Search

Short rotation woody crops (SRWCs) have potential to provide sustainable aviation fuels and exceptional carbon fiber for numerous products. However, many SRWCs are riparian species and measuring water use will ensure that large-scale plantations do not negatively impact surrounding hydrology. Traditionally, willows (Salix spp.) have been important SRWCs in cooler regions like northern Europe and the northeastern US. However, black willow (Salix nigra Marshall) is native to the southeastern US and could be grown in sites that are marginal for poplar (Populus) including heavy clay soils that tend to remain flooded into the growing season. Our research goals were to measure diurnal water use and its correlation with environmental drivers as well as compare physiological parameters including whole-stem water use efficiency (WUE) and productivity across black willow genotypes planted in the Lower Mississippi Alluvial Valley. Across genotypes, yearly aboveground productivity, and whole-stem WUE were positively correlated with each other and were both positively correlated with stomatal sensitivity to vapor pressure deficit. Likewise, whole-stem WUE and leaf carbon isotope ratios were positively correlated suggesting that the latter can estimate whole-stem water use efficiencies for black willow. Atmospheric parameters and shallow groundwater levels were more important in explaining variation in daily water use than soil moisture implying that trees were tapping groundwater resources. In total, this research suggests that black willow is a water use efficient and promising bioenergy crop for the southeastern US, and more work currently underway will continue to develop genotypes and growing practices that maximize biomass production. • Whole-stem water use efficiency was 5 g kg−1, similar to other studies and species. • Water use efficiency and productivity were positively correlated in black willow. • Leaf carbon isotope ratios were correlated with whole-stem water use efficiency. • Sapflow was driven by the atmosphere and groundwater as opposed soil moisture. • Nitrogen isotope ratios were very positive suggesting high denitification [ABSTRACT FROM AUTHOR]

Shrub willow (Salix spp.) is increasingly grown as a biomass crop and for a range of environmental applications. Merging the economic and environmental objectives of willow production may facilitate more widespread adoption by reducing production costs and justifying willow cultivation in traditional agricultural settings. Incorporating willow in agricultural-riparian transition areas, particularly in intensive or high-input agricultural systems, can enhance watercourse protection from diffuse pollutants, mitigate indirect agricultural N 2 O emissions, and sequester carbon. However, biomass accrual and economic feasibility needs quantification on localized scales. This study investigated the biomass accrual of 9 agricultural-riparian willow buffers in Prince Edward Island, Canada, receiving no direct fertilization. Carbon, nitrogen, and phosphorus assimilation was measured in stem and root biomass, limitations on growth assessed, and benefit-cost analysis was conducted to determine opportunities for bioenergy use and deployment. First rotation agricultural-riparian Salix viminalis displayed considerable site-to-site variation in biomass production, with water availability being the primary limiting factor on growth. Mean total plant biomass and annual yield ranged from 0.54 to 7.9 kg dry matter plant−1 and 0.25–16.59 Mg ha−1 yr−1 (mean 3.9), respectively. CO 2 fixation was 0.67–46.64 Mg CO 2 ha−1 yr−1, of which 0.23–15.7 Mg CO 2 ha−1 yr−1 was root biomass, indicative of long-term sequestration. Nitrogen and phosphorus removal was 6.05–39.1 (mean 23.3) and 1.1–4.8 (mean 2.8) kg ha−1 yr−1. Benefit-cost analysis revealed that shrub willow production can be economically viable for on-farm heating when yields exceeding 5.6 Mg dry matter ha−1yr−1 are achieved, but off-farm sale is not currently economically justified. • Agricultural-riparian Salix viminalis biomass production was 0.25–16.59 Mg dry matter ha−1 yr−1. • Root biomass, indicative of long-term CO 2 sequestration, was 0.23–15.7 Mg CO 2 ha−1 yr−1. • Water availability was the main factor that limited biomass growth. • Salix viminalis with yields exceeding 5.6 Mg dry matter ha−1 yr−1 are economically viable as fuel for on-farm heating. [ABSTRACT FROM AUTHOR]