Environmental and chemical factors regulating methane oxidation in a New Zealand forest soil

Abstract

Tropospheric methane (CH 4 ) is oxidised by soil microbes called methanotrophs. We examined them in soil samples from a pristine Nothofagus forest located in New Zealand. Laboratory incubations indicated the presence of high-affinity methanotrophs that displayed Michaelis-Menton kinetics (K m = 8.4 µL/L where K m is the substrate concentration at half the maximal rate). When the soil was dried from its field capacity water content of 0.34 to 0.16 m 3 /m 3 , CH 4 oxidation rate increased nearly 7-fold. The methanotrophs were thus metabolically poised for very high activity, but substrate availability was commonly limiting. When water content was held constant, CH 4 oxidation rate nearly doubled as temperature increased from 5 to 12 • C, a range found in the forest. By contrast, CH 4 oxidation rate did not change much from 12 to 30 • C, and it was zero at 35 • C. When water content and temperature were held constant, the optimal soil pH for CH 4 oxidation was 4.4, as found in the forest. Soil disturbance by nitrogen (N) and non-N salt amendment decreased CH 4 oxidation rate, but this depended on the amendment species and concentration. The methanotrophs were adapted to native conditions and exhibited a great sensitivity to disturbance.

Landscape analysis of soil methane flux across complex terrain

“…Research on soil-atmosphere CH 4 exchange has been conducted across a range of ecosystems Castaldi and Fierro, 2005;Luo et al, 2013), but assessing the spatial and temporal variability of CH 4 fluxes at the landscape scale has been limited. Studies focused on CH 4 oxidation have shown varied responses to commonly measured environmental variables such as soil moisture and temperature (e.g., Adamsen and King, 1993;Bradford et al, 2001;Price et al, 2004), nutrient variability (e.g., N species: Verchot et al, 2000; dissolved organic carbon: Sullivan et al, 2013). In addition to these physiological constraints, soil structure and texture create the physical landscape at the microbial scale by mediating how quickly soils drain and saturate, directly influencing transport and diffusion of substrates and O 2 (Dorr et al, 1993;Czepiel et al, 1995;Ball et al, 1997;von Fischer et al, 2009).…”

Short‐term effects of sheep excrement on carbon dioxide, nitrous oxide and methane fluxes in typical grassland of Inner Mongolia

“…Furthermore, the sandy texture and generally low water content during the study period could maintain a relatively high CH 4 diffusion rate from the atmosphere to the methanatrophs of soil. Decrease of CH 4 consumption after the application of NH 4 + fertilisers has been reported in many studies (Hutsch et al 1994;Price et al 2004;Wang et al 2004). With the increased applied NH4+-N to the soil from 13 to 96 kg N ha -1 , the percentage of methane oxidation being inhibited increased from 31 to 97% (Price et al 2004).…”

“…Decrease of CH 4 consumption after the application of NH 4 + fertilisers has been reported in many studies (Hutsch et al 1994;Price et al 2004;Wang et al 2004). With the increased applied NH4+-N to the soil from 13 to 96 kg N ha -1 , the percentage of methane oxidation being inhibited increased from 31 to 97% (Price et al 2004). This effect has been attributed to a competition between CH 4 and NH 3 for the same active site on the methane-and ammonia-monooxygenase (Knowles 1993).…”

Landscape analysis of soil methane flux across complex terrain

“…Studies focused on CH4 oxidation have shown varied responses to commonly measured environmental variables such as soil moisture and temperature (e.g. Adamsen and King, 1993;Bradford et al, 2001;Price et al, 2004), nutrient variability (e.g., N species: Verchot et al, 2000; and dissolved organic carbon: Sullivan et al, 2013). In addition to these physiological constraints, soil structure and texture create the physical landscape at the microbial scale by 25 mediating how quickly soils drain and saturate, directly influencing transport and diffusion of substrates and O2 (Dorr et al, 1993;Czepiel et al, 1995;Ball et al, 1997;von Fischer et al, 2009).…”