Simulated Regional Yields of Spring Barley in the United Kingdom under Projected Climate Change
This paper assessed the effect of projected climate change on the grain yield of barley in fourteen administrative regions in the United Kingdom (UK). Climate data for the 2030s, 2040s and 2050s for the high emission scenario (HES), medium emissions scenario (MES) and low emissions scenario (LES) were obtained from the UK Climate Projections 2009 (UKCP09) using the Weather Generator. Simulations were performed using the AquaCrop model and statistics of simulated future yields and baseline
... and baseline yields were compared. The results show that climate change could be beneficial to UK barley production. For all emissions scenarios and regions, differences between the simulated average future yields (2030s-2050s) and the observed yields in the baseline period ) ranged from 1.4 to 4 tons·ha −1 . The largest increase in yields and yield variability occurred under the HES in the 2050s. Absolute increases in yields over baseline yields were substantially greater in the western half of the UK than in the eastern regions but marginally from south to north. These increases notwithstanding, yield reductions were observed for some individual years due to saturated soil conditions (most common in Wales, Northern Ireland and South-West Scotland). These suggest risks of yield penalties in any growing season in the future, a situation that should be considered for planning adaptation and risk management. Climate 2016, 4, 54 2 of 21 and thereby increased biomass production and harvest index [5,           . With regard to threats, barley is sensitive to soil water and temperature regimes around establishment, anthesis and grain filling [17, 18] . While barley is known to be moderately tolerant to soil water deficit  , it is sensitive to anoxic conditions and heat stress, and compensates poorly with respect to reduced tillering in early stages. For example, simulation results show that intra-seasonal water deficits can reduce barley grain yields by up to 4.5 tons·ha −1 in the 2050s in Ireland  . Warmer conditions can also hasten phenophases and senescence of barley and thereby reduce harvest index [18, 20] . Thus, a combination of water and heat stress can potentially reduce the grain yield of barley in the UK. Crop simulation models can be used to estimate the effects of climate change on crops. Crop simulation models vary in complexity and data requirements depending on the nature of their growth models  . Crop models used previously to assess the impact of projected climate change scenarios on barley include CERES- Barley [14,     , CropSyst [26, 27] , WOFOST [3, 28] . While these models perform well, they are data-intensive. An evaluation of nine crop growth models for simulating spring barley yields in different climatic zones of Northern and Central Europe showed WOFOST as one of the top three performing models, with CropSyst showing large uncertainty  . Water-driven models, such as AquaCrop, (in which crop growth is mainly driven by water productivity and limited by soil water deficit) are now widely used because they are relatively simple, easy to use and less data intensive  . An evaluation of AquaCrop, CropSyst and WOFOST models under different soil water regimes showed comparable results  . In the current study, we used the AquaCrop model  because, although it has not been widely used in climate change studies, it is less data-intensive and its performance compares well with commonly used models. Moreover, it performed well during a calibration study involving three models and nine barley genotypes under Scottish conditions  .