The nutrient loads contained in the grassy fuel before fires, and of a
sh subsequently, were compared to determine the fluxes of macronutrien
ts, copper and zinc during fires at Kapalga in Kakadu National Park. T
he fluxes were estimated in three vegetation types: forest, woodland a
nd open woodland. The magnitudes of the fluxes were greatest in the fo
rest community where grassy fuel loads were highest at about 6.3 t ha(
-1). In these sites, 54-94% of all measured nutrients in the fuel were
transferred to the atmosphere during the fires. For each nutrient, th
e proportion transferred to the atmosphere as entrained ash was calcul
ated-by assuming that calcium was not volatilized during the fires. If
the transfer of entrained ash represents local redistribution only, t
hen rainfall accession and the deposition of these particulates should
replace most of the losses of all nutrients except nitrogen (N). Esti
mated rates of biological fixation of N appear to be insufficient to r
eplace the annual losses of N. It is therefore concluded that a regime
of annual fires that completely burn the available grassy fuel would
deplete N reserves in these savannas, unless there are other sources o
f biologically fixed N, which are unknown at present.