Litter Quality of Quercus Plants Growing in Enhanced Atmospheric CO₂ in Mediterranean-Type Ecosystems

Abstract

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.