The dynamics of Eucalyptus miniata/E. tetrodonta savanna was examined in the Early, Late and Unburnt regimes. Studies concentrated on the effects of fire on the survival and phenology of the dominant trees - Eucalyptus miniata, E. tetrodonta (both evergreens), E. porrecta, Erythrophleum chlorostachys (both semi-deciduous) and Terminalia ferdinandiana (fully deciduous) - and the composition and diversity of the grass-layer.

Tree survival is likely to decrease with increasing fire intensity. Phenology (the seasonality of growth and reproduction) is important not only for the life of plants within the savanna, but also for the availability of resources for fauna. Fire may affect these resources, because leaf flush, flowering and fruiting all peak during the late dry season. In contrast, the grass-layer is dormant during dry season, and fire may not affect it.

Tree survival declined linearly with increasing fire intensity; basal area declined only in the Late regime, by about 20% over the experiment. Survival varied with tree size - small saplings and old, large trees were more sensitive to increasing fire intensity than mid-sized trees. Both Erythrophleum and Terminalia were more fire-sensitive than the eucalypts.

Leaf phenology in Terminalia, which is deciduous over the dry season, was unaffected by fire. The Early fires scorched the canopies of the eucalypts and Erythrophleum , but all sprouted new leaves within a month - two or three months earlier than under Unburnt conditions. Leaf fall was more extensive in these four species following the Late fires, but resprouting was rapid, and at about the same time as leaf flush in the Unburnt trees. Flowering and fruiting were reduced by Late fires in four of the species, especially so in Terminalia and Eucalyptus porrecta. There was no apparent effect of Early fires on fruiting. However, seed abundance in both E. miniata and E. tetrodonta may be reduced by both Early and Late fires, and fire-free intervals of several years may be necessary for effective recruitment of seedlings of these trees. Flowering in Erythrophleum was low in all treatments and years, with no fire effect.

Within the grass-layer, there were few differences in the density of woody sprouts (juvenile trees < 2m tall) between regimes and species; survival was highest under the Early and Late regimes, and least under the Unburnt regime. Fire exclusion did not lead to invasion of the savanna by rainforest trees, at least in the short-to-medium term. Grass-layer composition and diversity were also unaffected by fire. Grass-layer dynamics were driven more by variation in annual rainfall and pre-existing sorghum cover than by fire. Similar findings were made for the understorey at nearby Munmarlary in Kakadu, and some woodlands in the Katherine region.

The generally rapid responses in understorey and tree canopy, and the relatively benign effects of fire on the grass-layer, indicates that savannas at Kapalga have a generally high level of resilience to fire. However, despite this, widespread, frequent late dry season fires is not a desirable fire regime, given the effects on ecosystem structure, and floral resources for fauna.