03499naa a2200265 a 450000100080000000500110000800800410001910000210006024501310008126000090021252027760022165000120299765000110300965000170302065000100303765000130304765000120306065000090307265300110308165300130309265300210310565300210312670000200314777300660316715547792017-02-03       1998    bl uuuu     u00u1 u    #d1 aCASTRO, E. A. de  aEcosystem structure in the Brazilian cerradoba vegetation gradient of aboveground biomass, root mass and consumption by fire.  c1998  aConversion to permanent agriculture is rapidly occurring over vast areas of the 1.8 million km2 Brazilian Cerrado; a region that is naturally a mosaic of grasslands, savannas and evergreen tropical woodlands. Yet, few studies have quantified total biomass of plant communities in this ecosystem, particulary the belowground component; a C pool of potencial global significance. Total biomass (aboveground and belowground), and the quantity of biomass consumed by fires were measured in four communities comprising a vegetation gradient from pure grassland (campo limpo) to a woodland with a closed canopy of tall shrubs and scattered trees (cerrado denso) near Brasilia, DF, Brasil. Total aboveground biomass (TAGB) increased along this gradient from 5.5 Mg ha-1 in campo limpo to 29.4 Mg ha-1 in cerrado denso. Vegetation structure varied among communities; trees were nonexistent in campo limpo, but were at a density of 1000 ha-1 and a biomass of 12.9 Mg ha-1 in cerrado denso. Fires consumed 92 and 84% of the TAGB in campo limpo (pure grassland) and campo sujo (savanna), respectively. In cerrado aberto and cerrado denso, trees and tall shrubs were little affected by fire. Combustion factors of the TAGB in these communities was 54 and 33%, respectively. The total biomass consumed by fire ranged from 5.0 Mg ha-1 in campo limpo to 13.5 Mg ha-1 in cerrado aberto. Compared to other widespread Brazilian ecosystems (tropical dry forest and evergreen forest), the Cerrado has a lower aboveground biomass. The TAGB of cerrado denso is &lt9% of that of Amazonian tropical evergreen forest. The total quantity of biomass consumed by fire, and hence emissions to the atmosphere is lower in intact Cerrado communities compared to fires in slashed tropical forest. Total belowground biomass (TBGB) increased from 16.3 Mg ha-1 in campo limpo, to 30.1 Mg ha-1 in campo sujo, to 46.5-1 Mg ha in cerrado aberto, and to 52.9 Mg ha-1 in cerrado denso. This quantity of belowground biomass is similar to, or exceeds that reported for many tropical dry moist forests. More than 80% of the TBGB occurred in the upper 30 cm of the soil, except for cerrado denso (71%) where a greater proportion of tree roots were present at deeper levels. Root shoot ratios were very high in all sites ranging from 2.9 in cerrado denso to 77. in campo sujo. Total ecosystem plant biomass (the total aboveground biomass and TBGB combined) ranged from 21.9 Mg ha-1 in campo limpo to 77.9 Mg ha-1 in cerrado denso. More than 71% of the live phytomass (aboveground biomass+root biomass) is belowground in the Brazilian Cerrado. At current rates of land cover change in the Brazilian Cerrado, these ecosystem pools are likely significant sources of increasing atmospheric C and other greenhouse grasses.  abiomass  aBrazil  afire ecology  aroots  aBiomassa  aCerrado  aRaiz  aBrasil  aBrasilia  aDistrito Federal  aEcologia do fogo1 aKAUFFMAN, J. B.  tJournal of Tropical Ecology, New Yorkgv.14, p.263-283, 1998.