Residue distribution and biomass recovery following biomass harvest of plantation pine
Forest biomass is anticipated to play a significant role in addressing an alternative energy supply. However, the efficiencies of current state-of-the-art recovery systems operating in forest biomass harvests are still relatively unknown. Forest biomass harvest stands typically have higher stand densities and smaller diameter trees than conventional stands which may result in reduced recovery efficiencies. In this study, we explore the spatial and temporal effects on residue distribution as a result of biomass harvest of 14-year- and 24-year-old loblolly pine (Pinus taeda) plantations at stand densities of 1500 and 1900 trees per hectare, respectively. Additionally, we explore biomass recovery efficiency by a harvesting system that was specifically designed for southern pine plantation biomass harvests. Pre-harvest aboveground biomass for the younger site was half that of the older site (240 vs. 420 t ha-1) with approximately 79% and 86% being merchantable biomass, respectively. The pre-harvest condition exhibited 100 percent ground cover; whereas, post-harvest conditions had nearly 20 percent of the area designated as bare based on the residue distribution assessments. The assessments found increased incidence of ground cover in the finer biomass classes in comparison to the larger debris and bare classifications. The harvesting operations recovered 85 percent of standing biomass in a 24-year old stand and 90 percent of the standing biomass in a 14-year old stand. In general, harvesting the plantations increased downed woody material on site and these unrecovered residues are expected to satisfy objectives related to maintaining site productivity, minimizing erosion, and preserving ecological values.