Impact of using the friction velocity filter on annual carbon estimates on natural pasture ecosystems

Ricardo Acosta, Gustavo Pujol Veeck, Tiago Bremm, Débora Regina Roberti, Osvaldo Luiz Leal de Moraes

Abstract


Annual carbon estimation of the most diverse ecosystems is a recurring theme in meetings that address climate change mitigation, as it is essential to have a realistic inventory of carbon stock in the biosphere and the ability to assimilate atmospheric carbon. Measurements of CO2 flux over ecosystems after being taken undergo rigorous post-processing to remove spurious and unrealistic data. In addition, a correction for low turbulence situations, where the eddy-covariance technique may be underestimated, is to take the friction velocity (u*) as a threshold to establish valid measurements, especially at night. This method, although widely used by the scientific community, is not unanimous. Especially since u* is itself a flow and consequently its value correlates with the time scale used for the analysis. This paper presents the annual carbon estimate of a natural pasture ecosystem, Pampa biome, in an experimental site established in Santa Maria - RS. We evaluated three distinct situations in the annual carbon estimate (NEP): i) without a u* filter; ii) with a fixed filter u* for all evaluated years and; iii) with the filter u* varying seasonally. The methodology used to estimate u* is the same as that used by Papale et al. (2006). The results show a total annual carbon sequestration variability of up to 10% depending on the methodology employed. The ecosystem in question, regardless of the method used, proved to be a carbon sink. However, the use of one methodology or another in ecosystem situations that are close to carbon assimaltion neutral should be closely scrutinized for an accurate annual balance.


Keywords


CO2 flux; Eddy covariance; Pampa biome; Friction velocity filter

References


ACEVEDO, O.; MORAES, O.; DEGRAZIA, G.; FITZJARRALD, D.; MANZI, A.; CAMPOS, J. Is friction velocity the most appropriate scale for correcting nocturnal carbon dioxide fluxes. Agricultural and Forest Meteorology, Elsevier, 149, 1-10, 2009.

ACOSTA, R. Estimativas das interações biosfera-atmosfera em ecossistema de pastagem natural do bioma Pampa. 84 f. Tese (Doutorado em Meteorologia) — Universidade Federal de Santa Maria, Santa Maria, 2019

BARR, A.; RICHARDSON, A.; HOLLINGER, D.; PAPALE, D. ARAIN, M.; BLACK, T.; BOHRER, G.; DRAGONI, D.; FISCHER, M. GU, L. Use of change-point detection for friction--velocity threshold evaluation in eddy-covariance studies. Agricultural and forest meteorology, Elsevier, 171, 31-45, 2013.

PAPALE,D.; REICHSTEIN, M.; AUBINET, M.; CANFORA, E.; BERNHOFER, C.; KUTSCH, W. LONGDOZ, B.; RAMBAL, S.; VALENTINI, R.; VESALA, T. Towards a standardized processing of Net Ecosystem Exchange measured with eddy covariance technique: algorithms and uncertainty estimation. Biogeosciences, Copernicus GmbH, 3, 571 – 583, 2006.

STULL, R. An introduction to boundary layer meteorology. Dordrecht: Kluwer Academic Publishers, 1988. 666 p.




DOI: https://doi.org/10.5902/2179460X45315

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Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

 

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