The interaction between natural and experimental gradients of productivity on competition intensity was tested by neighbour removal experiments. Water is the main limiting factor in this system and experimental gradients of productivity were obtained using a series of watering treatments. Competition was determined as the total effect of neighbours on per-capita seed production of Stipa capensis. Both absolute and relative competition intensity were calculated for three types of habitats, during two successive years, and under different watering treatments in each habitat-year combination. Both measures were positively correlated with productivity, but absolute competition intensity was more sensitive to changes in productivity than relative competition intensity. Natural gradients of productivity appeared to have stronger effects on competition intensity than experimental gradients, but this was largely due to their wider range. Keywords: competition, desert annuals, habitat heterogeneity, Jordan Rift Valley, neighbour removal, Stipa capensis.