Partitioning NEE for absolute C input into various ecosystem pools by combining results from eddy-covariance, atmospheric flux partitioning and ^sup 13^CO2 pulse labeling

• Published in: Plant and soil Vol. 390; no. 1-2; p. 61
• Main Authors: Riederer, M, Pausch, J, Kuzyakov, Y, Foken, T
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01.05.2015
• Subjects: Biogeochemistry; Carbon cycle; Carbon dioxide; Ecosystems; Environmental changes; Environmental conditions; Fluctuations; Grasslands; Respiration; Stable isotopes; Terrestrial ecosystems
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-014-2371-7

The complexity of ecosystem processes, especially under continuously changing environmental conditions, requires high-resolution insight into ecosystem carbon (C) fluxes. It is essential to gain not only information about relative C balance and fluxes (common for partitioning studies), but also to obtain these in absolute mass units. To evaluate absolute fluxes in belowground C pools, the results of 21-day eddy-covariance and stable isotope labeling experiment in summer 2010, were combined. Eddy-covariance based net ecosystem exchange was measured on extensively managed grassland and separated into underlying assimilation and ecosystem respiration through the use of a C flux partitioning model. Resultant CO2 assimilation served as absolute C input into the ecosystem and was further partitioned by applying the relative C distribution in subsidiary pools, gained by ^sup 13^C pulse labeling and tracing. The results form eddy-covariance measurements showed that the extensively managed grassland was a significant net C sink of -91 g C m^sup -2^ a^sup -1^ in 2010. The mean daily assimilation of -7.1 g C m^sup -2^ d^sup -1^ was partitioned into fluxes of 2.5, 0.8, 0.5, 2.3 and 1.0 g C m^sup -2^ d^sup -1^ into shoots, roots, soil, shoot respiration and CO2 efflux from soil, respectively. We conclude that the combination of EC measurements with isotope labeling techniques allowed determining the absolute C input into several ecosystem pools. Hence, the study demonstrates an approach to expand atmospheric flux measurements and to gain insight into the importance of individual ecosystem pools for soil C cycling.