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Wind as a main driver of the net ecosystem carbon balance of a semiarid Mediterranean steppe in the South East of Spain

Authors

  • Ana Rey,

    Corresponding author
    • Department of Desertification and Geoecology, Experimental Station of Arid Zones (EEZA), High Spanish Scientific Council (CSIC), Almería, Spain
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  • Luca Belelli-Marchesini,

    1. Department for Innovation in Biological, Agro-Food and Forest Systems (DIBAF), University of La Tuscia, Viterbo, Italy
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  • Ana Were,

    1. Department of Desertification and Geoecology, Experimental Station of Arid Zones (EEZA), High Spanish Scientific Council (CSIC), Almería, Spain
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  • Penelope Serrano-ortiz,

    1. Department of Desertification and Geoecology, Experimental Station of Arid Zones (EEZA), High Spanish Scientific Council (CSIC), Almería, Spain
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  • Giuseppe Etiope,

    1. Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy
    2. Faculty of Environmental Science and Engineering, Babes-Bolyai University, Cluj-Napoca, Romania
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  • Dario Papale,

    1. Department for Innovation in Biological, Agro-Food and Forest Systems (DIBAF), University of La Tuscia, Viterbo, Italy
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  • Francisco Domingo,

    1. Department of Desertification and Geoecology, Experimental Station of Arid Zones (EEZA), High Spanish Scientific Council (CSIC), Almería, Spain
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  • Emiliano Pegoraro

    1. Department of Desertification and Geoecology, Experimental Station of Arid Zones (EEZA), High Spanish Scientific Council (CSIC), Almería, Spain
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    • Deceased.

Correspondence: A. Rey, Museo Nacional de Ciencias Naturales CSIC, Serrano 115 E-28006, Madrid, Spain, tel. + 34 917 822 101, fax + 34 915 640 800, e-mail: arey@mncn.csic.es

Abstract

Despite the advance in our understanding of the carbon exchange between terrestrial ecosystems and the atmosphere, semiarid ecosystems have been poorly investigated and little is known about their role in the global carbon balance. We used eddy covariance measurements to determine the exchange of CO2 between a semiarid steppe and the atmosphere over 3 years. The vegetation is a perennial grassland of Stipa tenacissimaL. located in the SE of Spain. We examined diurnal, seasonal and interannual variations in the net ecosystem carbon balance (NECB) in relation to biophysical variables. Cumulative NECB was a net source of 65.7, 143.6 and 92.1 g C m−2 yr−1 for the 3 years studied, respectively. We separated the year into two distinctive periods: dry period and growing season. The ecosystem was a net source of CO2 to the atmosphere, particularly during the dry period when large CO2 positive fluxes of up to 15 μmol m−2 s−1 were observed in concomitance with large wind speeds. Over the growing season, the ecosystem was a slight sink or neutral with maximum rates of −2.3 μmol m−2 s−1. Rainfall events caused large fluxes of CO2 to the atmosphere and determined the length of the growing season. In this season, photosynthetic photon flux density controlled day-time NECB just below 1000 μmol m−2 s−1. The analyses of the diurnal and seasonal data and preliminary geological and gas-geochemical evaluations, including C isotopic analyses, suggest that the CO2 released was not only biogenic but most likely included a component of geothermal origin, presumably related to deep fluids occurring in the area. These results highlight the importance of considering geological carbon sources, as well as the need to carefully interpret the results of eddy covariance partitioning techniques when applied in geologically active areas potentially affected by CO2-rich geofluid circulation.

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