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The Taskomirsay section (South Kazakhstan) is a unique Pliensbachian-Toarcian sequence of lignites, clayey layers and silty-sandstones deposited in a fluvial/lacustrine environment with nearby swampy areas. This period, characterized by a drastic climate change, has been particularly studied in Western Tethyan marine environments, whereas very few studies focused on continental settings. Paleoflora analyses, associated with a multi-isotope approach, based on well-preserved Type-III bulk organic nitrogen isotopes ( δ 15 N org ) and hydrogen isotopic composition ( δ 2 H) of n -alkanes, were developed to document paleoclimatic changes in the area. Sporomorph associations and fossil woods revealed a globally warm- to cool-temperate climate – characterized by Xenoxylon , a conifer morphogenus biogeographically related to cool/humid settings – apart from slightly less humid and warmer conditions in the early Toarcian. Warmer conditions are supported by reconstructed Mean Annual Air Temperatures (MAATs), based on the first branched glycerol dialkyl glycerol tetraethers (brGDGTs) ever recorded in the Early Jurassic. Nevertheless, no drastic changes were recorded in the δ 15 N org values; its signal being attributed to tenuous equilibrium between water- and nutrient-availability via intense N-recycling. Based on n -alkane distributions, sources of organic matter were separated in two pools: (i) a purely terrestrial ( n -C 27 ) and (ii) an “aquatic” pool ( n -C 23 ) constituted of vegetation that thrived under almost permanent water supply. The n -alkane δ 2 H values (− 248 to − 151‰) as well as their amounts and average chain lengths (ACL) are in agreement with cool-temperate conditions in the Pliensbachian and less humid/warmer conditions in the early Toarcian. The isotopic difference between δ 2 H values of n -C 27 and n -C 23 (Δ 2 H ter-aq ) suggests enhanced seasonality during the Pliensbachian-Toarcian transition and low seasonality in the early Toarcian, in agreement with temperate climate-regime. Finally, contrasted response to paleoclimate changes between markers suggests different spatial integration of those proxies. The role of sea-level variations for δ 2 H values might also resolve this contrasted response. [ABSTRACT FROM AUTHOR]

The carbonization process induces significant physical, elemental, and structural transformations of wood. In this study, the modification of δ18O in wood during the carbonization process was investigated in conjunction with elemental analysis, infrared spectroscopy (FTIR), and Rock-Eval thermal analysis, to explore the connection between the chemical composition of the materials and the alterations in δ18O. Quercus petraea wood samples were experimentally burned at temperatures ranging from 200 °C to 1000 °C under inert (pyrolysis) and oxidative atmospheres. The results reveal that the modification of δ18O values in charred wood can be described as a sequential two-step process. The initial step, occurring below 300 °C, involves the volatilization and preferential degradation of thermolabile compounds, leading to an increase of +1.6‰ in δ18O. The subsequent step, below 700 °C, results in a decrease in δ18O values of –21.6‰, primarily driven by the thermal degradation of cellulose and lignin, as well as the increase of aromaticity and reorganization. The components and the δ18O of wood undergo distinct changes in combustion mode, due to different carbonization kinetics as evidenced by FTIR and elemental analysis. To assess the intensity of the carbonization process, influenced by temperature, oxygen availability, and wood characteristics, the H/C atomic ratio, a good indicator of aromaticity, is used. A non-linear regression model was established, relating δ18O to the H/C atomic ratio, thereby demonstrating that δ18O values undergo changes as wood aromatization progresses, independent of the carbonization conditions. The second order model has a mean confidence interval of 1.9‰ and a prediction interval of 8.1‰. This work provides a fundamental understanding of the connection between the chemical composition of woody materials, alterations in δ18O, and the carbonization process, offering valuable insights for further studies and applications related to oxygen-related information that may be preserved in charcoals. • Quercus petraea was charred in oxidative and reducing atmospheres. • The carbonization process alters δ18O in two steps due to structural changes. • The δ18O changes follow different pathway in combustion and pyrolysis. • Key chemical parameters for identifying the wood carbonization process are provided. • A non-linear regression model links δ18O to wood aromatization via H/C ratio. [ABSTRACT FROM AUTHOR]

Earthworms are known to have a major impact on organic matter dynamics in soils. The precise dynamics of carbon incorporation and/or decomposition in soil under the influence of earthworms still need to be investigated. In a mesocosm experiment, the fate of Ryegrass root and shoot litter was monitored in the soil, in the presence and absence of anecic earthworms Lumbricus terrestris L. Residues were 13 C labelled and deposited onto the soil surface. Incorporation of 13 C in surface casts and in the 0–20 and 40–60 cm soil layers was monitored 1, 2, 4, 8, 24 and 54 weeks after adding labelled litter. Organic carbon content and δ 13 C values were obtained for all samples, allowing the determination of the percentage of carbon derived from labelled litter (C lab ). Roots and shoots were incorporated in the 0–20 cm soil layer during the year of experiment, C lab reaching 11.4% of the soil organic carbon after 54 weeks. On the contrary, no significant contribution from labelled residues was observed in the 40–60 cm layer. Roots decomposed at a slower rate compared to shoots. Litter incorporation was observed in casts from the very first weeks of experiment (C lab from 34.8 to 51.4% after 2 weeks). In the soil, a significant effect of earthworms on the C lab was detected after 24 weeks. Earthworms accelerated root and shoot decomposition in the soil. They also enhanced, in the presence of shoot residues, the decomposition of the organic matter originally present in the soil. However, after one year, earthworms smoothed the difference between residue types in casts and to a lesser extent in soil, revealing their capacity to enhance the decomposition of both roots and shoots. [ABSTRACT FROM AUTHOR]