@miked Why does the Common need a fire?
‘There is just 10% left of the critically endangered veld type, Cape Flats Sand Fynbos, that only occurs in Cape Town and nowhere else. Like all fynbos – which is fire-prone and fire-dependent – it needs to burn otherwise it will gradually die. The ideal time for a burn is every ten to twelve years. Meadowridge Common contains a small remnant (5,39 hectares) of Cape Flats Sand Fynbos where some 137 different plant species have been recorded. The Common is a Biodiversity Agreement Site, but it is degraded due to a long history of pines and lack of fire – apart from a small wildfire in December 2003. After years of motivating for a fire, the time has finally come and a restoration burn has been planned’
The ‘common’ answer to this burning question in many areas of the world is that a heavy load of combustable material gives a severe burn which can burn soil and woody shrubs that might rely on resprouting so more frequent less severe burns keep the load down and allow higher biodiversity overall. Also need to consider the burning regime that the ecosystem has developed under and how it has changed due to deliberate supression of burning or invasive species.
All of this also interacts with climate change so the answer may be complex and different in different parts of the world, for example in uk moor burning may be to maximise production of just one species for shooting and so may not be the best system for overall biodiversity nor carbon storage. Everything in ecology is complex and needs careful understanding so any of these general statements may need to be adapted for local conditions.