Influence of nitrogen fertilization on methane uptake in temperate forest soils

Abstract

METHANE, a long-lived gas (8–10 years residence time), is important in the chemistry of the atmosphere and the Earth's radiation balance^1–3. The tropospheric abundance of CH₄ has been increasing by ˜1.1% yr^–1 over the past decade^4,5. The cause of this increase may be due to either increases in global sources or decreases in global sinks^1,6,7. Although considerable research has focused on measuring CH₄ emissions from major biological sources^7,8, much less is known about the magnitude of, and factors controlling, biological sinks of CH₄. The largest biological sinks for methane are microorganisms in aerobic soils⁷. Here we report a study of CH₄ uptake by aerobic temperate-forest soils. We measured CH₄consumption rates (up to 3.17 mg CH₄–C m^–1 day^–1) that were higher than reported previously. Globally, soils of temperate and boreal forests may consume up to 9.3 Tg CH₄–C yr^–1. We also found that the CH4 uptake rates of these soils were decreased significantly by elevated soil moisture (14%) and nitrogen additions (33%), implying that nitrogen fertilization may reduce this CH₄ sink.