The Effect of Overhead Shade on the Survival of Loblolly Pine Seedlings

Abstract

Loblolly pine (Pinus taeda) 1 seedlings, if they succeed in germinating under overhead shade and survive the first season or two, will almost inevitably die at some later period unless this competition is removed. This makes it impossible either to practice the single tree or pure selection system of silviculture, or to maintain successfully for an indefinite period a growing stock on the same area, from which only an amount equal to the annual growth is removed annually or even at 10-year intervals. Under such practice, conditions originally favoring the establishment of loblolly pine, caused by past cutting and fires, are gradually altered to favor the dominance of hardwoods of inferior species and quality, leading ultimately to elimination of loblolly pine. On the other hand, if loblolly pine seedlings start in the same year with competing hardwood sprouts, they have a more than even chance of outgrowing and dominating the hardwoods in spite of their lesser height growth in the first year compared with sprouts. Full sunlight or freedom from overhead shade permits loblolly pine rapidly to assume its normal rate of growth in height, which can exceed that of all competitors except red gum (Liquidambar styraciflua) by from 25 to 50 per cent. Gum, due to its narrow crown, is not always a serious competitor if the pine develops at the same time, but, with oaks and other hardwoods, it becomes so if it starts 2-3 years earlier. Observers are often confused by the fact that in a rather mature high forest of mixed pine and hardwoods, especially among the hardwoods, great numbers of young loblolly pine seedlings and small