Studies were conducted at Mina Recreio, Butiá, RS, on floristic and phytosociological aspects in a natural grassland area laying on a coal bank and in surface coal mining areas which had beem naturally reclaimed. Two main vegetation units denominated differential units a (AXONOPUS - ANDROPOGON) and B (AXONOPUS - PIPTOCHAETIUM), both of them with their respective sub-units of possibly associated species, were detected in the natural grassland area. The gradual spatial variation, detected in the natural grassland area, is mainly characterized by the set of conditions associated with land declivity and water table depth. In both surface coal mining areas II and III the vegetation units were not clearly defined, but were characterized as primary areas. The vegetation unit PIPTOCHAETIUM - AXONOPUS PURPUSII was detected in area II and a vegetation unit PIPTOCHAETIUM - CYNODON in area III. A greater floristic similarity was verified between area II and natural grassland than between area III and natural grassland. The species detected in mining areas present certain degree of pioneerism and tolerance in relation to the set of extreme conditions which they faced, and should, therefore, be the first to be tested on mining area recomposition.
Secondary succession; Mining; Revegetation; Plant ecology