Predicting the yield and water-use of poplar short rotation coppice under a future climate

Under the current climate there is significant spatial variation in the yield and water-use of<br/>bioenergy crops such as poplar short rotation coppice (SRC). Marked changes in patterns<br/>of precipitation and temperature are predicted globally as a result of anthropogenic climate<br/>change. This is likely to significantly impact on the yield and transpiration of poplar SRC.<br/>The response of poplar SRC to future climate change is unknown and represents a<br/>significant knowledge gap in the path to a sustainable future.<br/>This thesis used a land-surface scheme, JULES, to investigate the response of poplar SRC<br/>yield and transpiration to the interaction between changes in atmospheric CO2<br/>concentration and changes in climate. Empirical work generated poplar SRC specific<br/>parameter values for use JULES. It was found that Vmax, a key model photosynthetic<br/>parameter, was significantly lower when estimated under the assumption of infinite leaf<br/>internal conductance to CO2. This invalidated the assumption that internal CO2 transfer has<br/>a negligible impact on the drawdown of CO2 from ci to cc. The photosynthesis model in<br/>JULES is based on this assumption; however, inclusion of this additional CO2 transfer<br/>pathway in the model did not impact on the accuracy of the simulated carbon assimilation,<br/>because the value of Vmax used in the model compensated for the presence/absence of this<br/>pathway. It was concluded that, given the model’s high sensitivity to Vmax, it is essential to<br/>calibrate the model with a parameter value estimated under assumptions appropriate for the<br/>model. Further modification, calibration and validation enabled JULES to simulate the<br/>dynamic growth and water-use of poplar under a managed SRC cycle, which is a novel<br/>application for the model. Changes in climate were simulated using an ensemble of GCM<br/>anomalies and atmospheric CO2 concentration was simulated using the SRES A1B<br/>emissions scenario. Results of this work highlighted the influence of climate in modifying<br/>the yield and transpiration responses to elevated concentrations of atmospheric CO2.<br/>Additionally, for a future climate scenario, these simulations indicated higher yields but<br/>also higher water-use of poplar SRC, although the magnitude and direction of response<br/>was highly spatially variable.

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2010

Author dc:creator

• Oliver, Rebecca Joy

Advisors dc:contributor.advisor

• Finch, J.W.
• Taylor, Gail