# Carbon budget over 12 years in a production crop under temperate climate

Pauline Buysse, Bernard Bodson, Alain Debacq, Anne de Ligne, Bernard

Heinesch, T. Manise, Christine Moureaux, Marc Aubinet

► To cite this version:

Pauline Buysse, Bernard Bodson, Alain Debacq, Anne de Ligne, Bernard Heinesch, et al. Carbon budget over 12 years in a production crop under temperate climate. EGU 2017, European Geophysical Union General Assembly 2017, Apr 2017, Vienne, Austria. 1 p. hal-02735436

HAL Id: hal-02735436

https://hal.inrae.fr/hal-02735436

Submitted on 2 Jun 2020

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# Carbon budget over 12 years in a production crop under temperate climate

Pauline Buysse (1,2), Bernard Bodson (3), Alain Debacq (2), Anne De Ligne (2), Bernard Heinesch (2), Tanguy Manise (3), Christine Moureaux (2), and Marc Aubinet (2)

(1) INRA-AgroParisTech, Université Paris Saclay, UMR ECOSYS, Thiverval-Grignon, France (pauline.buysse@inra.fr), (2) University of Liège - Gembloux Agro-Bio Tech, TERRA, Ecosystems-Atmosphere Exchanges, Gembloux, Belgium, (3) University of Liège - Gembloux Agro-Bio Tech, TERRA, Crop Science, Gembloux, Belgium

Carbon dioxide ($CO_2$) exchanges between crops and the atmosphere are influenced by both climatic and crop management drivers. The investigated crop, situated at the Lonzée Terrestrial Observatory (LTO, candidate ICOS site) in Belgium and managed for more than 70 years using conventional farming practices, was monitored over three complete sugar beet (or maize)/winter wheat/potato/winter wheat rotation cycles from 2004 to 2016. Continuous eddy-covariance measurements and regular biomass samplings were performed in order to obtain the daily and seasonal Net Ecosystem Exchange (NEE), Gross Primary Productivity, Total Ecosystem Respiration, Net Primary Productivity, and Net Biome Production (NBP). Meteorological data and crop management practices were also recorded. The main objectives were to analyze the $CO_2$ flux responses to climatic drivers and to establish the C budget of the cropland.

Crop type significantly influenced the measured $CO_2$ fluxes. In addition to crop season duration, which had an obvious impact on cumulated NEE values for each crop type, the $CO_2$ flux response to photosynthetic photon flux density, vapor pressure deficit and temperature differed between crop types, while no significant response to soil water content was observed in any of them. Besides, a significant positive relationship between crop residue amount and ecosystem respiration was observed.

Over the 12 years, NEE was negative (-4.34 ± 0.21 kg C m-2) but NBP was positive (1.05 ± 0.30 kg C m-2), i.e. as soon as all lateral carbon fluxes – dominated by carbon exportation – are included in the budget, the site behaves as a carbon source. Intercrops were seen to play a major role in the carbon budget, being mostly due to the long time period it represented (59 % of the 12 year time period). An in-depth analysis of intercrop periods and, more specifically, growing cover crops (mustard in the case of our study), is developed in a companion poster (ref. abstract EGU2017-12216, session SSS9.14/BG9.46/CL3.13).

Although in line with preceding studies, the large C loss rate observed at LTO (NBP = + 87 ± 25 kg C m-2 yr-1) raises several questions as it corresponds to 1.8 % of the C stock in the top soil: is it realistic? Wouldn’t it be affected by an undetected systematic error? If correct, could soil properties be preserved on the long term? This result at least calls for extensive C stock inventory for (in)validation.