Objective Position-controlled afforestation creates spatial heterogeneity and competitive asymmetry from the beginning of stand formation. It not only retains the convenience of regular afforestation but also conforms to the randomization cultivation concept of adapting to nature. Understanding the structural characteristics of these stands is crucial for improving the quality and stability of planted forests.

Methods Based on survey data from the position-controlled afforestation experiment of Populus × euramericana‘Neva’ in Fangshan, Beijing in autumn 2018 and spring 2024, the changes in basic tree measurement factors, diameter at breast height (DBH) of trees distribution and spatial structure of the plantation in the five years were analyzed.

Results (1) Under high-density planting conditions, the survival rate in position-controlled plots reached 55.6%, compared to only 37.5% in full-planting uniform plots, indicating a significant difference in stand preservation; (2) The spatial ecological niches of trees in different structure units were significantly different. The mean dominance of uniform trees increased, from 0.495 (balanced state) in 2018 to 0.560 (extremely suppressed state) in 2024. The overall relative dominance of random trees remained relatively stable, changing slightly from 0.527 to 0.533 (suppressed state). The dominance of clustered trees increased from 0.521 (suppressed state) in 2018 to 0.445 (extremely dominant state) in 2024 (3) The crowding distribution of trees in different structure units was different. The crowding distribution of uniform trees was always right-skewed; for random trees, it shifted from left-skewed to right-skewed; and for clustered trees, it changed from normal to right-skewed.

Conclusions (1) The survival rate of trees in position-controlled planting is higher than that in full-density uniform plot. High mortality is related to high-density planting. (2) Spatial niche hierarchy (clustered > random > uniform trees) aligns with growth rates and supports the forest edge or gap effect theory, where microsite advantages drive differential resource capture. (3) The spatial niches of random trees remain relatively stable, while the dominance of uniform trees decreases significantly and clustered trees exhibit rapid dominance enhancement. These patterns align with both the random framework-stability hypothesis and the effective growing space theory.