Prescribed Burning

Prescribed burning is fire set on purpose, on a chosen piece of ground, under a written plan and a named person in charge. It is repeated on a cycle rather than done once. Grassland and savanna assembled under regular fire, so a burn is closer to maintenance than to intervention. It takes out the fine fuel - the dry grass and litter a wildfire runs on - before there is enough of it to carry one. It also sets back the shrubs and saplings that would otherwise close the ground in, bares mineral soil for seed to germinate on, and holds the open structure that deer, quail, turkey and dove depend on.

Fire has to be fed, and that is what most owners underestimate. Below roughly 1100 kg of fine fuel per hectare (1000 lb per acre) where low turf-forming grasses dominate, or 2200 kg per hectare (2000 lb per acre) under taller tussock grasses, the fire will not carry, and grazing is usually what removed it - so stock often come off a paddock for a season simply to grow enough grass to burn. What the fire then does to brush depends on the plant rather than on the fire. A juniper under about 1.2 m (4 ft) that cannot resprout is killed; one of the same size whose regrowth buds sit below ground mostly survives the same burn.

Escape is the failure everyone pictures, and it clusters where heat, dryness and wind coincide, with wind above about 10 metres per second (22 mph) the strongest single factor. Firebreaks are bladed down to bare mineral soil at least 3.7 m (12 ft) wide before ignition and kept open between burns, and the recurring work is the plan, weather watched on the day, a contingency arrangement naming who responds if fire gets away, and telling the neighbours. Smoke is the quieter problem, and it is what turns a technically clean burn into a complaint. The slower failure is a slipped rotation: burning every three years or less pushes resprouting woody plants back, while four years or more lets them regain both height and cover, so missing two turns can lose ground that took a decade to win.