McNamara Niall P, Chamberlain Paul M, Piearce Trevor G, Sleep Darren, Black Helaina I J, Reay David S, Ineson Phil
Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, LA1 4AP, UK.
Isotopes Environ Health Stud. 2006 Dec;42(4):379-90. doi: 10.1080/10256010600990765.
We investigated turnover of methane (CH4) in soils from a poorly drained UK forest. In situ, this forest exhibited a negligible soil-atmosphere CH4 flux, whereas adjacent grassland plots were sources of CH4. We hypothesised that the forest plots exhibited reduced anaerobic CH4 production through water-table draw down. Consequently, we exposed soil cores from under oak to high and low water-table conditions in the laboratory. Methane fluxes increased significantly in the high water-table (1925+/-1702 mug CH4 m(-2) h(-1)) compared to the low one (-3.5+/-6.8 microg CH4 m(-2) h(-1)). Natural abundance delta13C values of CH4 showed a strong depletion in high water-table cores (-56.7+/-2.9 per thousand) compared to methane in ambient air (-46.0 per thousand) indicative of methanogenic processes. The delta13C values of CH4 from low water-table cores (delta13C-46.8+/-0.2 per thousand) was similar to ambient air and suggested little alteration of headspace CH4 by the soil microbial community. In order to assess the CH4 oxidizing activity of the two treatments conclusively, a 13CH4 spike was added to the cores and 13CO2 production was measured as the by-product of CH4 oxidation. 13CH4 oxidation rates were 57.5 (+/-12.7) and 0.5 (+/-0.1) microg CH4 m(-2) h(-1) for high and low water-tables, respectively. These data show that the lower water-table hydrology treatment impacted methanogenic processes without stimulating methanotrophy.
我们研究了英国一片排水不良的森林土壤中甲烷（CH₄）的周转情况。在实地，这片森林的土壤-大气CH₄通量可忽略不计，而相邻的草地则是CH₄的排放源。我们推测，森林地块通过降低地下水位减少了厌氧CH₄的产生。因此，我们在实验室中将取自橡树下方的土壤芯暴露于高地下水位和低地下水位条件下。与低地下水位（-3.5±6.8微克CH₄ 米⁻² 小时⁻¹）相比，高地下水位（1925±1702微克CH₄ 米⁻² 小时⁻¹）下的甲烷通量显著增加。CH₄的自然丰度δ¹³C值显示，与环境空气中的甲烷（-46.0‰）相比，高地下水位土壤芯中的CH₄有强烈贫化（-56.7±2.9‰），这表明存在产甲烷过程。低地下水位土壤芯中CH₄的δ¹³C值（δ¹³C -46.8±0.2‰）与环境空气相似，表明土壤微生物群落对顶空CH₄的改变很小。为了最终评估两种处理方式下CH₄的氧化活性，向土壤芯中添加了¹³CH₄标记物，并测量了作为CH₄氧化副产物的¹³CO₂产量。高地下水位和低地下水位条件下的¹³CH₄氧化速率分别为57.5（±12.7）和0.5（±0.1）微克CH₄ 米⁻² 小时⁻¹。这些数据表明，较低的地下水位水文处理影响了产甲烷过程，而未刺激甲烷氧化作用。
