Seed biology of three species of Mesembryanthema in the southern succulent Karoo

Abstract

The seed biology of three Mesembryanthema species, Brownanthus ciliatus (Ait.) Schwant., Rhinephyllum macradenium (L. Bol.) Schwant. and Drosanthemum montaguense L. Bol. was studied at the Tierberg Karoo Research Centre in the Prince Albert district of the southern Karoo. Variation in capsule and seed numbers was recorded over three sampling periods representing different seed production events. In addition, the soil seed bank was investigated, as well as capsule opening rates and seed germination behaviour. Generally, there was a decline in capsule and seed numbers with time, suggesting that the canopy-stored seed bank is limited to the current year's seed production. Large soil seed banks did not appear to be characteristic of the species studied. Our estimates of seed production were larger than estimates of other researchers, possibly due to time of data collection. Our findings are related to the community structure and dynamics of the vegetation on the study site. Die saadbiologie van drie Mesembryanthema spesies, Brownanthus ciliatus (Ait.) Schwant., Rhinephyllum macradenium (L. Bol.) Schwant. and Drosanthemum montaguense L. Bol., is by die Tierberg Karoo Navorsingsentrum in die Prince Albert distrik, suidelike Karoo, bestudeer. Variasie in kapsule- en saadgetalle tussen drie versamelingsperiodes, wat verskillende saadproduksie-gebeure verteenwoordig het, is waargeneem. Die grondsaadbank, sowel as die oopspring van kapsules en die ontkieming van saad, is ondersoek. In die algemeen was daar oor 'n tydperk 'n afname in kapsule- en saadgetalle wat daarop dui dat die blaardak-gestoorde saadbank beperk is tot die huidige jaar se saadproduksie. Groot grondgestoorde saadbanke is blykbaar nie kenmerkend van die spesies wat bestudeer is nie. Ons skatting van saadproduksie was hoër as die skatting van ander narvorsers, wat moontlik toegeskryf kan word aan die seisoen waarin die data versamel is. Ons bevindinge hou verband met die gemeenskapstruktuur en dinamika van die plantegroei in die studiegebied.