Four ecologically different habitats within Riyadh desert (Central Saudi Arabia) were studied. Three different
plant communities dominated by Pulicaria crispa, Lycium shawii and Farsetia aegyptia form the vegetation
units inhabiting the first habitat represented by depressions and wadi terraces with deep and finely textured soil.
The seed content in the upper 2 cm of these soils ranged between 38304 and 71484 seeds/m2. The second habitat
is represented by the runnels dissecting gravelly areas with shallow and coarse-textured soil. This habitat
supported the growth of two plant communities dominated by perennial grassland species Cenchrus ciliaris and
Lasiurus scindicus with soil seed content amounting to 14855 and 9000 seeds/m2 in the two communities
respectively. Sandy plains represent the third investigated habitat which is inhabited by Rhazya stricta
community with soil seed content amounting to 41580 seeds/m2. Saline soils supporting growth of the
communities dominated by salt tolerant species Tamarix nilotica and Zygophyllum album formed the fourth
investigated habitat. The counted seeds in the upper 2 cm of the soil were 53352 and 15624 seeds/m2 in the
above communities, respectively. The present study showed that the emerged seedlings from the soils collected
from the recognized communities represented a low value ranged from 0.92 to 3.38% out of the total estimated
seed bank.