Whole-tree harvest and residue recovery in commercial aspen: Implications to forest growth and soil productivity across a rotation
Abstract
© 2019 Elsevier B.V. Harvest residues are an abundant by-product of commodity management in working forests, with significant potential as feedstock for bioenergy and advanced biomaterials. While contemporary experimental research programs seek to determine the short-term impacts of intensive residue removal on soil conditions and site productivity, rotation-length implications in operational settings remain speculative. Nonetheless, it is generally recognized that the effects of residue recovery are cover type and site dependent, and that production lands will be the primary source of increased utilization. We leveraged historical records across a 40-year chronosequence of 46 individual Populus spp. stands in upper Michigan harvested with Whole-tree harvest (WTH) and Stem-only harvest (STH) to observe and evaluate these practices on aboveground productivity and soil chemical properties. Stands were located across 4 contrasting soil types that are typical of site productivity and textural classes within the Great Lakes region. Results indicate a 36% reduction of residues in WTH treatments at 15.04 Mg ha−1 compared with 23.43 Mg ha−1 at stand establishment, yet residue levels in both treatments exceeded regional biomass retention guidelines, and differences were negligible by 16 years. The data further suggest that stand productivity is unaffected by harvest treatment. Soil C, N and macronutrients exhibited high variability across soil types, with mixed responses to treatments. These results highlight the significant amounts of residues remaining on site following operational WTH and that these practices do not appear to alter aboveground productivity of the Populus cover type across a range of soil types.