In memoriam - Jérôme Balesdent (1957-2020)
Jérôme Balesdent passed away on July 19, 2020, at the age of 63. The scientific community has lost an outstanding researcher and a colleague who has always been committed to teamwork and the involvement of the younger generation.
Jérôme has been creative throughout his career, starting in Nancy, then Versailles, Cadarache and finally, Aix-en-Provence. As an agronomist, he has left his mark on the world of soil science. He is among the most internationally recognized French researchers for his work on soils and the dynamics of soil organic matter.
Jérôme Balesdent was always one step ahead. He was the inventor of the use of 13C to trace constrain carbon dynamics in soils. Using 13C, he measured, as a function of time, the introduction of corn-derived carbon (C4 photosynthesis) into a soil that had only seen C3 plants. The constraint of the fast component of soil organic matter dynamics was born. This approach, published in 1987 , is today a reference with nearly 800 citations and many emulators. This stable carbon isotope was a complement to his toolbox, which already contained another carbon isotope, 14C, with which he had already studied the dynamics of the slower components of SOC . Beyond the design of novel methods and the acquisition of invaluable data, Jérôme was also a pioneer in the modelling of soil organic matter content . His 1995 paper was a landmark, and it is still this exponential form of the soil carbon age profile that is used in current models.
One will also recall his intervention at the French Academy of Agriculture in 1999 , during which he already affirmed that the soil "could be a huge potential source or sink of CO2 and that an annual increase in this reservoir of only 0.4% per year would store as much carbon as the burning of fossil carbon emits". It is this vision that served as the basis for the international initiative "4‰ - soils for food security and climate" that was launched by France in 2015 at the COP21, 15 years after his intervention at the Academy. In 2018, in a meta-analysis published in Nature , he insisted on the inertia of the carbon cycle in soils, particularly at depth, and therefore on the need to consider the soil profile in its entirety when it comes to modelling the global carbon cycle and its links with the climate. This paper illustrates the interest that Jérôme has always had in the modelling and conceptualization of soil carbon processes.
Beyond mathematical and conceptual approaches, Jérôme not only enjoyed teaching, but also putting his expertise and integrative vision at the service of public policies. He was, for example, a pillar in the conceptual development of the recent French INRAE report on the “4 per 1000” opportunities and costs [6-7].
Here we would like to pay tribute to the great soil scientist and generous man that Jérôme was. He will be greatly missed by the French and international soil science communities.
 Balesdent J., Mariotti A., Guillet B. (1987) Natural 13C abundance as tracer for studies of soil organic matter dynamics. Soil Biology & Biochemistry 19, 25-30.
 Balesdent J., Guillet B. (1982) Les datations par le 14C des matières organiques des sols - Contribution à l'étude de l'humification et du renouvellement des substances humiques. Science du Sol 2, 93-112.
 Elzein A., Balesdent J. (1995) Mechanistic simulation of vertical distribution of carbon concentrations and residence times in soils. Soil Science Society of America Journal 59, 1328-1335.
 Balesdent J., Arrouays D. (1999) Usage des terres et stockage de carbone dans les sols du territoire français. Une estimation des flux nets annuels pour la période 1900-1999. Compte rendus des séances de l'Académie d'Agriculture de France, 85(6), 265-277 (séance du 19 mai 1999)
 Balesdent J., Basile-Doelsch I., Chadoeuf J., Cornu S., Derrien D., Fekiacova Z., Hatté C. (2018) Atmosphere-soil carbon transfer as a function of soil depth. Nature 559, 599-602.
 Sylvain Pellerin et al., 2019. Stocker du carbone dans les sols français, Quel potentiel au regard de l’objectif 4 pour 1000 et à quel coût? Synthèse du rapport d'étude, INRA (France), 114 p.
 I. Basile-Doelsch, J. Balesdent, S. Pellerin (2020) Reviews and syntheses: The mechanisms underlying carbon storage in soil, Biogeoscience, doi.org/10.5194/bg-2020-49, in press
By Isabelle Basile-Doelsch, CEREGE and Delphine Derrien, INRAE