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This study is based on a 50-year data series (1964-2013) of total solar radiation (G) from the Kołobrzeg – station that is located on the Polish Baltic Sea coast and is characterised by a very high level of air quality. To find and remove gross errors, quality control checking procedures were applied in this study. Additionally, the homogeneity of the G series in this study has been tested on a monthly basis by using of the Standard Normal Homogeneity Test for single shifts. We found a statistically non-significant decrease in G during the period from 1964 to 2013. The decrease in the 5-year mean total solar radiation is evident from the beginning of the 1980s, with the minimum mean value occurring in the second half of the 1990s, while G slightly increased from the early 2000s. The analysis of seasonal G patterns shows that total solar radiation in summer is the most similar to the annual pattern and only the summer series trend shows a statistically significant decrease in G. We have also found two noticeable tendencies in monthly anomalies of G over the studied decades; they are negative trends in May and August. The shape of the decadal daily G histogram remained unchanged during the analysed decades.
Ecosystem respiration (Reco) plays an important role in estimating the global carbon balance of terrestrial ecosystems, and knowledge of respiration is required to correctly assess the gross primary (GPP) production of such ecosystems. In our paper, daytime Reco fluxes are compared with nighttime CO₂ fluxes which were measured manually by the closed chamber technique on a wetland site in Poland. The CO₂ fluxes measurements were performed between July 2008 and May 2009. Our study indicated that there are significant differences between modeled daytime and nighttime Reco fluxes and that these differences are higher when the nighttime fluxes are restricted only to nights with stable atmospheric conditions. The nighttime sums of cumulative Reco are much higher than the one estimated for daytime conditions, while there is nearly no difference between daytime and nighttime sums of cumulative Reco, when the nighttime fluxes are restricted only for nights with turbulent atmospheric conditions. Consequently, Reco models developed on the basis of nighttime data series can overestimate CO₂ fluxes when they are used to estimate daytime respiration. In order to reduce uncertainties in estimation of daily Reco fluxes on the basis of the nighttime chamber measurements, the nighttime Reco models should be restriced only to the fluxes that were measured in turbulent atmospheric conditions. The biases in nighttime chamber measurements (especially when conducted in stable atmospheric conditions) as well as differences in estimated daytime and nighttime Reco fluxes can have a significant effect on the assessment of global carbon balances of terrestrial ecosystems.
The assessment of net ecosystem exchange (NEE) and respiration of ecosystem (Reco) of terrestrial ecosystems is necessary to improve our knowledge about the carbon cycle. The aims of this paper were to present reliable measurements of CO₂ fluxes of a temperate bog ecosystem located in Poland using a closed dynamic chamber system and to obtain a daily dynamic course of CO₂ fluxes over the 2007 vegetation season. Measurements of CO₂ fluxes were carried out at Rzecin peatland ecosystem located in northwestern Poland using the set of two chambers (dark and transparent). Reco during the experiment period ranged from 2.65 to 14.76 μmolCO₂ ・m⁻²・s⁻¹. The daily run of NEE was inversed to PPFD and the values of NEE varied from 0.06 to -11.82 μmolCO₂・m⁻²・s⁻¹. We found differences between NEE and Reco in the wetland ecosystem with respect to term of measurements. The PPFD, air and soil temperatures explain most temporal variability of CO₂ fluxes at Rzecin. But vegetation structure, its phenology and water-level depth seem also to play important roles. The chamber technique is a useful tool for determining carbon dioxide exchange between wetland surface and the atmosphere.
Franz D., Acosta M., Altimir N., Arriga N., Arrouays D., Aubinet M., Aurela M., Ayres E., Lopez-Ballesteros A., Barbaste M., Berveiller M., Biraud S., Boukir H., Brown T., Brummer C., Buchmann N., Burba G., Carrara A., Cescatti A., Ceschia E., Clement R., Cremonese E., Crill P., Darenova E., Dengel S., D’Odorico P., Filippa G., Fleck S., Fratini G., Fub R., Gielen B., Gogo S., Grace J., Graf A., Grelle A., Gross P., Grunwald T., Haapanala S., Hehn M., Heinesch B., Heiskanen J., Herbst M., Herschlein C., Hortangl L., Hufkens K., Ibrom A., Jolivet C., Joly L., Jones M., Kiese R., Klemendsson L., Kljun N., Klumpp K., Kolari P., Kolle O., Kowalski A., Kutsch W., Laurila T., De Ligne A., Linder S., Lindroth A., Lohila A., Longdoz B., Mammarella I., Manise T., Maranon Jimenez S., Matteucci G., Mauder M., Meier P., Merbold L., Mereu S., Metzger S., Migliavacca M., Molder M., Montagnani L., Moureaux C., Nelsson D., Nemitz E., Nicolini G., Nilsson M. B., Op de Beeck M., Osborne B., Lofvenius M. O., Pavelka M., Peichl M., Peltola O., Pihlatie M., Pitacco A., Pokorny R., Pumpanen J., Ratie C., Rebmann C., Roland M., Sabbatini S., Saby N. P. A., Saunders M., Schmid H. P., Schrumpf M., Sedlak P., Serrano Ortiz P., Siebicke L., Sigut L., Silvennoinen H., Simioni G., Skiba U., Sonnentag O., Soudani K., Soule P., Steinbrecher R., Tallec T., Thimonier A., Tuittila E.-S., Tuovinen J. P., Vestin P., Vncent G., Vincke S., Vitalle D., Waldner P., Weslien P., Wingate L., Wohlfahrt G., Zahniser M., Vesala T.
International Agrophysics
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2018
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tom 32
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nr 4
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