THE ROLE OF SEED BANKS IN VEGETATION DYNAMICS AND RESTORATION OF DRY TROPICAL ECOSYSTEMS

This paper reviews studies on seed banks in tropical dry vegetation and, for comparison, some wet tropical and dry subtropical vegetation. A first general conclusion is that tropical seed banks are smaller than those in temperature ecosystems. Many studies are devoted to only one species, among which are several Acacia species, both tropical and subtropical, some of which reach densities in the seed bank of up to 10 000 seeds/m2. The lesser importance of the seed bank strategy in tropical species may be related to higher risks of seed loss through higher mortality (fire, predation, pathogens etc.), or to intermittent germination occasions in relation to ephemeral favourable conditions (e.g. rains during the dry season). Regarding vegetation dynamics, the importance of seed banks and regeneration from seeds is most pronounced in larger forest gaps. Examples are discussed of rapid succession to forest of savannas after protection from fire, which is partly due to regeneration from the seed bank. The significance of seed banks in vegetation restoration projects is outlined and the need for additional sowing of seeds of important species underlined.