Autecological studies on Audouinia capitata (Bruniaceae). 8. Role of fire in regeneration

In A. capitata the protracted juvenile phase, the longevity of plants and their effective vegetative fire regeneration, are all possibly adaptively linked to poor sexual reproduction. After a fire-free period of more than ten years, averages of only 4.7 and 0.4 seedlings per plant were recruited following summer and winter burns, respectively. The positive correlation between the prevalence of fynbos fires from January to March and the germination response of soil-borne seeds when treated with smoke at different times of the year, suggest that the species has evolved in a fire-prone vegetation in a climate with a seasonal rainfall distribution similar to the present one. The vegetative vigour of shoots, the size and numbers of inflorescences, and seed set were increased by fire. The continuation of a policy of late autumn and winter burns may be fatal for survival of the species. Plants responded favourably to fire at a post-fire age of 11 years. Some populations, however, were still vigorous and sexually productive at a post-fire age of 20 years. Die uitgerekte jeugfase, die langlewendheid van plante en die effektiewe vegetatiewe vuurregenerasie in A. capitata, hou evolusionêr moontlik verband met gebrekkige geslagtelike voortplanting. Gemiddeld 4.7 saailinge per volwasse plant is na brande in die somer en gemiddeld 0.4 saailinge na ’n brand in die winter aangetref. Die positiewe verband tussen die natuurlike frekwensieverspreiding van fynbosvure vanaf Januarie tot Maart, en die ontkiemingspersentasie van saad in die grond wat op verskillende tye van die jaar met rook behandel is, dui daarop dat die spesie in ’n vuur-onderhewigeplantgemeenskap in ’n klimaat met ’n jaarlikse reënvalverspreiding soortgelyk aan die huidige een, ontwikkel het. Die vegetatiewe groeikrag van lote, die grootte en getalle van bloeiwyses, en saadset is deur vuur verhoog. Die voortsetting van ’n beleid van laatherfs- en winterbrande sal waarskynlik fataal wees vir die oorlewing van die spesie. Plante het gunstig op ’n brand 11 jaar na die vorige vuur gereageer. Sommige populasies was egter nog steeds groeikragtig en geslagtelik produktief op ’n na-vuurse ouderdom van 20 jaar.