Abstract
AbstractThe bioenergy cropMiscanthus × giganteushas a high water demand to quickly increase biomass with rapid canopy closure and effective rainfall interception, traits that are likely to impact on hydrology in land use change. Evapotranspiration (ET, the combination of plant and ground surface transpiration and evaporation) forms an important part of the water balance, and fewETmodels have been tested withMiscanthus. Therefore, this study uses field measurements to determine the most accurateETmodel and to establish the interception of precipitation by the canopy (Ci). DailyETestimates from 2012 to 2016 using the Hargreaves–Samani, Priestley–Taylor, Granger–Gray, and Penman–Monteith (short grass) models were calculated using data from a weather station situated in a 6 haMiscanthuscrop. Results from these models were compared to data from on‐site eddy covariance (EC) instrumentation to determine accuracy and calculate the crop coefficient (Kc) model parameter. Ciwas measured from June 2016 to March 2017 using stem‐flow and through‐flow gauges within the crop and rain gauges outside the crop. The closest estimatedETto theECdata was the Penman‐Monteith (short grass) model. TheKcvalues proposed are 0.63 for the early season (March and April), 0.85 for the main growing season (May to September), 1.57 for the late growing season (October and November), and 1.12 over the winter (December to February). These more accurateKcvalues will enable betterETestimates with the use of the Penman‐Monteith (short grass) model improving estimates of potential yields and hydrological impacts of land use change. Ciwas 24% and remained high during the autumn and winter thereby sustaining significant levels of canopy evaporation and suggesting benefits for winter flood mitigation.
Highlights
The bioenergy crop Miscanthus 9 giganteus has a high water demand to quickly increase biomass with rapid canopy closure and effective rainfall interception, traits that are likely to impact on hydrology in land use change
Most precipitation was received during the winter with the exception of 2012 and 2016 where high rainfall was received during the summer. 2012 was the wettest of the 5 years reflecting national conditions with 2012 being one of the wettest years on record (Met Office, 2016b)
It was similar to the ETEC of around 5 mm dayÀ1 obtained in Hereford, UK, and within the range of the Met. Office Surface Energy Scheme (MOSES) model predictions both shown in the study carried out by Finch et al (2004)
Summary
In the UK, repeated flooding events have stimulated interest in identifying mitigation strategies and have highlighted the potential role for farmland and upland areas for buffering against high rainfall (Marshall et al, 2009; Christen & Dalgaard, 2013; Wynne-Jones, 2016) This need is leading to an interest in finding commercially viable climate change resilient crops (Environment Agency, 2015) that can be located within these landscapes to provide wide-ranging environmental benefits. Increased planting of Miscanthus could potentially increase evapotranspiration (ET) and affect ecosystem water dynamics through impacts on boundary layer temperatures, humidity, and solar radiation to the ground (Hickman et al, 2010; Milner et al, 2016) These traits may reduce flooding, soil erosion, and nutrient run-off. Information regarding these potential impacts is vital for accurate modelling of land use change scenarios to fully inform policymakers
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