Nitrate uptake by Eriophorum vaginatum controls N sub(2)O production in a restored peatland

The clear dependence of N sub(2)O production through denitrification on available nitrate, in soil has been shown in many studies. Since N availability similarly limits the growth of plants, the resource competition with vegetation limits the activity of denitrifying microbes and may consequently moderate the N sub(2)O emissions from peatlands. We used, uptake by Eriophorum vaginatum L. as a vegetation competition factor for microbes. The species was selected for the experiment because it has high nutrient use efficiency in low-nutrient conditions and high nutrient uptake efficiency in luxuriant nutrient conditions. We measured gaseous N flux as N sub(2)O (end product of denitrifier activity) in a restored peatland in central Finland with acetylene inhibition technique over a growing season from sample plots with varying, addition levels and E. vaginatum cover. The resource competition effects were analysed with a model that used exponential decay dependence of N sub(2)O flux on the leaf area of E. vaginatum, and saturating response of N sub(2)O flux to, addition level. The model explained the variation in N sub(2)O fluxes well (R super(2)=0.86). The model simulation showed that the increasing nutrient uptake of E. vaginatum decreased the N sub(2)O fluxes exponentially. Simultaneously, denitrification appeared to saturate even in conditions with high availability of, and low level of competition by vegetation. Thus, E. vaginatum is an effective competitor for, in sedge-dominated peatlands that controls the availability of, for denitrification, and consequently moderates the N sub(2)O emissions from peatlands.