Vegetation of inland sand knobs in South-Eastern Estonia was studied. 39 plant communities were described and thereafter classified into 7 syntaxonomic units: 1. Calluna vulgaris-Cladina spp. type, 2. Koeleria glauca-Cladina spp. type, 3. Juniperus communis-Arctostaphylos uva-ursi-Cladina spp. type, 4. Festuca ovina-Cladina spp. type, 4.1. Pinus sylvestris-Festuca ovina-Cladina spp. type, Deschampsia flexuosa variant, 4.2. Pinus sylvestris-Festuca ovina-Cladina spp. type, Thymus serpyllum variant, 4.3. Pinus sylvestris-Festuca ovina-Cladina spp. type, Pleurozium schreberi variant. Environmental variables determining the variation structure of samples are the amount (cover) of litter and the total cover of field and moss layers. The species richness of communities depends mostly on the amount of litter and marginally insignificantly (p = 0,051) also on humus horizon thickness. Interpreting the vegetation on 1×1 m sample quadrats as microcoenoses, 415 quadrats were clustered into 23 microcoenose types. The most frequent are the microcoenoses of Cladina arbuscula+Pycnothelia papillaria, Cladina arbuscula+Festuca ovina, Festuca ovina+Cladina arbuscula and Festuca ovina+Pilosella officinarum type, seldom occur microcoenoses of Cetraria islandica+Cladina stellaris and Polytrichum piliferum+Festuca ovina type. In all community types are presented Cladina arbuscula+Festuca ovina and Dicranum polysetum+Cladina arbuscula type microcoenoses but microcoenoses of any type are confined to only one type of communities. To maintain the peculiar features of Estonian inland sand knobs plant communities they must be kept open and in some places also the dense bottom layer vegetation must be removed.
