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Automated eddy covariance data quality control for long-term measurements
Šigut, Ladislav ; Mauder, M. ; Sedlák, Pavel ; Pavelka, Marian ; Špunda, Vladimír
Estimation of matter and energy exchange using the eddy covariance method is often organized into regional or global networks. To achieve comparability among sites, it is important to standardize and specify the methodology used. Currently, quality control (QC) is one of the most time-demanding steps in data processing within the Czech Carbon Observation System. Although manual QC (MQC) enables consideration of more complex test applications, it is often difficult to document. The aim of this study was to establish an automated QC (AQC) scheme based on available literature and post-processing software and test its effectivity and reliability on sites comprising an agroecosystem and a mature European beech forest. AQC successfully flagged low-quality CO2 fluxes and provided estimates of net ecosystem productivity similar to estimates based on MQC. The tests’ efficiency was particularly high for the agroecosystem, where AQC removed 13% less data than did MQC. We conclude that the adopted AQC displays satisfactory performance, especially for sites with low canopy heights.
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Preconditioning under high par of exposure to UV-A radiation both allow acclimation of the photosynthetic apparatus of barley transferred to UV-B radiation
Štroch, Michal ; Materová, Z. ; Vrábl, D. ; Šigut, Ladislav ; Špunda, Vladimír
The acclimation response of the barley photosynthetic apparatus was examined aft er transfer of plants grown under low and high PAR to common conditions both with the same PAR and acute dose of UV-A and/or UV-B radiation. The aim was to evaluate how PAR received during growth aff ects the induction of regulatory and protective mechanisms during UV exposure. Contrary to UV-B radiation, UV-A exposure of barley plants acclimated to low PAR had no negative impact on the function of photosynthetic apparatus. Th e UV-A spectral region we used (350–400 nm) can be eff ectively utilised in photosynthetic reactions, thus compensating low PAR. Th e presence of UV-A radiation during acclimation to simultaneous UVA and UVB treatment not only mitigated but completely eliminated any negative eff ect of UV-B radiation on the photosynthetic function. Th e eff ect of UV-A and UV-B exposure was similar in plants grown under high PAR – causing moderately enhanced photosystem II (PSII) photoinhibition. We proposed that the ability to accumulate a considerable amount of UVscreening compounds under high PAR itself contributes to the resistance of PSII to UV-B radiation.
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Improvement of CO2 eddy fluxes modelling in topographically complex terrain
Šigut, Ladislav
Annual sums of net ecosystem exchange (NEE) estimated by eddy covariance method (EC) are often used for comparisons among sites. But application of EC in topographically complex terrain restrains application of standard methods for their estimation. Analysis of friction air velocity response of night-time CO2 fluxes and estimation of mean daily ecosystem respiration from daytime NEE showed that night-time data and fluxes measured early after sunrise or late before sunset are not sufficiently reliable for computation of accurate annual sums of NEE. Therefore presented method takes into account auxiliary soil chamber measurements and applies correction factor in ecosystem respiration model calibrated to biomass inventory results. Also automated algorithm for computation of light response curve parameters in constrained range was established. This method produced accurate annual sums of NEE that were only 7.2% ± 5.2 higher than values determined by biomass inventory method.
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