Effects of tree density on seedling establishment in loblolly pine stand (Case study: Pylambra, Guilan)

In order to study the tree growth and natural regeneration of loblolly pine in a 33-year-old plantation in Pylambra region (Guilan province), 1.5 ha of well stocked stand was selected. This study was done as randomized complete block design with three treatments as: T_1, low density (15m² basal area ha^-1), T₂, medium density (20m2 basal area ha^-1) and T₃, high density (25m² basal area ha^-1) with four replicates. Soil surface scarification was carried out at the first year. Diameter at breast height, total height of trees in each plot (1000m²), number and height of pine regenerations in subplot with an area about 10 m² were measured. Results show that the height of Loblolly pine seedlings ranging from 10 to 150 cm were recorded in different treatments but in terms of the height growth, medium density treatment with 182 stem per ha showed better results and the difference with other treatments was statistically significant.