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Soils in sub-arctic and arctic environments contain large reservoirs of carbon stored in SOM, due principally to slow decomposition rates caused by the harsh climatic environment. Climatic warming due to the greenhouse effect is, however, expected to be of greater magnitude in the high northern latitudes compared to a global average warming. Thus, in a changing world, relationship between climate and soil respiration will likely be of key significance in cold environments (e.g. tundra and boreal forest biomes).

Although soil respiration in sub-arctic environments is clearly responsive to temperature variations (Sjogersten and Wookey, 2002) there is also a general opinion among ecosystem scientists that respiration often is nutrient-limited due to slow decomposition processes and/or poor litter quality (see, for example, Jonasson (1992), Shaver and Chapin (1995), Schmidt et al. (1997)). This project therefore focuses upon the potential role of mineral nitrogen and labile carbon availability for soil respiration in two sub-arctic ecosystems near Abisko, northern Sweden. Fieldwork was performed during the summer of 2002. Nitrogen was added as ammonium nitrate (NH₄NO₃) and carbon as glucose, (C₆H₁₂O₆), to replicate. plots (n=3) on each of the three occasions in June 2002. Carbon dioxide (C0₂) flux was measured ca. every second day over four weeks from 11 June to 5 July 2002, before, during, and after the period of chemical treatments.

The results show a significant difference in soil respiration between the two study-sites: respiration being considerably higher at the tundra site compared to the forest. Regarding the chemical treatments, the soil respiration responded significantly to the labile carbon addition at the tundra site, but not at the forest site: this suggests that the metabolism of decomposer- organisms at the tundra site was limited by the lack of labile carbon. By contrast, there was no effect of added mineral nitrogen, at either site, during the time-coarse of measurements here. The results suggest that quality and/or quantity of labile carbon may have a key role in modulating the responses of soil respiration to environmental change in these systems.