Effects of burn season and grazing on perennial grasses in wooded savanna, Kainji Lake National Park, Kwara State, Nigeria
Published source details
Afolayan T.A. (1979) Change in percentage ground cover of perennial grasses under different burning regimes. Vegetatio (now Plant Ecology). Plant Ecology, 35-41
Published source details Afolayan T.A. (1979) Change in percentage ground cover of perennial grasses under different burning regimes. Vegetatio (now Plant Ecology). Plant Ecology, 35-41
In African savannas, fire may be used to improve the quality and quantity of grass to enhance foraging conditions for wild ungulates and/or livestock. However, in the West African savanna zone little information is available on responses of grasses to burns undertaken at different times of the year. This study presents information on the effects of various burning and grazing regimes on perennial grasses in the Northern Guinean savanna zone of Nigeria, the aim being to allow managers to make more informed decisions in order to best improve the quality of the grass for grazers.
Study site: The work undertaken in Kainji Lake National Park, Kwara State, western Nigeria. Annual rainfall averages around 1,100, most falling between May and October (peaking in August and September); the hottest months are March and April.
Experimental burns: Burns were made in three vegetation types: Terminalia macroptera tree savanna, Isoberlinia tomentosa woodland and Burkea/Detarium savanna woodland. Six treatments were carried out in each: i) early burning each year with grazing; ii) early burning each year without grazing; iii) late burning each year with grazing; iv) late burning each year without grazing; v) fire excluded with grazing; vi) fire and grazing excluded.
(Vertebrate grazers in 'no grazing plots' were presumably excluded by fencing; no details are given in the original paper).
Monitoring: Changes in ground vegetation were monitored between October 1973 and October 1975. A 50 x 20 m plot was sampled in each vegetation type for each treatment. Data on grass species composition and ground cover (perennial grasses, annual grasses, forbs, litter, woody plants and bare ground) using the line-point transect method were recorded, and the percentage of each calculated. Tillers of the dominant perennial grass species were counted monthly in 20 randomly selected 1 x 1 m quadrats in each plot.
The results obtained in each of the three vegetation types more or less followed the same pattern. Perennial grasses established higher basal cover under late-season burn treatments than under early-season burn and no burn treatments. Late-season fires effectively burnt accumulated litter (which otherwise hinders grass growth); no burn treatments resulted in litter accumulation. Highest numbers of grass tillers were produced under late burn treatments, early burn plots had intermediate tiller counts, and the lowest were under the no burn treatments.
In contrast, annual grasses, forbs and woody plants exhibited better development under early burn and no burn treatments than under late burning. The results showed that late fires consumed litter which otherwise would have hindered grass growth, while no burning caused accumulation of litter especially at the beginning of the growing season.
The author recommends occasional late burning in controlled small blocks of land for optimum grass production in the study area.
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