The effects of increased nitrogen deposition and CO2 on Sphagnum angustifolium and S-warnstorfii

The differences in response to four levels of N deposition rates 0, 10, 30 and 100 kg ha(-1) a(-1) and ambient CO2 concentrations 350, 700, 1 000 and 2 000 ppm were studied in a greenhouse with Finnish material: Sphagnum angustifolium (Russow) C, Jens., a species occurring over a wide nutrient regime, and S. warnstorfii Russow, a meso-eutrophic species. With increased N deposition rate, capitulum density, capitulum and stem dry masses per unit length increased in S. warnstorfii. Length increments differed statistically among the N treatments, but in the highest experimental N deposition rate there was no fall in S. angustifolium comparable to that found in S. warnstorfii. In both species, raised CO2 concentrations caused increasing trends in capitulum and stem dry masses as well as length increments. Dry mass production of S. angustifolium increased at raised CO2 concentrations. Interaction between the two treatments was not so clear as their individual effects.