01644naa a2200205 a 450000100080000000500110000800800410001910000190006024500820007926000090016152011100017065000130128065000120129365000130130565300110131865300160132965300120134570000210135777300600137816908272005-08-02       2005    bl ---       0--  u    #d1 aBARBOSA, R. I.  aFire frequency and area burned in the Roraima savannas of Brazilian Amazonia.  c2005  aEstimates were made of the percentage of area buened and the fire frequency in different ecosystems of non-anthropic savannas located in the north and northeast portions of the state of Roraima, Brasil. Three years of abservations (june 1997-may 2000) indicated that mean percentage of area buened annually, weighted for all ecosystems,was 38 +_ 12%(S.D.). the mean frequency of fire (number of years for an area to burn again) was 2.5 years. Both parameters are dependent on the type (structure) of vegetation, the altitude of the climatic state (dry, wet or normal) of the year of the abservation. Using values for 2-month periods over the 3-year time series (n=18), a simple regression model was developed to forecast percentage area burned for grassy-woody savana ("clean field" types), using as the independent variable the mean precipitation in each 2-month period. The propose model explains 66% of the reported cases. These results are the  first developed for savanas in the Amazon region and are directly applicable to calculations of greenhouse-gas emissions from burning in this ecosytem type.  aAmazonia  aCerrado  aQueimada  aBrasil  aFrequência  aRoraima1 aFEARNSIDE, P. M.  tForest Ecoligy and Managementgv. 204, n.371-384, 2005.