Observations on savanna burning in the Olokemeji forest reserve, Nigeria.
Abstract
In the area studied [cf. F.A. 27 No. 28], the tree cover, measured in various ways, was not significantly related to the dry weight of the herb layer before or after burning. From the dry weights of the herb layer before and after burning, the % burnt can be calculated. Early in the dry season it was 25%, but it averaged 84% from Jan. onwards. Fire temperatures were measured with heat-sensitive paints. The temperatures were generally <more than> 540°C. at ground level and decreased with increasing height. The rate of fall was very rapid for early burning, in which ambient temperature was maintained at about 3 m. ; later burning produced temperatures over 100°C. through a height of 6 or 7 m. An energy-flow diagram for the non-woody aerial shoots shows that 3/4 of the annual production of the aerial shoots of herbs is lost to the biological system when the savanna is burnt after Dec. Late burning for 5 consecutive years reduced the tree population by 32%. Most of the losses were from the lower height and basal-area classes so that, even though the total loss of basal area was only 10%, regeneration was virtually prevented. Burkea africana and Lophira lanceolata were more tolerant of fire than other species in the area. From author's summary. KEYWORDS: Burkea africana \ Burning \ effects \ regeneration \ Burning \ effects \ stand structure \ stand characteristics \ plant ecology \ Energy transfer, plant/environment \ Fire ecological effects \ Fire \ savanna woodland \ Fire resistant species \ Lophira lanceolata