The ecological impact of fire regimes on plant diversity and soil fertility
has become a subject of intense discussion, 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) in plants and concentrations of C, N, P, K, Ca and Mg in
soil were collected from 10 delineated subplots in the burned and unburned
zones of four sites after annual wildfire had occurred. Ground cover was
significantly higher in the burned zones, increasing progressively from
January to April (dry season). Eleven herbaceous species in addition to 2
tree seedlings occurred and represented families of Asteraceae, Cyperaceae,
Fabaceae and Poaceae. Digitaria nuda, Brachiaria lata, Daniellia oliveri and
Aeschynomene indica were limited to the burnt zones while Cyperus tuberosus,
Mariscus alternifolius and Rottboellia cochinchinensis were restricted to the
unburned zones. DMY ranged from 0.32 g m-2 (Desmodium tortuosum) to 52.96 g
m-2 (Megathyrsus maximus). Average biomass in the burned and unburned sites
was 35.86 g m-2 and 28.42 g m-2, respectively. Soil C, N and P concentrations
decreased (positive deterioration index - DI), while those of K, Ca and Mg
improved (negative DI) in the burned sites. Burning altered the growth
(ground cover) and composition of plant species in the short term, and could
significantly influence soil nutrient dynamics in the long term, especially
with recurring fire events.
Short-term effects of elevated precipitation and nitrogen on soil fertility and plant growth in a Neotropical savanna