Heather burning is part of moorland management especially on grouse moors. Apparently the male grouse need some long heather some short heather and some medium length heather to enable him to hit his grousy groove thang, which is why you see all those patches.
It's kinda ironic that if a moor is not burned and the heather controlled then the moor is at risk of a serious fire as was the case with Fylingdales Moor.
As for Bracken, it's nasty assed stuff chocka full of carcinogens and home to a multitude of mothersuckin ticks. It's just a nasty invasive plant that we used to control by harvesting it for all sorts of puposes but now tend to leave alone. I don't think burning promotes bracken growth, I'd say that a managed moor has less bracken but is often far from free of the stuff.
I guess we could say that fire occurs naturally on moorland and is one of natures great levellers. However it should be noted that moorlands are essentially man-made deserts, monuments to mans prehistoric conquest of the landscape.