RESPONSE OF SPHAGNUM-FUSCUM TO N DEPOSITION AND INCREASED CO2

The length increment and production of Sphagnum fuscum with enhanced n itrogen deposition (0, 10, 30 and 100 kg N ha(-1) yr(-1)) and CO2 conc entration (350, 700, 1000 and 2000 ppm) were measured. The experiment was carried out in the glasshouse, where S. fuscum was grown with the water table maintained at 10 cm below the moss surface for 120 d. For length growth, 10 kg N ha(-1) yr(-1): and for biomass production, 30 k g N ha(-1) yr(-1) were found to be the optimal loads. A load of 100 kg N ha(-1) yr(-1) inhibited elongation and biomass production almost co mpletely. An increased CO2 concentration reduced length increment slig htly, but it did not have a significant effect on biomass production. However, above ambient CO2 concentrations increased capitulum density and stem dry mass per unit length. In addition, increased CO2 concentr ation accelerated relative growth in Sphagnum carpets when these also received additional nitrogen. The study highlights the high degree of spatial variability that occurs within Sphagnum fuscum. Differences in growth and biomass production between samples, not found in natural c onditions, emerged during the experiment. On the basis of our results, the present nitrogen deposition load in Southern Finland (ca 6-10 kg N ha(-1) yr(-1)) is quite suitable for the growth and production of S. fuscum. If N deposition increased substantially, differences in the v itality of the species might be expected.