Raised atmospheric CO₂ levels and increased N deposition cause shifts in plant species composition and production in <i>Sphagnum</i> bogs

Part of the missing sink in the global CO₂ budget has been attributed to the positive effects of CO₂ fertilization and N deposition on carbon sequestration in Northern Hemisphere terrestrial ecosystems. The genus Sphagnum is one of the most important groups of plant species sequestrating carbon in temperate and northern bog ecosystems, because of the low decomposability of the dead material it produces. The effects of raised CO₂ and increased atmospheric N deposition on growth of <i>Sphagnum</i> and other plants were studied in bogs at four sites across Western Europe. Contrary to expectations, elevated CO₂ did not significantly affect <i>Sphagnum</i> biomass growth. Increased N deposition reduced <i>Sphagnum</i> mass growth, because it increased the cover of vascular plants and the tall moss <i>Polytrichum strictum</i>. Such changes in plant species composition may decrease carbon sequestration in <i>Sphagnum</i>-dominated bog ecosystems.