Studies on flora of fallow lands of the Podlaski Przełom Bugu mesoregion were carried out between 2001 and 2003 in the area of 77 localities, situated in 20 communes. A systematic list of fallow land flora was made and its variation with respect to occurrence frequency, biological spectrum, persistence and belonging to geographic-historical and sociological-ecological groups was analyzed. Flora of fallow lands of the Podlaski Przełom Bugu mesoregion includes 442 species included in 60 families and 241 botanical genera. The most numerous group comprises very rare, rare and quite frequent species. In the floristic composition of the analysed flora, apophytes (72.2%) predominate over anthropophytes (2.8%) as well as perennials (61%) over ephemerals (39%). Considering the biological spectrum of flora, hemicryptophytes (49%) and terophytes (32%) predominate over other life forms. Forest and shrub species (18.5%) as well as meadow (17%) and xerothermic sward plants (17.4%) have the largest share in the flora. The abundant occurrence of segetal (15.8%) and long-lived ruderal communities (8.1%) was also noted. Moreover, the occurrence of 25 species endangered with extinction in fallow land communities of the Południowopodlaska Lowland was noted. They are as follows: <i>Nigella arvensis</i>, <i>Potentilla recta</i>, <i>Platanthera chlorantha</i>, <i>Agrostemma githago</i>, <i>Prunella grandiflora</i>, <i>Populus alba</i>, <i>Silene tatarica</i>, <i>Papaver argemone</i>, <i>Papaver rhoeas</i>, <i>Veronica polita</i>, <i>Hieracium floribundum</i>, <i>Bromus secalinus</i>, <i>Polygonum bistorta</i>, <i>Geum alleppicu</i>, <i>Astragalus arenarius</i>, <i>Centaurium erythraea</i>, <i>Veronica agrestis</i>, <i>Veronica verna</i>, <i>Cirsium rivulare</i>, <i>Allium oleraceum</i>, <i>Hierochloë odorata</i>, <i>Chenopodium polyspermum</i>, <i>Vinca minor</i>, <i>Dipsacus silvestris</i> and <i>Campanula latifolia</i>.
Colonization-extinction and patch dynamics of the perennial riparian plant, Silene tatarica
