ObjectiveThis paper aims to study the relationship between spatial distribution of main fine root traits and row spacing allocation of poplar.

MethodFour different horizontal spatial allocations of Populus × euramericana cv. ‘Nanlin-95’ plantations (plant spacing × row spacing 3 m × 8 m, 5 m × 5 m, 6 m × 6 m and 4.5 m × 8 m, respectively) were selected as the research objects, root drilling method was used to study fine root biomass and specific root length. The spatial distribution characteristics of root length and density were studied.

ResultThe results showed that horizontal spatial allocation had a significant effect on the spatial distribution characteristics of fine roots in poplar plantations. In vertical direction, fine root biomass, specific root length and root length density of low density (6 m × 6 m) stand were significantly higher than those of high density (3 m × 8 m, 5 m × 5 m). In horizontal direction, fine root biomass of rectangular (3 m × 8 m and 4.5 m × 8 m) stand was decreased as the distance from the trunk increased, while fine root biomass of square (5 m × 5 m and 6 m × 6 m) stand was negatively correlated with sampling distance. There was no significant correlation between the fine root length density, specific root length and sampling distance. 6 m × 6 m stand was higher than other stands at all horizontal distances.The fine root biomass, root length density and specific root length in the direction of plant spacing were always significantly lower than those in the direction of row spacing.

ConclusionThe fine root biomass of poplar plantations with small row spacing, limited growth and large row spacing will decrease significantly at a distance from the trunk, resulting in space waste. The main fine root growth characteristics of low-density square (6 m × 6 m) poplar plantations are the best among the four row spacing allocation stands, which is more suitable for the initial row spacing of poplar plantations.