Elevated atmospheric CO 2 has the potential to influence rates of C and N cycling in terrestrial ecosystems by altering plant litter chemistry and slowing rates of organic matter decomposition. We tested the hypothesis that the chemistry of leaf litter produced at elevated CO 2 would slow C and N transformations in soil. Soils were amended with Populus leaf litter produced under two levels of atmo‐spheric CO 2 (ambient and twice‐ambient) and soil N availability (low and high). Kinetic parameters for microbial respiration and net N mineralization were determined on soil with and without litter during a 32‐wk lab incubation. Product accumulation curves for CO 2 ‐C and inorganic N were fit to a first order rate equation [ y = A (1 − e − kt )] using nonlinear regression analyses. Although CO 2 treatment affected soluble sugar concentration in leaf litter (ambient = 120 g kg −1 , elevated = 130 g kg −1 ), it did not affect starch concentration or C/N ratio. Microbial respiration, microbial biomass, and leaf litter C/N ratio were affected by soil N availability but not by atmospheric CO 2 . Net N mineralization was a linear function of time and was not significantly different for leaves grown at ambient (50 mg N kg −1 ) and elevated CO 2 (35 mg N kg −1 ). Consequently, we found no evidence for the hypothesis that leaf litter produced at elevated atmospheric CO 2 will dampen the rates of C and N cycling in soil.
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Randlett et al. (1996) studied this question.