Looking across plot of 1.6 mm and 2.4 mm seedlings (root collar diameter) to a plot of 3.2, 4.0, and 4.8 mm seedlings; 1966 study at age 2 (man standing in buffer between plots).
On the left is a plot of 4.8 and 5.6 mm seedlings at age 3. On the right is a plot of 1.6 and 2.4 mm seedlings at age 3 (1966 study). No. 40 Loblolly Pine Seedling Grade Growth and Survival, by T.A. Dierauf.