Effect of elevated atmospheric CO(2) concentration on growth and leaf litter decomposition of Quercus acutissima and Fraxinus rhynchophylla

The atmospheric carbon dioxide (CO(2)) level is expected to increase substantially, which may change the global climate and carbon dynamics in ecosystems. We examined the effects of an elevated atmospheric CO(2) level on the growth of Quercus acutissima and Fraxinus rhynchophylla seedlings. We investigated changes in the chemical composition of leaf litter, as well as litter decomposition. Q. acutissima and F. rhynchophylla did not show differences in dry weight between ambient CO(2) and enriched CO(2) treatments, but they exhibited different patterns of carbon allocation, namely, lower shoot/root ratio (S/R) and decreased specific leaf area (SLA) under CO(2)-enriched conditions. The elevated CO(2) concentration significantly reduced the nitrogen concentration in leaf litter while increasing lignin concentrations and carbon/nitrogen (C/N) and lignin/N ratios. The microbial biomass associated with decomposing Q. acutissima leaf litter was suppressed in CO(2) enrichment chambers, while that of F. rhynchophylla was not. The leaf litter of Q. acutissima from the CO(2)-enriched chambers, in contrast with F. rhynchophylla, contained much lower nutrient concentrations than that of the litter in the ambient air chambers. Consequently, poorer litter quality suppressed decomposition.