An increase in both fine and coarse root biomass (438 g.m -2 of total roots) was found in the upper soil layer (0-5 cm) from March to August. A large decrease in total root biomass (from 700 to 230 g.m -2) was recorded in the 0-15 cm soil layer during the rainy period. A close negative linear relationship was observed for soil moisture content and root biomass in the upper soil layer. The calculated annual root disappearance (1070 g.m -2.yr -1) and the minimum estimate of root biomass increase (500 g.m -2.yr -1) indicate a very fast turnover of root biomass.