This study aimed to analyze spatial patterns and associations of the studied trees in the developmental stages for achieving required information to prevent undermining stability of Nour Forest Park, to implement close-to-nature silvicultural prescription and to simulate distributions of aforementioned species in non-protective situations. Product of volume and specific wood density were used for estimating biomass of Caspian poplar trees in the forest. Mathematical parameters were used instead of absolute variables of wood density for estimating bole mass and crown mass of each tree. After distinguishing the developmental stage in the studied forest, three plots with one hectare area of 100 × 100 m dimension were outlined and the trees were coordinated by using measurement or trigonometric relations. Spatial analysis resulted from univariate O-ring application showed that the distribution was aggregated in the initial and optimal stages in the specified distances. In the decay stage, as well as being aggregated and random distribution, regular pattern of Caspian poplar trees was observed in the distance of 36 and 40 meter. Furthermore, the results of bivariate O-ring indicated that there was an intra-species positive attraction between medium class of biomass (medium size) and small class of biomass (small size) in a similar distance (8 m) in both initial and decay stages. As such, the intra-species attraction in the optimal stage was in attraction format in definite distances, and associations in the other distances were independent. The results showed that the association of aboveground biomass between large size and small size of trees in the developmental stages, implying that the density of small size trees is not under effects of intra-species competition resulting from the large sizes of trees in the developmental stages.