Interactive effects of tree species and soil moisture on methane consumption

Methane consumption by temperate forest soils is a major sink for this important greenhouse gas, but little is known about how tree species influence CH4 uptake by soils. Here, we show that six common tree species in Siberian boreal and temperate forests significantly affect potential CH4 consumption in laboratory microcosms. Overall, soils under hardwood species (aspen and birch) consumed CH4 at higher rates than soils under coniferous species and grassland. While NH4+ addition often reduces CH4 uptake, we found no effect of NH4+ addition, possibly because of the relatively high ratio of CH4-to-NH4+ in our incubations. The effects of soil moisture strongly depended on plant species. An increase in soil moisture enhanced CH4 consumption in soils under spruce but had the opposite effect under Scots pine and larch. Under other species, soil moisture did not affect CH4 consumption. These results could be explained by specific responses of different groups of CH4-oxidizing bacteria to elevated moisture.