What is the definition of controlled burn?

Answer 1

In forestry, when a forest achieves a level of overgrowth such that a forest fire would easily become uncontrollable for firefighters, agents from the forestry service will deliberately set small, controlled fires in key areas that will create grid-like patterns in the forest to remove the overgrowth.

This is a preventative measure that keeps massive wildfires that may be started by lightning strike, carelessness, or arson from destroying both human habitation and local ecosystems.

Ironically, controlled burns can also be used to spur stagnant ecosystems, as damaged trees and plants can rebuild quite quickly. There are also plants that remain dormant for decades and only sprout when the heat from a wildfire "wakes" their seeds. These plants form the foundation for new growth in forests. Recently burned forests also attract birds and other animals that thrive on new-growth leaves and the insects they provide.