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Vegetation of 'hard' rock sea cliffs
'Hard' rock cliffs made of older resistant rocks tend to have stable, if thin,
soils on sloping cliffs, ledges and crevices. The nature of the vegetation is
determined by the degree of exposure to salt spray and the chemical composition
of the underlying rock type. Cliffs exposed to oceanic swell, onshore winds
and storms have a maritime vegetation dominated by salt tolerant plants, some
more typically found in saltmarshes. As the influence of sea spray diminishes
progressively more inland types of vegetation occur. Exposed slopes out of reach
of the direct influence of sea water and salt spray, support acid grassland
and heath on acid rocks and calcareous grasslands on chalk and other limestones
(such as at Flamborough head, see open State
1 cliffs). On the least exposed cliffs a variety of scrub and woodland
communities may develop naturally.
On inaccessible slopes exposure to wind, rain and salt spray help to keep the
vegetation low-growing, providing the best opportunities for the colonisation
and survival of the natural communities which occur there, including MC 1-5
and 8 and 9. Most of the NVC
Maritime Cliff (MC) vegetation types identified in the (Rodwell
2000) are found within this 'hard' rock habitat type. A summary of the
representation of the main plant communities in relation to exposure and accessibility
is given below:
| NVC |
Habitat |
Grazing
|
Location in Great Britain |
| MC1 |
Rock-crevice (exposed) |
Inaccessible
|
South & west |
| MC2 |
Rock-crevice (exposed) |
Inaccessible
|
North & west |
| MC3 |
Cliff-ledge (exposed) |
Inaccessible
|
North & north west |
| MC4 |
Cliff-ledge, partly eroding (sheltered/rare) |
Inaccessible
|
South |
| MC5 |
Shallow well-drained soils (exposed) |
Inaccessible
|
West |
| MC8 |
Deeper soils (exposed) |
Mostly Inaccessible
|
Mostly west & north |
| MC9 |
Deeper soils (partly sheltered) |
Accessible some grazing
|
West, north & north east |
| MC10 |
Deeper soils (sheltered, acid soils) |
Accessible sheep grazed
|
Mostly north, some west |
| MC11 |
Deeper soils (sheltered, calcareous soils) |
Accessible occasionally grazed
|
Scattered south & west |
| H 7 |
Base-poor soils (less exposed maritime) |
Accessible occasionally grazed |
Round most of GB |
| MC12 |
Deep soils (sheltered, non-calcareous) |
Inaccessible |
Scattered west |
Comment: The implication for nesting seabird colonies is not considered
in this guide and the seabird communities on maritime cliffs (MC 6 & 7)
have been excluded from the table above. On steep slopes and ledges the build
up of vegetation can, however, reduce the availability of nesting sites. Management
of these areas is difficult as they are inaccessible to most human interference,
except a few rock climbers.
References
Rodwell, J.S.
2000.
British Plant Communities. Volume 5 Maritime Communities and Vegetation of Open Habitats. Cambridge University Press, Cambridge, 512 pp.
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