Forest Bioenergy Research Articles

Coupling aquaculture with forest plantations for food, energy, and water resiliency

Freshwater aquaculture and forest bioenergy markets are expanding globally in areas concurrently experiencing human population growth, urbanization and water shortages. Coupling these agroecosystems can improve food, energy, and water resiliency by enhancing ecosystem services through fertilization, water-reuse, carbon storage, and bioenergy via biomass production. This study evaluated how a model aquaculture-managed forest plantation could (1) provision fish and woody biomass; (2) regulate carbon, groundwater infiltration, and groundwater quality; and (3) support nutrient cycling over a two-year period. A 0.5-hectare hardwood bioenergy plantation was established with 12 Populus spp. genotypes adjacent to a 0.6-hectare freshwater aquaculture operation (hybrid striped bass, Morone chrysops×M. saxatilis); pond waters were land-applied on the plantation for two years. The aquaculture operation produced ~3.5Mg of fish and trees yielded 5.9Mgha−1yr−1 of oven-dry biomass, sequestered 2.9Mg carbon (C) ha−1yr−1 and stored 0.028Mg nitrogen (N) ha−1yr−1. Biomass productivity, carbon storage, and nitrogen storage differed significantly among the evaluated Populus genotypes. Land application of pond water increased groundwater infiltration by 60% relative to the previous year. The integrated system regulated chlorophyll a, total organic carbon, and nitrogen in groundwater at concentrations below regulatory limits. This study demonstrated that coupled agroecosystems could deliver productive yields of food and bioenergy as well as support water re-use while meeting water quality regulations. More research is needed to evaluated long-term sustainability and economic viability of this coupled system and other land management practices that seek to improve food, energy, and water resiliency.

Decision support framework for evaluating the operational environment of forest bioenergy production and use: Case of four European countries

Complex policy-making situations around bioenergy production and use require examination of the operational environment of the society and a participatory approach. This paper presents and demonstrates a three-phase decision-making framework for analysing the operational environment of strategies related to increased forest bioenergy targets. The framework is based on SWOT (strengths, weaknesses, opportunities and threats) analysis and the Simple Multi-Attribute Rating Technique (SMART). Stakeholders of four case countries (Finland, Germany, Norway and Slovenia) defined the factors that affect the operational environments, classified in four pre-set categories (Forest Characteristics and Management, Policy Framework, Technology and Science, and Consumers and Society). The stakeholders participated in weighting of SWOT items for two future scenarios with SMART technique. The first scenario reflected the current 2020 targets (the Business-as-Usual scenario), and the second scenario contained a further increase in the targets (the Increase scenario). This framework can be applied to various problems of environmental management and also to other fields where public decision-making is combined with stakeholders’ engagement. The case results show that the greatest differences between the scenarios appear in Germany, indicating a notably negative outlook for the Increase scenario, while the smallest differences were found in Finland. Policy Framework was a highly rated category across the countries, mainly with respect to weaknesses and threats. Intensified forest bioenergy harvesting and utilization has potentially wide country-specific impacts which need to be anticipated and considered in national policies and public dialogue.

Range and uncertainties in estimating delays in greenhouse gas mitigation potential of forest bioenergy sourced from Canadian forests

AbstractAccurately assessing the delay before the substitution of fossil fuel by forest bioenergy starts having a net beneficial impact on atmospheric CO2 is becoming important as the cost of delaying GHG emission reductions is increasingly being recognized. We documented the time to carbon (C) parity of forest bioenergy sourced from different feedstocks (harvest residues, salvaged trees, and green trees), typical of forest biomass production in Canada, used to replace three fossil fuel types (coal, oil, and natural gas) in heating or power generation. The time to C parity is defined as the time needed for the newly established bioenergy system to reach the cumulative C emissions of a fossil fuel, counterfactual system. Furthermore, we estimated an uncertainty period derived from the difference in C parity time between predefined best‐ and worst‐case scenarios, in which parameter values related to the supply chain and forest dynamics varied. The results indicate short‐to‐long ranking of C parity times for residues < salvaged trees < green trees and for substituting the less energy‐dense fossil fuels (coal < oil < natural gas). A sensitivity analysis indicated that silviculture and enhanced conversion efficiency, when occurring only in the bioenergy system, help reduce time to C parity. The uncertainty around the estimate of C parity time is generally small and inconsequential in the case of harvest residues but is generally large for the other feedstocks, indicating that meeting specific C parity time using feedstock other than residues is possible, but would require very specific conditions. Overall, the use of single parity time values to evaluate the performance of a particular feedstock in mitigating GHG emissions should be questioned given the importance of uncertainty as an inherent component of any bioenergy project.

Assessment of forest bioenergy potential in a coal-producing area in Asturias (Spain) and recommendations for setting up a Biomass Logistic Centre (BLC)

The socio-economic crisis of the past few years has led to a progressive and marked decline in the production of coal power plants in Europe. This situation affects the regions where coal is the main traditional energy source. Energy from forests is considered to be a good alternative to coal. The exploitation of forest biomass in these regions could counteract the negative effects posed by the marked decline in traditional coal mining activities. Given the abundance of forest in Asturias, Spaińs main coal mining area, the present work was conducted on the Central Coal Basin (CCB). This study focuses on the territory of the mining areas within the CCB, known as municipalities. The main goal was to evaluate the existing biomass resources in order to assess its sustainable energy potential and its replicability in other coal mining regions in Europe. The multiscale methodology used considers a combination of mass, energy and costs of the biomass available, to estimate the bioenergy obtainable and the assessment of the techno-economic feasibility of solid biofuel production as a source of alternative energy. A detailed evaluation of forest residues was carried out including the economic and environmental constraints. The average collection efficiency was 43.0% resulting in an estimated biomass total cost of 84.10€/dryt. Finally, the conclusion was made to locate the Biomass Logistic Centre (BLC) in Oviedo due to its favourable technical, economical and geographical characteristics. The proposed BLC would have a production capacity of 17drykt/year of pellets, 8drykt/year of wood chips and 3drykt/year of briquettes, of which 40% (31drykt/year) would be collected within a 50km radius. Such production would avoid 51kt/year of CO2 emissions.

Global spatially explicit CO2 emission metrics for forest bioenergy.

Emission metrics aggregate climate impacts of greenhouse gases to common units such as CO2-equivalents (CO2-eq.). Examples include the global warming potential (GWP), the global temperature change potential (GTP) and the absolute sustained emission temperature (aSET). Despite the importance of biomass as a primary energy supplier in existing and future scenarios, emission metrics for CO2 from forest bioenergy are only available on a case-specific basis. Here, we produce global spatially explicit emission metrics for CO2 emissions from forest bioenergy and illustrate their applications to global emissions in 2015 and until 2100 under the RCP8.5 scenario. We obtain global average values of 0.49 ± 0.03 kgCO2-eq. kgCO2−1 (mean ± standard deviation) for GWP, 0.05 ± 0.05 kgCO2-eq. kgCO2−1 for GTP, and 2.14·10−14 ± 0.11·10−14 °C (kg yr−1)−1 for aSET. We explore metric dependencies on temperature, precipitation, biomass turnover times and extraction rates of forest residues. We find relatively high emission metrics with low precipitation, long rotation times and low residue extraction rates. Our results provide a basis for assessing CO2 emissions from forest bioenergy under different indicators and across various spatial and temporal scales.

A spatial assessment of potential biomass for bioenergy in Australia in 2010, and possible expansion by 2030 and 2050

AbstractThis paper provides spatial estimates of potentially available biomass for bioenergy in Australia in 2010, 2030 and 2050 (under clearly stated assumptions) for the following biomass sources: crop stubble, native grasses, pulpwood and residues (created either during forest harvesting or wood processing) from plantations and native forests, bagasse, organic municipal solid waste and new short‐rotation tree crops. For each biomass type, we estimated annual potential availability at the finest scale possible with readily accessible data, and then aggregated to make estimates for each of 60 Statistical Divisions (administrative areas) across Australia. The potentially available lignocellulosic biomass is estimated at approximately 80 Mt per year, with the major contributors of crop stubble (27.7 Mt per year), grasses (19.7 Mt per year) and forest plantations (10.9 Mt per year). Over the next 20–40 years, total potentially available biomass could increase to 100–115 Mt per year, with new plantings of short‐rotation trees being the major source of the increase (14.7 Mt per year by 2030 and 29.3 Mt per year by 2050). We exclude oilseeds, algae and ‘regrowth’, that is woody vegetation naturally regenerating on previously cleared land, which may be important in several regions of Australia (Australian Forestry 77, 2014, 1; Global Change Biology Bioenergy 7, 2015, 497). We briefly discuss some of the challenges to providing a reliable and sustainable supply of the large amounts of biomass required to build a bioenergy industry of significant scale. More detailed regional analyses, including of the costs of delivered biomass, logistics and economics of harvest, transport and storage, competing markets for biomass and a full assessment of the sustainability of production are needed to underpin investment in specific conversion facilities (e.g. Opportunities for forest bioenergy: An assessment of the environmental and economic opportunities and constraints associated with bioenergy production from biomass resources in two prospective regions of Australia, 2011a).

Modelling impacts of forest bioenergy use on ecosystem sustainability: Lammi LTER region, southern Finland

Increasing the use of forest biomass for energy production is an important mitigation strategy against climate change. Sustainable use of natural resources requires that these policies are evaluated, planned and implemented, taking into account the boundary conditions of the ecological systems affected. This paper describes the development and application of a quantitative modelling framework for evaluating integrated impacts of forest biomass removal scenarios on four key environmental sustainability/ecosystem service indicators: (i) carbon sequestration and balance, (ii) soil nutrient balances (base cations and nitrogen), (iii) nutrient leaching to surface waters (nitrogen and phosphorus), and (iv) dead wood biomass (used as proxy indicator for impacts on species diversity). The system is based on the use of spatial data sets, mass balance calculations, loading coefficients and dynamic modelling. The approach is demonstrated using data from an intensively studied region (Hämeenlinna municipality) encompassing the Lammi LTER (Long-Term Ecosystem Research) site in southern Finland. Forest biomass removal scenarios were derived from a management-oriented large-scale forestry model (MELA) based on sample plot and stand-level data from national forest inventories. These scenarios have been developed to guide future Finnish forest management with respect to bioenergy use. Using harvest residues for district heat production reduced fossil carbon emissions but also the carbon sink of forests in the case study area. Calculations of the net removal of base cations of the different scenarios ranged between −36 to −43meqm−2a−1, indicating that the supply of base cations (soil weathering+deposition) would be enough to sustain also energy-wood harvesting. Greatly increased nutrient removal values and increasing nitrogen limitation problems were however predicted. Clear-cuttings and site preparation were predicted to increase the load of total nitrogen (4.0%) and total phosphorus (4.5%) to surface waters, compared with background leaching. The amount of dead wood has been identified as a key factor for forest species diversity in Finland. A scenario maximising harvest residues used for bioenergy production, would decrease stem dead wood biomass by about 40%, compared with a business-as-usual scenario. Clear trade-off situations could be observed in the case study area between maximising the use of energy-wood and minimising impacts on species diversity, soil carbon and nutrient stores, and nutrient leaching. The developed model system allows seeking for optimised solutions with respect to different management options and sustainability considerations.

Inventory and classification of United States federal and state forest biomass electricity and heat policies

As of September 2013, federal and state governments had nearly 500 policies to support production of electricity and heat from forest biomass. This research used a four-tier classification structure to categorize policy instruments used in these policies based on: approach (incentive, regulation, information), type (e.g. tax incentive), subcategory (e.g. tax exemption), and specification (e.g. sales tax exemption). More (113) of these policies were enacted in 2007 and 2008, more than in any other two-year period, and there was a significant increase in the number of forest bioenergy (46) and biomass specific (36) policies by 2013. Cluster analysis provided evidence that neighboring states adopted similar numbers and types of policies. Oregon (in cluster by itself) had the highest number of tax incentives and biomass-specific policies, while most Southern, Southeast, Southern Appalachia and Midwestern states (the most dissimilar cluster to Oregon) had a limited number of policies. Most states in remaining clusters offered a mix of integrated policies, rather than policies focused on regulations and technology improvement. Our findings provide guidance for policy development by enabling the transfer of policy approaches among different states and regions.

Cultural sustainability in reference to the global reporting initiative (GRI) guidelines

Purpose – Forest industries affect cultural sustainability profoundly, but little information exists on integration of cultural sustainability aspects into their Corporate Social Responsibility (CSR) management. Global Reporting Initiative (GRI) guidelines comprising assessments of economic, ecological and social aspects are one of the most comprehensive CSR frameworks applied widely also in forest industries. The purpose of this paper is to evaluate, how the GRI guidelines encompass cultural sustainability when assessing forestry and forest industry operations in a global context and to recognize the cultural sustainability themes that need additional information in forest industry companies’ CSR reporting. Design/methodology/approach – In the qualitative analysis, expert interview material on indicators identified for assessing the cultural sustainability of forest bioenergy production in North Karelia was compared with the contents of the GRI guidelines. The focus on classifying the cultural indicators according to GRI contents was to recognize in the context of forest bioenergy production, the links between cultural sustainability and other sustainability dimensions and to illustrate the new themes that cultural sustainability integration would bring to CSR management of the business. In addition, information was acquired from the general themes of cultural sustainability which are currently lacking from the GRI guidelines. Findings – The results of the show that most of the cultural indicators in the expert interview material were associated with aspects of economic, environmental or social sustainability when classified according to the GRI guidelines. Despite this, it seems that a more profound integration of cultural sustainability evaluations in CSR management is required. The analysis of this study showed that the themes “Impacts on landscape,” “Timeline of impacts,” “Spiritual values,” “Persistence of traditions” and “Adaptability to cultural change” are not approached in the GRI guidelines at all. All of the identified themes approach issues, which have been found to be crucial in forest industries’ operations not only in a local, but also in a global context. Research limitations/implications – The analysis of this study was limited to cultural characteristics of forestry and forest industries especially in the case of forest bioenergy production in North Karelia, Eastern Finland. Due to this, the results cannot be generalized directly into other CSR management contexts of forest industries in different geographical areas. Despite this, the results of this study indicate that when aiming to enhance the acceptability of forest industries in energy production as well as in other branches of forest industries, new insights are needed on the integration of cultural aspects in CSR management. Originality/value – The pressures toward using local forest resources are increasing internationally. As a result of this, the managers and politicians responsible for making decisions on forest sector are less seldom familiar with local traditions and the ways of balancing different needs related to forests in various geographical contexts. In enhancing the environmental, social and economic sustainability of forest resource usage it is crucial to ensure that the decisions made do not conflict with cultural values of localities traditionally dependent on forests. Despite this, general information on cultural sustainability issues related to forests and especially CSR management in forest sector is scarce.

The climate effect of increased forest bioenergy use in Sweden: evaluation at different spatial and temporal scales

Bioenergy from boreal forests managed for productive purposes (e.g., pulp, timber) is commonly held to offer attractive options for climate change mitigation. However, this view has been challenged in recent years. Carbon balances, cumulative radiative forcing, and average global temperature change have been calculated for a variety of bioenergy management regimes in Swedish forests, and the results support the view that an increased use of forest biomass for energy in Sweden can contribute to climate change mitigation, although methodological (e.g., spatial scales) and parameter value choices influence the results significantly. We show that the climate effect of forest‐based bioenergy depends on the forest ecosystems and management, including biomass extraction for bioenergy and other products, and how this management changes in response to anticipated market demands; and on the energy system effects, which determine the fossil carbon displacement and other greenhouse gas (GHG) mitigation effects of using forest biomass for bioenergy and other purposes. The public and private sectors are advised to consider information from comprehensive analyses that provide insights about energy and forest systems in the context of evolving forest product markets, alternative policy options, and energy technology pathways in their decision‐making processes. WIREs Energy Environ 2016, 5:351–369. doi: 10.1002/wene.178This article is categorized under: Bioenergy > Climate and Environment

THE ROLE OF THE FOREST IN AN INTEGRATED ASSESSMENT MODEL OF THE CLIMATE AND THE ECONOMY

This paper develops the FOR-DICE model to explore the potential role of the global forest in reducing climate change. It presents a basic framework for assessing the boreal, tropical, and temperate forests as both a source of renewable energy and a resource to sequester and store carbon. The focus of the paper is to explore whether climate policies should focus on increasing the forest biomass, to sequester and store carbon, or on increasing the use of the forest biomass as a source of energy, to substitute fossil fuels. The paper shows that the global forest can play an important role in reducing atmospheric carbon. The main finding at the global level is that it is better to increase the forest biomass rather than increase the use of forest bioenergy. The reason for this is that the decrease in forest carbon stock created by increased bioenergy harvests is not offset by avoided fossil fuel emissions. This finding suggests that setting high bioenergy targets, without considering the dynamics of the forest stock and the efficiency of bioenergy, will be detrimental to climate change mitigation.

An integrated assessment approach to optimal forest bioenergy production for young Scots pine stands

Bioenergy is re-shaping opportunities and imperatives of forest management. This study demonstrates, through a case study in Scots pine (Pinus sylvestris L.), how forest bioenergy policies affect stand management strategies. Optimization studies were examined for 15 Scots pine stands of different initial stand densities, site types, and temperature sum regions in Finland. Stand development was modelled using the PipeQual stand simulator coupled with the simulation-optimization tool OptiFor Bioenergy to assess three forest bioenergy policies on energy wood harvest from early thinnings. The optimal solutions maximizing bare land value indicate that conventional forest management regimes remain optimal for sparse stands. Energy harvests occurred only when profitable, led to lower financial returns. A forest bioenergy policy which included compulsory energy wood harvesting was optimal for denser stands. At a higher interest rate (4 %), increasing energy wood price postponed energy wood harvesting. In addition, our results show that early thinning somewhat reduced wood quality for stands in fertile sites. For less fertile sites, the changes were insignificant. A constraint of profitable energy wood harvest is not rational. It is optimal to carry out the first thinning with a flexible forest bioenergy policy depending on stand density.

Methodology for Selecting the Best Model for Forecasts: The Case Study of Forest Bioenergy

Methodology for Selecting the Best Model for Forecasts: The Case Study of Forest Bioenergy

Current and potential use of forest biomass for energy in Tasmania

Although Tasmania, Australia's southernmost state, has a large forest resource per capita there is no reliable information on the potential use of harvest residues, low quality logs or processing residues for energy production. In order to address the current knowledge gap we: i) quantified the current use and the potential sustainable supply of forest biomass in Tasmania, ii) compared those results with the use of forest biomass in Bavaria, a comparable state in Southeast Germany, and iii) analysed the low Tasmanian production of energy from forest biomass considering economic, legislative and social drivers. The current use of forest biomass for energy (400 kt y−1 of bone dry material) represents about 6% of Tasmania's total annual energy supply. The potential supply of forest biomass for energy production is estimated at 1800 kt y−1 of bone dry material equivalent to about 30% of Tasmania‘s current total annual energy supply. In contrast to Bavaria and other European countries, forest bioenergy production is small in Tasmania relative to the available resource and could be more than quadrupled from a resource availability perspective. A weak domestic market for energy wood leading to low prices, the lack of political stimuli and a low social acceptance are likely key factors. As a strong increase in market prices for forest biomass is unlikely, political incentives are necessary in order to increase the use of forest biomass. Addressing social acceptance will be a prerequisite for the success of initiatives or legislation to achieve this potential.

Carbon balance indicator for forest bioenergy scenarios

AbstractA carbon (C) balance indicator is presented for the evaluation of forest bioenergy scenarios as a means to reduce greenhouse gas (GHG) emissions. A bioenergy‐intensive scenario with a greater harvest is compared to a baseline scenario. The relative carbon indicator (RC) is defined as the ratio between the difference in terrestrial C stocks – that is the C debt – and the difference in cumulative bioenergy harvest between the scenarios, over a selected time frame T. A value of zero indicates no C debt from additional biomass harvests, while a value of one indicates a C debt equal to the amount of additionally harvested biomass C. Multiplying the RC indicator by the smokestack emission factor of biomass (approximately 110 t CO2/TJ) provides the net cumulative CO2 emission factor of the biomass combustion as a function of T, allowing a direct comparison with the emission factors of comparable fossil fuels. The indicator is applied to bioenergy cases in Finland, where typically the rotation length of managed forests is long and the decay rate of harvest residues is slow. The country‐level examples illustrate that although Finnish forests remain as a C sink in each of the considered scenarios, the efforts of increasing forest bioenergy may still increase the atmospheric CO2 concentrations in comparison with the baseline scenario and use of fossil fuels. The results also show that the net emission factor depends – besides on forest‐growth or residue‐decay dynamics – on the timing and evolution of harvests as well. Unlike for the constant fossil C emission factor, the temporal profile of bioenergy use is of great importance for the net emission factor of biomass.

Cost of turning forest residue bioenergy to carbon neutral

Harvesting branches, unmerchantable tree tops and stumps for bioenergy reduces the carbon stock and the sink capacity of forest. We analyzed forest management changes that are financially viable for a forest owner to compensate for carbon loss resulting from the forest harvest residue extraction, and thus lead to truly carbon-neutral forest bioenergy. The management options studied included forest fertilization, elongated rotation periods, varying the type of forest residues extracted, and leaving high stumps. The costs of carbon loss compensation varied widely from 5 to 4000€ha−1 between the management options. The lowest costs resulted from harvesting quickly decomposing branches combined with low levels of fertilization. Harvesting all residues and applying intensive fertilization regimes or postponing final felling generated the highest costs. A requirement for fast carbon loss compensation increased the costs. The results indicated that changes in the forest management improve the carbon benefits of forest bioenergy, and some of these changes are inexpensive for the forest owner. The optimization results suggested that the longer time period was allowed for the carbon loss compensation, the fewer cost-effective silvicultural measures existed in the optimal combination of management regimes for the compensation.

Sustainability of forest bioenergy feedstock supply chains: Local, national and international policy perspectives

AbstractIn 2009, the European Union (EU) Renewable Energy Directive (RED) mandated that 20% of the EU’s final energy consumption consist of renewable sources by 2020, and included sustainability criteria for liquid biofuels. Discussions around extending criteria to solid and gaseous biomass, including wood pellets, have been ongoing. Continued investment in forest bioenergy feedstock production is partly dependent on the stability of global market demand and the economic viability of feedstock production and trade. For trans‐boundary governance mechanisms such as the RED to be efficient, a proper assessment of the specific forest and land policy contexts of wood pellet exporters that the mechanism will affect, such as Canada, the USA, and Russia, is crucial. This paper builds on sustainability criteria for biodiversity protection and assurance of sustainable forest management (SFM) for woody biomass that are currently under discussion for inclusion in the RED and compares them with national and local regulations of those three countries. This illustrates potential challenges in the establishment of sustainability criteria related to: differences in land definitions, delineation and reporting systems; lack of a uniform definitional paradigm for SFM; and difficulties in establishing efficient monitoring/auditing systems. Regulators wanting to implement supra‐national sustainability schemes such as the EU RED need to be aware of challenges that such schemes carry and make efforts to reduce or eliminate pitfalls. There is also a need to assess the aggregated effects of these various tools, and a need for communication, collaboration and outreach among stakeholders. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd

Evaluating the impact of uncertainty and variability on the value chain optimization of a forest biomass power plant using Monte Carlo Simulation

ABSTRACTMathematical programming models have been used to optimize the design and management of forest bioenergy supply chains. A deterministic mathematical model is beneficial for making optimum decisions; however, its applicability to real-world problems may be limited because it does not capture all the complexities, including uncertainties in the parameters, in the supply chain. In this paper, a combination of Monte Carlo Simulation and optimization model is used to evaluate the impact of uncertainty in biomass quality, availability and cost, and electricity prices on the supply chain of a forest biomass power plant. The optimization model is a deterministic mixed integer non-linear model with monthly time steps over a 1-year planning horizon. Variability in biomass quality, i.e. moisture content (MC) and higher heating value (HHV), based on the historical data of a real case study is studied in detail and fitted probability distributions are used in the model, while for electricity prices different scenarios are considered. The results show that the impact of variability in the MC on profit is higher than that of uncertainty in HHV. It is observed that the annual profit ranges between $13.3 million and $17.9 million in the presence of all possible uncertainties while its average is $15.5 million. Uncertainty in biomass availability and cost and electricity price results in the risks of having annual profit of less than $14 million and low monthly storage levels.

The Burning Question: Does Forest Bioenergy Reduce Carbon Emissions? A Review of Common Misconceptions about Forest Carbon Accounting

Critical errors exist in some methodologies applied to evaluate the effects of using forest biomass for bioenergy on atmospheric greenhouse gas emissions. The most common error is failing to consider the fate of forest carbon stocks in the absence of demand for bioenergy. Without this demand, forests will either continue to grow or will be harvested for other wood products. Our goal is to illustrate why correct accounting requires that the difference in stored forest carbon between harvest and no-harvest scenarios be accounted for when forest biomass is used for bioenergy. Among the flawed methodologies evaluated in this review, we address the rationale for accounting for the fate of forest carbon in the absence of demand for bioenergy for forests harvested on a sustained yield basis. We also discuss why the same accounting principles apply to individual stands and forest landscapes.

Shrew response to variable woody debris retention: Implications for sustainable forest bioenergy

Shrews are integral components of forest food webs and may rely on downed woody debris to provide microhabitats that satisfy high moisture and metabolic requirements. However, woody biomass harvests glean downed woody debris to use as a bioenergy feedstock. Biomass Harvesting Guidelines (BHGs) provide guidance on the amount and distribution of downed woody debris retained after harvest to ensure ecological sustainability of woody biomass harvesting and limit detrimental effects on wildlife. However, the success of Biomass Harvesting Guidelines at reaching sustainability goals, including conservation of wildlife habitat, has not been tested in an operational setting. Thus, we compared shrew captures among six woody biomass harvesting treatments in pine plantations in North Carolina, USA from April to August 2011–2014 (n=4) and Georgia, USA from April to August 2011–2013 (n=4). Treatments included: (1) woody biomass harvest with no BHGs; (2) 15% retention with woody biomass dispersed; (3) 15% retention with woody biomass clustered; (4) 30% retention with woody biomass dispersed; (5) 30% retention with woody biomass clustered; and (6) no woody biomass harvested. We sampled shrews with drift fence arrays and compared relative abundance of shrews among treatments using analysis of variance. Additionally, we used general linear regression models to evaluate the influence of downed woody debris volume and vegetation structure on shrew capture success at each drift fence for species with >100 captures/state/year. In 53,690 trap nights, we had 1,712 shrew captures representing three species, Cryptotis parva, Blarina carolinensis, and Sorex longirostris. We did not detect consistent differences in shrew relative abundance among woody biomass harvest treatments, but relative abundance of all species increased over time as vegetation became established. In North Carolina, total shrew capture success was negatively related to volume of downed woody debris within 50m of the drift fence array (P=0.05) in 2013 and positively related to bare groundcover in 2013 (P=0.02) and 2014 (P<0.01). In Georgia, total shrew capture success was negatively related to herbaceous groundcover (P<0.01) and leaf litter groundcover (P=0.02) and positively related to woody vegetation groundcover (P<0.01) and vertical vegetation structure (P=0.03) in 2013. Our results suggest that shrews in our study area were associated more with vegetation characteristics than downed woody debris and that woody biomass harvests may have little influence on shrew abundances in the southeastern United States Coastal Plain.