Plant dispersal strategies, seed bank distribution and germination of Negev desert species

In a natural flat area of deep loess soil in the Negev Desert of Israel, near Sede Boker, thedistribution of seeds of different species, in the seed bank, is a result of their strategies ofseed dispersal, seed size and structure and seed germination. Samples were collected in summerfrom 39 plots measuring 350 cm2. In Carrichtera annua (L.) DC., which has a protectionstrategy, seeds are enclosed in lignified structures as aerial seed banks on the dry and lignifiedplant until they are dispersed by rain. Of 3244 C. annua seeds, 3110 were found in theaerial seed bank. In Spergularia diandra (Guss.) Heldr. & Sart., which has an escape strategy, the tiny dust-like mature seeds are dispersed into cracks in the soil by wind. Of 1043 seeds,896 were found in the upper 0-1 cm layer of soil and only 99 at a depth of 1-2 cm. No seedsremained on the dry plants. Neotorularia torulosa (Desf.) Hedge & J. Léonard has developed adual dispersal strategy. Of 954 N. torulosa seeds, 630 were found protected in the aerial seedbank. The rest were dispersed by wind, 177 escaped into the upper 0-1 cm layer of soil and147 were at a depth of 1-2 cm.