Effect of Climatic Changes (CO₂, Temperature) on Grassland Ecosystems: First Five Months’ Experimental Results

Summary

The C and N cycles were examined in an experiment concerning the impact of climate change (CO₂, temperature) on perennial grassland ecosystems (Lolium perenne cultivated on a loamy soil), at two levels of inorganic N application. The various experimental techniques are summarised here, as well as the first experimental results of the effects of climate change on the utilisation of water resources and dry matter accumulation in roots, stubble, litter and the coarse OM fraction. At a similar, limited water supply, the beneficial effect on water consumption, water use efficiency and harvestable production of increasing atmospheric CO₂ to 350 ppm disappears when the temperature is also increased by 3°C. This is because of drought. Further analysis will show how N interception by roots is involved in dry matter production and increases under doubled atmospheric CO₂. This results in a lowering of the applied N productivity. Organic accumulation at the soil level is increased by 21% (N+) to 31% (N−) in the case of CO₂ doubling, but does not occur with supplemental temperature elevation.