ROOT FORAGING STRATEGIES AND SOIL PATCHINESS IN A HUMID SAVANNA

In Lamto (Cote d'Ivoire), the savanna is a patchy environment as far a s soil is concerned: tree clumps and termite mounds lead to higher nut rient contents than in the surrounding savanna. Mature Borassus aethio pum (Mart.) specimens are tall palm trees dominating the community, wi th aerial parts located out of these nutrient-rich patches. Palm root densities were compared under tree clumps and in the surrounding savan na, and were also sampled along transects between palm trees and nutri ent-rich patches (two clumps and one mount). Palm root densities were far higher (up to 10 times) in the nitrogen-rich soil of both clumps a nd termite mounds than in the surrounding savanna. Evidence is given t hat palm trees are able to extend their root system as far as 20 m tow ards these nutrient-rich patches where they proliferate. These results point out a particular root foraging strategy, which is one of the fi rst known for a woody perennial. They also provide new insights for un derstanding nitrogen cycling and savannas high rate of primary product ion.