Objective To study the forest spatial structure of the permanent 50-ha forest dynamics project plot on Barro Colorado Island (BCI), Panama.

Method The seventh censuses (2010) of stems ≥ 1 cm DBH alive trees data of BCI plot was analyzed by the neighborhood-based variables of forest spatial structure, and the spatial structure of canopy trees and understory trees were compared.

Result The pattern of live trees followed a random distribution (W=0.504) in the whole plot, 74.7% of the live trees in the state of high mingling degree, few individuals in the status of low mingling degree (M_i=0). Most of understory trees were in higher dominance degree and superior status of mingling. Large numbers of individuals in the plot were small trees (1 cm ≤ DBH < 20 cm), to this degree, they were in a status of disadvantage and belonged to inferior trees.Regardless live trees in the whole plot, the canopy or the understory, almost all individuals were in superior mingling status. At the scale of four neighboring trees around the reference tree within the whole plot, the ratio of conspecific neighbor trees (M_i=0, W_i=0.25) closed to zero. This indicated that the aggregate distribution of conspecific individuals in such a small scale was non-existence.

Conclusion The forest was in a state of high mingling.More than half of the trees in the plot followed a random pattern, the trees with different dominance degrees had a similar frequency. It is suggested that the aggregate distribution of conspecific individuals in such a small scale (four neighboring trees around the reference tree) is non-existence.