A model of episodic, abiotic dispersal for oaks (Quercus robur)

The role of flooded rivers as dispersal agents for Quercus robur L. was investigated adjacent to the Disa River in the Orange Kloof Forestry Station, Cape Peninsula, South Africa. Three months after the floods, a systematic sampling of acorns was undertaken using 100, 4 m x 4 m quadrats. It was found that those quadrats in areas that had been flooded contained more than four times the number of acorns found in the quadrats of the unflooded areas. Further, flooded areas had a greater percentage of intact acorns and seedlings. It was also found that acorns beneath an oak canopy germinated poorly and that ungerminated acorns had a higher mortality. Since the flooding of this river must be considered a rare event, the efficiency of large scale, episodic dispersal was compared to the continuous low density dispersal carried out by the alien squirrel Sciurus carolinensis Gmelin. S. Afr. J. Bot. 1985, 51: 265–269 Die rol van oorstromende riviere as ‘n verspreidingsagent vir Quercus robur L. was langs die Disarivier in die Oranjekloof-bosboustasie, Kaapse Skiereiland, Suid-Afrika, ondersoek. Drie maande na die oorstromings was akkermonsters stelselmatig in 100, 4 m x 4 m kwadrate geneem. Daar is gevind dat daar vier maal meer akkers in die oorstroomde kwadrate as in die nie oorstroomde kwadrate voorgekom het. Daar het verder ook ‘n groter persentasie van lewensvatbare akkers en saailinge in die oorstroomde gebiede voorgekom. Verder is gevind dat die oppervlaktes onder die kroon van die eike die sade swak gekiem het en dat daar ‘n hoë akkersterftesyfer voorgekom het. Aangesien die oorstroming van die rivier as ‘n seldsame gebeurtenis beskou moet word, was die doeltreffendheid van grootskaalse episodiese verspreiding vergelyk met die voortdurende, maar lae digtheid, verspreiding deur die uitheemse eekhorinkie Sciurus carolinensis Gmelin. S.-Afr. Tydskr. Plantk. 1985, 51: 265–269