Non-steady-state chambers are often used for greenhouse gas flux measurements, and while there are recommendations on how long to keep the chamber closed, it is less investigated to what extent the length of the chamber closure period affects the estimated flux rates and which closure periods may provide the most accurate linear and non-linear flux estimates. Previous studies have shown that the closure of non-steady-state chambers induces a non-linear concentration development inside the chamber, even across short chamber closure periods, and that both linear and non-linear flux estimates are impacted by the chamber closure period itself. Based on 3,159 individual soil CO₂ and CH₄ flux measurements, we analyzed how linear regression and Hutchinson and Mosier (1981) modeled flux estimates are affected by the length of the chamber closure period by increasing it in increments of 30 sec, with a minimum and maximum chamber closure period of 60 and 300 sec, respectively. Across all detected flux measurements, the effect of chamber closure period length varied between 1.4–8.0 % for linear regression estimates and between 0.4–17.8 % for Hutchinson–Mosier estimates, and the largest effect sizes were observed in high flux regions. While both linear regression and Hutchinson–Mosier based estimates decreased as the chamber closure period increased, we observed a clear convergence of flux estimates as shorter and longer chamber closure periods were used for linear regression and Hutchinson–Mosier based estimation, respectively. This suggests using closure periods as short as possible for linear regression flux estimation or ensuring long-enough closure periods to observe a stabilization of Hutchinson–Mosier flux estimates over time. This analysis was based on soil flux measurements, but because the perturbation of the concentration gradient is related to the non-steady-state chamber technique rather than the measured ecosystem component, our results have implications for all flux measurements conducted with non-steady-state chambers.

中文翻译：

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优化关闭期以提高基于暗室的温室通量估计的准确性


非稳态暗室通常用于温室通量测量，虽然有关于保持暗室关闭多长时间的建议，但很少研究暗室关闭期的长度在多大程度上影响估计的通量率，以及哪些关闭期可能提供最准确的线性和非线性通量估计。以前的研究表明，非稳态腔室的关闭会导致腔室内的非线性浓度发展，即使在较短的腔室关闭期内也是如此，并且线性和非线性磁通量估计都受到腔室关闭期本身的影响。基于 3,159 个单独的土壤 CO₂ 和 CH₄ 通量测量值，我们分析了线性回归和 Hutchinson 和 Mosier （1981） 建模的通量估计如何受到腔室关闭期长度的影响，以 30 秒的增量增加腔室关闭期，最小和最大腔室关闭期为 60 和 300 秒。 分别。在所有检测到的通量测量中，线性回归估计的腔室闭合期长度的影响在 1.4-8.0 % 之间变化，Hutchinson-Mosier 估计在 0.4-17.8 % 之间变化，并且在高通量区域观察到最大的效应量。虽然线性回归和基于 Hutchinson-Mosier 的估计值都随着腔室关闭期的增加而减少，但我们观察到通量估计值的明显收敛，因为线性回归和基于 Hutchinson-Mosier 的估计分别使用较短和较长的腔室关闭期。这表明使用尽可能短的闭合期进行线性回归通量估计，或者确保足够长的闭合期以观察 Hutchinson-Mosier 通量估计随时间的稳定。 该分析基于土壤通量测量，但由于浓度梯度的扰动与非稳态室技术有关，而不是与测量的生态系统成分有关，因此我们的结果对使用非稳态室进行的所有通量测量都有影响。