Effects of seedling density on the growth of Corsican pine (Pinus nigra var. maritima Melv.), Scots pine (Pinus sylvestris L.) and Douglas-fir (Pseudotsuga menziesii Franco) in containers

Corsican pine, Scots pine and Douglas-fir seedlings were grown in containers at a constant volume at densities ranging from 100 to over 1 000 plants m -2. Both shoot and root dry weight of each species decreased with increasing density, especially at densities greater than 500 m-2 . In contrast, shoot height of Corsican and Scots pine increased at high densities, but the height of Douglas-fir was unaffected by density. Shoot height was not correlated with dry weight in Douglas-fir and Scots pine, and was negatively correlated in Corsican pine. Root collar diameter was positively correlated with seedling weight in all three species. Increasing the volume of tray cells only increased seedling size in Douglas-fir at densities lower than 400 m-2. Survival of outplanted Douglas-fir seedlings was reduced in plants grown at the highest density (1 550 m-2). Height and diameter increments were greatest in plants raised at intermediate densities around 780 m-2. (© Inra/Elsevier, Paris.)