TREE AND GRASS ROOTING PATTERNS IN AN AFRICAN HUMID SAVANNA

Spatial and temporal soil partitioning between roots of the two savann a plant components, i.e. trees and grasses, were investigated in a Wes t African humid savanna. Vertical root phytomass distribution was desc ribed for grass roots, large (> 2 mm) and fine (< 2 mm) tree roots, in open sites and beneath tree canopies. These profiles were established monthly over one year of vegetation growth. Natural C-13 abundance me asurement was used to determine the woody/herbaceous phytomass ratio i n root samples. Tree and grass root distributions widely overlapped an d both were mostly located in the top 20 cm of the soil. Grass root ph ytomass decreased with depth whereas woody root phytomass peaked at ab out 10 cm depth. No time partitioning was detected. These structural r esults do not support the hypothesis of soil resource partitioning bet ween trees and grasses and are thus consistent with functional results previously reported.