IMPACTS DES FEUX RÉPÉTÉS SUR LES SOLS DE SAVANES DU SECTEUR DE LOATSHI
The “Aubréville’s fire plots “ constitute an unique trial in the world in which the effects of brush fires, alight every year, on vegetation is studied since 1936. The complete protection against fires is compared there with “early fires” effects (beginning of the dry season or 15 December) and with “late fires” (10 March, end in season dry).
After 60 years of experimentation, the plot in complete protection is a dense secondary semi-deciduus forest. The “late fires” create a “steppe“ overheaded by aging trees. The “early fires” allowed to reconstitute a dense forest on the richest soils and to maintain a wooded savanna on the poorest soils.
On each of the three plots, a composite sample of soil (5 cores mixed together) has been taken from the horizon 0-15 cm. A sixth carrot of soil no “altered“ has been taken to do measures of porosity by mean of mercury.
The “protected potl” logically present the most elevated contents of nutrients and the highest absorbent complex notably for Mg and K. All parcels are poor in assimilated P. The organic matter rate passes 3,32% for the complete protection to 2,63% for the “late fires” and 1,79% for the “early fires” (savanna). The C/N ratio evolves in the same proportion.
Globally, the burnt “plots“ soils are less porous and present in relation to the “protected plot” 1) a more important microporosity, 2) a more important mesoporosity with a superiority of the “early fires” and 3) a decrease of the macroporosity of the order of 50%.
At the level of the soil’s macrofauna, termites are everywhere present whereas earthworms are distinctly more abundant in the “protected plot”.
Keywords: brush fires, protection, vegetation, soil, porosity, soil fauna, Côte d’Ivoire
