Effects of elevated atmospheric CO2 concentration and increased nitrogen deposition on growth and chemical composition of ombrotrophic Sphagnum balticum and oligo-mesotrophic Sphagnum papillosum

The ombrotrophic Sphagnum balticum (Russ.) C. Jens. and the oligo-mesotroph ic Sphagnum papillosum Lindb. were grown at ambient (360 mu l l(-1)) and at elevated (720 mu l l(-1)) atmospheric CO2 concentrations and at different nitrogen deposition rates, varying between 0 and 30kg N ha(-1) yr(-1), The growth response to elevated atmospheric CO2 differed between species and th is difference also varied with the measured growth parameters. Structural b iomass of S. papillosum was significantly stimulated by elevated CO2, where as S. balticum did not respond. In both species, soluble sugar content in t he capitula and stems was significantly increased by elevated CO2 in the ab sence of nitrogen deposition, but not at elevated CO2 and high nitrogen dep osition. The ability of both Sphagnum species to respond to elevated CO2 by enhancement of growth was independent of nitrogen deposition level and pla nt nitrogen status. The response to increased nitrogen addition was in line with the response to elevated CO2; the oligo-mesotrophic S. papillosum sho wed an increased growth, while the ombrotrophic S. balticum again did not r espond. The species-dependent growth response to elevated CO2 and increased nitrogen deposition, may have considerable implications for interspecific competition between these species. Doubling atmospheric CO2 reduced total nitrogen content in both Sphagnum sp ecies. Elevated CO2 did not promote secondary metabolite production, such a s soluble phenols. An increase in soluble phenol content in S. papillosum w as observed when plants were grown with increased nitrogen deposition.