Abstract:
The seed bank dynamics of five selected vegetation types within the Tembe Elephant Park, Maputaland, northern KwaZulu-Natal, South Africa, were investigated. The different vegetation types from which soil samples were randomly collected during the entire year of 2001 are (a) the very rare and unique Licuati forest and (b) Licuati thicket vegetation, (c) a bare or sparsely vegetated zone surrounding the forest edges, the forest/grassland ecotone, dominated by cat’s tail grass (Perotis patens), (d) grassland and (e) woodland (dense savanna). The main idea of this study was to gain a better understanding of the dynamics of some of Maputaland’s most interesting and unique vegetation types. The aims were to obtain an estimate of the seed bank size, determine the species composition of the soil seed bank flora and compare the species composition with the aboveground vegetation, as well as to compare species richness between the seed bank and the standing vegetation in these selected vegetation types. Seed bank size and species composition was determined mainly by using the seedling emergence method. Soil samples were collected at three-month intervals to obtain a measure of the temporal variation in size and composition. The comparison between the seed bank flora and standing vegetation was done by means of a transect method. The depth distribution of seeds in the soil profile was investigated by collecting soil samples at six different soil depths. Soil seed densities obtained by the seedling emergence and flotation methods were also compared. Results showed that the forest/grassland ecotone and grassland vegetation types produced the largest soil seed bank in terms of seed densities and the Licuati forest and thicket vegetation the smallest, in fact the latter had almost no persistent seed bank. Within each vegetation type the seed bank size showed clear seasonal variation. Seed distribution was concentrated in the upper soil layers. The flotation and physical separation method produced much larger seed numbers than the seedling emergence method. Generally, there is no or very little correspondence between the number of species recorded in the seed bank and that of the standing vegetation. It was found that the seed bank of the different vegetation types, if present, was a fairly poor predictor of the species composition of the existing vegetation, especially in terms of woody species.
