Foliage, Stem, and Root Interrelations in Young Loblolly Pine

Leaf area has been proposed as a sensitive indicator of competition in loblolly pine, but it is difficult to measure in the field. Stem diameter is easier to measure and has been demonstrated to be more sensitive to competition than height growth. The objective of the study was to determine the interrelations of total needle surface area, specific leaf area, stem cross-sectional area, and root volume in young loblolly pine seedlings. Stem cross-sectional area was found to be linearly related to both total needle surface area (R² = 0.96) and root volume (R² = 0.95). These strong relationships suggest the presence of a closely regulated, physiological feedback system in seedlings of loblolly pine. Thus, stem cross-sectional area would be a good predictor of competition-induced leaf area changes. Specific leaf area was significantly affected by seedling and needle age with a range from 260 cm²/g in 1-year-old seedlings to 150 cm²/g in 4- and 5-year-old seedlings. Present year needles had consistently higher specific leaf areas. Changes in leaf specific gravity appeared to be the cause of the specific leaf area changes. Forest Sci. 31:891-898.