Litter quality of Quercus plants growing in enhanced atmospheric CO2 in Mediterranean-type ecosystems

The impact of elevated atmospheric CO2 on the litter quality and litter C and N turnover rates was evaluated for two Mediterranean oak species (Quercus cerris L. and Quercus pubescens Willd.). Litter from 30-year-old trees was collected (1) in the vicinity of a CO2-emitting spring with 500+/-32 ppm CO2 and (2) in a control area with 360+/-5 ppm CO2, away from the spring. Litter quality was determined by chemical analysis and by tracking CO2 evolution and N mineralization from litter incubated for about 4 months under controlled conditions. Total C, C/N ratio, lignin, cellulose, lignin/N, cellulose/N, and (cellulose+lignin)/N ratios were not affected by elevated CO2. However, total N content of Quercus cerris litter grown in elevated CO2 was about 8% lower than in ambient conditions. Elevated atmospheric CO2 did not depress rates of C decomposition and N mineralization of the litter. Therefore we may expect that effects on litter quality play no role in changing the C balance of these Mediterranean-type ecosystems under future higher levels of atmospheric CO2.