The biodiversity of a territory on the level of organisms (species pool) is realized within biocoenoses. The diversity of biocoenoses (coenodiversity) can be studied by means of delimitation, classification and mapping of phytocoenoses which fix terrestrial biocoenoses to the Earths surface. The geobotanical research offers two types of evidence as a basis for this - inventories of vegetation units (syntaxa) and maps of vegetation units. Three geobotanical methods for monitoring coenodiversity changes in a region can be used - 1 repeated inventory of syntaxa (associations), 2 repeated vegetation mapping, and 3 long-term monitoring of plant community and habitat changes on permanent plots. The actual biodiversity both at an organismal and ecosystemic level is threatened especially by these factors - 1 reduction of biotope diversity of a landscape by large-scale agricultural management, 2 eutrophication ard acidification of soils by acid rains rich in nitrogen, and 3 expansion of aggressive plants into natural and semi-natural plant communities.