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Conference abstract2007

Decadal addition of nitrogen to a boreal mire decreases the emission of methane

Eriksson, Tobias; Nilsson, Mats

Abstract

Methane emission from a peatland is the net of the methane produced by methanogenes and the oxidation of methane by methanotrophs. Deposition of nitrogen, which is increasing in many areas, onto mires, can affect these two processes at different scales; e.g. by NH4+ inhibition of methane oxidation (biochemical scale), by a shift in vegetation composition or effects on bacterial communities (community scale), and by increased photosynthetic CO2 fixation and changed allocation pattern of carbon to roots (ecosystem scale). In order to study the effects of nitrogen on these scales, long-term field experiments are needed, since the process scales have different time constants. The effects of nitrogen additions (30 kg ha-1 yr-1), sulfur additions (20 kg ha-1 yr-1) and greenhouse treatment, on methane emission were studied in a lawn plant community at an oligotrophic boreal minerogenic mire in northern Sweden. Methane emissions were measured 5-10 times each growing season during 1995-1997 and 2005-2006 respectively. The treatment effects were analyzed with mean water table and sedge cover (SC) included as covariates in the models. The first years of measurements revealed that nitrogen additions decreased the methane emission when SC was high and were close to zero when SC was low. The greenhouse treatment, which increase air and soil temperature, positively effected methane emission when SC was high, but showed no effect when SC was low. Another 8 years of nitrogen additions have significantly increased sedge cover and drastically decreased Sphagnum cover. Methane emission was, despite the change in vegetation cover, still negatively affected by nitrogen additions, even though SC has a positive effect on methane emission. Possible controls on the decreased methane emission will be discussed. Further, the results indicate reduced methane emission by the greenhouse treatment

Conference

Carbon in peatlands: state of the art and future research