In desert plant communities, annual plant species interact both positively and negatively with perennial shrubs.
In this study, the influence of Artemisia monosperma shrubs on soil nutrients, plant density and biomass of
annual plants underneath and outside the canopy was examined. Two desert habitats were compared with similar
soil texture but with different climatic attributes. Levels of soil nitrogen, phosphorus and organic matter were
significantly higher underneath than between shrubs, but differed between the two habitats which may be
attributed to differences in climatic conditions. Despite higher availability of nutrients underneath the canopy,
density and biomass of most ephemerals were lower than between shrubs. An hypothetic explanation could be
the difference in canopy shading or water supply as well as allelopathic effects of oil leachates from the shrubs.