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Allolee to Walltown is the name given to a
Site of Special Scientific Interest
A Site of Special Scientific Interest (SSSI) in Great Britain or an Area of Special Scientific Interest (ASSI) in the Isle of Man and Northern Ireland is a conservation designation denoting a protected area in the United Kingdom and Isle of ...
(SSSI) in
Northumberland
Northumberland () is a county in Northern England, one of two counties in England which border with Scotland. Notable landmarks in the county include Alnwick Castle, Bamburgh Castle, Hadrian's Wall and Hexham Abbey.
It is bordered by land on ...
, England. The site, which follows the path of a section of
Hadrian's Wall
Hadrian's Wall ( la, Vallum Aelium), also known as the Roman Wall, Picts' Wall, or ''Vallum Hadriani'' in Latin, is a former defensive fortification of the Roman province of Britannia, begun in AD 122 in the reign of the Emperor Hadrian. R ...
, is notable for an unusually wide range of grassland types growing on thin soil above the Whin Sill, a rock formation peculiar to the Northern Pennines.
Location and natural features
Allolee to Walltown is situated in the north-east of England, some east-north-east of Greenhead and north-north-west of Haltwhistle. It is an east-west corridor of land straddling Hadrian's Wall for a distance of between
Milecastle 45
Milecastle 45 (Walltown) was a milecastle on Hadrian's Wall ().
Description
Milecastle 45 is located on the top of Walltown Crags.Turret 43B in the east, just short of the fort of
Aesica
Aesica (with the modern name of Great Chesters) was a Roman fort, one and a half miles north of the small town of Haltwhistle in Northumberland, England.
It was the ninth fort on Hadrian's Wall, between Vercovicium (Housesteads) to the east and ...
(Great Chesters). Milecastle 44 (Allolee) is found at approximately the middle point of the east-west SSSI site.
The site is situated on the Whin Sill,
igneous
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or ...
rock
dolerite
Diabase (), also called dolerite () or microgabbro,
is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine-grained ...
found in
County Durham
County Durham ( ), officially simply Durham,UK General Acts 1997 c. 23Lieutenancies Act 1997 Schedule 1(3). From legislation.gov.uk, retrieved 6 April 2022. is a ceremonial county in North East England.North East Assembly â€About North East E ...
and Northumberland, which outcrops as high, rocky cliff lines, and which was used by the builders of Hadrian's Wall to full strategic advantage. The particular rock of the Winn Sill gives rise to conditions less acidic than comparable types, and the overlying soil is thin and
peat
Peat (), also known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem covers and is the most efficien ...
y; it provides a habitat for glasses than tolerate dry conditions, notably wild chives (''
Allium schoenoprasum
Chives, scientific name ''Allium schoenoprasum'', is a species of flowering plant in the family Amaryllidaceae that produces edible leaves and flowers. Their close relatives include the common onions, garlic, shallot, leek, scallion, and ...
''), rare in Northumberland other than on the Whin Sill.
Vegetation
Besides wilc chives, the thin soil of the site supports biting stonecrop ('' Sedum acre''), hairy stonecrop ('' S. villosum''), wild thyme (''
Thymus praecox
''Thymus praecox'' is a species of thyme. A common name is mother of thyme, but "creeping thyme" and "wild thyme" may be used where ''Thymus serpyllum'', which also shares these names, is not found. It is native to central, southern, and western ...
''), parsley piert (''
Aphanes arvensis
''Alchemilla arvensis'' (syn. ''Aphanes arvensis''), known as parsley-piert, is a sprawling, downy plant common all over the British Isles where It grows on arable fields and bare wastelands, particularly in dry sites. The short-stalked leaves h ...
''), common whitlow-grass (''
Erophila verna
''Draba verna'' ( syn. ''Erophila verna'') the spring draba, shadflower, nailwort, common whitlowgrass, vernal whitlow grass, early witlow grass or whitlow-grass is a species of plant in the mustard family, Brassicaceae. ''D. verna'' has the uniq ...
''), early hair-grass (''
Aira praecox
''Aira praecox'' is a species of grass known by several common names, including early hair-grass, yellow hairgrass and spike hairgrass. It is native to Europe, where it is found in dry, sandy places, on rocky outcrops, and in heath grassland. It ...
Saxifraga tridactylites
''Saxifraga tridactylites'', the rue-leaved saxifrage or " nailwort", is a species of plant in the family Saxifragaceae
Saxifragaceae is a family of herbaceous perennial flowering plants, within the core eudicot order Saxifragales. The tax ...
'') and long-stalked cranesbill ('' Geranium columbinum'').
Grassland surrounding drier areas is composed of red fescue ('' Festuca rubra''), common bent (''
Agrostis capillaris
''Agrostis capillaris'', the common bent, colonial bent, or browntop, is a rhizomatous and stoloniferous perennial in the grass family (Poaceae). It is native to Eurasia and has been widely introduced in many parts of the world. Colonial ben ...
''), sweet vernal-grass (''
Anthoxanthum odoratum
''Anthoxanthum odoratum'', known as sweet vernal grass, is a short-lived perennial grass that is native to acidic grassland in Eurasia and northern Africa. It is grown as a lawn grass and a house plant, due to its sweet scent, and can also be f ...
Danthonia decumbens
''Danthonia decumbens'' (formerly ''Sieglingia decumbens'') is a species of grass commonly known as the heath grass, heath-grass, or staggers grass It is a tussock grass native to Europe and adjacent parts of Asia and North Africa. It may also be ...
''). Crags and north-facing scarp slopes support bilberry (''
Vaccinium myrtillus
''Vaccinium myrtillus'' or European blueberry is a holarctic species of shrub with edible fruit of blue color, known by the common names bilberry, blaeberry, wimberry, and whortleberry. It is more precisely called common bilberry or blue whortle ...
'') and heather (''
Calluna vulgaris
''Calluna vulgaris'', common heather, ling, or simply heather, is the sole species in the genus ''Calluna'' in the flowering plant family Ericaceae. It is a low-growing evergreen shrub growing to tall, or rarely to and taller, and is found wid ...
Cryptogramma crispa
''Cryptogramma crispa'', the parsley fern, is an Arctic–alpine species of fern. It produces separate sterile and fertile fronds, up to tall, and is a pioneer species on acidic screes.
Description
The fronds of ''C. crispa'' are long ...
''). Green spleenwort (''
Asplenium viride
''Asplenium viride'' is a species of fern known as the green spleenwort because of its green stipes and rachides. This feature easily distinguishes it from the very similar-looking maidenhair spleenwort, ''Asplenium trichomanes''.
Taxonomy
Gr ...
'') is found on
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
outcrops.
More
calcareous
Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.
In zoology
''Calcareous'' is used as an adje ...
areas support a herb-rich grassland with meadow oat-grass ('' Avenula pratensis''), quaking grass ('' Briza media''), dyer's greenweed (''
Genista tinctoria
''Genista tinctoria'', the dyer's greenweed or dyer's broom, is a species of flowering plant in the family Fabaceae. Its other common names include dyer's whin, waxen woad and waxen wood. The Latin specific epithet ''tinctoria'' means "used as a ...
Sanguisorba officinalis
''Sanguisorba officinalis'', commonly known as great burnet, is a plant in the family Rosaceae, subfamily Rosoideae. It is native throughout the cooler regions of the Northern Hemisphere in Europe, northern Asia, and northern North America.
It ...
'') and salad burnet ('' S. minor'').
On unit of the site, a dip slope east of Allolee has poor drainage, which supports a 'most unusual' species-rich grassland dominated by purple moor-grass (''
Molinia caerulea
''Molinia caerulea'', known by the common name purple moor-grass, is a species of grass that is native to Europe, west Asia, and north Africa. It grows in locations from the lowlands up to in the Alps. Like most grasses, it grows best in acid so ...
'') and having quaking grass, meadow oat-grass, spring
sedge
The Cyperaceae are a family of graminoid (grass-like), monocotyledonous flowering plants known as sedges. The family is large, with some 5,500 known species described in about 90 genera, the largest being the "true sedges" genus ''Carex'' wit ...
(''
Carex caryophyllea
''Carex caryophyllea'' is a species of plant in the family Cyperaceae first described by Marc Antoine Louis Claret de La Tourrette. Two varieties are listed in the World Checklist of Selected Plant Families
The World Checklist of Selected Pla ...
Galium verum
''Galium verum'' (lady's bedstraw or yellow bedstraw) is a herbaceous perennial plant of the family Rubiaceae. It is widespread across most of Europe, North Africa, and temperate Asia from Israel, Lebanon and Turkey to Japan and Kamchatka. It is ...
Succisa pratensis
''Succisa pratensis'', also known as devil's-bit or devil's-bit scabious, is a flowering plant in the honeysuckle family Caprifoliaceae. It differs from other similar species in that it has four-lobed flowers, whereas small scabious and field s ...