Transfer of live aspen root fragments, an effective tool for large-scale boreal forest reclamation

Abstract

An operational-scale transfer of salvaged forest floor material (FFM) containing trembling aspen (Populus tremuloides Michx.) roots was done to explore its feasibility for aspen forest restoration on heavily disturbed lands. This technique takes advantage of aspen’s ability of regenerate vegetatively from root fragments. Surface soils from an intact 4 ha aspen forest were salvaged at two depths (15 cm and 40 cm) and immediately placed onto a reclamation site of the same size and at the same two depths. Over the next two growing seasons, aspen sucker density, mortality, and height growth were assessed in relation to root fragment density, burial depth, and root fragment size. Sucker density, height growth, and survival increased with salvage and placement depth, likely related to the fact that deeper salvage depths allowed for more roots to be in good mineral soil contact and proportionately fewer roots to be placed close to the surface (0–5 cm), decreasing their risk of exposure. Large-diameter root fragments buried deeper than 20 cm did not produce viable suckers, so placement of FFM thicker than 20 cm cannot be recommended for the vegetative regeneration of aspen. However, if possible, a deeper salvage of the FFM that contains the aspen root system could allow the material containing the roots to be spread over a larger area and still achieve vegetative regeneration of aspen from suckering, although the overall root propagule density is lower.