Measurement of ethylene and methane production in a temperate forest soil using inhibition of acetylene and carbon monoxide

Abstract

We studied in the laboratory the effects of acetylene (C₂H₂) concentrations on the accumulation and consumption of ethylene and methane in a temperate pine forest soil, and in situ ethylene and methane production and flush effects of nitrogen sources on both productions in the pine forest stand (Pinus sylvestris L.). The addition of C₂H₂ at concentrations more than 50 Pa C₂H₂ in the headspace caused a more than 95% reduction in rates of ethylene and methane consumption in forest soil compared to those with no C₂H₂. Furthermore, addition of acetylene within a range of 50 to 10, 000 Pa C₂H₂ induced a similar rate of methane accumulation in forest soil. Hence, it can be concluded that presence of more than 50 Pa C₂H₂ in the headspace is an effective method to measure methane production in forest soil. The addition of C₂H₂ at concentrations more than 50 Pa C₂H₂ induced an increasing concentration of ethylene in the headspace (P⩽0.05), indicating the reduction of acetylene to ethylene in forest soil. Using inhibition of 0.5 kPa C₂H₂ in combination with 5 kPa carbon monoxide that inhibits the reduction of acetylene in a short term, it was observed that there was a larger in situ methane production rate (218 ± 26 μg C m⁻² h⁻¹ (μg C per square meter per hour, the same below)) than in situ ethylene production rate (92 ± 6 μg C m⁻² h⁻¹) in the pine forest soil. The addition of nitrogen sources such as urea, urea plus a nitrification inhibitor dicyandiamide, and potassium nitrate, could induce a 5-fold greater increase in rates of in situ ethylene and methane production compared to those in the control, particularly in the latter (P⩽0.05). The results can promote in situ measurement of ethylene and methane production in forest soils at different sites.