Summary• Limited information on likely supply and spatial yield of bioenergy crops exists for the UK. Here, productivities are reported of poplar (Populus spp.) and willow (Salix spp.) grown as short-rotation coppice (SRC), using data from a large 49-site yield trial network.• A partial least-squares regression technique was used to upscale actual field trial observations across England and Wales. Spatial productivity was then assessed under different land-use scenarios.• Mean modelled yields ranged between 4.9 and 10.7 oven-dry tonnes (odt) ha -1 yr -1 . Yields were generally higher in willow than in poplar, reflecting the susceptibility of older poplar genotypes to rust and their tendency for single stem dominance. Replacing 10% of arable land, 20% of improved grassland and 100% of set-aside grassland in England and Wales with the three most productive genotypes would yield 13 Modt of biomass annually (supplying 7% of UK electricity production or 48% of UK combined heat and power (CHP) production).• Results show existing SRC genotypes have the immediate potential to be an important component of a mixed portfolio of renewables and that, in future, as new and improved genotypes become available, higher yields could extend this potential further.

Accurate estimation of the greenhouse gas (GHG) mitigation potential of bioenergy crops requires the integration of a significant component of spatially varying information. In particular, crop yield and soil carbon (C) stocks are variables which are generally soil type and climate dependent. Since gaseous emissions from soil C depend on current C stocks, which in turn are related to previous land management it is important to consider both previous and proposed future land use in any C accounting assessment. We have conducted a spatially explicit study for England and Wales, coupling empirical yield maps with the RothC soil C turnover model to simulate soil C dynamics. We estimate soil C changes under proposed planting of four bioenergy crops, Miscanthus (Miscanthus  giganteus), short rotation coppice (SRC) poplar (Populus trichocarpa Torr. & Gray  P. trichocarpa, var. Trichobel), winter wheat, and oilseed rape. This is then related to the former land use -arable, pasture, or forest/seminatural, and the outputs are then assessed in the context of a life cycle analysis (LCA) for each crop. By offsetting emissions from management under the previous land use, and considering fossil fuel C displaced, the GHG balance is estimated for each of the 12 land use change transitions associated with replacing arable, grassland, or forest/seminatural land, with each of the four bioenergy crops. Miscanthus and SRC are likely to have a mostly beneficial impact in reducing GHG emissions, while oilseed rape and winter wheat have either a net GHG cost, or only a marginal benefit. Previous land use is important and can make the difference between the bioenergy crop being beneficial or worse than the existing land use in terms of GHG balance.

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Woody biomass produced from short rotation coppice (SRC) poplar (Populus spp.) and willow (Salix spp.) is a bioenergy feedstock that can be grown widely across temperate landscapes and its use is likely to increase in future. Process-based models are therefore required to predict current and future yield potential that are spatially resolved and can consider new genotypes and climates that will influence future yield. The development of a process-based model for SRC poplar and willow, ForestGrowth-SRC, is described and the ability of the model to predict SRC yield and water use efficiency (WUE) was evaluated. ForestGrowth-SRC was parameterized from a process-based model, ForestGrowth for high forest. The new model predicted annual above ground yield well for poplar (r 2 = 0.91, RMSE = 1.46 ODT ha À1 yr À1) and willow (r 2 = 0.85, RMSE = 1.53 ODT ha À1 yr À1), when compared with measured data from seven sites in contrasting climatic zones across the United Kingdom. Average modelled yields for poplar and willow were 10.3 and 9.0 ODT ha À1 yr À1 , respectively, and interestingly, the model predicted a higher WUE for poplar than for willow: 9.5 and 5.5 g kg À1 respectively. Using regional mapped climate and soil inputs, modelled and measured yields for willow compared well (r 2 = 0.58, RMSE = 1.27 ODT ha À1 yr À1), providing the first UK map of SRC yield, from a process-based model. We suggest that the model can be used for predicting current and future SRC yields at a regional scale, highlighting important species and genotype choices with respect to water use efficiency and yield potential.

Background: Biomass has been identified as an important source of renewable energy. However, growing demand for dedicated energy crops could lead to conflicts with food production and ecosystem services. This study uses a geographic information systems-embedded modeling approach to assess the spatial supply of short-rotation coppice, taking into account social, economic and environmental constraints. Results: Results suggest that 7.5 million tons of biomass (from short-rotation coppice) is realistically available in England. Such production would require 0.8 million ha and could be grown almost entirely on poor quality marginal lands. Conclusion: We therefore conclude that short-rotation coppice energy crops have the potential to play an important role in meeting UK renewable energy targets without compromising environmental sustainability or food production.