Shem-Tov, S., Unit for Ecophysiology Plant, Wyler Dept. for Drylands Agriculture, Sede Boker Campus 84990, Israel
Zaady, E., Unit for Ecophysiology Plant, Wyler Dept. for Drylands Agriculture, Sede Boker Campus 84990, Israel
Gutterman, Y., Unit for Ecophysiology Plant, Wyler Dept. for Drylands Agriculture, Sede Boker Campus 84990, Israel

Germination of Carrichtera annua seeds on soil crusts and soil samples from beneath shrub canopies, collected from 9 or 10 locations along a rainfall gradient, was tested under laboratory conditions at 15°C in light. The germination trends are correlated to soil traits and average rainfall at the sites from which soil samples were collected. The average annual rainfall ranges from 50 mm in the central Negev Desert to 325 mm in the northern Negev. Germination of C. annua seeds on soil crusts was negatively correlated with the average annual precipitation at the source site. Total carbon content of the microphytic soil crusts was negatively correlated with C. annua seed germination. Soil crust microbial activity was positively correlated with the rainfall gradient. According to our findings, it seems that the properties of the soil substrate may affect seed germination and, therefore, distribution of plant species along the desert landscape.