Methane Oxidation in Forest, Successional, and No‐till Agricultural Ecosystems

Methane oxidation in well‐aerated soils is a significant global sink for atmospheric methane. We examined the effects of soil disturbance (simulated tillage) and N‐fertilizer additions on methane oxidation in old‐growth forest, mid‐successional, and no‐till maize ecosystems in southwest Michigan, USA. We found highest oxidation rates in forest sites (about 30 μg CH 4 –C m −2 h −1 on average), with average rates in successional and agricultural sites about 75 and 12% of this, respectively. In the forest and successional sites a one‐time N‐fertilizer addition (100 kg NH 4 NO 3 –N ha −1 ) significantly suppressed oxidation for the several weeks that inorganic N pools were elevated. There was no effect of fertilizer addition in the agricultural site, where available N was already high and oxidation rates low. Soil disturbance by itself had no detectable effect on fluxes in any of the sites. Results confirm the overriding importance of elevated N for suppressing CH 4 oxidation in managed and unmanaged ecosystems, and suggest further that recovery of CH 4 suppression following agriculture is related to slow‐changing soil properties such as soil organic matter composition or microbial community structure.