Chalk grassland

Biodiversity

The lichen 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 widespread Lecideetum watsomiae association found on chalk pebbles and flints, and the more restricted Fulgensietum fulgentiscommunity. These lichen communities require specific conditions to grow, including areas of open ground created through natural or human disturbance, such as rabbit grazing, 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 like landslips create suitable habitats. Key factors promoting lichen diversity include the presence of stable flints, areas of nutrient-poor soil, and the presence of a small loess (windblown silt) fraction in the soil. Characteristic species include Gyalolechia fulgens and various Cladonia 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.