Understanding seasonal and diurnal dynamics of ecosystem respiration (R_eco) in forests is challenging, because R_eco can only be measured directly during night‐time by eddy‐covariance flux towers. R_eco is the sum of soil respiration (R_soil) and above‐ground respiration (in theory, R_AG = R_eco − R_soil). R_soil can be measured day and night and can provide a check of consistency on R_eco, as the difference in magnitude and time dynamic between R_eco and R_soil should be explained by R_AG. We assessed the temporal patterns and climatic drivers of R_soil and R_eco in a mature eucalypt woodland, using continuous measurements (only at night for R_eco) at half‐hourly resolution over 4 years (2014–2017). Our data showed large seasonal and diurnal (overnight) variation of R_eco, while R_soil had a low diurnal amplitude and their difference (R_eco − R_soil, or R_AG) had a low seasonal amplitude. This result implies at first glance that seasonal variation of R_eco was mainly influenced by R_soil while its diurnal variation was mainly influenced by R_AG. However, our analysis suggests that the night‐time R_eco decline cannot realistically be explained by a decline of R_AG. Chamber measurements of autotrophic components at half‐hourly time resolution are needed to quantify how much of the R_eco decline overnight is due to declines in leaf or stem respiration, and how much is due to missing storage or advection, which may create a systematic bias in R_eco measurements. Our findings emphasize the need for reconciling bottom‐up (via components measured with chambers) and direct estimates of R_eco (via eddy‐covariance method).

中文翻译：

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桉树林地土壤和生态系统呼吸的同步测量：优势，经验教训和问题

了解森林中生态系统呼吸（R _eco）的季节性和昼夜动态具有挑战性，因为R _eco仅可在夜间由涡度协方差通量塔直接测量。R _eco是土壤呼吸（R _Soil）和地上呼吸的总和（理论上，R _AG  = R _eco  -R_土壤）。R_土壤可以白天和黑夜进行测量，并且可以检查R _eco的一致性，因为R _eco和R_土壤之间的量级和时间动态差异应由R _AG解释。。我们使用连续四年（2014年至2017年）半小时分辨率的连续测量（仅对R _eco而言为夜间），评估了成熟的桉树林地中R_土壤和R _eco的时间格局和气候驱动因素。我们的数据表明，R _eco的季节性和昼夜（过夜）变化较大，而R_土壤的昼夜振幅较低，而它们之间的差异（R _eco  -R_土或R _AG）的季节振幅较低。这个结果乍一看意味着R _eco的季节变化主要受R_土壤的影响，而其日变化主要受R _AG的影响。。但是，我们的分析表明，夜间R _eco的下降不能用R _AG的下降来现实地解释。需要在半小时的时间分辨率下对自养成分进行室内测量，以量化一夜中R _eco下降的多少是由于叶片或茎呼吸的下降，以及多少是由于缺少存储或对流而造成的，这可能会造成系统性偏差在R _eco测量中。我们的发现强调需要协调自下而上（通过使用腔室测量的组件）和直接估算R _eco（通过涡动协方差方法）。