Elevated atmospheric CO2 affects the turnover of nitrogen in a European grassland

The availability of nutrients in the soil is key to the potential response of a plant to elevated CO 2 and is central to correctly predicting the response of terrestrial communities to climate change. In order for a plant to fully realise the potential of increased atmospheric CO 2, it must increase its nutrient uptake for the increased production of biomass as well as biochemical compounds. In this study the stable isotope 15N was used to follow the fate of nitrogen contained in litter in order to determine the effect elevated atmospheric CO 2 had on the loss of nitrogen from decomposing litter and the eventual re-use of this nitrogen. During the decomposition study, on a mass basis more 15N was transferred from the litter despite the litter grown in elevated CO 2 initially having a lower 15N signal. This was primarily related to a higher decomposition rate of the elevated CO 2 grown litter. Despite more nitrogen entering the below-ground community under elevated atmospheric CO 2, the additional N did not stay within the terrestrial community and was not exploited by the plants. The results confirm previous suggestions that Lolium perenne plants growing in elevated CO 2 have to derive at least a proportion of their nitrogen from a source external to either added fertiliser or decomposing litter