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

Abstract

The ombrotrophic Sphagnum balticum (Russ.) C. Jens. and the oligo-mesotrophic Sphagnum papillosum Lindb. were grown at ambient (360 μ11⁻¹) and at elevated (720 μ11⁻¹) 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 this difference also varied with the measured growth parameters. Structural biomass of S. papillosum was significantly stimulated by elevated CO₂, whereas S. balticum did not respond. In both species, soluble sugar content in the capitula and stems was significantly increased by elevated CO₂ in the absence of nitrogen deposition, but not at elevated CO₂ and high nitrogen deposition. The ability of both Sphagnum species to respond to elevated CO₂ by enhancement of growth was independent of nitrogen deposition level and plant nitrogen status. The response to increased nitrogen addition was in line with the response to elevated CO₂; the oligomesotrophic S. papillosum showed an increased growth, while the ombrotrophic S. balticum again did not respond. 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 species.

Elevated CO₂ did not promote secondary metabolite production, such as soluble phenols. An increase in soluble phenol content in S. papillosum was observed when plants were grown with increased nitrogen deposition.