Ecology and dynamics of Herniaria incana population at the northernmost locality of its current central and western European distribution

Herniaria incana Lam. var. angustifolia Fenzl in Ledeb. grows at only one locality in the Czech Republic, near the village of Hřímeždice, central Bohemia, which is at present the species' northernmost occurrence in central and western Europe. The species population, dynamics was studied during 1987-91. In the mown part of the dry grassland, the total area covered by the species increased considerably over the research period. In unmown sites, the population tended to retreat. Its spread was, however, encouraged by the hot and dry summer of 1990 in both unmown and mown areas. Considering the locality as a whole, an overall trend for the population to increase was a result of various dynamic processes (increase and decrease in both number and size, emergence and disappearance of individuals) at the level of individual plants. The population at the locality studied successfully reproduces by seed. It grows more frequently in sites with a shallow soil layer. The species occurrence is considered allochthonous at the locality. Some aspects relevant to the protection of the species are discussed .