Good question! As you are hinting to, a monoculture forest like a plantation isn’t going to have as much biodiversity in the understory as a more natural forest. In terms of how rapidly the ecosystem recovers following fire, it will depend on the species that were present within and adjacent to the site prior to the fire. If it’s longleaf pine tree, they will probably survive the fire. However, in more natural ecosystems, the longleaf would survive and the many understory plants (grasses, forbs, woody plants) would also survive and resprout after the burn. In pine plantations, site preparation treatments are often used to minimize vegetative that can compete with pines. These treatments tend to reduce understory diversity and cover (that’s kind of the point). Similarly, densely planted pine plantations tend to have little understory diversity due to a lack of sunlight available at the forest floor.