DECOMPOSITION OF TREE LEAF LITTERS GROWN UNDER ELEVATED CO2 - EFFECT OF LITTER QUALITY

Ash (Fraxinus excelsior L.), birch (Betula pubescens Ehrh.), sycamore (Acer pseudoplatanus L.) and Sitka spruce (Picea sitchensis (Bong.) Ca rr.) leaf litters were monitored for decomposition rates and nutrient release in a laboratory microcosm experiment. Litters were derived fro m solar domes where plants had been exposed to two different CO2 regim es: ambient (350 mu L L(-1) CO2) and enriched (600 mu L L(-1) CO2). El evated CO2 significantly affected some of the major litter quality par ameters, with lower N, higher lignin concentrations and higher ratios of C/N and lignin/N for litters derived from enriched CO2. Respiration rates of the deciduous species were significantly decreased for litte rs grown under elevated CO2, and reductions in mass loss at the end of the experiment were generally observed in litters derived from the 60 0 ppm CO2 treatment. Nutrient mineralization, dissolved organic carbon , and pH in microcosm leachates did not differ significantly between t he two CO2 treatments for any of the species studied. Litter quality p arameters were examined for correlations with cumulative respiration a nd decomposition rates: N concentration, C/N and lignin/N ratios showe d the highest correlations, with differences between litter types. The results indicate that higher C storage will occur in soil as a conseq uence of litter quality changes resulting from higher atmospheric conc entrations of CO2.