Gas exchange analysers exhibit large measurement error driven by internal thermal gradients
Gas exchange analysers exhibit large measurement error driven by internal thermal gradients
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DOI：
10.1111/nph.18347
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发表时间：
2022-07-30
期刊：
影响因子：
9.4
通讯作者：
Michaletz, Sean T.
中科院分区：
文献类型：
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作者：
Garen, Josef C.;Branch, Haley A.;Michaletz, Sean T.
便携式气体交换分析仪为了解植物-大气碳和水通量以及为预测气候变化影响和反馈的地球系统模型参数化提供关键数据。我们表征了Li-Cor LI-6400 XT和LI-6800中的温度测量误差，并估计了推导量的下游误差，包括气孔导度（g（sw））和叶细胞间CO2浓度（C-i）。LI-6400 XT的空气温度误差（报告的空气温度与叶片附近测量的空气温度之间的差异）高达7.2摄氏度，叶片温度误差高达5.3摄氏度，g（sw）和C-i的相对误差随着温度偏离环境而增加。这导致叶-气温关系、同化-温度曲线和CO2响应曲线出现误差。最大Rubisco羧化速率（V-cmax）和最大RuBP再生速率（J（max））的温度依赖性显示的误差分别为12%和35%。这些错误很可能是特殊的，并且可能因机器和环境条件而异。LI-6800显示出小得多的误差。地球系统模型的预测可能是错误的，因为它们的大部分参数化数据是在LI-6400 XT系统上测量的，这取决于所使用的方法。我们为LI-6400 XT中最小化错误和纠正数据提出建议。我们还建议过渡到LI-6800，以便将来进行数据收集。
Portable gas exchange analysers provide critical data for understanding plant-atmosphere carbon and water fluxes, and for parameterising Earth system models that forecast climate change effects and feedbacks. We characterised temperature measurement errors in the Li-Cor LI-6400XT and LI-6800, and estimated downstream errors in derived quantities, including stomatal conductance (g(sw)) and leaf intercellular CO2 concentration (C-i). The LI-6400XT exhibited air temperature errors (differences between reported air temperature and air temperature measured near the leaf) up to 7.2 degrees C, leaf temperature errors up to 5.3 degrees C, and relative errors in g(sw) and C-i that increased as temperatures departed from ambient. This caused errors in leaf-to-air temperature relationships, assimilation-temperature curves and CO2 response curves. Temperature dependencies of maximum Rubisco carboxylation rate (V-cmax) and maximum RuBP regeneration rate (J(max)) showed errors of 12% and 35%, respectively. These errors are likely to be idiosyncratic and may differ among machines and environmental conditions. The LI-6800 exhibited much smaller errors. Earth system model predictions may be erroneous, as much of their parametrisation data were measured on the LI-6400XT system, depending on the methods used. We make recommendations for minimising errors and correcting data in the LI-6400XT. We also recommend transitioning to the LI-6800 for future data collection.