 | This articlefocuses too much on specific examples. Please helpimprove it by adding sources thatevaluate within broader context. Relevant discussion may be found on thetalk page.(July 2023) (Learn how and when to remove this message) |
Calcareous grassland (oralkaline grassland) is anecosystem associated with thinbasicsoil, such as that onchalk andlimestonedownland.[1]
There are large areas of calcareous grassland in northwesternEurope, particularly areas of southernEngland, such asSalisbury Plain and theNorth andSouth Downs.
Themachair forms a different kind of calcareous grassland, where fertile low-lying plains are formed on ground that iscalcium-rich due to shell sand (pulverisedsea shells).
Plants on calcareous grassland are typically short andhardy, and includegrasses and herbs such asclover. Calcareous grassland is an important habitat for insects, particularlybutterflies and ants,[2] and is kept at aplagioclimax bygrazinganimals, usually sheep and sometimes cattle.Rabbits used to play a part but due to the onset ofmyxomatosis their numbers decreased so dramatically that they no longer have much of a grazing effect.
Thelichen flora of chalk grasslands represents an often overlooked component of calcareous grassland biodiversity. A comprehensive survey of English chalk grasslands in the 1990s identified two main lichen communities: the widespreadLecideetum watsomiae association found on chalk pebbles and flints, and the more restrictedFulgensietum fulgentiscommunity. These lichen communities require specific conditions to grow, including areas of open ground created through natural or human disturbance, such as rabbitgrazing,trampling, or historical agricultural practices. The richest lichen sites are often found where soil has been disturbed within the past century or where natural factors likelandslips create suitable habitats. Key factors promoting lichen diversity include the presence of stableflints, areas of nutrient-poor soil, and the presence of a smallloess (windblown silt) fraction in the soil. Characteristic species includeGyalolechia fulgens and variousCladonia species. Many calcareous grassland lichen communities have shown significant decline since the mid-20th century, attributed to factors such as reduced grazing, nitrogen deposition, and habitat loss.[3]
