What would happen to a forest ecosystem if a fire killed most of it is producers?

New trees grow. Some species of tree seeds can ONLY grow after they've been burned; for them, fires are part of their life cycle. Many of the animals who lived in that forest would have been killed, but once the fire is out, other animals will move in on the newly vacated territory.

The problem is that our current "Extinguish all small fires" policy of forest management allows the forest floor to accumulate an ENORMOUS fuel load. So instead of periodic small fires, we get rare CONFLAGRATIONS which spread much farther and faster than they might otherwise have. So the forests are more severely damaged, and take longer to recover. But they DO recover.