Fynbos is a fire-adapted vegetation that requires regular burning for its persistence. In the absence of fire, fynbos is gradually replaced by thicket species. It thrives on infertile soils and fire is the mechanism that recycles precious nutrients from old moribund growth into the soil. Fire in fynbos is far from a disaster, but rather a crucial trigger that resets the fynbos ‘succesional clock’. It provides the stimulus for dormant seeds to germinate and the opportunity for many annuals, short-lived perennials and bulbs to grow, flower and seed during times of abundant nutrients and sunlight. They complete their short life cycles, returning to the soil as the larger shrubs overwhelm them, and remain dormant until the next fire. The optimal fire cycle for fynbos is between 10-14 years. Shorter fire cycles can wipe out slow maturing species, while species start dying when intervals become too long.
Fires are more common in fynbos than in any other heathlands in the world and it’s rare to find fynbos stands of more than 20 years of age. Some species re-establish by sprouting from a woody root-stock (these plants are known as resprouters); while others germinate from seed that has been stored in the soil or on plant canopies between fires (reseeders). Some resprouters, including many of the larger Proteaceae, protect their trunks from fire with a thick, insulating layer of corky bark and resprout from buds buried in the trunk following fire. Unlike sprouters, the seeders have a complete turnover in generations after each fire and are therefore subjected to a greater frequency of natural selection and higher speciation. The high diversity of species in fynbos can, at least in part, be ascribed to population fragmentation and regular turnover in generations as a result of fire.
The huge 2006 fire that swept across the Agulhas Plain was frightening to witness, yet the subsequent regrowth and succession of fynbos over the last five years has been a wonder to behold. Part of this blog will revisit the amazing impact of this 60 000 hectare blaze on the flora and fauna of the region in the Fire Diary – a week by week record of the remarkable recovery of the Walker Bay fynbos since 2006.