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Forests are an increasingly important source of feedstock for bioenergy as global efforts to mitigate atmospheric CO2 concentrations increase. In keeping with the principles of sustainable forest management, it is important that feedstock procurement not have negative impacts on the environment, including biodiversity. Impacts of land use, including forest management, can be evaluated along all stages in the production of these goods and services, using life cycle assessment (LCA), which is a potentially powerful tool for organizing and evaluating the impacts of production. There is growing recognition of the need to integrate land-use impacts into LCA for forest products such as bioenergy, especially on biodiversity. Integrating quantitative indicators of biodiversity into LCAs of biomass production systems is particularly challenging because biodiversity is a multidimensional concept that can never be fully represented by a single number, and yet many proposed approaches rely on this. Reliance on a single metric oversimplifies ‘biodiversity’ and might lead to inappropriate conclusions on local land management practices. LCA is not suited to providing reliable site-specific assessment of forest product systems in regard to the complexities of biodiversity. Nevertheless, the global and comprehensive nature of LCA makes it a useful tool for preventing a shift in environmental problems or burdens across the value chain because of local land management decisions. In this context, complementary site-specific and/or regional studies or analyses may help mitigate against inaccurate conclusions being drawn from LCA. WIREs Energy Environ 2016, 5:670–683. doi: 10.1002/wene.211 For further resources related to this article, please visit the WIREs website.

Department of Civil Engineering, University of Toronto, 35St. George Street, Toronto, Ontario M5S 1A4, CanadaAbstractForest bioenergy can contribute to climate change mitigation by reducing greenhouse gas (GHG) emissions asso-ciated with energy production. We assessed changes in GHG emissions resulting from displacement of coal withwood pellets for the Atikokan Generating Station located in Northwestern Ontario, Canada. Two contrastingbiomass sources were considered for continuous wood pellet production: harvest residue from current harvestoperations (residue scenario) and fibre from expanded harvest of standing live trees (stemwood scenario). Forthe stemwood scenario, two metrics were used to assess the effects of displacing coal with forest biomass onGHG emissions: (i) time to carbon sequestration parity, defined as the time from the beginning of harvest towhen the combined GHG benefit of displacing coal with biomass and the amount of carbon in regenerating for-est equalled the amount of forest carbon without harvest for energy production; and (ii) time to carbon debtrepayment, defined as the time from the beginning of harvest to when the combined GHG benefit of displacingcoal with biomass and the amount of carbon in the regenerating forest equalled forest carbon at the time of har-vest. Only time to carbon sequestration parity was used for the residue scenario. In the residue scenario, carbonsequestration parity was achieved within 1 year. In the stemwood scenario, times to carbon sequestration parityand carbon debt repayment were 91 and 112 years, respectively. Sensitivity analysis showed that estimates wererobust when parameter values were varied. Modelling experiments showed that increasing growth rates forregenerating stands in the stemwood scenario could substantially reduce time to carbon sequestration parity.We discuss the use of the two metrics (time to carbon sequestration parity and time to carbon debt repayment)for assessing the effects of forest bioenergy projects on GHG emissions and make recommendations on terminol-ogy and methodologies for forest bioenergy studies.

The effect of litter quality and climate on the rate of decomposition of plant tissues was examined by the measurement of mass remaining after 3 years’ exposure of 11 litter types placed at 18 forest sites across Canada. Amongst sites, mass remaining was strongly related to mean annual temperature and precipitation and amongst litter types the ratio of Klason lignin to nitrogen in the initial tissue was the most important litter quality variable. When combined into a multiple regression, mean annual temperature, mean annual precipitation and Klason lignin:nitrogen ratio explained 73% of the variance in mass remaining for all sites and tissues. Using three doubled CO2 GCM climate change scenarios for four Canadian regions, these relationships were used to predict increases in decomposition rate of 4–7% of contemporary rates (based on mass remaining after 3 years), because of increased temperature and precipitation. This increase may be partially offset by evidence that plants growing under elevated atmospheric CO2 concentrations produce litter with high lignin:nitrogen ratios which slows the rate of decomposition, but this change will be small compared to the increased rate of decomposition derived from climatic changes.

Betula papyrifera (White birch) is a common tree throughout the boreal forest of Canada; makes up 12 % of the total tree volume in insular Newfoundland. It forms pure stands after harvesting and wildfire disturbance and it is a common component in most softwood stands. Little is known regarding the environmental impact of whole-tree or conven- tional harvesting of this species and variation in impact related to variation in soil and site conditions.