American bison (Bison bison L.) have recovered from the brink of extinction over the past century. Bison reintroduction creates multiple environmental benefits, but impacts on greenhouse gas emissions are poorly understood. Bison are thought to have produced some 2 Tg yr⁻¹ of the estimated 9–15 Tg yr⁻¹ of pre-industrial enteric methane emissions, but few measurements have been made due to their mobile grazing habits and safety issues associated with measuring non-domesticated animals. Here, we measure methane and carbon dioxide fluxes from a bison herd on an enclosed pasture during daytime periods in winter using eddy covariance. Methane emissions from the study area were negligible in the absence of bison (mean ± standard deviation = −0.0009 ± 0.008 µmol m⁻² s⁻¹) and were significantly greater than zero, 0.048 ± 0.082 µmol m⁻² s⁻¹, with a positively skewed distribution, when bison were present. We coupled bison location estimates from automated camera images with two independent flux footprint models to calculate a mean per-animal methane efflux of 58.5 µmol s⁻¹ per bison, similar to eddy covariance measurements of methane efflux from a cattle feedlot during winter. When we sum the observations over time with conservative uncertainty estimates we arrive at 81 g CH₄ per bison d⁻¹ with 95 % confidence intervals between 54 and 109 g CH₄ per bison d⁻¹. Uncertainty was dominated by bison location estimates (46 % of the total uncertainty), then the flux footprint model (33 %) and the eddy covariance measurements (21 %), suggesting that making higher-resolution animal location estimates is a logical starting point for decreasing total uncertainty. Annual measurements are ultimately necessary to determine the full greenhouse gas burden of bison grazing systems. Our observations highlight the need to compare greenhouse gas emissions from different ruminant grazing systems and demonstrate the potential for using eddy covariance to measure methane efflux from non-domesticated animals.

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来自美洲野牛群的甲烷外排

美洲野牛（Bison bison L.）在过去的一个世纪里已从灭绝边缘恢复过来。野牛的重新引入创造了多种环境效益，但是对温室气体排放的影响知之甚少。据认为，野牛在工业化前肠内甲烷排放量的估计9-15 Tg yr ^-1中产生了约2 Tg yr ^-1，但由于其移动放牧习惯和与测量非食用性甲烷相关的安全性问题，因此很少进行测量。驯养的动物。在这里，我们使用涡度协方差来测量冬季白天白天封闭牧场上的野牛群中的甲烷和二氧化碳通量。在没有野牛的情况下，研究区域的甲烷排放量可以忽略不计（平均值 ± 标准偏差） =  - 0.0009  ±  0.008  μ摩尔米^-2 小号^-1）和比零显著更大，0.048  ±  0.082  μ摩尔米^-2 小号^-1，具有正偏态分布，当野牛存在。我们将来自自动照相机图像的野牛位置估计与两个独立的通量足迹模型结合起来，计算出 每野牛的平均动物平均甲烷外排量为58.5  µ mol s ^-1，类似于冬季牛饲养场中甲烷外排的涡度协方差测量。当我们将随时间变化的观测值与保守的不确定性估计值相加时，得出的结果为81 g CH ₄ 每野牛d ^-1与54和109克CH之间95％置信区间₄ 每野牛d ^-1。不确定性主要由野牛位置估计（占总不确定性的46％）决定，然后是流量足迹模型（33％）和涡流协方差测量（21％），这表明对动物进行较高分辨率的位置估计是合理的起点降低总不确定性。最终需要进行年度测量以确定野牛放牧系统的全部温室气体负担。我们的观察结果突出了需要比较不同反刍动物放牧系统的温室气体排放，并证明了使用涡度协方差来测量非驯养动物甲烷排放的潜力。