Oxygen isotope/salinity relationship in the Northern Indian Ocean

International audienceWe analyze the surface •5•80-salinity relationships of the Bay of Bengal and the Arabian Sea, in the northern Indian Ocean, known for their contrasting hydrological conditions. New measurements of these tracers show a very low •5•80-salinity slope associated with the strong dilution in the Bay of Bengal, but a slope more typical of this latitude in the Arabian Sea. Although this region is marked by a complex monsoonal regime, numerical modeling using a box model and a general circulation model is able to capture the •5•SO-salinity slope and its geographical variation. Both models clearly show that the low •5•SO-salinity slope is due to the evaporation-minus-precipitation balance, with an important contribution of the continental runoff in the Bay of Bengal. Although the low value of these slopes (-0.25) makes past salinity reconstructions uncertain, insight into the Last Glacial Maximum conditions shows a probable stability of these slopes and limited error on paleosalinity

Conseqüències de la biodegradabilitat de la matèria orgànica en les propietats físiques i químiques dels substrats

L'ús de nous materials de naturalesa orgànica provinents de l'agricultura, de la indústria i d'unes altres activitats humanes en la preparació de substrats per al cultiu de plantes fora del sòl natural requereix el coneixement de llur bioestabilitat, ja que aquesta propietat determina la variació de les característiques físiques i químiques dels substrats en el decurs del temps. En una recerca conjunta duta a terme pels dos grups de recerca pertanyents als departaments de referència de l'INRA a França i de l'IRTA a Catalunya, s'ha estudiat la bioestabilitat de sis materials orgànics: torba d'esfagne, compost d'escorça de pi, compost de residus verds de jardineria, compost de residus de bosc, fibra de coco i compost de fems de vacum, i alhora de set barreges binàries formulades amb les matèries abans esmentades. Al mateix temps s'han estudiat els efectes de la bioestabilitat en la variació de les propietats físiques i químiques de tots els substrats.Considerant els índexs de bioestabilitat respectius, les matèries primeres s'han classificat en tres grups: han resultat materials molt estables la fibra de coco, el compost d'escorça de pi i el compost de residus de jardineria; s'ha provat que són materials estables la torba d'esfagne i el compost de residus forestals; i, finalment, el compost de fems de vacum presenta una bioestabilitat moderada. S'hi mostra que, considerant els materials estudiats, la variació relativa de certes propietats físiques, com ara l'aigua disponible i l'aigua difícilment disponible, i també la de certes propietats químiques, com la capacitat de bescanvi catiònic, es correlacionen linealment, amb significació estadística, amb l'índex de bioestabilitat dels substrats estudiats en les dues localitzacions experimentals. Considerant només les matèries primeres, la regressió lineal entre llur capacitat d'aireació i llur índex de bioestabilitat presenta un coeficient de correlació també estadísticament significatiu. Per contra, l'índex de bioestabilEl uso de nuevos materiales de naturaleza orgánica procedentes de la agricultura, de la industria y de otras actividades humanas en la preparación de sustratos para el cultivo de plantas fuera del suelo natural requiere el conocimiento de su bioestabilidad, ya que esta propiedad determina la variación de las características físicas y químicas de los sustratos en el transcurso del tiempo. En una investigación conjunta realizada por los dos grupos de investigación que pertenecen a los departamentos de referencia del INRA, en Francia, y del IRTA, en Catalunya, se ha estudiado la bioestabilidad de seis materiales orgánicos: turba de esfagno, compost de corteza de pino, compost de residuos verdes de jardinería, compost de residuos de bosque, fibra de coco y compost de estiércol de bovino. También se ha estudiado este parámetro sobre siete mezclas binarias formuladas con las primeras materias antes citadas. Igualmente, se han estudiado los efectos de la bioestabilidad en la variación de las propiedades físicas y químicas de todos los sustratos. Considerando los respectivos índices de bioestabilidad, las primeras materias se han clasificado en tres grupos: materiales muy estables han resulta-do ser la fibra de coco, el compost de corteza de pino y el compost de residuos de jardinería; materiales estables se ha probado que lo son la turba de esfagno y el compost de residuos forestales. Finalmente, el compost de estiércol de bovino presenta una bioestabilidad moderada. Se muestra que, considerando los materiales estudiados, la variación relativa de ciertas propiedades físicas, como por ejemplo el agua disponible y el agua difícilmente disponible, y también la de ciertas propiedades químicas, como la capacidad de intercambio catiónico, se correlacionan linealmente, con significación estadística, con el índice de bioestabilidad de los sustratos estudiados en las dos localizaciones experimentales. Considerando sólo las primeras materias, la regresión lineal entre su capacidad

Past summer temperatures inferred from dendrochronological records of Fitzroya cupressoides on the eastern slope of the northern Patagonian Andes

Estimating summer temperature fluctuations over long timescales in southern South America is essential for better understanding the past climate variations in the Southern Hemisphere. Here we developed robust 212 year long basal area increment (BAI) and δ13C chronologies from living temperature‐sensitive Fitzroya cupressoides on the eastern slope of the northern Patagonian Andes (41°S). After removing the increasing trend from the growth records likely due to the CO2 fertilization effect, we tested the potential to reconstruct past summer temperature variations using BAI and δ13C as predictors. The reconstruction based on δ13C records has the strongest predictive skills and explains as much as 62% of the total variance in instrumental summer temperature (n = 81, p < 0.001). The temperature signal recorded in tree‐ring growth is not substantially different to that present in δ13C and consequently does not provide additional information to improve the regression models. Our δ13C‐based reconstruction shows cold summer temperatures in the second part of the 19th century and in the mid‐20th century followed by a warmer period. Notably, the 20th and the early 21st centuries were warmer (+0.6°C) than the 19th century. Reconstructed summer temperature variations are modulated by low‐latitude (El Niño–Southern Oscillation) and high‐latitude (Southern Annular Mode) climate forcings. Our reconstruction based on δ13C agrees well with previous ring width based temperature reconstructions in the region and comparatively enhances the low‐frequency variations in the records. The present study provides the first reconstruction of summer temperature in South America south of 40°S for the period 1800–2011 entirely based on isotopic records

Erosion of quantitative host resistance in the apple × Venturia inaequalis pathosystem

Theoretical approaches predict that host quantitative resistance selects for pathogens with a high level of pathogenicity, leading to erosion of the resistance. This process of erosion has, however, rarely been experimentally demonstrated. To investigate the erosion of apple quantitative resistance to scab disease, we surveyed scab incidence over time in a network of three orchards planted with susceptible and quantitatively resistant apple genotypes. We sampled Venturia inaequalis isolates from two of these orchards at the beginning of the experiment and we tested their quantitative components of pathogenicity (i.e., global disease severity, lesion density, lesion size, latent period) under controlled conditions. The disease severity produced by the isolates on the quantitatively resistant apple genotypes differed between the sites. Our study showed that quantitative resistance may be subject to erosion and even complete breakdown, depending on the site. We observed this evolution over time for apple genotypes that combine two broad-spectrum scab resistance QTLs, F11 and F17, showing a significant synergic effect of this combination in favour of resistance (i.e., favourable epistatic effect). We showed that isolates sampled in the orchard where the resistance was inefficient presented a similar level of pathogenicity on both apple genotypes with quantitative resistance and susceptible genotypes. As a consequence, our results revealed a case where the use of quantitative resistance may result in the emergence of a generalist pathogen population that has extended its pathogenicity range by performing similarly on susceptible and resistant genotypes. This emphasizes the need to develop quantitative resistances conducive to trade-offs within the pathogen populations concerned

Climate and atmospheric history of the past 420,000 years from the Vostok ice core,

Antarctica has allowed the extension of the ice record of atmospheric composition and climate to the past four glacial-interglacial cycles. The succession of changes through each climate cycle and termination was similar, and atmospheric and climate properties oscillated between stable bounds. Interglacial periods differed in temporal evolution and duration. Atmospheric concentrations of carbon dioxide and methane correlate well with Antarctic air-temperature throughout the record. Present-day atmospheric burdens of these two important greenhouse gases seem to have been unprecedented during the past 420,000 years. The late Quaternary period (the past one million years) is punctuated by a series of large glacial-interglacial changes with cycles that last about 100,000 years (ref. 1). Glacial-interglacial climate changes are documented by complementary climate records 1,2 largely derived from deep sea sediments, continental deposits of flora, fauna and loess, and ice cores. These studies have documented the wide range of climate variability on Earth. They have shown that much of the variability occurs with periodicities corresponding to that of the precession, obliquity and eccentricity of the Earth&apos;s orbit 1,3 . But understanding how the climate system responds to this initial orbital forcing is still an important issue in palaeoclimatology, in particular for the generally strong ϳ100,000-year (100-kyr) cycle. Ice cores give access to palaeoclimate series that includes local temperature and precipitation rate, moisture source conditions, wind strength and aerosol fluxes of marine, volcanic, terrestrial, cosmogenic and anthropogenic origin. They are also unique with their entrapped air inclusions in providing direct records of past changes in atmospheric trace-gas composition. The ice-drilling project undertaken in the framework of a long-term collaboration between Russia, the United States and France at the Russian Vostok station in East Antarctica (78Њ S, 106Њ E, elevation 3,488 m, mean temperature −55 ЊC) has already provided a wealth of such information for the past two glacial-interglacial cycles [4][5][6][7][8][9] Here we present a series of detailed Vostok records covering this ϳ400-kyr period. We show that the main features of the more recent Vostok climate cycle resemble those observed in earlier cycles. In particular, we confirm the strong correlation between atmospheric greenhouse-gas concentrations and Antarctic temperature, as well as the strong imprint of obliquity and precession in most of the climate time series. Our records reveal both similarities and differences between the successive interglacial periods. They suggest the lead of Antarctic air temperature, and of atmospheric greenhousegas concentrations, with respect to global ice volume and Greenland air-temperature changes during glacial terminations. The ice record The data are shown in Figs 1, 2 and 3 (see Supplementary Information for the numerical data). They include the deuterium content of the ice (dD ice , a proxy of local temperature change), the dust content (desert aerosols), the concentration of sodium (marine aerosol), and from the entrapped air the greenhouse gases CO 2 and CH 4 , and the d 18 O are defined in the legends to Figs 1 and 2, respectively.) All these measurements have been performed using methods previously described except for slight modifications (see The detailed record of dD ic

Hydrogen and oxygen isotopic composition of aqueous salt solutions by gas–water equilibration method

International audienc

Coherent Isotope History of Andean Ice Cores over the Last Century

[1] Isotope records from Andean ice cores provide detailed and high-resolution climate information on various time scales. However, the relationship between these valuable isotope records and local or regional climate remains poorly understood. Here we present results from two new drillings in Bolivia, from the Illimani and the Sajama ice caps. All four high altitude isotope signals in the Andes now available (Huascaran, Quelccaya, Illimani and Sajama) show near identical decadal variability in the 20th century. Comparison with general circulation model results and meteorological data suggest that the Andean high altitude records are primarily controlled by precipitation variability over the Amazon basin

High sensitivity measurements of water contents and D/H ratios in periodotites

International audienc