Components and Nutrient Concentrations of Small-Diameter Woody Biomass for Energy

Abstract

The growing interest in using woody biomass for energy offers a potential opportunity to commercially remove cohorts of small-diameter trees (Ͻ 25 cm dbh) during thinning operations that otherwise have little or no economic value. However, there is little information about the quantity of biomass and the nutrients that would be removed during small-diameter harvests in oak stands of the Central Hardwood Region. The objectives of the study were to quantify biomass removals by component (foliage, twigs, bark, and stemwood) and the nutrient concentrations within components for estimating quantities of both wood and nutrients that would be removed under alternative harvest prescriptions. White oak was the most common species harvested; others included post oak, black oak, mockernut hickory, American elm, persimmon, white ash, and dogwood. Sampling indicated that heartwood and sapwood comprised most of the biomass (78-79%) followed by bark (15%), twigs (4-5%), and leaves (about 2%). Estimated nutrient removals during a small-diameter harvest in this region were 1.3-3 times greater than during conventional sawlog harvests. The relatively high nutrient removals that can occur for biomass harvesting compared to traditional sawlog harvests underscore an ongoing need to ensure that nutrient removals during biomass harvesting do not exceed inputs from soil mineral weathering and the atmosphere.

Idaho forest growth response to post‐thinning energy biomass removal and complementary soil amendments

“…While it is difficult to make generalizations that can be applied in every forest type, biomass harvesting from nutrient limited sites will have a proportionally greater impact than harvesting from nutrient abundant sites (Thiffault et al, 2011). Small-diameter biomass removal will likely impact site conditions less than whole-tree harvesting (Kabrick et al, 2013;Klockow et al, 2014) as smaller quantities of biomass will be removed, but soil impacts will depend on the harvest method (e.g., skidder, forwarder), how much slash remains after harvesting, soil conditions, and climatic regime (Page-Dumroese et al, 2010).…”

Forest soil respiration and exoenzyme activity in western North America following thinning, residue removal for biofuel production, and compensatory soil amendments

“…Clear cutting shifts soil microbial function from nutrient limited and ectomycorrhizal dominated toward carbon limited and saprobe dominated (Kyaschenko, Clemmensen, Hagenbo, Karltun, & Lindahl, ). Yet with thinning, soil microbial shifts are less definitive (Adamczyk, Adamczyk, Kukkola, Tamminen, & Smolander, ), which supports the idea that small‐diameter biomass removal from precommercial thinning will likely impact site conditions less than clear‐cut harvesting (Kabrick, Dwyer, Shifley, & O'Neil, ; Klockow, D'Amato, & Bradford, ; Sherman, Page‐Dumroese, & Coleman, ) because, with thinning, much of the overstory structure is retained and less biomass is removed.…”