Short-term survival and long-term mortality of Acacia drepanolobium after a controlled burn

We investigated the shortand long-term effects of a controlled burn in Acacia drepanolobium woodland in Laikipia, Kenya in 1998. Fire temperatures averaged 250!C at ground level, with a maximum of over 500!C, but were rarely >100!C at 1.5 m above the ground or more. Nine months after the fire, virtually all A. drepanolobium trees had survived the fire. Some smaller trees were burnt to ground level, but most were only ‘top-killed’ and had coppiced. Taller trees suffered less damage than smaller trees. However, a 2003 satellite image suggested a dramatic reduction in A. drepanolobium canopy cover at the site. A survey of the site in 2006 revealed that the density of larger A. drepanolobium trees was nearly three times greater in adjacent control areas than in the old burn, with a lesser reduction in the density of smaller trees. These data suggest that short-term measures of postburn survivorship may be deceptive, and that an additional source of tree mortality (perhaps elephants) was concentrated on trees in burned areas, even many months after the burn, with long-term consequences for tree and ecosystem dynamics.