IDM KwaZulu-Natal - Proteas and Fire
Proteas must burn. Almost all are adapted to fire-prone ecosystems in some way. The most important strategy is resprouting. This is accomplished by having an underground bole that survives the fires. From these the plants resprout after a fire. Species such as Protea parvula, Protea simplex, Leucospermum innovans, Leucospermum gerrardii and Leucadendron spissifolium, appear to be designed to burn every year - even in the absence of fires the Proteas' branches may die in the cold season.
Others have the ability to grow thicker stems allowing a transformation from a resprouter to a tree, when conditions allow. These tree-favouring conditions are usually a respite from fire: the plants immediately abandon the rootstock and try and attain height, thus surviving by being above the fires. Examples of species using this strategy are Protea caffra, Protea comptonii, Protea gaguedi, Faurea rochedana and Faurea saligna. These species also maintain buds under the stem, allowing the plants to resprout from the stem should a very hot fire damage the canopy. Not all species try and attain tree-hood: tree forms are virtually unknown in Protea welwitschii and Protea dracomontana in Natal.
Two species seem singularly badly adapted to frequent fires. These are Protea roupelliae and Protea subvestita. Both grow fast and thus escape by being too tall for fires. But they survive fires only by escaping. Neither have buds beneath the bark - and they can only survive cool fires. Hot fires that kill the growing tips kill the branches and - when fires are very hot - even the plant. However, by not investing in epicormic (under-bark) buds and rootstocks, they can invest more resources in growth and seeds. This translates to a high potential to colonize under favourable conditions - however, the down side is a high potential extinction rate when conditions are unfavourable. There is a weak link in the cycle. That is the attainment of adulthood. Resprouting species have a hedge against fires - young plants survive it. The problem is that tree-species seldom fiower until they have become trees. In regularly bumed areas, this may take several decades.
Most proteas can cope with frequent fires very well. The two exceptions are Protea roupelliae and Protea subvestita. These have the problem that too frequent fires will kill all the young every year, and there will be a generation gap. A very hot fire may eliminate all the adults and the species will become locally extinct. Too few fires and the grass and brush may build up to levels where the fires will be hot enough to kill all the plants (young and old) and the species will become locally extinct. What are the ideal conditions for these species? Perhaps, a fire cycle of 3-4 years, with heavy grazing to reduce the fuel load? Perhaps, even very heavy grazing? More research is needed! Your atlas data will help to answer some of these questions!