What is ‘special’ about Mariandyrys SSSI?

Mariandyrys has 3 special features.

As well as the features listed above, Mariandyrys has other habitats and earth science features that contribute to the special interest. These include gorse scrub and limestone pavement (flat blocks of limestone dissected by natural cracks). This diversity of habitats supports a wide range of species and these too are a key component of the special interest of the site, including various flowering plants such as pale flax, columbine, mountain everlasting, autumn lady’s tresses and fragrant orchid, uncommon insects, for example Ashworth’s rustic moth, and a range of butterfly species including Grayling. Unless it is specified below, management of this site should aim to look after these habitats and species as well as the listed features of interest.

What do we want Mariandyrys to look like?

The site should support a mixture of limestone grassland, heathland and scrub habitats. Heathland, dominated by small growing shrubs, should cover the majority of the site. The areas of limestone grassland should be maintained at their current extent and kept free of trees or shrubs. Scrub woodland, a mixture of gorse, birch, ash and oak, should cover remaining areas. These areas are good for nesting birds as well as giving shelter for invertebrates and livestock. The limestone grassland should cover approximately 2ha of the site and include lime tolerant plants such as spring cinquefoil, common rockrose and wild thyme. Heathland should cover approximately 3ha of the site and be characterised by a mixture of acid loving plants including heather, bell heather and western gorse along with lime tolerant species such as common rockrose and salad burnet. These heathland species should have a varied structure of older and younger plants, with some bare ground (approximately 5%) in between. Scrub should comprise European gorse, elder, hawthorn, blackthorn, ash, sessile oak, sycamore and bramble and should not exceed 30% of the site. Limestone pavement should be kept free of scrub to enable its distinctive structure to be visible and to develop its characteristic flora.

What management is needed on Mariandyrys SSSI and why?

Although Mariandyrys is an excellent place for wildlife/geology it will only remain so if the necessary management continues. CCW’s aim is to work with you to ensure that this management is carried out.

What does this mean in practice?

There are many factors that could damage the special features at Mariandyrys if they are not properly managed. These are the ones we regard as most important:

Fertility: Low soil fertility enables the limestone grassland plants and the heathers and western gorse to compete with the more aggressive “agricultural” grasses. There should be no application of fertiliser, slurry or farmyard manure. Livestock should not be given silage, supplementary feeds or hay on site, except at agreed “sacrificial” locations.

Grazing: Light grazing removes excess herbage and encourages the development and maintenance of a low growing heath. Heavy autumn grazing destroys heather. However when areas have recently been cleared of scrub heavy grazing is often necessary to stem vigorous gorse re-growth. Grazing should continue at a stocking level of about 0.7-0.9LSU/ha (1horse/ha) throughout the year. The nature of boundary fencing dictates that only cattle or ponies can be grazed on the common. They are less selective than sheep enabling more plants to flower and set seed, whilst breaking up dense clumps of gorse. They also produce minor poaching of the ground enabling seedlings to establish. Gazing should be maintained on the rest of the site using sheep if necessary.

Burning: Burning rejuvenates heather and gorse and can help reduce soil fertility. Wildfires can cause serious damage to invertebrates, reptiles, mosses and lichens. A rotation of controlled small patch burning during the winter should be used where appropriate to enable grazing. Fire-breaks should be established to prevent the spread of wildfires.

Cutting / Mowing: Cutting or mowing of heathland can open up dense dwarf-shrub vegetation but should be followed with grazing. Mowing / cutting us a recommended alternative to burning where western gorse dominance is a problem. Cutting is often used in the first instance to provide firebreaks. Cuttings must be removed from the site.

Scrub and bracken control: In the past scrub and bracken were controlled by stock grazing, trampling, cutting and the collection of firewood. Mechanical scrub control may be required today but should be accompanied by grazing. For areas inaccessible to machinery, hand cutting of scrub is the only option. It is then possible to treat the stumps with herbicide to prevent re-growth.

Trampling by heavy animals during the growth phase helps to control bracken. Cattle or ponies should graze such areas of the site in early summer.

Invasive species: Turkey oak, montbretia and other garden escapes not naturally found in this area, which threaten to spread at the expense of native species, should be removed where possible.

Understanding of the site: The part of the site managed as a nature reserve is open to the public and used for dog walking. It is important that neighbours and visitors are made aware of what makes the site special.


Our knowledge of wildlife is far from complete. It is possible that new features of value may appear and new management issues may arise in the future, whilst other issues may disappear. This statement is written with the best information we have now, but may have to change in the future as our understanding improves. Any information you can provide on the wildlife of your site, its management and its conservation would be much appreciated.

If you would like to discuss any aspect of your SSSI, or have any concerns about your SSSI, please contact your local CCW office.

Your local office is;

Cyngor Cefn Gwlad Cymru/Countryside Council for Wales

Llys y Bont,

Ffordd y Parc,

Parc Menai,


Gwynedd, LL57 4BN,

Telephone: 01248 672500

Fax: 01248 679259