Installing cables did not affect annual radial increment in co-dominant stems of red oaks

Arborists install cables to support co-dominant stems. The adaptive growth hypothesis predicts that doing so will alter radial increments in the stems because their motion will have been restricted. To facilitate the wind-induced motion of cabled stems, cables made of more extensible material have been suggested as an alternative to systems made of steel. Cables made of steel and polypropylene were installed in red oaks (Quercus rubra L.). Trees were harvested after five years and annual radial increment was measured for the previous sixteen years in four directions (incident with and perpendicular to the direction of the cable) on five discs removed from two co-dominant stems that were cabled in each tree. Annual radial increment did not change in response to the installation of cables with one exception: in the three years following installation, it was greater incident with the cable on two discs immediately proximal and distal to the eyebolt in each co-dominant stem to which steel cables were attached. The exception appears to be due to the formation of wound wood. The results contradict the adaptive growth hypothesis, but this was likely due to cables not restricting wind-induced motion to the extent achieved in previous studies.