11 Jun 2020
11 Jun 2020
Status: this discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The manuscript was not accepted for further review after discussion.

Cereal-legume mixtures increase net CO2 uptake in a forage system of the Eastern Pyrenees

Mercedes Ibañez1,2, Núria Altimir2,a, Àngela Ribas2,3,4, Werner Eugster5, and Maria-Teresa Sebastià1,2 Mercedes Ibañez et al.
  • 1GAMES group, Dept. HBJ, ETSEA, University of Lleida (UdL). Av. Alcalde Rovira Roure, 191, 25198, Lleida, Spain
  • 2Laboratory of Functional Ecology and Global Change (ECOFUN), Forest Science and Technology Centre of Catalonia (CTFC). C/ de Sant Llorenç, 0, 25280 Solsona, Lleida, Spain
  • 3Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain
  • 4Centre for Ecological Research and Forestry Applications (CREAF), 08193, Bellaterra, Spain
  • 5ETH Zürich, Institute of Agricultural Sciences, Universitätstrasse 2, 8092, Zürich, Switzerland
  • acurrent address: Institute for Atmospheric and Earth System Research (INAR), University of Helsinki, Physicum, Kumpula campus, Gustaf Hällströmin katu, 2 , 00560, Helsinki, Finland

Abstract. Forage systems are the major land use, and provide essential resources for animal feeding. Assessing the influence of forage species on net ecosystem CO2 exchange (NEE) is key to develop management strategies that can help to mitigate climate change, while optimizing productivity of these systems. However, little is known about the effect of forage species on CO2 exchange fluxes and net biome production (NBP), considering: species ecophysiological responses; growth and fallow periods separately; and the management associated with the particular sown species. Our study assesses the influence of cereal monocultures vs. cereal legume mixtures on (1) ecosystem scale CO2 fluxes, for the whole crop season and separately for the two periods of growth and fallow; (2) potential sensitivities of CO2 exchange related to short-term variations in light, temperature and soil water content; and (3) NBP during the growth period; this being the first long term (seven years) ecosystem scale CO2 fluxes dataset of an intensively managed forage system in the Pyrenees region. Our results provide strong evidence that cereal-legume mixtures lead to higher net CO2 uptake than cereal monocultures, as a result of higher gross CO2 uptake, while respiratory fluxes did not significantly increase. Also, management associated with cereal legume mixtures favoured vegetation voluntary regrowth during the fallow period, which was decisive for the cumulative net CO2 uptake of the entire crop season. All cereal legume mixtures and some cereal monocultures had a negative NBP (net gain of C) during the growth period, indicating C input to the system, besides the yield. Overall, cereal legume mixtures enhanced net CO2 sink capacity of the forage system, while ensuring productivity and forage quality.

Mercedes Ibañez et al.

Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Mercedes Ibañez et al.

Mercedes Ibañez et al.


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Short summary
Our study unravels the influence of forage species on ecosystem scale CO2 fluxes, and is the first long term dataset of a forage system in the Pyrenees. We found strong evidence that cereal legume mixtures enhanced system's CO2 sink capacity compared to cereal monocultures, by enhancing photosynthesis and voluntary regrowth, decisive for the net CO2 budget. This knowledge is crucial to develop climate change mitigation strategies, while ensuring productivity of forage systems.