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Bush-Control Studies in the Drier Areas of Kenya. IV. Effects of Controlled Burning on Secondary Thicket in Upland Acacia Woodland
D. B. Thomas and D. J. Pratt
Journal of Applied Ecology
Vol. 4, No. 2 (Nov., 1967), pp. 325-335
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/2401339
Page Count: 12
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Observations on two burning regimes extending over 3 years showed that burning can be a practical method of clearing thicket species in Acacia woodland under medium rainfall/altitude conditions in Kenya and that the susceptibility of plants to fire depends as much on burning regime as on species. The five main constituent species, each represented by about twenty selected bushes, were equally tolerant of one fire, but differed in susceptibility to subsequent fires. Thus, A. brevispica was tolerant of three annual burns but only semi-tolerant of burning in 1958 and 1960; whereas Aspilia sp. was tolerant of the latter treatment but sensitive (40% kill) to the former, and Maytenus putterlickioides was semi-tolerant (30% kill) of both treatments. Both Acalypha fruticosa and Crotalaria saxatilis were intolerant of three annual burns (70-80% kill), but Acalypha was sensitive to the two burns treatment (60% kill) while Crotalaria was tolerant. In these data, only in Maytenus are plant size and fire susceptibility associated (all plants killed were over 8 ft tall), but counts in supplementary quadrats of complete populations of Aspilia, in which half were less than 1 ft tall, indicate that seedling plants of this species are intolerant of even one fire. Other factors controlling fire susceptibility are the size of the root crown, the numbers of shoots produced after burning and their rate of growth, and the combustibility of the dead stems: in particular, if numerous shoots appear after a first burn the species is likely to be sensitive to later burns. The thicket association studied appears to have become established at a time when fires were less frequent or lacking. To restore open woodland frequent burning is necessary initially, with preliminary slashing in dense thicket. Under local conditions, this approach is safe and economic.
Journal of Applied Ecology © 1967 British Ecological Society