Abstract
This study predicts the effects of climate change on crop yields, timber volumes and soil organic carbon in grassland, arable, ash woodland, poplar plantation, and silvopastoral and silvoarable systems in Northern Ireland. We modified a version of the biophysical Yield-SAFE agroforestry model that includes a RothC soil carbon module and also the effect of atmospheric CO2 fertilisation. The model was calibrated using existing field measurements and weather data from 1989 to 2021. The effect of two future climate scenarios were modelled, based on two representative concentration pathways (RCP 4.5 and RCP 8.5) for 2020–2060 and 2060–2100. The study revealed that the impact of future climate scenarios on grass and arable yields, and tree growth were positive with the effect of CO2 fertilisation more than offsetting a generally negative effect of increased temperatures and drought stress on yields. The predicted land equivalent ratio (LER) remained relatively constant between the baseline and the future climate scenarios for the silvopastoral system (1.08 to 1.11). The corresponding values for the silvoarable system were 0.87–0.92 based on arable and timber yields alone, or 1.11–1.17 if grass yields were included. In the silvopastoral system, but not the silvoarable system, the model suggested that climate change would benefit tree growth relative to the understorey crop. Greater losses of soil organic carbon were predicted under barley-only (1.02–1.18 t C ha− 1 yr− 1) than grassland (0.48–0.55 t C ha− 1 yr− 1), with relatively small differences between the baseline and climate scenarios. However, the analysis indicated that these losses could be mitigated by planting trees, but this effect was not immediate as soil organic matter would continue to decline for the first 10 years until the trees were well-established. The model was also used to examine the effect of different tree densities on the trade-offs between timber volume and understorey crop yields.