Soil seedbank patterns of four trees and shrubs from arid Australia

The seedbanks of four arid trees from Australia were examined using periodicrecovery of seeds buried in nylon mesh bags in the field. Casuarina pauper did not maintain a soil seedbank. Seeds were not dormant at release and available rainfall will govem the timing of germination events. Three Acacia species have seedbanks of varying longevities. In A. oswaldii, the seedbank was very shortlived with most seeds from any one annual seed-crop having germinated in the first 1–2 years after release. In A. ligulata the seedbank was persistent, although it did vary between different populations. A. loderi had a relatively short-lived seedbank, with only 5% of seeds from an annual seed-crop surviving in the soil for between 3–5 years. Both C. pauper and A. oswaldii must rely on the production of annual seed-crops to maintain a seedbank through time and hence, take advantage of infrequent and irregular rains promoting germination and establishment. For A. ligulata and A. loderi, occasional seed production is all that is required to ensure the presence of a soil seedbank.