Here is the way Long-leaf Pine forests should look, with an open understory. Long-leaf grows in a ball or grass stage for several years, gathering nutrients, then suddenly growing 5-10 feet in a sudden burst. This is so when ground fires occur, they have reached a height that the fire won't harm them.
In conclusion, biologists and ecologists have learned the value of fire as an important resource management tool. The picture below says it better than any words can. The right side is what happens when fire is removed from the natural cycle, and the left side of the break is where fire has been reintroduced.