What was done
Two species common to dune grasslands (Calamagrostis epigejos L. and Vicia lathyroides L.) and two species common to peatlands (Carex rostrata Stokes and Sphagnum recurvum) of the Netherlands were collected and grown in greenhouses fumigated with air containing 390 and 700 ppm CO2 for up to five months.  After senescence occurred, leaf litter was collected to study the effects of elevated CO2 on litter quality and decomposition rates in different mixture combinations.

What was learned
Elevated CO2 significantly affected leaf litter quality in all studied species, except Sphagnum.  Indeed, atmospheric CO2 enrichment reduced leaf litter nitrogen concentrations by 28, 29 and 48% in Vicia, Carex, and Calamagrostis, respectively.  In turn, these changes contributed to CO2-induced increases in litter C:N ratios of 42, 37 and 61%, for the same respective species.  In addition, elevated CO2 increased leaf litter phenolic concentrations by 20 and 32% in Vicia and Carex, respectively.

With respect to decomposition, elevated CO2 did not significantly affect cumulative respiration from leaf litter mixtures containing Carex and Sphagnum; but it reduced the cumulative respiration of leaf litter mixtures containing Vicia and Calamagrostis.

What it means
As the atmospheric CO2 concentration increases, leaf litter quality of Vicia, Calamagrostis and Carex will likely be altered in such a way that their decomposition rates will be slightly reduced, while Sphagnum litter and its decomposition rate will likely remain unchanged.  Thus, carbon sequestration in ecosystems dominated by these species should increase with future increases in the air's CO2 content, as greater amounts of biolitter decompose at slower rates.