Lymm Dam Management
Management and preservation
When Warrington Borough Council began managing Lymm Dam in the early 1980s, the area was suffering considerable erosion problems. In the early 1980s the Ranger Service embarked on a programme of upgrading the existing path network. Properly constructed paths encourage people to use the same route through an area, allowing the path margins and surrounding area to recover. Path reconstruction is always based on existing informal routes and paths are surfaced with an aggregate material which is in keeping with the character of the site. Timber steps are constructed where slopes have to be negotiated. Again this helps to protect the vegetation on banks and also affords access to a wider cross section of visitors.
Woodland management at Lymm Dam is based on the following principles:
- Reflect and build upon the existing landscape character
- Ensure continuity of woodland canopy
- Maintain and enhance ecological value
- Increase age and structural diversity
- Control invasives and promote development of native species
- Maintain overall character of woodland
- Maintain a safe and enjoyable public amenity
Selective thinning of canopy species helps to promote development of the best specimens into maturity. Removal of invasive trees helps to stop the spread of non-native species which have poor associated wildlife value. Sycamore, for example, is a vigorously competitive tree which if not kept in check, can dominate woodland and compromise its ecological potential.
Below the canopy, some areas of the understorey are subject to a coppice regime (mainly species such as holly, hawthorn, hazel and blackthorn). Coppicing is an ancient woodland management technique which involves shrubs being cut back to ground level on a cyclical basis (usually every seven years). In the past this was done commercially (with hazel) to provide straight wooden poles for a variety of uses. However coppicing also prolongs the life of the tree and has many associated ecological benefits. As the coppice re-grows, it benefits a range of flora and fauna.
All tree-thinning operations increase the level of light reaching the woodland below. This aids the development of younger and understorey trees and also helps the woodland wildflowers to flourish.
Where appropriate the trunks of trees to be removed are 'ringbarked' and left as a standing pole rather than felled from ground level. Ring barking causes the timber to die and decay which attracts a range of invertebrates, making the standing trunk very attractive to birds such as treecreeper, nuthatch and woodpecker. Much of the timber produced by felling operations is kept on site in log or brash piles - which have their own role in the woodland ecosystem - providing cover, nesting and feeding opportunities. Cornflower and corn marigold, typical of the 'agricultural weeds' which were once a common sight on Britain's unimproved pasture
Meadow areas at Lymm Dam, in common with most of the UK's grassland are 'improved'. This means that at some stage, man has altered them for amenity, agricultural or aesthetic reasons. The areas on the opposite side of the lake were managed as part of the former Beechwood Estate, and those on this side were once in agricultural use. Unfortunately, many of Britain's variety of herbaceous plants and meadow wildflowers flourish in 'unimproved' grassland. Grassland which has been 'improved' results in nutrient-rich soils preferred by vigorous plants such as nettle and hogweed, which then dominate to the exclusion of a greater variety of plants which flourish on 'poorer' soil.
For several years, all the meadow areas were mown once a fortnight. Since the late 1980s however, the mowing patterns have been altered to promote and preserve the ecological variety of the meadows. The meadows on this side of the lake are mown once or twice a year allowing wildflowers to grow. Mowing takes place at specific times in order to prevent the more vigorous species from setting their seed. Cuttings are removed in order to prevent them rotting down and increasing the nutrient level. On the other side of the lake, the meadows tend to be used as an amenity, so they are mown more often.
Where possible however, unmown 'buffer zones' are left around woodland. An added benefit of leaving grass unmown is that it increases the habitat value of a meadow, particularly in terms of the size and variety of the invertebrate population. A revetment helps to stabilise the bank and steps prevent it from being eroded as people climb it Hazel immediately after coppicing and after two years of regrowth.