The prevalence of mixtures of these two species across much of the South suggests consideration of the forest cover type. Mixed forests of these pines occur over a major area of both the Coastal Plain and the Piedmont provinces. Oaks and hickories are generally associated with them, but some 50 broadleaf species invade and frequently take over the site. Sweetgum, blackgum, hickories, red oak, and post oak often replace the loblolly pine-shortleaf pine-hardwood subclimax types.
In the western sector of the range, hybridization and back-crossing of the two species is apparent, resulting in numerous intermediate forms that cannot be readily classified as belonging to either species. Bark, cones, seed, foliage, buds, and seedling progeny are intermediary. Foresters may find themselves in a quandary when tallying tree volumes by species in a timber cruise.
Forest geneticists suggest wide variation in inheritance as well as interbreeding as possible causes for the intermediate forms. No doubt both take place, but the latter seems more probable in spite of the time difference in pollen dissemination, usually March for loblolly pine and April for shortleaf pine. The two species have similar silvical characteristics; together they respond to the same silvicultural treatments as either of the pure types.19
Was this article helpful?