The importance of crop growth modeling to interpret the Δ14CO2 signature of annual plants

[1] The 14C/C abundance in CO2(¿14CO2) promises to provide useful constraints on regional fossil fuel emissions and atmospheric transport through the large gradients introduced by anthropogenic activity. The currently sparse atmospheric ¿14CO2 monitoring network can potentially be augmented by using plant biomass as an integrated sample of the atmospheric ¿14CO2. But the interpretation of such an integrated sample requires knowledge about the day¿to¿day CO2 uptake of the sampled plants. We investigate here the required detail in daily plant growth variations needed to accurately interpret regional fossil fuel emissions from annual plant samples. We use a crop growth model driven by daily meteorology to reproduce daily fixation of ¿14CO2 in maize and wheat plants in the Netherlands in 2008. When comparing the integrated ¿14CO2 simulated with this detailed model to the values obtained when using simpler proxies for daily plant growth (such as radiation and temperature), we find differences that can exceed the reported measurement precision of ¿14CO2(~2‰). Furthermore, we show that even in the absence of any spatial differences in fossil fuel emissions, differences in regional weather can induce plant growth variations that result in spatial gradients of up to 3.5‰ in plant samples. These gradients are even larger when interpreting separate plant organs (leaves, stems, roots, or fruits), as they each develop during different time periods. Not accounting for these growth¿induced differences in ¿14CO2 in plant samples would introduce a substantial bias (1.5–2¿ppm) when estimating the fraction of atmospheric CO2 variations resulting from nearby fossil fuel emission

Multidecadal CO2uptake variability of the North Atlantic

The multidecadal variability of air-sea CO(2)fluxes in the North Atlantic under preindustrial atmospheric CO(2) conditions is simulated, using a coupled biogeochemical/circulation model driven by long-term surface forcing reconstructed from the leading modes of sea level pressure observations from 1850 to 2000. Heat fluxes are of great importance for the multidecadal CO(2) fluctuations, about equal in magnitude to wind stress, in contrast to their less prominent role for CO(2) flux variability on interannual timescales. Another difference, compared to higher frequencies, is the dominance of the North Atlantic Oscillation in driving the variability of the air-sea CO(2) fluxes. Two spatially distinct regimes lead to large anomalies in the CO(2) fluxes but compensate to a large degree. The first regime is advective and has its clear signature southeast of Greenland while the second one, in the vicinity of the Labrador Sea and off Newfoundland, is convective. In both regimes, the multidecadal CO(2) fluctuations are driven mainly by variations in temperature, salinity, and DIC content at the sea surface while the role of the biological pump is of minor importance in this particular model. The magnitude of the simulated multidecadal CO(2) uptake changes is on the order of 0.02 Pg C/yr and amounts to 10-15% of the estimated annual anthropogenic CO(2) uptake of the North Atlantic

Maîtrise des fermentations alcooliques en flore mixte : vers un nouveau concept technologique en cidrerie et en oenologie

Ce projet avait comme objectif final d’apporter aux filières « vin » et « cidre » les moyens pour mieux maîtriser l’étape fermentaire, mais en prenant en compte le risque d’uniformisation excessive liée à une simplification excessive de la flore levurienne. Il s’agissait de comprendre les relations entre les levures des genres Hanseniaspora et Saccharomyces en conditions cidricoles et oenologiques afin d’envisager leur utilisation en flores mixtes, afin d’obtenir des produits finis plus aromatiques. Les essais pilotes et en ateliers cidricoles ont permis de définir et valider les conditions d’utilisation de la technologie flore mixte jusqu’à une étape pré-industrielle. Sur le plan de l’amélioration des qualités aromatiques des vins, les fabrications réalisées ont montré le potentiel important des souches non Saccharomyces. Les dégustations effectuées à plusieurs stades de l’élaboration des vins à l’aide de jurys entraînés montrent que les vins résultants de fermentations en flores mixtes sont appréciés en général pour leur complexité aromatique et leurs caractéristiques gustatives