Fluxes of the powerful greenhouse gas nitrous oxide (N₂O) are mainly quantified using manually operated or automatic non-steady-state chambers. With both systems, fluxes are calculated as the change in N₂O concentration over time using linear or non-linear regression, but the type of regression selected can have a strong influence on the N₂O flux magnitude. The HMR package, a regression-based implementation of the Hutchinson & Mosier Regression, is a widely used software for trace gas flux calculation that provides a recommendation on the most appropriate regression method based on several criteria. New parameters were recently introduced which allow for pre-filtering based on sample variance (pfvar and pfalpha), and for constraining the curvilinearity of concentration-time series(SatPct and SatTimeMin). Currently, there are no guidelines on how to choose the best parameters for specific user conditions. Here we address this knowledge gap using datasets from manual and automatic chambers, and sensitivity analyses. We found that the effect of parameter settings on the cumulative fluxes was greater for manual chamber data compared to the automatic chamber data, with ranges of up to 67.3% and 1.5%, respectively. The parameter pfvar was identified as highly sensitive for both manual and automatic chambers; it is, therefore, critical to select a threshold for when to allow for non-linear flux calculation that accurately represents the given measurement precision. This can be estimated from the variance of N₂O measurements at ambient concentration levels. The parameter SatTimeMin was critical for manual chamber data where the curvature is much less constrained due to the lower number of observations. The parameter pfalpha was the least sensitive and can be set at a p-value equal to 0.05 following common statistical practice. Parameter values depend on the expected flux characteristics with a given chamber design and are currently best selected based on visual inspection of the data. This study identifies where and how specific care should be taken for the selection of parameters in the HMR package, which may contribute to standardizing the methodologies used worldwide for N₂O flux calculations, supporting initiatives in which data from many studies need to be combined.

中文翻译：

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使用自动和手动腔室确定温室气体通量估算标准：N2O 的案例研究

强大的温室气体一氧化二氮 (N ₂ O) 的通量主要使用手动操作或自动非稳态室进行量化。对于这两个系统，使用线性或非线性回归将通量计算为 N ₂ O 浓度随时间的变化，但所选回归类型会对 N ₂ O 通量大小产生很大影响。HMR 软件包是 Hutchinson & Mosier 回归的基于回归的实现，是一种广泛使用的痕量气体通量计算软件，可根据多个标准提供最合适的回归方法建议。最近引入了新参数，允许基于样本方差（pfvar和pfalpha）进行预过滤，并用于约束浓度-时间序列（SatPct和SatTimeMin）的曲线。目前，没有关于如何为特定用户条件选择最佳参数的指南。在这里，我们使用来自手动和自动腔室的数据集以及敏感性分析来解决这一知识差距。我们发现，与自动腔室数据相比，参数设置对手动腔室数据的累积通量影响更大，范围分别高达 67.3% 和 1.5%。参数pfvar被确定为对手动和自动腔室都高度敏感；因此，选择一个阈值来确定何时允许进行精确表示给定测量精度的非线性通量计算至关重要。这可以根据环境浓度水平下 N _{2 O 测量值的变化来估计。}参数SatTimeMin对于手动腔室数据至关重要，其中由于观察次数较少，曲率受到的限制要小得多。参数pfalpha是最不敏感的，可以设置为p-值等于 0.05，遵循常见的统计实践。参数值取决于给定腔室设计的预期通量特性，目前最好根据数据的目视检查来选择。这项研究确定了在选择 HMR 包中的参数时应特别注意的地方和方式，这可能有助于标准化全球用于 N ₂ O 通量计算的方法，支持需要合并来自许多研究的数据的举措。