INTRASPECIFIC AND INTERSPECIFIC COMPETITI ON BETWEEN SEEDLINGS OF ARTEMISIA-HERBA-ALBA ASSO AND ANTHYLLIS-HENONIANA BATT, CHAMEPHYTES OF PRESAHARIAN TUNISIA

Intra- and interspecific competition between seedlings of two presahar ian chamephytes was experimentally studied. For the two species raised separately we found an increase in interspecific competition with inc reasing density. In the mixed culture, Artemisia herba-alba competes b etter than Anthyllis henoniana for water, with an increase of mortalit y rate and a decrease of the biomass of Anthyllis henoniana being obse rved. Modelisation of changes in the mortality rate allow us to discer n between three factors (date, treatment and density) those responsibl e of the mortality during soil drying. For Artemisia herba-alba the da te and density effects explain the evolution of mortality rate, for An thyllis henoniana the model includes interactions between the three fa ctors.