Short term effects of early-season fire on herbaceous composition, dry matter production and soil fertility in Nigeria’s guinea savanna

Background/Question/Methods: The ecological impact of fire regimes on plant diversity and soil fertility has become subject of intense discussions, especially in savannas where recurring incidences are common. This study assessed the short-term effects of early-season fire on herbaceous composition, dry matter yield and soil fertility in the guinea savanna belt of Nigeria. Data on ground cover, dry matter yield (DMY) and concentration of C, N, P, K, Ca and Mg were collected from 10 delineated subplots in the burned and unburned zones of four sites after annual wildfire had occurred.

Results/Conclusions: Ground cover of species was significantly higher in the burned zones and increased progressively from January through April (dry season). Eleven (11) herbaceous species, in addition to 2 tree seedlings, occurred and were distributed among families of Asteraceae, Cyperaceae, Fabaceae and Poaceae. Digitaria nuda, Brachiaria lata, Aeschynomene indica and Daniellia oliveri were limited to the burnt zones while Cyperus tuberosus, Mariscus alternifolius and Rottboellia cochinchinensis were restricted to the unburned zones. Dry matter yield range between 0.32 g m^-2 (Desmodium tortuosum) and 52.96 g m^-2 (Megathyrsus maximus). Average biomass was higher in the burnt sites (35.86 g m^-2), but not significantly different from the unburned sites (28.42 g m^-2). Soil C, N and P decreased (positive deterioration index - DI), while K, Ca and Mg improved (negative DI). No significant differences exist for soil nutrients in the burned and unburned zones of the sites. The study concluded that burning altered growth (ground cover) and composition of species in a short-term, but may significantly influence soil nutrient dynamics on a long-term, especially with recurring fire events.