Carbon dioxide and methane exchange of a subarctic heath in response to climate change related environmental manipulations

Responses of CO2 and CH4 exchange to NPK fertilization, soil warming and shading were investigated at a tree line heath site near Abisko in subarctic Sweden. Respiration increased with fertilization and decreased with shading after seven yr of treatment. Warming caused small overall changes in respiration. Photosynthesis was stimulated by fertilizer application to an extent which exceeded the increase in respiration and hence caused the system to increase its atmospheric CO2 sink strength. Warming, on the contrary, tended to increase the CO2 efflux from the ecosystem. Shading caused no significant net change in carbon flux but a significant reduction in the carbon turnover rate. Significant CH, consumption rates suggested that subarctic heath systems may constitute a significant sink for atmospheric CH4. inorganic nitrogen fertilization increased CH4 consumption which was unexpected since N addition normally inhibits CH4 consumption rates in natural and arable ecosystems. As expected from the relatively weak temperature dependency of microbial CH4 oxidation reported in previous studies, warming caused no increase in CH4 consumption rates.