Mortalidade pós-fogo em espécies lenhosas de campo sujo submetido a três queimadas prescritas anuais

fire is one of the agents with most significant effect on the structure and composition of plant communities in savanna ecosystems. this study evaluated the effects of fire on the mortality rates of individual plants, individuals with aerial mortality and basal or underground sprouts (top kill), and the number of destroyed stems which include aerial mortality and dead individuals. the annual prescribed fires were performed in 1998, 1999 and 2000, in a campo sujo area at the reserva ecológica do ibge (brasília, df, brazil). in a 2,500 m2 area all plants of woody layer with diameter equal or greater than 2 cm at 30 cm from soil level were surveyed. the data were evaluated with chi-square test (p<0,05). the survey counted 39 species and 636 individuals. the mortality rates for annual fires were 22.5% (1998), 7.9% (1999) and 11.5% (2000), reducing by 37% the number of live individuals in the area. mortality impacted mainly the small individuals - height between 1 and 2 m high, and 2 and 3 cm diam. after the three burnings, the dead individuals and those with aerial mortality represented 73% of total individuals.