Biomass production of willow short-rotation coppice across sites and determinants of yields for SV1 and SX61

Shrub willow (Salix spp.) is a perennial woody crop that has been studied as a sustainable source of biomass energy. Understanding biomass production of willow short-rotation coppice and yield as a function of climate and soils is fundamental to deriving a sustainable supply. This study summarized biomass production of willow short-rotation coppice planted across 16 yield trials in the Northeastern and Midwestern US and explored the determinants of yields for two willow cultivars, SV1 and SX61, across 18 yield trials in the Northeastern and Midwestern US by modeling yields on climatic and soil factors. Mean yield of each site ranged from 2.9 to 10.9 dry Mg ha-1 yr-1 in the first rotation. Mean yield of the top five cultivars ranged from 3.1 to 13.9 dry Mg ha-1 yr-1. A Monte Carlo Simulation suggested the mean yield of a five-cultivar site in the first rotation can be expected to range from 9.2 to 9.8 dry Mg ha-1 yr-1 for future plantations. The biomass production of willow cultivars in the first rotation responded differently to environmental conditions. Temperature and precipitation played a more important role in determining yields of SV1 than soil properties. Higher yields of SX61 responded more to higher temperature in the beginning of the growing season.