POST FIRE CHANGES IN THE STRUCTURE AND COMPOSITION OF THE WOODY VEGETATION OF A MESOTROPHIC CERRADO OVER A FIVE-YEAR PERIOD (1997-2002) IN NOVA XAVANTINA, MT, BRAZIL

Two inventories in an area of cerrado stricto sensu of mesotrophic type, were carried out, the first in 1997 and the second in 2002. The data were collected in 28 contiguous permanent plots with an area of 15 x 15 in each (0.63 ha). All individuals with stems of diameter >= 3 cm at 0.30 m above ground level were identified and measured. During the first inventory 1266 individuals belonging to 32 families, 55 genera and 72 species were recorded. While in the second there were 1045 individuals in 33 families, 55 genera and 71 species. The diversity index of Shannon was high in both samples (3.10 and 3.13 nats/ind., respectively). The results show that the fires affected relative species abundance but not overall richness. The families Fabaceae, Vochysiaceae, Malpighiaceae, Erythroxylaceae, Apocynaceae, Combretaceae and Malvaceae showed the highest floristic richness in both inventories. The largest mortality rate occurred in the smallest diameter classes (to about 13 cm), where species recruitment was not high enough to compensate for it. Three rare species were lost between the two inventories and two others appeared. The variations found are in agreement with the patterns of other studies in cerrado vegetation.