DUNNET BAY S.S.S.I. - HISTORICAL AND
CURRENT LAND USE AND VEGETATION
Initially 366 hectares of land were to be planted by the Forestry Commission at Dunnet Bay, but after initial planting proved a commercial failure, most of this land was sold back to the original owners. The land included within the S.S.S.I. boundary is separated into eight areas by ownership and this has played an important part in present day ecology, since different management regimes appear to have modified vegetation types.
The dune ridge and land on the seaward side of the county road, apart from the two extreme ends, was purchased by the Highland Regional Council with the intention of developing the area for recreational purposes, car parks, toilet facilities and a caravan site were provided. In the past increased erosion of the dunes was due to grazing by farm animals and large numbers of rabbits, nowadays recreational use is creating similar problems. Tracks through the dunes, damage to the dune fronts by visitors, all-terrain motor-bikes, fires and removal of sand from the dune face all damage the fragile soil and plant network which hold the sand in place.
Vegetation in this area falls into three main types; strand-line vegetation and areas of bare sand on the dune fronts and in blow-outs, the areas of fixed dune with skeletal soil and the flat areas on the leeward side of the dunes next to the road.
Strand-line/fore-dune vegetation is dominated by marram grass although the covering is not continuous and areas of bare sand are visible between tussocks. Other pioneer perennials able to withstand winter storms are Lyme Grass, Sand Twitch and Sea Sandwort. Typical strand-line, salt-tolerating annuals and biennials are Sea Rocket, Atriplex species and Sea Mayweed.
The fixed dunes are still dominated by Marram Grass, but with patches that are species rich. There is also variation between areas of tall and low growing species. Taller plants include Angelica, Meadowsweet, Scottish Lovage, Hogweed and Ragwort while the more open areas have coverings of Coltsfoot, Wild Pansy, Self-heal, Kidney Vetch, Eyebright and Lady's Bedstraw among others.
Ground on the leesward side of the dune ridge and up to the road
would have been continuous with the ground on the opposite side of the road at one time and shares the same soil types with the Links area i.e. brown calcareous soil, calcareous ground-water gley and an inter-mix of the two. This area gives an indication of the effects of zero grazing on these soil types. Marram is again dominant and growing very robustly with other fairly tall species in between - Angelica, Meadowsweet, Tufted vetch, Yorkshire Fog, Ragwort, Sedge species and Yarrow. In damper areas tall growth is not as vigorous and Creeping Willow, Sand Sedge and Equisetum species can be found.
Apart from the forest and the land immediately behind it, the Links divide into three areas by ownership, The Links of Old Tain, The Links of Greenland and between them on the south-east a walled-off section belonging to West Greenland.
The Links of Old Tain are used for grazing cattle only, there have been no sheep for 15 years. No fertilizer has been applied to the area during the present ownership of 40 years. Vegetation of this area is described (Mitchell 1984) as species-poor grassland dominated by Creeping Fescue with marram locally dominant. There are occasional herb-rich patches and wet flushes. Some areas are very heavily grazed forming a short species-poor turf and some plants indicating over-grazing have been noted. (Tilbrook 1984), Spear Thistle, Ragwort and Cocksfoot.
The land belonging to West Greenland has been used for cattle only during the past 21 years. Before a management agreement was reached with the Nature Conservancy Council, high nitrogen fertiliser was applied. During the summer 100 cows plus their calves graze the area and, due to the sandy nature of the soil and consequent dryness some over-winter there too. Again, the vegetation on the bulk of this area is similar to the Links of Old Tain with Ragwort and Thistles being a problem,.
On both these pieces of land, towards the Burn of Midsands are damper areas exhibiting a dune slack vegetation with Common Sedge, Baltic Rush and Creeping Willow.
The Links of Greenland have been sub-divided by wire fencing and attempts to re-seed some fields have been made. This has involved the introduction of agricultural species such as rye grass and the application of fertiliser. A mix of sheep, cattle and rabbits graze the whole of this area.
Four vegetational types occur in this area. The first, found on drier ground, has extensive areas of fine sparse turf with Baltic Rush, Sedges, Creeping Willow and abundant mosses and a fair amount of bare disturbed ground. Occasionally Rue-leaved Saxifrage and the rare Tortella fragilis mosses are found.
The second type is a Marram/Fescue grassland with good moss cover. Hummocks of the first type of vegetation exist alongside dune slack areas with Creeping Willow and Baltic Rush.
The third type corresponds to an area of uninterrupted brown calcareous soil on the edge of Sandy Burn, an area of deep sand and good drainage which promotes the growth of a drier dune grassland community with Mouse-ear Hawkweed, abundant lichen cover and areas of species rich Creeping Fescue turf containing Grass of Parnassus, Creeping Willow, Crowberry, Scottish Primrose, Mountain Everlasting, Wild Pansy, Eyebright species, Ribwort Plantain, Autumn Felwort, Wild Thyme, Bird's-foot Trefoil, Lady's Bedstraw plus others.
The fourth area consists of partially improved grassland with some areas still rich in Scottish Primrose and Dactylorluza hybrids and drier knolls supporting Moonwort.
Along the Burn of Midsands and its tributaries areas of fen and marsh exist. The tall fen contains such species as Iris, Meadowsweet, Water-mint, Branched Bur-reed and Tufted Hair Grass.
Underlying the whole of the links area discussed so far are the same soil types, yet there are obvious differences in species richness between the main sections. The Links of Old Tain are adjacent to the dunes therefore distance from the shore and a possible diminishing supply of sand does not appear to be a major factor in this change. At present then it seems that the grazing regime plays an important part in controlling species diversity with mixed stocking i.e. sheep and cattle, with a contribution by rabbits, producing the most varied flora.
The forest area is now very disturbed due to ditching, ploughing and planting. In some parts buried peat has been brought to the surface and other factors such as reduced grazing, increased shelter and reduced light in thicker areas will all alter vegetation.
Open areas within the trees, particularly near the road, still retain Links vegetation with Scottish Primrose, Fairy Flax, Mountain Everlasting, Kidney Vetch and Harebell, and there are some areas of marsh and flush vegetation, but generally deeper into the forest there are fewer herb-rich clearings. There is some grazing by rabbits and moderate trampling by walkers help to keep vegetation low in some parts encouraging Links vegetation.
Immediately behind the forest is a square of land grazed by cattle and sheep. In this area the Links soil is being modified by podzolisation. Here the vegetation is predominantly a Calluna dwarf-shrub heath interspersed with Fescue and Purple Moor-grass grassland. The wetter areas have Creeping Willow, Grass of Parnassus, Devil's-bit Scabious and Cross-leaved Heath. While the drier areas have Crowberry, Bell-heather, Mountain Everlasting and Scottish Primrose. This land exhibits elements from both the calcareous Links area and the surrounding acid peatlands.
It can be seen that the attractive species diversity of the vegetation at Dunnet cannot be assumed to maintain itself unaided. Zero grazing is as harmful to the lowgrowing herbs as is ploughing and re-seeding and from current evidence alterations in the species of grazing animals can also have a detrimental effect.
|This article first appeared in the Caithness Field Club Bulletin|