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Nitrogen isotope fractionation by Pearl Millet (Pennisetum americanum L. and P. mollissimum L.) grown on nitrate was associated with nitrate reductase activity. Fractionation was evidenced at the step of nitrate reduction when the substrate-to-enzyme ratio was high (possibly saturating for the active sites of the nitrate reductase enzyme), for instance in(More)
Isolated savannas enclosed by forest are especially abundant in the eastern part of the Congolese Mayombe. They are about 3000 years old, and were more extensive some centuries ago. The boundary between forest and savanna is very abrupt, as a consequence of the numerous savanna fires lit by hunters. Floristic composition and vegetation structure data,(More)
The Petit-Saut hydroelectric reservoir was filled in 1994 on the Sinnamary River in French Guiana (Amazonian basin). Flooding of the equatorial rain forest led to anoxia in most of the water column and enhanced mercury methylation in the reservoir hypolimnion. We selected the benthivorous/omnivorous fish species Curimata cyprinoides to investigate total(More)
The use of stable isotope probing of fatty acid methyl esters (FAME-SIP) is a powerful tool to study the microorganisms involved in xenobiotic biodegradation in soil. Nevertheless, it is important to determine how representative these molecules are of microorganisms both qualitatively and quantitatively. Using Cupriavidus necator JMP134 as a simple(More)
The ability of earthworms to assimilate soil organic pools of different ages was investigated in field conditions through natural 13C labelling. Provided that 13C natural abundance of earthworm tissues is determined by their diet, the assimilation of soil organic matter by earthworms was estimated by measuring 13C/12C ratio of tissues of earthworms sampled(More)
Increasing diffuse nitrate loading of surface waters and groundwater has emerged as a major problem in many agricultural areas of the world, resulting in contamination of drinking water resources in aquifers as well as eutrophication of freshwaters and coastal marine ecosystems. Although empirical correlations between application rates of N fertilizers to(More)
Most savanna water balance models assume water partitioning between grasses and shrubs in a two-layer hypothesis, but this hypothesis has not been tested for humid savanna environments. Spatial partitioning of soil water between grasses and shrubs was investigated in a West African humid savanna by comparing the isotopic composition (oxygen-18 and(More)
In India, the stability of the forest savanna boundary (ecotone) has been questioned. To investigate the possibility of vegetation change at this boundary, we used the natural difference in the stable carbon isotope ratio (13C/12C, expressed as δ13C) of C3 (forest) and C4 (savanna) plants, which is preserved in the isotopic composition of soil organic(More)
The possibility of ecosystem boundary changes in northern Brazilian Amazonia during the Holocene period was investigated using soil organic carbon isotope ratios. Determination of past and present fluctuations of the forest-savanna boundary involved the measurement of natural 13C isotope abundance, expressed as δ13C, in soil organic matter (SOM). SOM 13C(More)
The sink capacity of the stalk in Zea mays L. (cv DEA) during the elongation period was previously investigated with (13)C and (15)N tracing. The chase experiment described here demonstrates the different behavior of intermediary reserves for C and N remobilization until full maturity of the kernels. Carbon incorporated during stalk elongation participated(More)