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Management of Marshalls Heath
There have been two management plans for the site over the years. The first dates from 1969, but this was replaced by a much more comprehensive one, drawn up under the auspices of the Herts & Middx Wildlife Trust, which was adopted in 1993. The main points of this plan are summarised below. There has been some deterioration in the grassland and heathland habits over the past few years, with brambles, scrub and woodland extending across much of the important heath areas, and some critical species have been lost. It is hoped that this will be rectified with appropriate management in 2003 and 2004.
1993 Management Plan (now in force) - Summary of main points
As the name implies, heathland is one of the habitats represented on site, however, it is only remaining as a remnant, occupying just 8% of the total area. Heathland is typically the result of past exploitation and management practices on poor, usually acid, sandy or gravely soils.
The character of the acid grass heath habitat is steadily changing. These changes, resulting from a reduction in management pressure over a long period, will in time eliminate the heathland habitat and its associated species. Scrub in limited amounts is however an important component of the structural and habitat diversity of heathland. Secondary woodland has progressively spread across the site over the years.
In all, 1370 species of wildlife, including 290 species of plant, 23 species of mammal or reptile and 696 species of butterfly or moth have been recorded in recent years. 48 of these species are now on national lists of threatened species. (These values updated to 2003). This represents a considerable diversity of wildlife on such a small site.
The key issue is how to maintain the present area of heathland against the steady encroachment of woodland and thereby ensuring the present diversity of wildlife is retained.
Heathland is traditionally maintained by grazing and, at least in more recent times, by burning in some localities. Clearly the latter option is not viable at Marshalls Heath but grazing also presents many problems.
Mowing is the most practical management method in the short term. However, unlike the gradual removal of plant material under a grazing regime, creating a varied sward, mowing is a sudden, all or nothing approach, resulting in a uniform sward. The timing of mowing is also problematical. Whenever it is carried out it will affect some of the wildlife interest through the loss of the upper part of the plants and their associated invertebrates.
In summary, within the nature reserve it is suggested that 50% of the grassland to the west of the road should be mown every summer, in early to mid-July, with all of the area cut annually in September/October. To the east of the road 50% should be cut annually in September/October with the remaining half cut in the following year. Areas dominated by invasive species should be included in the summer cutting regime to try and control the spread.
Scrub removal and heathland restoration
It is important that scrub does not encroach further on to the grassland. Encroaching scrub should thus be cut each autumn as required. Stumps should be chemically treated to prevent re-growth.
Plans for 2003
The need for management this winter
The anthills provide a well-drained habitat favoured by the heathland plants that remain at this site, but many anthills are now disappearing and have become inactive beneath the undergrowth. Some of the bushes of ten years ago have grown into tall saplings that are presently shading out the smaller, rarer plants. They also scatter leaves over the heathland, and this increases its fertility, but the plants that grow there depend upon low soil fertility, so are dying out because the soil is too rich.
An urgent priority is the clearing of the brambles, rosebay willowherb, scrub and woodland that has invaded the heathland clearings where the prominent anthills are. It is recommended that saplings and small trees on the southern side of the main anthill areas be removed, so that the heathland clearings have more light. The grass should also be cut and the cuttings removed to keep the soil fertility low. In the longer term it is suggested that a balance of 40% acid grass heathland, 40% woodland and 20% scrub be maintained at this site. However, this ultimate aim should be carried out in gradual stages, and the wildlife monitored at each stage, to ensure that all threatened species are benefitting.
Suggested management plans for 2003
The map shows the southern part of Marshalls Heath, including all the areas where anthills are found. Different sections of the Heath are given numbers and letters: numbers 1 to 6 indicate areas that were still acid grass heath in 1992, whilst letters A to F designate areas that were acid grass heath until about 1970, but have since succumbed to scrub and woodland encroachment.
Map of Marshalls Heath
Updated 23 Feb 2003