THE REGENERATION POTENTIAL OF THE SEED BANK OF AN EPHEMERAL FLOODPLAIN IN SOUTH-AFRICA

Germination from the seed banks of ephemeral floodplain wetlands of th e Nyl River in South Africa was quantified in a glasshouse experiment to examine the potential of the seed bank for revegetation. Sediments from three sites with different wetting and drying histories (permanen t, seasonal and occasional inundation) were collected in late summer a fter flooding and germination but before the seed bank was replenished . Samples were flooded artificially after dry, wet or wet/dry pretreat ment and germination was recorded. Samples were then dried and reflood ed to assess germination from the residual seed bank. All sites had a species-rich germinable seed bank, The water regime history of each si te did not influence the number of species or individuals present in a ny trial or pretreatment. More species and individuals germinated in t he first germination trial than the second. Fewer species germinated f rom the samples collected from above the water line than from underwat er Sixteen species (12 aquatic) and 1392 individuals germinated in the first trial. Most species from the field communities also germinated from the seed bank. Twelve species, including 2 new species, germinate d from the residual seed bank. Many of the species from these wetlands have persistent seed banks with staggered germination of propagules. Species maintain themselves over space (sites), conditions (water regi mes) and time (trials) by a range of life-cycle patterns. Wetland comm unities that depend on their seed banks for revegetation between wetti ng and drying events may be altered by human-induced changes to water regimes. (C) 1998 Elsevier Science B.V.