Elevated CO2 affects field decomposition rate and palatability of tree leaf litter: Importance of changes in substrate quality

Field decomposition rates of ash (Fraxinus excelsior L.) and sycamore (Acer pseudoplatanus L.) leaf litters were measured for litters grown at ambient and elevated concentration of atmospheric CO2 inside solar domes. Litter raised at 600 μl l−1 CO2 retained significantly more mass at the end of the first year of field decomposition than material raised at 350 μl l−1. This reduction in decomposition could be related to changes in tissue quality resulting from growing the plants at higher CO2 concentrations, with C-to-N ratios and lignin contents being significantly increased. The elevated CO2 treatment also affected the rate of consumption of ash leaf litter by Oniscus asellus L. (Isopoda: Oniscoidea), with significantly less (−16%) material being consumed for litter derived from the high CO2 regime. Our results indicate that changes in litter quality, which we may expect under elevated CO2, may affect litter palatability for soil fauna.