University of Lorraine

About: University of Lorraine is a education organization based out in Nancy, France. It is known for research contribution in the topics: Population & Nonlinear system. The organization has 11942 authors who have published 25010 publications receiving 425227 citations. The organization is also known as: Lorraine University.

Does the addition of labile substrate destabilise old soil organic matter

Abstract: Input of organic matter to soil may stimulate microbial activity and alter soil carbon storage by modifying the mineralization of native soil organic carbon (SOC). Assessing the age of SOC affected by the altered mineralization is a major challenge as the destabilisation of old SOC would be much more damageable for the overall carbon budget than the mobilization of recent SOC. Here, we investigated the microbial populations sequentially activated after the addition of a labile substrate. We questioned whether they have distinct metabolic potential and we characterised the age of the native SOC they primed. We used soils from Congolese Eucalyptus plantations that were previously under savannah and which old and recent SOC exhibited different delta C-13. Soils were amended with glucose, in an amount sufficient to induce microbe growth, and incubated for one week. The delta C-13 of respired CO2 was continuously recorded using a tuneable diode laser spectrometer (TDLS). The combination of two glucose treatments with different delta C-13 signatures allowed partitioning the various sources of CO2 over time (recent SOC, old SOC and glucose). This was combined with phospholipids fatty acids (PLFA) analyses and potential metabolic activities measurements after 40 h and seven days of incubation. A peak of glucose mineralization occurred after 17 h of incubation. Before this peak (Stage 1), some specific communities with a strong feeding preference for recent SOC were activated. After the glucose peak (Stage 2), over-mineralization of native SOC occurred for some days. The recent 0 SOC was first preferentially used (Stage 3), while the old C4 SOC was destabilised in a later stage (Stage 4). Metabolic functions and composition of microbial communities also differed between Stages 3 and 4.Microbial populations collected at Stage 4 were slower compared to Stage 3, but more efficient in decomposing nutrient-containing substrates. Gram negative bacteria (16:1w7c and 18:1w7c) were stimulated at Stage 3 only, while Gram negative bacteria (cy17:0) were stimulated at both Stages 3 and 4. Our results demonstrated that the input of labile substrate alters the microbial community composition, potential metabolic activities, and the SOC pools utilisation. They pointed out the necessity to assess the age of destabilised SOC when investigating the impact of priming on carbon storage in soil. (C) 2014 Elsevier Ltd. All rights reserved.

Sulfur and lead isotopic evidence of relic Archean sediments in the Pitcairn mantle plume

Abstract: The isotopic diversity of oceanic island basalts (OIB) is usually attributed to the influence, in their sources, of ancient material recycled into the mantle, although the nature, age, and quantities of this material remain controversial. The unradiogenic Pb isotope signature of the enriched mantle I (EM I) source of basalts from, for example, Pitcairn or Walvis Ridge has been variously attributed to recycled pelagic sediments, lower continental crust, or recycled subcontinental lithosphere. Our study helps resolve this debate by showing that Pitcairn lavas contain sulfides whose sulfur isotopic compositions are affected by mass-independent fractionation (S-MIF down to Δ33S = −0.8), something which is thought to have occurred on Earth only before 2.45 Ga, constraining the youngest possible age of the EM I source component. With this independent age constraint and a Monte Carlo refinement modeling of lead isotopes, we place the likely Pitcairn source age at 2.5 Ga to 2.6 Ga. The Pb, Sr, Nd, and Hf isotopic mixing arrays show that the Archean EM I material was poor in trace elements, resembling Archean sediment. After subduction, this Archean sediment apparently remained stored in the deep Earth for billions of years before returning to the surface as Pitcairn´s characteristic EM I signature. The presence of negative S-MIF in the deep mantle may also help resolve the problem of an apparent deficit of negative Δ33S anomalies so far found in surface reservoirs.

Coordination and trade-offs among hydraulic safety, efficiency and drought avoidance traits in Amazonian rainforest canopy tree species.

Abstract: Predicting responses of tropical forests to climate change-type drought is challenging because of high species diversity. Detailed characterization of tropical tree hydraulic physiology is necessary to evaluate community drought vulnerability and improve model parameterization. Here, we measured xylem hydraulic conductivity (hydraulic efficiency), xylem vulnerability curves (hydraulic safety), sapwood pressure-volume curves (drought avoidance) and wood density on emergent branches of 14 common species of Eastern Amazonian canopy trees in Paracou, French Guiana across species with the densest and lightest wood in the plot. Our objectives were to evaluate relationships among hydraulic traits to identify strategies and test the ability of easy-to-measure traits as proxies for hard-to-measure hydraulic traits. Xylem efficiency was related to capacitance, sapwood water content and turgor loss point, and other drought avoidance traits, but not to xylem safety (P50 ). Wood density was correlated (r = -0.57 to -0.97) with sapwood pressure-volume traits, forming an axis of hydraulic strategy variation. In contrast to drier sites where hydraulic safety plays a greater role, tropical trees in this humid tropical site varied along an axis with low wood density, high xylem efficiency and high capacitance at one end of the spectrum, and high wood density and low turgor loss point at the other.