Responses of mature roadside trees to root severance treatments

•A root pruning (trenching) study was carried out on mature roadside Quercus virginiana.•Water stress symptoms were present for 440 days when trenches were made at 3 times DBH.•Root pruning reduced shoot elongation and leaf area one growing season after root severance.•The trunk diameters of trees closest to a road grew less than those further away.•Root pruning in trenches should not be undertaken closer than 6 times DBH. Conflicts between trees and infrastructure installation or repair occur frequently in the urban environment and may result in damage to or complete removal of tree roots. We monitored the responses of trees to linear root cutting and examined the effects of the presence of a road within tree root zones. Mature Quercus virginiana Mill trees (n = 31) were exposed to three root pruning treatments (plus a control) consisting of a trench on one side of the tree, offset by a distance as a multiple of trunk diameter (3x, 6x and 12x). Roots were severed manually, and their diameters were measured at the cut point to estimate a total cross-sectional area of severed roots. The total severed root cross-sectional area was subsequently expressed as a ratio of whole trunk cross-sectional areas (termed Ar(BH)), as well as trunk conductive sapwood areas (termed As(BH)) at breast height (1.4 m). The shortest horizontal distance between the tree bases and the edge of a nearby road was also recorded and included in statistical analyses as a continuous variable. Linear root cutting reduced shoot extension and leaf area by as much 146.13 mm (p