Response of Acacia sieberiana to Repeated Experimental Burning

Abstract

We conducted a study on how Acacia sieberiana respond to repeated burning in the Kidepo National Park in northeastern Uganda. The study was conducted to understand effects of common burning regimes (early dry season, late dry season, and no burn [control]) in the area on Acacia sieberiana. The three treatments were applied for three consecutive years to 14 replicate blocks in a randomized block design. All A. sieberiana trees were number tagged and monitored for height and girth (diameter at breast height) growth. All fires were set as head-fires and attained intensity ranging between 422 and 5693 kW ? m21. Both early and late dry season burning increased the number of small (< 49 cm) A. sieberiana trees after 2 yr. Burning did not affect the growth rates. Although the number of trees < 49 cm increased after 2 yr, the mortality in this height class was also increased by the late dry season burning, and after 3 yr of consecutive burning there were no statistical treatment differences in the height class < 49 cm. Late dry season burning also led to high mortality among trees > 250 cm in the third year. Mortality attributed to elephant browsing was important in all treatments but a substantial portion of mortality could not be attributed to any particular cause. In the late burn, fire was the most important mortality factor. Thus, 2 yr of burning may be used as a tool to stimulate recruitment of A. sieberiana, but additional years of late dry season burning will increase the mortality of older trees.