Windthrow in a tropical savanna in Kakadu National Park, northern Australia

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Abstract
Windthrow was assessed following a convective storm in a stand of tropical savanna in Kakadu National Park, northern Australia. Over an area of 3 ha, 79 out of 810 trees (9.8%) were damaged; 27 of them were either uprooted or snapped off at the trunk. Logistic regression showed that both species and tree height were significant determinants of the probability of wind damage. Branch loss and either uprooting or trunk snapping was highest in the canopy sub-dominant Eucalyptus porrecta. Damage was lowest in the sub-dominant trees Erythrophleum chlorostachys, a species which is relatively resistant to termite damage, and Terminalia ferdinandiana, a deciduous species which is generally shorter than the main canopy dominants. Damage was intermediate in the two most common canopy dominants, Eucalyptus tetrodonta and E. miniata. Wind damage was greatest in trees taller than 9 m and relatively minor in trees below this height. Wind disturbs savanna trees in a manner opposite to that of fire, because wind damage is greatest in taller trees, whereas fire damage is greatest in smaller trees. This, coupled with significant within-patch variability in the extent of wind damage, may act to increase small-scale environmental heterogeneity in savannas.