The class Calluno-Ulicetea comprises vegetation of Nardus stricta dominated grasslands and heathlands. Both of these vegetation types are confined to nutrient-poor, acidic soils, and the core of their species composition includes stress-tolerant dwarf shrubs and hemicryptophytes. These plants are poor competitors, which tend to disappear after nutrient enrichment under pressure of taller grasses. In the past this vegetation was regularly grazed and depleted of nutrients, but due to abandonment and increased atmospheric nitrogen deposition, they are being replaced by more productive grasslands. Since most of the typical species of the Calluno-Ulicetea, especially the dwarf shrubs, are sensitive to winter frosts, the class has an oceanic to suboceanic distribution in Europe.