Natural Regeneration of Longleaf Pine (N.C. Forest Service)
Through careful planning and timing, longleaf pine can successfully regenerate naturally. Longleaf pine has several characteristics that we must consider in selecting the right regeneration method.

Shortleaf Pine Natural Regeneration (N.C. Forest Service)
Natural regeneration offers a viable low cost choice using the trees annual seed crop. Shortleaf pines forests are able establish seedlings naturally due to its prolific seed production. For shortleaf pine the seed tree and shelterwood harvest regeneration methods are most often recommended.

Natural Regeneration Using Seed Trees (Mississippi State University Extension)
All forestry endeavors either start with or eventually end up at the regeneration stage, but many landowners do not realize that several options are available and that regeneration work should start long before the harvest of the current crop of trees.

Natural regeneration: Growing a new stand from natural seedlings (University of Minnesota)
A stand should be regenerated when most of its trees are economically mature, when it is stocked with undesirable tree species or poor quality trees, or when it is greatly understocked. Tree stands may be reproduced through natural or artificial means (planting) or by a combination of the two. The choice of how best to reproduce a stand depends on the tree species involved, financial considerations, and management objectives.

Harvesting for Natural Pine Regeneration (Alabama Forestry Commission)
This article discusses two harvesting systems typically used in the Southeast that leave 4 to 60 well-spaced,
good quality trees (seed trees) per acre to provide natural regeneration of pine stands.