The class Scheuchzerio palustris-Caricetea nigrae comprises sedge-moss fen vegetation with an admixture of horsetails, dicot herbs and grasses. Productivity is low. The sites in which this vegetation occurs are permanently saturated with water and poor in nitrogen and phosphorus. The class includes also hollows in ombrotrophic bogs, which are fed by rain water and poor in minerals. Substrates are either deep peat, gley with a shallow organic layer, or chalk. Nutrients are therefore not mineralized and stay bound either as organic compounds in peat or carbonates in chalk sediments. In the Czech Republic, shrubs and trees are usually absent and many present localities are, or were, mown for hay. Species composition of this class is highly diverse, varying mainly along the gradient of pH and mineral richness, known as the poor-rich gradient. The subdivision of the class into alliances reflects this gradient. Other factors such as stability of water regime, nutrient availability, peat depth, management and site history are mostly reflected at the level of associations. This class is widespread in the boreal zone of Eurasia and North America, and less frequently it also occurs in the temperate zone.