When they are disturbed by cutting, fire, storm, infestation or disease, they bounce back rapidly. Others will grow from the damaged trees' stumps and roots. More seedlings will develop from seeds stored in the leaf duff on the forest floor, and from seed that blows in from nearby trees. Yet other seeds will be carried into disturbed areas by birds and animals. Different tree species have developed different regeneration strategies over millions of years of evolution.
Some trees produce many, small seeds and depend upon the wind for their dispersal.
Other trees produce a few, large seeds and depend upon animals for their dispersal. If there are seedlings of desirable species already established when a forest is cut or otherwise disturbed, a new, high quality forest can develop immediately. Many of our best timber stands developed in this way after heavy cutting in the past. For whatever reasons, conditions were right for germination and growth of those seedlings and sprouts before the overstories were harvested. Unfortunately however, the opposite is more often the case.