Development and evaluation of ForestGrowth‐ SRC a process‐based model for short rotation coppice yield and spatial supply reveals poplar uses water more efficiently than willow

Abstract Woody biomass produced from short rotation coppice (SRC) poplar (Populusspp.) and willow (Salixspp.) 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 forSRCpoplar and willow, ForestGrowth‐SRC, is described and the ability of the model to predictSRCyield and water use efficiency (WUE) was evaluated. ForestGrowth‐SRCwas parameterized from a process‐based model, ForestGrowth for high forest. The new model predicted annual above ground yield well for poplar (r2 = 0.91,RMSE = 1.46 ODT ha−1 yr−1) and willow (r2 = 0.85,RMSE = 1.53 ODT ha−1 yr−1), when compared with measured data from seven sites in contrasting climatic zones across theUnited Kingdom. Average modelled yields for poplar and willow were 10.3 and 9.0 ODT ha−1 yr−1, respectively, and interestingly, the model predicted a higherWUEfor poplar than for willow: 9.5 and 5.5 g kg−1respectively. Using regional mapped climate and soil inputs, modelled and measured yields for willow compared well (r2 = 0.58,RMSE = 1.27 ODT ha−1 yr−1), providing the firstUKmap ofSRCyield, from a process‐based model. We suggest that the model can be used for predicting current and futureSRCyields at a regional scale, highlighting important species and genotype choices with respect to water use efficiency and yield potential.