Predicting yields of short-rotation coppice willow (Salix spp.) for the contiguous US

Background/Question/Methods

The cultivation of fast-growing willow (Salix spp.) within short rotation coppice (SRC) can provide a potentially sustainable energy source which can decrease net greenhouse gas emission. Predictions of willow growth under various growing conditions, soils and climates are critical to evaluate the feasibility of its production in different environments. Previous mathematical models which can accurately predict willow biomass potential under different conditions estimate biomass growth using a concept of radiation use efficiency (RUE), which is based on simple diurnal representation of environmental factors without much consideration given to biochemical and biophysical characteristics of plants. 

Results/Conclusions

Here, we described in detail the biochemical and physiological processes of a previously published generic mechanistic eco-physiological model, BioCro, which was adapted and developed from WIMOVAC. BioCro was parameterized for willow in coppicing subroutine, perennating, leaf-photosynthesis, canopy CO₂ assimilation, allocation, phenology and growth. The model was able to realistically predict biomass yield at a range of 16 sites from European studies and 3 sites from US studies. The regional projection suggests that willow yield varies considerably with differences in soil and climate, and reaching as much as 52 Mg ha^-1 in Eastern, the upper Midwest and New England regions after 3-year growth. This study provides forest managers and policy makers with a process-based modeling approach to estimate the yield potential of willow for a given climate and soil and thus could guide further research, policy and management decisions.