Woodland Management - Honing the Technique

ManagementScience

15 Dec

Woodland restoration is an evolving technique based on both science and what is known about the local conditions in each individual wood. The Bovey Valley Woods are a good case in point as they are varied in their species makeup and located on Dartmoor, where steep ground and high humidity are typical.

Continuous Cover Forestry is a form of ecological forest management, where the character of the woodland is gradually changed from one where planted conifers dominate the landscape, to one that has a more semi-natural appearance. This is managed as a gradual process, where the conifer canopy is opened up to increase the sunlight that reaches the lower levels of vegetation. In theory, the increased sunlight will prompt an understorey of more natural woodland trees to develop, and it takes time. One of the difficulties with this method is the browsing by deer which can hit the regenerating woodland; new shoots are often nipped off before they are knee-high.

Map showing the corner posts of six new ‘exclosures’ in Hisley and Houndtor Woods

For several years, the Woodland Trust sites along the Bovey Valley at Houndtor, Hisley and Pullabrook Woods have been used as an outdoor laboratory to test different methods of allowing woodland regeneration to be undisturbed by browsing deer.

Small, fenced exclusion areas have been constructed around the valley to test the success of tree regrowth in differing conditions, with varying results. As this method is improved and honed, the experiment is ongoing and recently, a new set of ‘exclosures’ has been built to a higher specification. At six locations in Hisley and Houndtor Woods, these semi-permanent fences with chestnut posts will stand for many years.

Exclosure No.1 - near Houndtor Bridge

This ‘exclosure’ stands under a crop of well thinned and spaced Douglas fir and expands an area that was previously contained within a temporary fence. Regeneration of native shrubs been successful here, so the larger protected area should give the restoration a good boost. In a few years’ time this area should demonstrate how a conifer canopy can stand over a native broadleaved shrub layer and provide a good balance of sustainable timber and wildlife habitat.

An open woodland structure will encourage new growth at exclosure No.1

Exclosure No.2 - in Houndtor Wood

A little further up the hill, another ‘exclosure’ stands where some hazel and other shrubs are growing well in the sunlight levels that have improved after a few cycles of Douglas fir thinning. Here, the fenced area has been expanded where the regeneration has a good chance of doing well.

Once the gate is finished, exclosure No.2 will prevent wild woodland flora from being disturbed

Exclosure No.3 - at the top of Houndtor Wood

Adjacent to the earthwork remnants of the small Iron Age fort on Houndtor ridge, another ‘exclosure’ has been built in a small forest clearing. Another method of CCF being trialled is the creation of small clearings or glades where semi natural woodland can regain a foothold in patches around the valley. This method was considered suitable in the proximity to an important heritage feature and where the overall visual impact of the valley can be improved.

The difference in regrowth inside and outside the fence will become apparent at No.3

Exclosure No.4 – high in Hisley Wood near Lustleigh Cleave

Hisley Wood is a mixed woodland with some interesting habitats and biodiversity. In recent years, the larch trees that were planted there several decades ago are being thinned out in small clusters to maintain the gradual transition to a more semi natural composition. An exclosure has been built here in one of the glades. This one is likely to be planted with flowering and fruiting woodland plants with the aim of providing a wildlife hotspot and refuge that will expand naturally over time.

Tree planting will suppress bracken growth and provide a wildlife hotspot at No.4

Exclosure No.5 - in the middle of Hisley Wood

Adjacent to the remains of the Boveycombe ancient farmstead, a glade has been created by felling larch and coppicing some hazel. As the vegetation regenerates here, it will provide a suitable site for wildflowers and invertebrates, improving the patchwork of habitats throughout the woods. The difference in the regrowth inside and outside the fenced area will be interesting to observe here. Vegetation surveys will provide an accurate picture of how the habitat is restoring itself.

No.5 Woodland glades will provide a diverse structure of plant growth

Exclosure No.6 – in lower Hisley Wood

On the slope just above Hisley Bridge, an ongoing thinning programme is underway. For the last five years, small strips have been felled from the edges of a block of plantation larch. The regeneration of the shrub layer here is showing some good results but the regrowth of hazel coppice is still under threat from deer browsing. This fenced area will reveal an interesting difference in the growth rate and botanical mix of vegetation in the absence of deer.

Regrowth of hazel coppice will benefit from fence No.6

Unfenced areas

There are many areas around Hisley Wood where conifers have been felled but there are no fenced ‘exclosures’. The regeneration here may be affected by browsing as the new shoots appear. In the true sense of a scientific experiment, these areas will be treated as ‘control’ plots. Vegetation will regrow here, but it is likely to be different in terms of its composition. In other words, it may look more like a woodland glade or meadow for some time which may help to create a diverse habitat patchwork. The outcome of this restoration project is not certain but, what we do know is, an interesting blend of trees and other woodland plants will grow to give many important woodland wildlife species a better chance of survival in challenging times.