Many dune systems, including Holkham NNR, Newborough Warren, and Ainsdale NNR have substantial areas of conifer plantation. These were planted originally to stabilise the dunes, but are now mainly also managed for timber production. Not only do these plantations represent a loss in terms of area of duneland, but mature trees can cause problems by seeding into adjacent areas of open duneland and slack. Corsican Pine, for example, does not usually produce a heavy cone crop until it is 25-30 years old, but once this stage is reached, prolific regeneration can occur.
At Ainsdale, woods of Austrian pine (Pinus nigra), maritime pine (Pinus pinaster), Scots pine (Pinus sylvestris) and beach pine (Pinus contorta) surround many of the interesting slacks. These shelter the slacks, and provide a seed source, which together cause rapid invasion of the slacks. An approach to the problem suggested by Rothwell (in Doody, 1985) includes:
- removal of main seeding trees surrounding the slack
- removal of seedlings and saplings from the slacks by either spraying, cutting or pulling, or by scraping the vegetation off using a low ground-pressure bulldozer.
Although removal of seed trees will reduce the spread, continual management is likely to be needed to keep areas clear. In some cases, removal of seed source may be impossible, so removal of seedling invaders is the only solution.
Total clearance of forest is a major operation, as all stumps have to be removed before they rot and increase the nutrient status of the soil. The accumulated leaf litter will have caused the top layer of soil to become acidified, thus removal of this layer may also be necessary. When planning felling operations, keep the following points in mind:
- The amount of felling and thinning which a given site can tolerate must be found by experimentation. When in doubt, it is best to underthin. Overthinning opens up the area to wind erosion and leaves the remaining trees subject to wind-throw.
- At all stages, the seaward edge of the plantation must present an oblique face to the wind. If it runs at right angles to storm winds, the front rows of trees are very liable to undermining and wind-throw. You should also thin so that the seaward face is not uniformly dense, otherwise you will create a too-solid barrier against which the wind can push.
- When thinning and felling, avoid creating paths aligned with dominant winds. Even in the centre of an afforested area these are subject to wind-throw. The same applies to regularly mown firebreaks within the plantation.
- Build as few fires as possible to dispose of trimmings.
- ‘Landscaping’ may also be needed, to recreate dunes and slacks within the cleared areas, with the aim of ‘remobilising’ the dunes.
Besides the slacks within the forest. other areas which may develop their own ecological value are the rides and firebreaks. For example, in the forest at Newborough, the firebreaks support an interesting plant community including unusual winter-flowering annuals. Rotovation should therefore be done before the main period of autumn germination.
The need for any removal of woodland should be publicised locally, especially where public access is allowed, as any removal of trees is likely to cause adverse public reaction.
Instead of clear-felling, another approach is to slowly diversify conifer woods by planting species such as oak, birch, willow, alder and holly. This maintains the shelter and landscape feature of the woodland, while making it ecologically more interesting.
