Table of Contents
1 Designation
Pteridium aquilinum - Galium saxatile grassland (U20) is Grade I SSSI,
- Candidate SAC,
- UK BAP Key Habitat status (1995).
- Identified in Annex 1 of the EC Habitats Directive as a priority habitat and will form part of the Natura 2000 Network.
Size:
- Pteridium aquilinum-Galium saxatile U20a (NVC)=29.7 ha.
- Dense bracken 1.8 ha.
2 Description
U20 Pteridium aquilinum-Galium saxatile, A low altitude type acid grassland with bracken as the sole dominant, which permits a sparse vernal contribution from low ground cover of associated flora before it casts its deep shade in mid-summer. A number of bryophytes may occur sometimes in local patches. Bracken is associated with important fauna of conservation interest. Bracken was a valuable resource traditionally, with uses for cuttings, including litter, soap making and composting for gardens.
3 Current condition and status of feature
- Extent U20a, Within LACs
- Extent Dense bracken, within LACs
- Frequency of constant and frequent species: within LACs.
- Species indicative of change, within LACs
- Succession to Scrub: Within LACs
Current Status:
- Favourable Maintained, as of December 2001. This assertion is based upon the 2000/2001 survey.
4 Attributes selected as performance indicators
The bracken and communities will be considered to be in favourable condition provided the following attributes are within LACs:
4.1 Extent
- Pteridium aquilinum-Galium saxatile grassland (U20a).
- Dense bracken may invade grassland and heath. The bracken front may advance into grassland/heath, which is undesirable.
4.2 Quality
Pteridium aquilinum-Galium saxatile grassland (U20a):
- Quality will be confirmed by presence of the range of typical species within the sub-community
5 Attributes and Operational Limits
5.1 Objective statement
To maintain the Pteridium aquilinum - Galium saxatile grassland community with its usual plants in favourable condition, and control an advancing front of dense Bracken WHERE,
5.2 Extent
Total area U20a community remains at the target level.
- Target level: 29.7 ha. of 323 ha
- Upper limit: 110% of year 2000 level.
- Lower limit: 70% of year 2000 level.
- An increase in U20a is permitted only at the expense of dense bracken.
- A decrease in U20a is permitted only if lost to bracken-scrub.
- Monitor: woody species.
Total area dense bracken remains at target level
- Target Level: There is no dense bracken
- Lower limit: 1O0% of year 2000 level.
- No increase in extent of dense bracken is permitted.
- Monitor/surveillance:
- Extent of U20a
- Extent of dense bracken
5.3 Quality
Target: U20a, The following conditions are met in 95% by extent
- Upper and lower limits: As stated in NVC floristic tables
- Monitor frequency of Pteridium aquilinum-Galium saxatile
A set of associated plants as indicators of change:
Upper limit: None Set
Lower Limits: 6 out of 7 species at 50% current frequency.
Monitor frequency of:
- Gallium saxatile, Potentilla erecta, Vaccinium myrtillus, Agrostis capillaris, Viola riviniana, Campanula rotundiflora, Veronica chamaedrys, V. officianalis.
6 Management Rationale and Projects
6.1 Mapping the Bracken
It is important to make a distinction between important bracken and scrub sites, and dense bracken colonising heathland and unimproved grassland, where control of invasion is required. (refer to Feature: Dense/Scattered scrub). Bracken on the northern slopes of the Gt. Orme has an understorey of violets, (food of heath fritillary butterfly), which indicates a former site of woodland. In the past, bracken habitats have been considered of low wildlife value, but this is not always the case.
Festuca ovina, a constant grass of the U20a community, is particularly susceptible to being shaded out; a decline in its prevalence indicates a stand of increasing density of bracken.
- Note presence and % cover of Festuca Ovina amongst bracken.
- Identify and map U20a area, dense bracken and invasive bracken on grassland.
- Cut the bracken front of U20a community twice annually.
6.2 Succession to woodland scrub
Bracken habitats are transitional in nature, and cessation of grazing and bracken cutting results in succession to woodland. On these hard northern limestones, scrub replaces fern-dominated communities in primary succession, developing into Fraxinus excelsius-Acer campestre-Mercurialis perennis woodland (W8). Annual cutting will remove this threat.
Large areas may be cut with tractor-mounted-swipe, 4-5 ha on difficult terrain per 8 hour day. A more rapid re-establishment of heath on cut rather than sprayed ground is attributed to disturbance of the litter layer. Cut late 1st week of July if once, when less nourishment has reached the roots.
- Cut U20a community once annually, 1st week of July, with tractor-mounted-swipe.
- Monitoring and Limits: refer to performance indicators; Extent.
6.3 Controlling the Bracken front
Bracken is rhizomous, and a prolific spore-producer, able to tolerate open sunlight and semi-shade, and thus able to spread.
It is possible that bracken stands have a limited life-span in a shifting mosaic, therefore the bracken front is where control of spread will be best targeted. Depletion by cutting and removal may take 10's of years or longer to achieve. Cutting once reduces biomass slowly, 20-30% in 7 years; cutting twice a year, mid June and late July, is more effective reducing biomass (to below 10% within 3 years and maintaining it at this level).
Goats may feed on young bracken, and so help in the control of bracken.
- Cut the bracken front twice annually with tractor-mounted-swipe.
- Monitoring and Limits: as for woodland scrub.
Restoring/protecting bracken invaded grasslands/heath:
- Refer to heathland and calcicolous conservation feature plans