Abstract
Short‐rotation coppice (SRC) has great potential for supplying biomass‐based heat and energy, but little is known about SRC's ecological footprint, particularly its impact on the water cycle. To this end, we quantified the water use of a commercial scale poplar (Populus) SRC plantation in East Flanders (Belgium) at tree and stand level, focusing primarily on the transpiration component. First, we used the AquaCrop model and eddy covariance flux data to analyse the different components of the stand‐level water balance for one entire growing season. Transpiration represented 59% of evapotranspiration (ET) at stand scale over the whole year. Measured ET and modelled ET were lower as compared to the ET of reference grassland, suggesting that the SRC only used a limited amount of water. Secondly, we compared leaf area scaled and sapwood area scaled sap flow (F s) measurements on individual plants vs. stand scale eddy covariance flux data during a 39‐day intensive field campaign in late summer 2011. Daily stem diameter variation (∆D) was monitored simultaneously with F s to understand water use strategies for three poplar genotypes. Canopy transpiration based on sapwood area or leaf area scaling was 43.5 and 50.3 mm, respectively, and accounted for 74%, respectively, 86%, of total ecosystem ET measured during the intensive field campaign. Besides differences in growth, the significant intergenotypic differences in daily ∆D (due to stem shrinkage and swelling) suggested different water use strategies among the three genotypes which were confirmed by the sap flow measurements. Future studies on the prediction of SRC water use, or efforts to enhance the biomass yield of SRC genotypes, should consider intergenotypic differences in transpiration water losses at tree level as well as the SRC water balance at stand level.
Highlights
Short-rotation coppice (SRC) of fast-growing and highyielding hardwood species as poplar and willow offers an important and environmentally sustainable way of producing heat and electricity from a renewable energy source (Herrick & Brown, 1967; Graham et al, 1992; Gustavsson et al, 1995; Berndes et al, 2003; Kauter et al, 2003; Aylott et al, 2008)
We further focused on tree-level measurements of plant water use during an intensive field campaign performed during the same growing season
Using detailed tree-level measurements of Fs and ΔD, we quantified the contribution of Ec to ET across three genotypes and we identified intergenotypic differences in plant water use
Summary
Short-rotation coppice (SRC) of fast-growing and highyielding hardwood species as poplar and willow offers an important and environmentally sustainable way of producing heat and electricity from a renewable energy source (Herrick & Brown, 1967; Graham et al, 1992; Gustavsson et al, 1995; Berndes et al, 2003; Kauter et al, 2003; Aylott et al, 2008). For the entire growing season of 2011, we analysed the stand-level water balance of the poplar SRC using the AquaCrop model (Hsiao et al, 2009; Raes et al, 2009; Steduto et al, 2009) complemented with eddy covariance measurements of ET.
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