Abstract

The effectiveness of competition in predicting the increase in diameter (DI) for Brutian pine trees (Pinus brutia Ten.) in Duhok Governorate, northern Iraq, was evaluated. The results indicated that competition is a significant factor in determining growth in these forests. That competition varies locally, with variable tree densities and relatively complex tree structures, creating heterogeneous conditions. This study was conducted at different and varied sites regarding climate and topography by selecting three distinct density levels, from each of which (10) circular samples with a radius of (11 m) were chosen. From these, various data and geographical coordinates were collected, including diameter, height, crown center height, crown radius, basal area, number of trees per unit area, distance between competing trees and the target tree, and then developing several equations representing the relationship between competition indices based on distance as an independent variable and diameter growth as a dependent variable. The R² values for the low-density level were (CI6 = 0.21, CI7 = 0.42, CI8 = 0.21, CI9 = 0.42). For the medium-density level, they were (CI6 = 0.45, CI7 = 0.43, CI8 = 0.83, CI9 = 0.43). For the high-density level, they were (CI6 = 0.24, CI7 = 0.69, CI8 = 0.70, CI9 = 0.83).and then developing several equations representing the relationship between competition indices based on distance as an independent variable and diameter growth as a dependent variable. The R² values for the low-density level were (CI6 = 0.21, CI7 = 0.42, CI8 = 0.21, CI9 = 0.42). For the medium-density level, they were (CI6 = 0.45, CI7 = 0.43, CI8 = 0.83, CI9 = 0.43). For the high-density level, they were (CI6 = 0.24, CI7 = 0.69, CI8 = 0.70, CI9 = 0.83).