Chalk heath
Encyclopedia
Chalk heath is a rare habitat, in the Temperate grasslands, savannas, and shrublands
biome
, formed of a paradoxical mixture of shallow-rooted calcifuge
("calcium-hating") and deeper-rooted calcicole
("calcium-loving") plants, growing on a thin layer of acid
ic soil over an alkali
ne substrate. Chalk heath is intermediate between two much more widespread habitats, chalk grassland
and heathland
.
or sand
) overlies a basic
(alkaline) one, such as chalk
. Shallow-root
ed plants grow only in the acidic soil (typically a few centimetres thick), and so these are species characteristic of acidic habitats. Deeper-rooted plants can reach the underlying alkaline substrate, and so these include species characteristic of alkaline habitats. Plants also occur which are able to tolerate both acidic and basic conditions. There are no plants restricted entirely to chalk heath, and the animals are also those characteristic of chalk grassland and heathland. The vegetation structure of chalk heath resembles grass heath, being short grassy vegetation with heather growing up through it, with some scattered heather bushes.
Chalk heath often occurs at the tops of slopes, at the thin margins of acidic deposits which often cap the flatter tops of chalk hills. It usually gives way to chalk grassland on lower slopes where these deposits have been eroded away, and often to heathland on the hilltops where the acidic deposits are thicker. Chalk heath tends to occur as narrow strips and scattered fragments, being limited to places where the conditions are exactly right for its development and survival.
Chalk heath is a grazing
habitat, created and maintained by livestock
(usually sheep and cattle
) and rabbit
s.
includes calcicoles such as salad burnet
(Sanguisorba minor), dropwort (Filipendula vulgaris) and common milkwort (Polygala vulgaris), and calcifuges such as bell heather (Erica cinerea
), ling heather (Calluna
vulgaris), heath grass (Danthonia decumbens
), sheep's sorrel (Rumex acetosella) and betony (Stachys officinalis
). It also includes plants which can tolerate both acidic and basic conditions, such as common bent (Agrostis capillaris
), wood sage (Teucrium scorodonia
) and sometimes juniper (Juniperus communis
).
ing, which mixes the thin layer of acidic soil with the chalk beneath.
Temperate grasslands, savannas, and shrublands
Temperate grasslands, savannas, and shrublands is a terrestrial biome whose predominant vegetation consists of grasses and/or shrubs. The climate is temperate and semi-arid to semi-humid....
biome
Biome
Biomes are climatically and geographically defined as similar climatic conditions on the Earth, such as communities of plants, animals, and soil organisms, and are often referred to as ecosystems. Some parts of the earth have more or less the same kind of abiotic and biotic factors spread over a...
, formed of a paradoxical mixture of shallow-rooted calcifuge
Calcifuge
A calcifuge is a plant that does not tolerate alkaline soil. The word is derived from the Latin 'to flee from chalk'. These plants are also described as ericaceous, as the prototypical calcifuge is the genus Erica...
("calcium-hating") and deeper-rooted calcicole
Calcicole
A calcicole or calciphyte is a plant that does not tolerate acidic soil. The word is derived from the Latin 'to dwell on chalk'. Under acidic conditions, aluminium becomes more soluble and phosphate-less. As a consequence, calcicoles grown on acidic soils often develop the symptoms of aluminium...
("calcium-loving") plants, growing on a thin layer of acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
ic soil over an alkali
Alkali
In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...
ne substrate. Chalk heath is intermediate between two much more widespread habitats, chalk grassland
Calcareous grassland
Calcareous grassland is an ecosystem associated with thin basic soil, such as that on chalk and limestone downland. Plants on calcareous grassland are typically short and hardy, and include grasses and herbs such as clover...
and heathland
Heath (habitat)
A heath or heathland is a dwarf-shrub habitat found on mainly low quality acidic soils, characterised by open, low growing woody vegetation, often dominated by plants of the Ericaceae. There are some clear differences between heath and moorland...
.
Ecology
Chalk heath occurs where a thin layer of acidic soil (often loessLoess
Loess is an aeolian sediment formed by the accumulation of wind-blown silt, typically in the 20–50 micrometre size range, twenty percent or less clay and the balance equal parts sand and silt that are loosely cemented by calcium carbonate...
or sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
) overlies a basic
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...
(alkaline) one, such as chalk
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....
. Shallow-root
Root
In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...
ed plants grow only in the acidic soil (typically a few centimetres thick), and so these are species characteristic of acidic habitats. Deeper-rooted plants can reach the underlying alkaline substrate, and so these include species characteristic of alkaline habitats. Plants also occur which are able to tolerate both acidic and basic conditions. There are no plants restricted entirely to chalk heath, and the animals are also those characteristic of chalk grassland and heathland. The vegetation structure of chalk heath resembles grass heath, being short grassy vegetation with heather growing up through it, with some scattered heather bushes.
Chalk heath often occurs at the tops of slopes, at the thin margins of acidic deposits which often cap the flatter tops of chalk hills. It usually gives way to chalk grassland on lower slopes where these deposits have been eroded away, and often to heathland on the hilltops where the acidic deposits are thicker. Chalk heath tends to occur as narrow strips and scattered fragments, being limited to places where the conditions are exactly right for its development and survival.
Chalk heath is a grazing
Grazing
Grazing generally describes a type of feeding, in which a herbivore feeds on plants , and also on other multicellular autotrophs...
habitat, created and maintained by livestock
Livestock
Livestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...
(usually sheep and cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
) and rabbit
European Rabbit
The European Rabbit or Common Rabbit is a species of rabbit native to south west Europe and north west Africa . It has been widely introduced elsewhere often with devastating effects on local biodiversity...
s.
Vegetation
Chalk heath in southern BritainGreat Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
includes calcicoles such as salad burnet
Salad Burnet
Sanguisorba minor is a plant in the family Rosaceae that is native to western, central and southern Europe; northwest Africa and southwest Western Asia; and which has naturalized in most of North America...
(Sanguisorba minor), dropwort (Filipendula vulgaris) and common milkwort (Polygala vulgaris), and calcifuges such as bell heather (Erica cinerea
Erica cinerea
Erica cinerea is a species of heather, native to western and central Europe. It is a low shrub growing to tall, with fine needle-like leaves long arranged in whorls of three...
), ling heather (Calluna
Calluna
Calluna vulgaris is the sole species in the genus Calluna in the family Ericaceae. It is a low-growing perennial shrub growing to tall, or rarely to and taller, and is found widely in Europe and Asia Minor on acidic soils in open sunny situations and in moderate shade...
vulgaris), heath grass (Danthonia decumbens
Danthonia decumbens
Danthonia decumbens is a species of grass commonly known as common heath grass. It is a perennial with a decumbent habit: it lies on the ground with the tips turned upward....
), sheep's sorrel (Rumex acetosella) and betony (Stachys officinalis
Stachys officinalis
Stachys officinalis, is commonly known as Purple Betony, Betaine , Betonie , Bishopwort, Lousewort, Wild hop, Wood betony , or Bishop's wort....
). It also includes plants which can tolerate both acidic and basic conditions, such as common bent (Agrostis capillaris
Agrostis capillaris
Agrostis capillaris is a rhizomatous and stoloniferous perennial in the grass family . It is native to Eurasia and has been widely introduced in many parts of the world...
), wood sage (Teucrium scorodonia
Teucrium scorodonia
Teucrium scorodonia, common name the Wood Sage or Woodland germander, is a perennial herb belonging to the genus Teucrium of the Lamiaceae family. It is cultivated as an ornamental plant in gardens.-Description:...
) and sometimes juniper (Juniperus communis
Juniperus communis
Juniperus communis, the Common Juniper, is a species in the genus Juniperus, in the family Cupressaceae. It has the largest range of any woody plant, throughout the cool temperate Northern Hemisphere from the Arctic south in mountains to around 30°N latitude in North America, Europe and Asia.-...
).
Conservation
Chalk heath has suffered a parallel decline to those of heathland and chalk grassland, but because of the scattered and fragmented distribution of suitable soil conditions it has declined even more than those habitats. Many examples have disappeared due to agricultural improvement, or to a lack of grazing management, which leads to replacement by species-poor scrub and woodland. Chalk heath is especially sensitive to soil disturbance such as ploughPlough
The plough or plow is a tool used in farming for initial cultivation of soil in preparation for sowing seed or planting. It has been a basic instrument for most of recorded history, and represents one of the major advances in agriculture...
ing, which mixes the thin layer of acidic soil with the chalk beneath.
Example locations
- Headley Heath in SurreySurreySurrey is a county in the South East of England and is one of the Home Counties. The county borders Greater London, Kent, East Sussex, West Sussex, Hampshire and Berkshire. The historic county town is Guildford. Surrey County Council sits at Kingston upon Thames, although this has been part of...
, EnglandEnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
. Small areas of chalk heath surrounding a larger plateau of heathland. - Lullington HeathLullington HeathLullington Heath is a Site of Special Scientific Interest and National Nature Reserve within the South Downs Area of Outstanding Natural Beauty, in the county of East Sussex, England. It is of interest because of its uncommon habitat of chalk grassland and chalk heath....
in East SussexEast SussexEast Sussex is a county in South East England. It is bordered by the counties of Kent, Surrey and West Sussex, and to the south by the English Channel.-History:...
, England. Relatively large areas of chalk heath with some chalk grassland. - Kingley Vale National Nature Reserve, in West SussexWest SussexWest Sussex is a county in the south of England, bordering onto East Sussex , Hampshire and Surrey. The county of Sussex has been divided into East and West since the 12th century, and obtained separate county councils in 1888, but it remained a single ceremonial county until 1974 and the coming...
, England. Small areas of chalk heath at the top of a steep chalk escarpmentEscarpmentAn escarpment is a steep slope or long cliff that occurs from erosion or faulting and separates two relatively level areas of differing elevations.-Description and variants:...
. - PortonPortonPorton is a small village situated in Salisbury in Wiltshire, England, in the United Kingdom.It is most notable for being home to the military installation of Porton Down....
Down, in WiltshireWiltshireWiltshire is a ceremonial county in South West England. It is landlocked and borders the counties of Dorset, Somerset, Hampshire, Gloucestershire, Oxfordshire and Berkshire. It contains the unitary authority of Swindon and covers...
, England. Chalk heath surrounded by extensive chalk grassland.