Intensive Utilization of Harvest Residues in Southern Pine Plantations: Quantities Available and Implications for Nutrient Budgets and Sustainable Site Productivity

Abstract

The rising costs and social concerns over fossil fuels have resulted in increased interest in and opportunities for biofuels. Biomass in the form of coarse woody residues remaining after traditional timber harvest in the southeastern USA is a potentially significant source of biomass for bioenergy. Questions remain regarding whether the removal of this material would constitute a sustainable silvicultural practice given the potential impact on soil nutrient cycling and other ecosystem functions. Our objective is to review existing studies to estimate quantities of residual materials on southern pine forests that may be available, potential nutrient removals, and potential replacement with fertilizer. Regionally, it is estimated that 32 million Mg year −1 of dry harvest residues may be available as a feedstock. At the stand level, between 50 and 85 Mg ha −1 of material is left on site after typical stem-only harvests, of which half could be removed using chippers at the landing. Based on these estimates, increase in midrotation fertilization rates of 45% to 60% may be needed on some sites to fully replace the nutrients from harvesting residues removed for bioenergy. Field experiments suggest that residue removals do not degrade forest productivity in many cases, but more data are needed to assess the effects of frequent removals (i.e., from short-rotation systems) over longer periods and identify sites that may be particularly sensitive to the practice. A benefit of developing markets for previously nonmerchantable materials may create incentives for improved forest management by landowners.

Learning for the Future: Educating Career Fisheries and Wildlife Professionals

“…These approaches seek to minimize shortterm impacts and avoid long-term deterioration of key indicators of sustainability-water quality, soil productivity, wildlife habitat, and biodiversity. Forest biofuels that rely on removal of timber residues such as branches, bark and tree APLU Boards on Natural Resources and Oceans, Atmosphere, and Climate -59 tops that are commonly left on the ground are likely to decrease ground-level habitat for wildlife and arthropods (Webster et al 2010, Rupp et al 2012) and reduce site productivity (Eisenbies et al 2009) and water quality (Schilling 2009). Forest biofuel production that removes logs and snags may reduce biodiversity (NRC 2011, Rupp et al 2012.…”

Economic Impact of Net Carbon Payments and Bioenergy Production in Fertilized and Non-Fertilized Loblolly Pine Plantations

“…The residues (including bark, tree tops, branches, and foliage) that are obtained at the time of harvest were assumed to be sold as bioenergy for electricity production (Using whole-tree harvesting residue for bioenergy is a typical means of obtaining biomass for bioenergy. It is important to note that there is currently significant debate on the ecological impacts of removing residue that historically would be left on site [28].) A real discount rate of 5% was used in all economic calculations.…”

Sustainable Production of Bioenergy Feedstock from the Industrial Forest: Potential and Challenges of Operational Scale Implementation

“…More intensive management could include fertilization, denser plantings, more frequent thinning of noncrop trees, or understory harvest. Forest residues could be an important bioenergy feedstock, making up 13 % of the US potential biomass [12] and displacing about 3 % of electricity sector carbon (based on 1997 FIA and energy data) [13]. Figure 1, produced by the National Renewable Energy Laboratory based on US Forest Service data, shows residues available for biomass removal.…”

“…Eisenbies et al [12] synthesized study data on biomass left after current stem-only harvest and found that whole-tree harvest could remove 20-50 % of material now retained after harvest. They cite conflicting evidence as to which sites are most resilient, but that it is possible to remove residue without depleting nutrients and reducing site productivity.…”