Forest fires can burn down all of the trees and plants living in an area. however, new growth can spring from the decaying organic matter left behind. what is the gradual, sequential regrowth of a community of species after a forest fire? *

The answer would be secondary succession.

Primary succession happens before an ecosystem is established. In contrast to it, secondary succession happens after a disaster that destroys most of the species in the land.
In this case, the ecosystem is already established. The forest fire is the disasters that destroy the ecosystem, allowing the secondary succession.