comes from Shropshire, though this woodland experiment has been in Devon!) was primarily concerned about soil erosion, and worked with his forester, Phillip Hutt, to develop a system of continuous cover, that was based on a very organised and regimented system of coupes. The idea was based around plots of nine trees, arranged in nine blocks, with a thinning and felling regime every six years. Working around each small plot in turn gave an overall cycle of 54 years. So in a small area of 18 metres squared you can find trees of all ages from up to 54 years (see diagram).
The first thing to say about the system is it works! Management costs are a bit higher, but early thinning means that the woodland tends to produce a higher proportion of quality timber and lower volumes of low value thinnings. The resulting woodland structure is both diverse and contains quite a few broadleaves in amongst the understorey. It dies achieve the original aim of much reduced soil erosion, and with no major clear felling it is also a system that is kind to the landscape.
There are of course challenges, with trees having to establish in more shady conditions than in an open system. This has limited some species choices, and there is more Western Hemlock than most would like. On the other hand, Douglas Fir, one of the most valuable softwoods, also does very well, and in some places the Plan is being overtaken by a more informal mix with prolific natural regeneration. That led for some fun once on a planting job we did back in the late eighties……
Natural regeneration is a further benefit of continuous cover; if conditions are right for it, the woodland owner benefits from very low planting costs – an occasional re-spacing can be all that is needed. If you have an accountant, that will keep him (or her) happy, because commercial returns are often calculated using net discounted revenue. Now I’m straying out of my comfort zone, but that involves measuring returns against the initial investment, and adding in a percentage for the tied up capital needed for the initial planting.
The Forestry Commission in the south west have worked hard to promote a system of continuous cover in many of their woodlands. The photograph below was taken in Cardinham Woods, near Bodmin. Most of the woods are a plantation on ancient woodland, and thus the target for conversion back to native broadleaves. But the woods are far from the caricature of a dense dark conifer wood, with amongst many other things a thriving dormouse population. Someone forgot to tell them that they are supposed to be in hazel coppice!
This leaves room for thought. The Government want the Forestry Commission to be more commercial, yet we are potentially removing income streams if these woods are converted back to broadleaves. How much do we value sustainable timber production over pure nature conservation? How does this link to jobs in the rural economy? And what sort of woodland management are we directly supporting if we have to increase our timber imports? I guess they are beginning to look like leading questions, for I think that we should embrace the ideas of continuous cover forestry, and get the some of the best of all worlds. The best way to protect a woodland in the long term is to have a sustainable and profitable management, with the sale or use of produce underpinning that management.
http://www.woodlandheritage.org/library/articles/item/216-coupe-de-grace-a-silvercultural-experiment-near-tavistock.html?tmpl=component&print=1 Reprint of Forestry and British Timber article about Bradford Hutt system.
http://www.forestry.gov.uk/fr/INFD-63CCQB Forestry Commission information page, with links to more technical publications