Lianhai Wu, Anita Shepherd, David Chadwick and Phil Murray
Sustainable Soils and Grassland Systems Department, Rothamsted Research

Global average surface temperature has increased by ca. 0.7°C in the last century and is projected to increase by another 1.1-6.4°C in this century. Long-term trends in precipitation amount were spatially variable in the last century and precipitation amount is likely to increase in high latitudes and decrease in most subtropical land regions this century. Climate controls the processes of plant growth and development, and plant response to climate change will not be determined solely by photosynthesis, but also the partitioning of photosynthesate between plant organs and the progress of its development. On the other hand, climate change may also control the decomposition rate of organic matter in soils, and other biogeochemical processes including nitrogen cycling which may impact on the magnitude and pattern of diffuse water pollution and in greenhouse gas (GHG) emissions.
Appropriate field management could lessen the negative effects on the environment or increase plant N uptake. It would be difficult to assess quantitatively the effect of climate change scenarios on the mitigation measures on diffuse water pollutants, GHG emissions and nutrients cycling using field experiments. However, simulation models can be an efficient way to explore directions of change and potential interactions in the complex agricultural system. The well developed SPACSYS model was used, and combined with location-specific projections of climate change, to evaluate the effect of changing environment on grassland in SW England. Seven UKCP09 projections were produced: 3 timeslices for medium emission scenarios and 3 timeslices for high emissions (representing 2020, 2050 and 2080) plus historic climate for the location. Two types of land coverage in our recently designed Farm Platform, pure grass and the mixture of grass and clover, were used as landuse types. Preliminary simulation results show that annual nitrate leaching loss will increase from 2020 to 2050, while different grazing strategies can affect annual N uptake by grass.