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Key Message: Leaves of seedlings from five oak species (Quercus robur L.; Q. pubescens L.; Q. suber L.; Q. afares Pomel; Q. ilex L.) displayed large, mainly inter-specific, differences in leaf mass-to-area ratio (LMA) and lignin content, as well as in the 13C composition of bulk leaf biomass. The variation in leaf lignin content and LMA did not impact the offset between the 13C composition measured in bulk leaf material versus soluble sugars. This observation, as well as the similar correlations between intrinsic leaf water use efficiency and the 13C compositions of bulk material or soluble sugars extracted from leaves, confirms their reliable use as a proxy for the former even when there is a large variation in LMA or lignin among samples. Context: Carbon isotope composition (δ13C) of bulk leaf biomass is frequently used as a proxy for intrinsic water use efficiency (iWUE) in large-scale intra- and inter-specific comparisons. However, post-photosynthetic 13C discrimination during the synthesis of lignin combined with differences in leaf mass-to-area ratio (LMA) may bias the relationship between δ13C of bulk leaf matter and iWUE and thus its use as a proxy of iWUE. Aims: To quantify the impact of differences in lignin content and LMA on the relationship between δ13C of bulk leaf biomass and iWUE over a large gradient of lignin contents across five oak species (deciduous: Quercus robur, Q. pubescens, Q. afares and evergreen: Q. ilex and Q. suber). Methods: We measured lignin content, LMA, and δ13C of bulk leaf biomass and of soluble sugars extracted from the leaves, as well as intrinsic water use efficiency (derived from leaf gas exchange) in seedlings of the five oak species grown under common conditions in a greenhouse and measured in a climate chamber. Results: There was a large range (mainly across species) in lignin content (4 to 33%) and LMA (60–180 g m−2). δ13C of bulk leaf biomass and soluble sugars were tightly correlated, showing a significant mean offset of − 0.4‰. This offset was stable across species and not correlated to the lignin content of the leaves. A very loose correlation was found between the offset and LMA, mainly due to one species. Conclusion: Our results are a demonstration that potential variations in leaf lignin content or LMA have no or only a little effect on the δ13C of bulk leaf biomass. They are unlikely to cause a bias when using bulk leaf δ13C as a proxy for variations in intrinsic water use efficiency among Mediterranean and temperate broad-leaf forest tree species. [ABSTRACT FROM AUTHOR]

Abstract Key Message Leaves of seedlings from five oak species (Quercus robur L.; Q. pubescens L.; Q. suber L.; Q. afares Pomel; Q. ilex L.) displayed large, mainly inter-specific, differences in leaf mass-to-area ratio (LMA) and lignin content, as well as in the 13C composition of bulk leaf biomass. The variation in leaf lignin content and LMA did not impact the offset between the 13C composition measured in bulk leaf material versus soluble sugars. This observation, as well as the similar correlations between intrinsic leaf water use efficiency and the 13C compositions of bulk material or soluble sugars extracted from leaves, confirms their reliable use as a proxy for the former even when there is a large variation in LMA or lignin among samples. Context Carbon isotope composition (δ 13 C) of bulk leaf biomass is frequently used as a proxy for intrinsic water use efficiency (iWUE) in large-scale intra- and inter-specific comparisons. However, post-photosynthetic 13C discrimination during the synthesis of lignin combined with differences in leaf mass-to-area ratio (LMA) may bias the relationship between δ 13 C of bulk leaf matter and iWUE and thus its use as a proxy of iWUE. Aims To quantify the impact of differences in lignin content and LMA on the relationship between δ 13 C of bulk leaf biomass and iWUE over a large gradient of lignin contents across five oak species (deciduous: Quercus robur, Q. pubescens, Q. afares and evergreen: Q. ilex and Q. suber). Methods We measured lignin content, LMA, and δ 13 C of bulk leaf biomass and of soluble sugars extracted from the leaves, as well as intrinsic water use efficiency (derived from leaf gas exchange) in seedlings of the five oak species grown under common conditions in a greenhouse and measured in a climate chamber. Results There was a large range (mainly across species) in lignin content (4 to 33%) and LMA (60–180 g m−2). δ 13 C of bulk leaf biomass and soluble sugars were tightly correlated, showing a significant mean offset of − 0.4‰. This offset was stable across species and not correlated to the lignin content of the leaves. A very loose correlation was found between the offset and LMA, mainly due to one species. Conclusion Our results are a demonstration that potential variations in leaf lignin content or LMA have no or only a little effect on the δ 13 C of bulk leaf biomass. They are unlikely to cause a bias when using bulk leaf δ 13 C as a proxy for variations in intrinsic water use efficiency among Mediterranean and temperate broad-leaf forest tree species.

The natural gas resources in the Sichuan Basin are abundant and exhibit various phenomena, for example, mixed sources, mixed maturities and overlapping combinations, resulting in great difficulties in identifying natural gas sources. In this study, several groups of thermal simulation experiments were conducted on various types of kerogens using closed and/or semi‐open systems to investigate the characteristics of the carbon isotope compositions of light hydrocarbon gases derived from different typical kerogens. The results showed that the carbon isotope compositions and variation trends of methane and ethane are controlled by the kerogen type, thermal simulation system and thermal evolution degree. The carbon isotope compositions of light hydrocarbon gases derived from different types of kerogens exhibit some differences with increased thermal evolution degree. When the thermal simulation temperature increases from 320 to 550°C, the methane carbon isotope of typically marine source rocks, mainly type I and type II1 kerogens, is slightly higher than or equivalent to that of ethane. However, the ethane carbon isotope of terrestrial source rocks, primarily types II2 and III kerogens, is significantly heavier than methane. By comparison, the evolution trend of carbon isotope compositions of actual natural gas is well consistent with that of light hydrocarbon gases cracked from thermal simulation experiments with increased thermal evolution degree. These findings are of great importance to identify the source rock of actual natural gas with high thermal maturities, as well as to determine the sources of deep shale gas in the southern Sichuan Basin, the Yuanba gas field and the Puguang gas field. Finally, a fitting method of carbon isotope values of methane and ethane of light hydrocarbon gases can be used to more finely differentiate the sources of natural gas in complex areas with mixed sources, mixed maturities and overlapping combinations. [ABSTRACT FROM AUTHOR]

Rootstocks are used in modern apple production to increase productivity, abiotic and biotic stress tolerance, and fruit quality. While dwarfing for apple rootstocks has been well characterized, the physiological mechanisms controlling dwarfing have not. Previous research has reported rootstock effects on scion water relations. Root architecture and variability in soil moisture across rooting depths can also contribute to these differences among rootstocks in the field. To exclude these effects on rootstock behavior, scions were grafted onto four different rootstocks with varying effects on scion vigor (B.9, M.9, G.41 and G.890). Non-grafted rootstocks were also grown to examine whether the effects of rootstock occurred independently from scion grafting. Plants were grown in a greenhouse under near steady-state hydroponic conditions. Carbon (δ13C), oxygen (δ18O) and nitrogen (δ15N) isotope composition were evaluated and relationships with carbon assimilation, water relations, and shoot growth were tested. Rootstocks affected scion shoot growth, aligning with known levels of vigor for these four rootstocks, and were consistent between the two scion cultivars. Furthermore, changes in water relations influenced by rootstock genotype significantly affected leaf, stem, and root δ13C, δ18O, and δ15N. Lower δ13C and δ18O were inconsistently associated with rootstock genotypes with higher vigor in leaves, stems, and roots. G.41 had lower δ15N in roots, stems, and leaves in both grafted and ungrafted trees. The effects of rootstock on aboveground water relations were also similar for leaves of ungrafted rootstocks. This study provides further evidence that dwarfing for apple rootstocks is linked with physiological limitations to water delivery to the developing scion. [ABSTRACT FROM AUTHOR]

Rootstocks are used in modern apple production to increase productivity, abiotic and biotic stress tolerance, and fruit quality. While dwarfing for apple rootstocks has been well characterized, the physiological mechanisms controlling dwarfing have not. Previous research has reported rootstock effects on scion water relations. Root architecture and variability in soil moisture across rooting depths can also contribute to these differences among rootstocks in the field. To exclude these effects on rootstock behavior, scions were grafted onto four different rootstocks with varying effects on scion vigor (B.9, M.9, G.41 and G.890). Non-grafted rootstocks were also grown to examine whether the effects of rootstock occurred independently from scion grafting. Plants were grown in a greenhouse under near steady-state hydroponic conditions. Carbon (δ13C), oxygen (δ18O) and nitrogen (δ15N) isotope composition were evaluated and relationships with carbon assimilation, water relations, and shoot growth were tested. Rootstocks affected scion shoot growth, aligning with known levels of vigor for these four rootstocks, and were consistent between the two scion cultivars. Furthermore, changes in water relations influenced by rootstock genotype significantly affected leaf, stem, and root δ13C, δ18O, and δ15N. Lower δ13C and δ18O were inconsistently associated with rootstock genotypes with higher vigor in leaves, stems, and roots. G.41 had lower δ15N in roots, stems, and leaves in both grafted and ungrafted trees. The effects of rootstock on aboveground water relations were also similar for leaves of ungrafted rootstocks. This study provides further evidence that dwarfing for apple rootstocks is linked with physiological limitations to water delivery to the developing scion.

An acceleration of the genetic advances of durum wheat, as a major crop for the Mediterranean region, is required, but phenotyping still represents a bottleneck for breeding. This study aims to define durum wheat ideotypes under Mediterranean conditions by selecting the most suitable phenotypic remote sensing traits among different ones informing on characteristics related with leaf pigments/photosynthetic status, crop water status, and crop growth/green biomass. A set of 24 post-green revolution durum wheat cultivars were assessed in a wide set of 19 environments, accounted as the specific combinations of a range of latitudes in Spain, under different management conditions (water regimes and planting dates), through 3 consecutive years. Thus, red-green-blue and multispectral derived vegetation indices and canopy temperature were evaluated at anthesis and grain filling. The potential of the assessed remote sensing parameters alone and all combined as grain yield (GY) predictors was evaluated through random forest regression models performed for each environment and phenological stage. Biomass and plot greenness indicators consistently proved to be reliable GY predictors in all of the environments tested for both phenological stages. For the lowest-yielding environment, the contribution of water status measurements was higher during anthesis, whereas, for the highest-yielding environments, better predictions were reported during grain filling. Remote sensing traits measured during the grain filling and informing on pigment content and photosynthetic capacity were highlighted under the environments with warmer conditions, as the late-planting treatments. Overall, canopy greenness indicators were reported as the highest correlated traits for most of the environments and regardless of the phenological moment assessed. The addition of carbon isotope composition of mature kernels was attempted to increase the accuracies, but only a few were slightly benefited, as differences in water status among cultivars were already accounted by the measurement of canopy temperature. [ABSTRACT FROM AUTHOR]

Simultaneous analysis of carbon and nitrogen isotope ratios by SIMS was applied for the first‐time to a natural diamond from the Kelsey Lake kimberlite, State Line Distinct, Colorado (UWD‐1). This in situ procedure is faster, reduces sample size for analysis, and measures both isotope ratios from a single ~ 10 μm diameter pit, a critical advantage for zoned diamonds. The carbon isotope ratio (expressed as δ13CVPDB) of the bulk UWD‐1 crystal, determined by the conventional combustion method in the present study, is ‐5.9‰ ± 0.2‰ (VPDB, 2s). Nitrogen mass fraction ([N]) and isotope ratio (expressed as δ15NAir) were determined by stepwise combustion and gas‐source mass‐spectrometry, resulting in 553 ± 64 μg g‐1 and ‐6.7‰ ± 1.1‰ (Air, 2s), respectively. Secondary ions of 12C2‐, 12C13C‐, 12C14N‐, and 12C15N‐ were simultaneously measured by SIMS using three Faraday cups and one electron multiplier. The spot‐to‐spot reproducibility of δ13C and δ15N values for the UWD‐1 (178 spots on sixteen chips, 10 μm spots), were 0.3‰ and 1.6‰, respectively (2s). While 12C14N‐/12C2‐ ratios, which are an indicator for [N], varied up to 12% among these sixteen chips, such variation did not correlate with either δ13C or δ15N values. We propose that UWD‐1 is a suitable reference sample for microscale in situ analysis of δ13C and δ15N values in diamond samples. [ABSTRACT FROM AUTHOR]

The composition of biomarker hydrocarbons in crude oil samples from Middle Devonian deposits of the Western Tebuk, Dzh"er, and Michayu oil fields of the Omra–Lyzha saddle in the Timan–Pechora oil-and-gas province was studied. Significant effect of the Upper Devonian Domanik source rocks on the formation of the composition of these crude oils was revealed. The main parameters demonstrating the genetic relationship of the oils from Middle Devonian reservoirs with this source rocks are distribution of steranes С27 : С28 : С29, ratio of isoprenoid to normal alkanes, and distribution of normal alkanes. All these characteristics sharply distinguish the crude oils under consideration from paraffinous oils syngenetic to Middle Devonian deposits, characteristic of deposits in the southern part of the Pechora–Kozhva megarampart. [ABSTRACT FROM AUTHOR]

An acceleration of the genetic advances of durum wheat, as a major crop for the Mediterranean region, is required, but phenotyping still represents a bottleneck for breeding. This study aims to define durum wheat ideotypes under Mediterranean conditions by selecting the most suitable phenotypic remote sensing traits among different ones informing on characteristics related with leaf pigments/photosynthetic status, crop water status, and crop growth/green biomass. A set of 24 post–green revolution durum wheat cultivars were assessed in a wide set of 19 environments, accounted as the specific combinations of a range of latitudes in Spain, under different management conditions (water regimes and planting dates), through 3 consecutive years. Thus, red–green–blue and multispectral derived vegetation indices and canopy temperature were evaluated at anthesis and grain filling. The potential of the assessed remote sensing parameters alone and all combined as grain yield (GY) predictors was evaluated through random forest regression models performed for each environment and phenological stage. Biomass and plot greenness indicators consistently proved to be reliable GY predictors in all of the environments tested for both phenological stages. For the lowest-yielding environment, the contribution of water status measurements was higher during anthesis, whereas, for the highest-yielding environments, better predictions were reported during grain filling. Remote sensing traits measured during the grain filling and informing on pigment content and photosynthetic capacity were highlighted under the environments with warmer conditions, as the late-planting treatments. Overall, canopy greenness indicators were reported as the highest correlated traits for most of the environments and regardless of the phenological moment assessed. The addition of carbon isotope composition of mature kernels was attempted to increase the accuracies, but only a few were slightly benefited, as differences in water status among cultivars were already accounted by the measurement of canopy temperature.

Carbon isotope stratigraphy is an important means to subdivide and correlate the Cambrian strata. Based on the carbon isotope analysis of the carbonate strata of Lütuogou Section, northern Henan Province, it is found the δ13C value of carbonate samples collected from the base of the Drumian Stage at Lütuogou Section, northern Henan, ranges from 3.1‰ to -1.7‰, and the δ18O value ranges from -3.9‰ to -9.4‰. No covariance exists between δ13C and δ18O, which implies that the carbon isotope composition is nearly stable. Value of δ13C around the base of the Drumian Stage consists of a negative excursion, the amplitude of the negative excursion is 3.0‰, and the minimum value of δ13C is -1.7‰, which occurs at the place 15 m below the first occurrence of trilobite protasaphiscus. The position and amplitude of the negative excursion are similar to those of the drum carbon isotope excursion (DICE) tested in the Wangcun Section, western Hunan, South China, and the Drum Mountains section in Utah, USA, which suggests that the DICE can be used as a global indicator for the correlation of the Drumian Stage. Furthermore, the cyan shale with thin limestone at the position of minimum δ13C overlies the oolitic limestone; therefore, DICE occurs in the transgressive succession in the early Miaolingian.

Gas seep and fluid flows from the seabed are an environment-forming factor of the aquatic environment, mainly due to their influence on the dissolved gases in the water, including dissolved oxygen. During the summer seasons from 2019 to 2021 in the area of shallow water gas emission site off the southern coast of the Heracles Peninsula, series of vertical probing profiles were carried out to determine hydrological parameters of the water: dissolved oxygen concentration (O2), temperature (T), salinity (S), and flow velocity (U). The study area is an underwater ledge with faults in the form of three canyons composed of dense limestones, two of which contained bubble gas emissions. Significant variability in O2 was identified in canyons where gas emissions are observed: from 1 to 80% saturation in the bottom layer, in contrast to normoxia at the background sites. Hypoxia was observed in the bottom layer above the emission sites in the absence of turbulence at temperature stratification. The values S decreased with depth, and the maximum difference reached 0.4‰. The bubble gas was dominated by methane (68.5–75.5%), and the carbon isotope composition of the bubble methane gas varied from –67.9 to –59.8‰ VPDB in 2019 and 2020, respectively. This generally indicates that the CH4 is of predominantly microbial genesis, was formed under different conditions, and matured in various periods of research during the monitoring period. Bacterial mats (mostly sulfur-oxidizing bacteria) were found in the areas of gas emissions. [ABSTRACT FROM AUTHOR]

Understanding the water use efficiency (WUE) and adaptation strategies of plants in high-temperature and rainy areas is essential under global climate change. The leaf carbon content (LCC) and intrinsic WUE of 424 plant samples (from 312 plant species) on Hainan Island were measured to examine their relationship with geographical and climatic factors in herbs, trees, vines and ferns. The LCC ranged from 306.30 to 559.20 mg g−1, with an average of 418.85 mg g−1, and decreased with increasing mean annual temperature (MAT). The range of intrinsic WUE was 8.61 to 123.39 μmol mol−1 with an average value of 60.66 μmol mol−1. The intrinsic WUE decreased with increasing altitude and relative humidity (RH) and wind speed (WS), but increased with increasing latitude, MAT and rainy season temperature (RST), indicating that geographical and climatic factors affect the intrinsic WUE. Stepwise regression suggested that in tropical regions with high temperature and humidity, the change in plant intrinsic WUE was mainly driven by WS. In addition, the main factors affecting the intrinsic WUE of different plant functional types of plants are unique, implying that plants of different plant functional types have distinctive adaptive strategies to environmental change. The present study may provide an insight in water management in tropical rainforest. [ABSTRACT FROM AUTHOR]

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In this study, we describe the variation in δ13C value in the litter of two species of peat-forming plants: Sphagnum fuscum and Eriophorum vaginatum, during 3 years of field decomposition in oligotrophic bog ecosystems drained for the purpose of forest melioration and fire affected and at the stage of post-pyrogenic restoration. Litterbags were periodically retrieved in the autumn and the δ13C value in the residual litter was related to mass loss, litter chemistry, and hydrothermal conditions. Sph. fuscum decomposes much more slowly than E. vaginatum. Low rate of transformation for Sph. fuscum is observed in drained and post-pyrogenic sites, while for E. vaginatum minimal rate of transformation is observed in the native site. During the decomposition of Sphagnum residues, 13C enrichment occurs, and during the decomposition of E. vaginatum, we observed 12C enrichment. The changes in the isotope composition of carbon for investigation sites are insignificant for Sphagnum fuscum, but it was observed for E. vaginatum, the largest of 13C depletion is observed in the drained site (−28.3‰) and minimal in the postpyrogenic site (−27.4‰). [ABSTRACT FROM AUTHOR]

Gases were sampled from 7 surface gas seeps including 2 mud volcanoes in the Niigata oil and gas basin. Based on the gas compositions and isotope compositions, the origin, maturity, migration, and alteration of gases were studied. A seep gas from the paddy field is interpreted to be microbial. The other 6 gases are thermogenic, or mixtures of thermogenic and microbia!・ The methane, ethane, and propane carbon isotope compositions suggest that the thermogenic gases were generated in the peak to late oil generation stage. Some gases show high C1 (C2 + C3), suggesting molecular fractionation during the migration to the surface. The 13C-enriched propane and heavy values (>+2 %) of CO2 in some gases, especially in gases from the mud volcanoes, indicate active processes of the secondary microbial methanogenesis accompanied 'by biodegradation of petroleum. The microbial processes could proceed during the residence time in the mud chambers, which are estimated to exist several hundred meters below the mud volcanoes. [ABSTRACT FROM AUTHOR]

Water use efficiency (WUE) is central to the global cycles of water and carbon. However, whether increasing tree diversity in forests can increase WUE remains poorly understood because the variation in WUE may result from multiple mechanisms acting concurrently. Disentangling their relative importance represents a major challenge.Here, we conducted a forest biodiversity experiment in subtropical China to assess the effects of neighbouring tree diversity on the foliar WUE of Cunninghamia lanceolata, a widespread tree plantation species in China. We measured foliar δ13C as a proxy for the change in intrinsic WUE. To disentangle the relative importance of water and nutrient‐mediated mechanisms in altering WUE, we determined foliar nutrient concentrations and foliar δ18O. Foliar δ18O was used as a surrogate for stomatal conductance and is known to be related to plant water use.Foliar WUE of focal trees increased with specific root length and leaf nitrogen content dissimilarities between focal trees and neighbours. The positive neighbourhood dissimilarity effect on foliar WUE was stronger under a more shaded neighbourhood. Foliar P concentration increased with neighbourhood specific root length dissimilarity. However, neither neighbourhood trait dissimilarities nor species richness significantly affect foliar δ18O. Results from structural equation model suggested that neighbourhood dissimilarity in specific root length indirectly enhanced foliar WUE and tree growth of focal trees via increasing foliar P concentration.Synthesis. Our results demonstrate the potential role of neighbourhood trait dissimilarity in modulating tree WUE in species‐rich communities. Our finding implies that the functional diversity of tree species at the local neighbourhood level has a fundamental ability to control water and nutrient cycles in forests. [ABSTRACT FROM AUTHOR]

Kerogens of the Upper Jurassic Gol'chikha, Yanovstan, Sigov and Tochin formations in the northeastern West Siberia have been studied using modern analytical methods. Quantitative characteristics of samples (ash content, moisture), elemental composition (contents of carbon, hydrogen, sulfur, nitrogen, and oxygen), carbon isotope composition, and pyrolytic characteristics of kerogens were determined. The type and catagenesis of organic matter (OM) and generation potential of oil source rocks were estimated. It was found that the oxidizing conditions of accumulation of organic matter had a significant effect on the composition of kerogens in the northeastern West Siberia. Compositional variations of kerogens depending on the OM type and catagenesis have been revealed. The proportions of biochemical components (lipids, proteins and carbohydrates) in the initial OM in rocks and their influence on the elemental composition of kerogens have been discussed. [ABSTRACT FROM AUTHOR]

Composite trees combine optimal traits from both the rootstock and the scion. Dwarfing rootstocks are commonly used to reduce shoot vigour and improve fruit quality and productivity. Although growth habits of different rootstocks have been clearly described, the underlying physiological traits affecting scion vigour are not well understood. Plant water status and stem water potential are strongly influenced by water supply and demand through the soil–plant–atmosphere continuum. In the scion, stomata regulate water loss and are essential to prevent hydraulic failure. Stomatal conductance influences leaf carbon isotope composition. Combined, the effects of reduced stomatal conductance and, consequently, carbon fixation may affect tree growth. These differences could also correspond to differences in scion vigour controlled by rootstock genotype. Here, vegetative growth, gas exchange, stem water potential and leaf δ13C were compared to determine how rootstocks affect scion water relations and whether these differences correspond to shoot vigour. There was a range in vigour among rootstocks by almost 2-fold. Net leaf carbon assimilation rates were lower in rootstocks with lower vigour. Rootstock vigour was closely associated with leaf gas exchange and stem water potential in the scion and was reflected in leaf δ13C signatures. Dwarfing was strongly affected by changes to plant water status induced by rootstock genotype and these changes are distinguishable when measuring leaf and stem δ13C composition. These observations indicate that scion water relations and leaf carbon isotope discrimination were affected by rootstock genotype. These results have implications for better understanding dwarfing mechanisms in apple rootstocks and the relationship with water-use traits. [ABSTRACT FROM AUTHOR]

The ratio of net CO2 uptake (Anet) and stomatal conductance (gs) is an intrinsic measurement of leaf water use efficiency (WUEi) however its measurement can be challenging for large phenotypic screens. Measurements of leaf carbon isotope composition (δ13Cleaf) may be a scalable tool to approximate WUEi for screening because it in part reflects the competing influences of Anet and gs on the CO2 partial pressure (pCO2) inside the leaf over time. However, in C4 photosynthesis the CO2 concentrating mechanism complicates the relationship between δ13Cleaf and WUEi. Despite this complicated relationship, several studies have shown genetic variation in δ13Cleaf across C4 plants. Yet there has not been a clear demonstration of whether Anet or gs are the causal mechanisms controlling WUEi and δ13Cleaf. Our approach was to characterize leaf photosynthetic traits of two Zea mays recombinant inbred lines (Z007E0067 and Z007E0150) which consistently differ for δ13Cleaf even though they have minimal confounding genetic differences. We demonstrate that these two genotypes contrasted in WUEi driven by differences in the speed of stomatal responses to changes in pCO2 and light that lead to unproductive leaf water loss. These findings provide support that differences in δ13Cleaf in closely related genotypes do reflect greater WUEi and further suggests that differences in stomatal kinetic response to changing environmental conditions is a key target to improve WUEi., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

The oil and gas potential prospects of the Magnitogorsk trough in the South Urals were studied and substantiated using the data of the geological survey and deep-well drilling. Based on the results of the seismic, gravity, and magnetic explorations, a large unit was detected in the Lower-Middle Carboniferous carbonates of the Kizil zone. The oil and gas blowouts were registered in the drill holes. To further explore the oil and gas potential of the region, the features of black shales were analyzed. It was shown that the Kumak ore field shales are promising sources of oil, depression analogues of the Lower-Middle Carboniferous shelf carbonates. Therefore, we recommend that the black shales of the South Urals should be further studied for their oil and gas potential. The major tasks for future research are as follows: localization of facies of the carbonate sedimentation basin within the Magnitogorsk trough and the East Urals uplift, as well as development of its geological and geophysical model; assessment of the oil and gas potential prospects of the region with the help of the developed model; substantiation of regional CMP seismic surveys.

Stomata control CO2 uptake for photosynthesis and water loss through transpiration, thus playing a key role in leaf thermoregulation, water-use efficiency (iWUE), and plant productivity. In this work, we investigated the relationship between several leaf traits and hypothesized that stomatal behavior to fast (i.e. minutes) environmental changes co-determines, along with steady-state traits, the physiological response of grapevine to the surrounding fluctuating environment over the growing season. No relationship between iWUE, heat stress tolerance, and stomatal traits was observed in field-grown grapevine, suggesting that other physiological mechanisms are involved in determining leaf evaporative cooling capacity and the seasonal ratio of CO2 uptake (A) to stomatal conductance (g s). Indeed, cultivars that in the field had an unexpected combination of high iWUE but low sensitivity to thermal stress displayed a quick stomatal closure to light, but a sluggish closure to increased vapor pressure deficit (VPD) levels. This strategy, aiming both at conserving water under a high to low light transition and in prioritizing evaporative cooling under a low to high VPD transition, was mainly observed in the cultivars Regina and Syrah. Moreover, cultivars with different known responses to soil moisture deficit or high air VPD (isohydric versus anisohydric) had opposite behavior under fluctuating environments, with the isohydric cultivar showing slow stomatal closure to reduced light intensity but quick temporal responses to VPD manipulation. We propose that stomatal behavior to fast environmental fluctuations can play a critical role in leaf thermoregulation and water conservation under natural field conditions in grapevine. [ABSTRACT FROM AUTHOR]

The paper presents original data on the composition of hydrocarbon biomarkers and the carbon isotope composition of fractions of some oils in the Middle Devonian–lower Frasnian terrigenous rock complex in the Timan–Pechora basin. The oils typically contain high concentrations of paraffin hydrocarbons. The oils of hydrocarbon systems were generated at the catagenesis of terrigenous organic matter in the host rocks. The complex of hydrocarbon biomarkers of the oils shows features indicating that the paraffin-rich dominant component of the oils mixed with oils from other hydrocarbon systems, namely, from the Domanik–Tournaisian and Lower Paleozoic carbonate rock complexes. [ABSTRACT FROM AUTHOR]

Straw application is an effective and common measure to improve soil quality but generally increases greenhouse gas (GHG) emissions. The combined application of biochar and straw has been proposed to mitigate these emissions. However, the effects of the combined application of biochar and maize straw, particularly at different proportions, on GHG emissions remain inadequately understood. In this study, an incubation experiment was conducted with five treatments: soil only (CK), 1 % maize straw application (TS), 0.7 % maize straw +0.3 % biochar application (S7B3), 0.5 % maize straw +0.5 % biochar application (S5B5) and 0.3 % maize straw +0.7 % biochar application (S3B7). The study also considered the effect of 1 % biochar application (TB) from our previous study with the same soil type and incubation condition. Carbon isotope technology was utilized to trace CO 2 sources and assess the priming effects on soil organic carbon (SOC) mineralization. The results showed that TB reduced CO 2 emission, while TS increased CO 2 emission due to maize straw decomposition and its positive priming effect on native SOC mineralization. S7B3, S5B5 and S3B7 also increased CO 2 emissions, but with significantly lower emissions than TS, in the order of TS > S7B3 > S5B5 ≥ S3B7. The positive priming effects of S7B3, S5B5 and S3B7 on native SOC mineralization weakened over time and eventually turned negative. TB, TS and combined applications reduced N 2 O emission due to decreased substrates (NH 4 + and NO 3 −) for nitrification and denitrification, induced by promoting microbial fixation of inorganic nitrogen. The reduction effects on N 2 O emission of combined applications were superior to those of TS and TB, with S5B5 demonstrating the best efficacy. TS increased CH 4 emission, while S7B3, S5B5 and S3B7 reduced CH 4 emission. The reduction effects of CH 4 emission with combined applications were superior to that of TB, and S5B5 exhibited the lowest CH 4 emission. Unlike soils with higher nitrogen content, where N 2 O emission dominated the global warming potential (GWP), CO 2 emission dominated the GWP in this study, resulting in increased GWP in TS, S7B3, S5B5 and S3B7, but with significantly lower values for S7B3, S5B5 and S3B7 compared to TS. In conclusion, our study suggests that the combined application of biochar and maize straw, especially S5B5, could effectively mitigate GHG emissions promoted by maize straw application, especially in soils with higher nitrogen content. [Display omitted] • Biochar and maize straw co-application reduced CO 2 emission promoted by maize straw application. • The priming effect of co-application on SOC shifted from positive to negative over time. • Co-application reduced stimulation of CH 4 emission caused by maize straw application. • Co-application exhibited superior efficacy in reducing N 2 O emissions. • The optimal co-application ratio for mitigating greenhouse gas emissions was 1:1. [ABSTRACT FROM AUTHOR]

Using gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS), the soluble organic matter was analyzed for the first time in twenty-two sediment samples from the eastern slopes of the Gongga Mountain, China, at high altitudes between 4,600 and 6,700 m. The C11-C33n-alkanes and C9-C33n-alkan-2-ones were identified in these samples. Both compounds were dominated by odd carbon numbers in the long-chain molecules and contained a maximum of n-C27 or n-C29, indicating that the sediments were predominantly of higher plant origin. However, the short-chain n-alkan-2-ones, with a maximum content of n-C17 or i-C18 (phytone, 6, 10, 14-trimethylpentadecan-2-one), did not show a predominance of odd and even numbers, suggesting that they were predominantly derived from bacteria and algae. Therefore, we suggest that the organic matter in Gongga Mountain comes from three sources, i.e. bacteria, algae, and higher plants. Stable carbon isotope (δ13C) values ranged from −24.6‰ to −27.3‰, indicating that C3 plants were the dominant organic input to the sediments and suggesting a relatively colder and drier depositional environment. However, C4 plants increase sharply at high altitudes of 6,300–6,600 m, suggesting that the paleoclimate of Gongga Mountain became drier and wetter with the increase of altitude.

Understanding the water use efficiency (WUE) and adaptation strategies of plants in high-temperature and rainy areas is essential under global climate change. The leaf carbon content (LCC) and intrinsic WUE of 424 plant samples (from 312 plant species) on Hainan Island were measured to examine their relationship with geographical and climatic factors in herbs, trees, vines and ferns. The LCC ranged from 306.30 to 559.20 mg g−1, with an average of 418.85 mg g−1, and decreased with increasing mean annual temperature (MAT). The range of intrinsic WUE was 8.61 to 123.39 μmol mol−1 with an average value of 60.66 μmol mol−1. The intrinsic WUE decreased with increasing altitude and relative humidity (RH) and wind speed (WS), but increased with increasing latitude, MAT and rainy season temperature (RST), indicating that geographical and climatic factors affect the intrinsic WUE. Stepwise regression suggested that in tropical regions with high temperature and humidity, the change in plant intrinsic WUE was mainly driven by WS. In addition, the main factors affecting the intrinsic WUE of different plant functional types of plants are unique, implying that plants of different plant functional types have distinctive adaptive strategies to environmental change. The present study may provide an insight in water management in tropical rainforest.

In C 3 plants, carbon isotope composition (δ13C) is influenced by isotopic effects during diffusion from the atmosphere to the chloroplasts and carboxylation reactions. This work aimed to demonstrate if δ13C of leaf soluble carbohydrates (δ13C leaves) and of dry matter from new-growth shoots (δ13C shoots) of Prunus plants subjected to a period of water deficit was related to water use efficiency (WUE). For this purpose, three interspecific Prunus hybrids rootstocks (6–5, 7-7 and G × N) were gradually subjected to drought and then rewatered. Soil water content (SWC) decreased from 26.1 to 9.4% after 70 days of water shortage, when plants reached values of predawn leaf water potential (LWP) ranging from −3.12 to −4.00 MPa. Gas exchange, particularly net photosynthetic and transpiration rates, differed among the three hybrids, leading to different values of WUE. After 70 days of drought, a significant δ13C increase of 5.86, 4.28 and 4.99‰ was observed in 6–5, 7-7 and G × N, respectively. Significant correlations between δ13C and other parameters (substomatal CO 2 /atmospheric CO 2 ratio, stomatal conductance and stem water potential) were found in all hybrids. The rewatering phase caused a recovery of the physiological status of the plants. The isotope composition of δ13C shoots was correlated with the average WUE measured during the whole experiment. δ13C leaves and δ13C shoots were positively related (r = 0.87; p < 0.001). The isotopic signature was a reliable screening tool to identify Prunus genotypes tolerant to drought stress. The results suggest the possibility of using δ13C as an integrated indicator of level of drought stress in plants subjected to prolonged stress conditions. • Three interspecific Prunus hybrids were subjected to drought and then rewatered. • Plant water status and gas exchange were followed throughout the trial. • δ13C was measured in leaf soluble carbohydrates and dry matter of new-growth shoots. • δ13C was closely and positively related to WUE and other physiological parameters. • The isotopic signature can be a reliable screening tool to identify genotypes tolerant to drought among Prunus genotypes. [ABSTRACT FROM AUTHOR]

Coffee is an important crop in the global south. However, ongoing changes in the climate system reinforce the need to quantify coffee plants' ecological and eco‐physiological traits to assure coffee production in the future. One way to assess how environmental changes affect coffee performance is via leaf traits, most notably leaf carbon and nitrogen concentrations (to reflect the nutrient status), leaf stable carbon isotope composition (δ13C) to determine intrinsic water use efficiency (WUEi), and specific leaf area (SLA) to describe carbon gain relative to water loss within a plant canopy as these traits are related to yields. Therefore, we sampled coffee plants growing at contrasting elevations using a space‐for‐time substitution approach for warming and superimposed a canopy cover gradient to assess whether increasing canopy cover could modulate responses to temperature. Three coffee shrubs were sampled in each of 59 coffee farms in southwest Ethiopia across elevations of 1500–2160 m a.s.l. and along canopy cover gradients from open to deep shade. Soil nutrient concentrations, light availability, soil temperature and moisture were quantified for each coffee shrub. Elevation and shade tree canopy cover significantly and interactively affected WUEi. Elevation was found to be the driving factor for microclimate and soil factors which indirectly influenced both SLA and WUEi. Both of these coffee leaf traits are moderately governed by soil temperature whereas leaf N and C:N are mainly controlled by soil temperature and soil chemical variables. As elevation increased, WUEi kept increasing at light (< 35%) to intermediate shade levels (35–65%), and the values decreased at dense shade levels (65–100%) at high elevations, suggesting that coffee plants growing at high elevations with light shade can assimilate more CO2 with minimum evaporative water loss. SLA declined with elevation. Leaf N and leaf C:N responded negatively and positively to shade canopy cover, respectively. In sum, elevation and canopy cover interactively determined microclimate and coffee leaf traits. Our findings are useful to adjust the intensity of shade, along with other tree‐level management tools, to modulate climate‐change effects on coffee at the farm level. [ABSTRACT FROM AUTHOR]

The selection of drought-tolerant genotypes is globally recognized as an effective strategy to maintain the growth and survival of commercial tree species exposed to future drought periods. New genomic selection tools that reduce the time of progeny trials are required to substitute traditional tree breeding programs. We investigated the genetic variation of water stress tolerance in New Zealand-grown Pinus radiata D. Don using 622 commercially-used genotypes from 63 families. We used quantitative pedigree-based (Genomic Best Linear Unbiased Prediction or ABLUP) and genomic-based (Genomic Best Linear Unbiased Prediction or GBLUP) approaches to examine the heritability estimates associated with water stress tolerance in P. radiata. Tree seedling growth traits, foliar carbon isotope composition (δ13C), and dark-adapted chlorophyll fluorescence (Y) were monitored before, during and after 10 months of water stress. Height growth showed a constant and moderate heritability level, while the heritability estimate for diameter growth and δ13C decreased with water stress. In contrast, chlorophyll fluorescence exhibited low heritability after 5 and 10 months of water stress. The GBLUP approach provided less breeding value accuracy than ABLUP, however, the relative selection efficiency of GBLUP was greater compared with ABLUP selection techniques. Although there was no significant relationship directly between δ13C and Y, the genetic correlations were significant and stronger for GBLUP. The positive genetic correlations between δ13C and tree biomass traits under water stress indicated that intraspecific variation in δ13C was likely driven by differences in the genotype's photosynthetic capacity. The results show that foliar δ13C can predict P. radiata genotype tolerance to water stress using ABLUP and GBLUP approaches and that such approaches can provide a faster screening and selection of drought-tolerant genotypes for forestry breeding programs. [ABSTRACT FROM AUTHOR]

Interactions between carbon isotope composition (δ13C), foliar nitrogen concentration (foliar N), and biomass accumulation (growth) merit further investigation in soybean (Glycine max (L.) Merr.) and other species as these metrics may be valuable for assessing moisture stress and for screening of drought-resistant varieties. To this end, we examined the response of six soybean genotypes to water-deficit stress in a greenhouse study. Two treatments were imposed: low soil moisture (5–10% volumetric water content) and high soil moisture (30–38% volumetric water content). Above-ground biomass accumulation, foliar N, and δ13C were measured at the end of the experiment. Leaf water potential and midday gas exchange (net assimilation, stomatal conductance, and transpiration) were measured multiple times throughout the experiment. All measurements were affected by water-deficit stress. Significant, but weak, positive relationships were found between δ13C and biomass accumulation in both soil moisture treatments. Foliar N was significantly, but weakly, correlated to growth in the high soil-moisture treatment, but not in the low soil-moisture treatment. The data suggest that selection for genotypes with higher δ13C values could result in improved biomass accumulation. The relationship between foliar N and δ13C was negative under high soil-moisture conditions and positive under low soil-moisture conditions. The relationships between δ13C and foliar N could be a highly informative metric to help understand the effects of water-deficit stress and may further indicate whether water or nitrogen acquisition is limiting in a specific environment, which should help in breeding improved soybean cultivars. [ABSTRACT FROM AUTHOR]

Low maturity coal samples were taken from the Ordos Basin to conduct gold tube thermal simulation experiment in a closed system, and the characteristics of the products were analyzed to find out the fractionation mechanism of carbon isotopes and the causes of abnormal carbon isotopic compositions of natural gas. At the heating rates of 2 °C/h (slow) and 20 °C/h (rapid), the low maturity coal samples of the Ordos Basin had the maximum yields of alkane gas of 302.74 mL/g and 230.16 mL/g, the δ13C1 ranges of −34.8‰ to −23.6‰ and −35.5‰ to −24.0‰; δ13C2 ranges of −28.0‰ to −9.0‰ and −28.9‰ to −8.3‰; and δ13C3 ranges of −25.8‰ to −14.7‰ and −26.4‰ to −13.2‰, respectively. Alkane gas in the thermal simulation products of rapid temperature rise process showed obvious partial reversal of carbon isotope series at 550°C, and at other temperatures showed positive carbon isotope series. In the two heating processes, the δ13C1 turned lighter first and then heavier, and the non-monotonic variation of the δ13C1 values is because the early CH4 is from different parent materials resulted from heterogeneity of organic matter or the carbon isotope fractionation formed by activation energy difference of early enriched 12CH4 and late enriched 13CH4. The reversal of carbon isotope values of heavy hydrocarbon gas can occur not only in high to over mature shale gas (oil-type gas), but also in coal-derived gas. Through thermal simulation experiment of toluene, it is confirmed that the carbon isotope value of heavy hydrocarbon gas can be reversed and inversed at high to over mature stage. The isotope fractionation effect caused by demethylation and methyl linkage of aromatic hydrocarbons may be an important reason for carbon isotope inversion and reversal of alkane gas at the high to over mature stage.

The selection of drought-tolerant genotypes is globally recognized as an effective strategy to maintain the growth and survival of commercial tree species exposed to future drought periods. New genomic selection tools that reduce the time of progeny trials are required to substitute traditional tree breeding programs. We investigated the genetic variation of water stress tolerance in New Zealand-grown Pinus radiata D. Don using 622 commercially-used genotypes from 63 families. We used quantitative pedigree-based (Genomic Best Linear Unbiased Prediction or ABLUP) and genomic-based (Genomic Best Linear Unbiased Prediction or GBLUP) approaches to examine the heritability estimates associated with water stress tolerance in P. radiata. Tree seedling growth traits, foliar carbon isotope composition (δ13C), and dark-adapted chlorophyll fluorescence (Y) were monitored before, during and after 10 months of water stress. Height growth showed a constant and moderate heritability level, while the heritability estimate for diameter growth and δ13C decreased with water stress. In contrast, chlorophyll fluorescence exhibited low heritability after 5 and 10 months of water stress. The GBLUP approach provided less breeding value accuracy than ABLUP, however, the relative selection efficiency of GBLUP was greater compared with ABLUP selection techniques. Although there was no significant relationship directly between δ13C and Y, the genetic correlations were significant and stronger for GBLUP. The positive genetic correlations between δ13C and tree biomass traits under water stress indicated that intraspecific variation in δ13C was likely driven by differences in the genotype’s photosynthetic capacity. The results show that foliar δ13C can predict P. radiata genotype tolerance to water stress using ABLUP and GBLUP approaches and that such approaches can provide a faster screening and selection of drought-tolerant genotypes for forestry breeding programs.

Carbon isotope composition (indicated by leaf δ13C) reflects plants' strategies to balance carbon acquisition and water loss, which is directly linked to water use efficiency. At a large scale, leaf δ13C has been demonstrated to be closely related to climate and plant functional types; however, at a regional scale, its variation across an aridity gradient and species categories and its covariation with traits in leaf economic spectrum (LES) traits are still unclear. Here, a multivariate statistical analysis was carried out with 271 observations of leaf δ13C from 22 sampling sites on the Loess Plateau. Our results showed that (1) mean leaf δ13C did not differ significantly among life forms in C3 plants, with the maximum mean values occurring in geophytes (−26.31‰) and the minimum values occurring in lianas (−28.29‰); (2) the leaf δ13C responses of different life forms, families and species categories to climates were consistent for C3 plants, namely, they presented similar response rates to changes along the aridity gradient (represented by the moisture index); (3) climate, soil, species category, and leaf economic spectrum traits jointly explained 78.4% of the variation in leaf δ13C for C3 plants. Species category was the largest determinant of leaf δ13C variations for both C3 and C4 plants. Revealing the variation in leaf δ13C of the Loess Plateau plants not only helps us to understand plant adaptation strategies under arid conditions but also provides scientific support for ecological management in vegetation restoration regions.

A higher frequency and intensity of droughts will impair forest productivity. Therefore, improving our understanding of which factors enhance tree growth resilience against drought has become a crucial issue, but we lack information at the intraspecific level.In this study, we investigate the role played by climatic conditions and tree characteristics in the growth response to severe droughts in two deciduous Fagaceae species near their southern distribution limit: the temperate European beech Fagus sylvatica and the Mediterranean pubescent oak Quercus pubescens. The study area is located in Catalonia, NE Spain, where 149 trees were cored covering the water availability gradient of the species in the region. In addition, tree size (diameter and height) and an ensemble of stem, leaf and hydraulic traits were collected for each tree. Growth responses to extreme droughts during the period 1980–2015 were assessed using resilience indicators based on residual basal area increment series predicted by a model including growing season water balance.Although resistance was unrelated to drought intensity, higher water availability improved recovery and reduced drought legacy effects. Taller trees showed higher resilience against drought, which could be explained by the relationship between the variation in tree height and functional traits, such as leaf nitrogen concentration, leaf turgor loss point and resistance to xylem embolism. For both species, trees with lower cavitation resistance, higher leaf nitrogen concentration and tighter stomatal regulation (suggested by less negative turgor loss point and carbon isotope composition) displayed better performance during and after severe droughts. Both species showed a progressive decrease in resilience and increase in legacy effects.Synthesis. This study highlights the relevance of analysing intraspecific variation of functional traits involved in tree water and carbon balance to improve our understanding of the resilience and variability of growth responses to drought within species. [ABSTRACT FROM AUTHOR]

This study evaluates the changes caused by breeding in the genotype by environment (G × E) interaction of the durum wheat varieties most widely cultivated in Spain after the Green Revolution. A set of 12 cultivars was tested in 27 environments, which are understood as the combination of different sites, years, and treatments (water regime and planting dates), representative of the durum wheat growing conditions in Spain with average grain yields (GY) ranging between 2.8 and 9.1 Mg ha−1. The most important environmental factors affecting the G × E interaction for yield were themaximum and the mean temperature during the entire crop cycle. An improvement in genetic yield was observed in warm environments and under optimal water conditions that resemble those where the germplasm originated (essentially as advanced lines) before its release in Spain. Therefore, the adaptation of semi-dwarf durum in Spain has shown a tendency to specific adaptation rather than large-scale adaptation. Two different patterns of selection have been reported due the G × E interaction and changes in the ranking of genotypes: in the high yielding environments (GY > 5 Mg ha−1), plants favor increased water uptake, with higher levels of transpiration and more open stomata (more negative values of carbon isotope composition, δ13C, and higher canopy temperature depression, CTD), whereas, in low yielding environments (GY < 5 Mg ha−1) plants close their stomata and favor greater water use efficiency (less negative δ13C values and lower CTD values).

Abstract Background Drought stress is a major limiting factor of soybean [Glycine max (L.) Merr.] production around the world. Soybean plants can ameliorate this stress with improved water-saving, sustained N2 fixation during water deficits, and/or limited leaf hydraulic conductance. In this study, carbon isotope composition (δ13C), which can relate to variation in water-saving capability, was measured. Additionally, nitrogen isotope composition (δ15N) and nitrogen concentration that relate to nitrogen fixation were evaluated. Decrease in transpiration rate (DTR) of de-rooted soybean shoots in a silver nitrate (AgNO3) solution compared to deionized water under high vapor pressure deficit (VPD) conditions was used as a surrogate measurement for limited leaf hydraulic conductance. A panel of over 200 genetically diverse soybean accessions genotyped with the SoySNP50K iSelect BeadChips was evaluated for the carbon and nitrogen related traits in two field environments (Athens, GA in 2015 and 2016) and for transpiration response to AgNO3 in a growth chamber. A multiple loci linear mixed model was implemented in FarmCPU to perform genome-wide association analyses for these traits. Results Thirty two, 23, 26, and nine loci for δ13C, δ15N, nitrogen concentration, and transpiration response to AgNO3, respectively, were significantly associated with these traits. Candidate genes that relate to drought stress tolerance enhancement or response were identified near certain loci that could be targets for improving and understanding these traits. Soybean accessions with favorable breeding values were also identified. Low correlations were observed between many of the traits and the genetic loci associated with each trait were largely unique, indicating that these drought tolerance related traits are governed by different genetic loci. Conclusions The genomic regions and germplasm identified in this study can be used by breeders to understand the genetic architecture for these traits and to improve soybean drought tolerance. Phenotyping resources needed, trait heritability, and relationship to the target environment should be considered before deciding which of these traits to ultimately employ in a specific breeding program. Potential marker-assisted selection efforts could focus on loci which explain the greatest amount of phenotypic variation for each trait, but may be challenging due to the quantitative nature of these traits.

In this study, we describe the variation in δ13C value in the litter of two species of peat-forming plants: Sphagnum fuscum and Eriophorum vaginatum, during 3 years of field decomposition in oligotrophic bog ecosystems drained for the purpose of forest melioration and fire affected and at the stage of post-pyrogenic restoration. Litterbags were periodically retrieved in the autumn and the δ13C value in the residual litter was related to mass loss, litter chemistry, and hydrothermal conditions. Sph. fuscum decomposes much more slowly than E. vaginatum. Low rate of transformation for Sph. fuscum is observed in drained and post-pyrogenic sites, while for E. vaginatum minimal rate of transformation is observed in the native site. During the decomposition of Sphagnum residues, 13C enrichment occurs, and during the decomposition of E. vaginatum, we observed 12C enrichment. The changes in the isotope composition of carbon for investigation sites are insignificant for Sphagnum fuscum, but it was observed for E. vaginatum, the largest of 13C depletion is observed in the drained site (−28.3‰) and minimal in the postpyrogenic site (−27.4‰).

Key message: Juglans, Fraxinus, Quercus and Pinus species seem to better maximize the carbon–water ratio providing useful indications on species selection for forestry plantations in areas with increasing drought risk. Maximizing carbon sequestration for a given water budget is extremely important in the contest of climate change in the Mediterranean region, which is characterized by increasing temperatures and rising water stress. This issue is fundamental for plantation stands, where limited water availability during the growing season reduces CO2 assimilation and, consequently, tree growth. In this study, the main objective was to investigate the performances in terms of carbon–water balance of conifer (Pinus halepensis and Cupressus sempervirens) and hardwood (Quercus robur, Juglans regia, Fraxinus excelsior and Populus spp.) mixed plantations. To this aim, we used carbon isotope signatures to evaluate the intrinsic water-use efficiency (iWUE) and the species-specific relationship between basal area increments (BAI) and iWUE. At the species level, the highest iWUE values corresponded to the lowest carbon accumulation in terms of BAI, for water-saving species such as Cupressus. Conversely, Populus had the lowest iWUE and the highest BAI accumulation. Juglans, Fraxinus, and Pinus showed the most balanced ratio between BAI and iWUE. Overall, no clear correlation of iWUE and BAI was evident within all species, except for Populus and Cupressus. Considering projected aridification and increased temperatures that will negatively impact the growth, our data suggest that Pinus, for conifers, and Quercus, Juglans, Fraxinus for hardwood species should be preferred when choosing species for forestry plantation, as they performed better in terms of BAI and iWUE ratio. [ABSTRACT FROM AUTHOR]

Plant response to drought is a critical process for the survival and development of resilient cropping systems. However, drought studies are often based on short-term experiments under controlled environments which may not reflect compounding stress factors experiences under field conditions, such as high air and soil temperature, high light irradiance, among others. In composite plants like apple, both rootstock and scion combine to modulate drought response. Nonetheless, the effect that apple rootstock genotypes have on scion response to water limitations have not been extensively studied. The objective of this study was to measure physiological responses of different apple rootstocks to drought under both field and greenhouse conditions. For both experiments, ‘Honeycrisp’ apple was grafted onto G.41, G.890, M.9, and B.9 rootstocks. Two irrigation treatments were established: drought (~ 50% of field capacity (FC) and control (~ 100% FC). Leaf gas exchange, mid-day stem water potential (Ψmd), quantum yield of PSII (ΦII) and shoot growth were measured bi-weekly. At the end of each experiment, total leaf area and root, stem and leaf carbon isotope composition (δ13C) were measured. In the field, ‘Honeycrisp’ that was grafted onto G8.90 and exposed to water limitations had lower stomatal conductance, net CO2 exchange rates, ΦII, and shoot growth. In contrast, B.9 maintained stomatal conductance and shoot growth when water-limited and δ13C was the highest among rootstocks. There were no rootstocks differences for trees grown in the greenhouse. These results show how rootstock can affect scion response to water limitations in apple and how field experiments can magnify these responses. [ABSTRACT FROM AUTHOR]

Leaf gas exchanges play a critical role in determining crop productivity as they control both CO2 gain and water loss. CO2 gain and water loss influence water use efficiency (WUE) and carbon isotope composition (δ13C). Responses in leaf gas exchanges to water stress are species-specific. However, the extent of this variation in C3 crops is less studied. A field study was carried out to investigate the influence of water stress on leaf gas exchanges of triticale and cowpea. Crops were grown under water stress and well-watered conditions and leaf gas exchanges were determined at flowering. The results showed that triticale maintained a higher stomatal conductance (gs), transpiration rate(E) and intercellular CO2 concentration (ci) compared to cowpea but did not differ in photosynthetic rate(A). As a result, triticale discriminated against 13C more than cowpea. These results suggest a higher influence of ci on δ13C than A. Despite triticale maintaining higher rates of ci, A and gs, it had lower WUE compared to cowpea. Consequently, triticale grain yield was more sensitive to water stress than cowpea. The findings of this study showed significant variation in leaf gas exchanges and δ13C between two drought-tolerant C3 crops suggesting differences in their response mechanism to water stress.

The carbon isotope composition of oil in the various regions of Tatarstan was found out to range from δ13C = –32.5 to –28.6‰. Oil in sedimentary rocks in the central part of the South Tatar Arch (STA) is characterized by a lighter carbon isotope composition (δ13C < –29‰) than oil in the southeastern STA slope (δ13C > –29‰), whose rocks are broken by deep faults. The oil of relatively heavy carbon isotopic composition is shown to be characterized by a high sulfur content, contains relatively much polar fractions, and is less catagenically mature that the oil with a relatively light carbon isotope composition. The source organic matter of oils, regardless of their carbon isotopic composition, in the South Tatar Arch was sapropelic material with an admixture of a bacterial component, which was transformed under reducing conditions when hosted in clay–carbonate sediments. The Devonian (D2 gv) oil of the Bavlinskoye field (Well 475) in the southeast slope of the South Tatar Arch differs in composition from the other oils. Along with high contents of saturated (53%) and aromatic (36%) hydrocarbons, this oil is characterized by a relatively heavy carbon isotope composition and a sublinear curve of the isotope-fractional distribution of components. A similar distribution of components with a heavy isotope composition of the asphaltene carbon is typical the Devonian (D3 psv) oil of the Abdrakhmanovskoye field (Wells 719 and 312) in the crest STA part, which generally has a relatively light carbon isotope composition and a contains low concentrations of polar fractions. [ABSTRACT FROM AUTHOR]

Ecologists and physiologists have documented extensive variation in water use efficiency (WUE) in Arabidopsis thaliana, as well as association of WUE with climatic variation. Here, we demonstrate correlations of whole-plant transpiration efficiency and carbon isotope composition (δ(13)C) among life history classes of A. thaliana. We also use a whole-plant cuvette to examine patterns of co-variation in component traits of WUE and δ(13)C. We find that stomatal conductance (g s) explains more variation in WUE than does A. Overall, there was a strong genetic correlation between A and g s, consistent with selection acting on the ratio of these traits. At a more detailed level, genetic variation in A was due to underlying variation in both maximal rate of carboxylation (V cmax) and maximum electron transport rate (Jmax). We also found strong effects of leaf anatomy, where lines with lower WUE had higher leaf water content (LWC) and specific leaf area (SLA), suggesting a role for mesophyll conductance (g m) in variation of WUE. We hypothesize that this is due to an effect through g m, and test this hypothesis using the abi4 mutant. We show that mutants of ABI4 have higher SLA, LWC, and g m than wild-type, consistent with variation in leaf anatomy causing variation in g m and δ(13)C. These functional data also add further support to the central, integrative role of ABI4 in simultaneously altering ABA sensitivity, sugar signaling, and CO2 assimilation. Together our results highlight the need for a more holistic approach in functional studies, both for more accurate annotation of gene function and to understand co-limitations to plant growth and productivity.

In this work we describe the distribution of stable carbon isotopes in hydrocarbon gases from four wells located in the southern and central parts of the Western Siberia. The main goal was to understand the influence of the lithological composition and geological settings on isotopic composition of gases and their formation. Two genetically different groups of hydrocarbon gases were identified based on the author’s research, as well as analysis of archival and literature materials on the isotope composition of hydrocarbons. We estimated the close relationship between the main factors of the migration, degree of metamorphism of organic matter and the isotope composition of hydrocarbon gases produced by the Bazhenov formation.

The correlation of carbon isotope discrimination (△13C) with photosynthetic gas exchange and water use efficiency (WUE) in maize was investigated under low rainfall conditions with or without superabsorbent polymer (SAP). SAP (45 kg/ha) was mixed into the top 10 cm soil layer at sowing in lysimeters. Compared with the control plants not treated with SAP, the application of SAP increased net photosynthesis rate; stomatal conductance (gs); transpiration rate; chlorophyll content (Chl) and intrinsic water use efficiency at leaf level (WUEi), but decreased intercellular CO2 concentration (Ci) and leaf △13C. In plants supplied with SAP, leaf △13C was positively correlated with Ci (r = 0.864, P < 0.01) and negatively correlated with gs and WUEi (r = -0.860 and -0.626, P < 0.01, respectively). Leaf △13C was not correlated with Chl with or without SAP. Grain △13C significantly decreased by 12.4% and showed a significant negative correlation with grain WUE under SAP treatments (r = -0.670, P < 0.05). These results suggest that in the presence of SAP, maize leaf and grain △13C could be good indicators for evaluating maize WUE during periods of low rainfall.

Estimates of seasonal variation in plant stoichiometry and water use efficiency (WUE) are critical for predicting the time courses of carbon and water fluxes. However, the relationship between seasonal stoichiometry and WUE, and their relationship with climatic factors remains unclear. The carbon isotope composition has been widely used to evaluate the WUE. We hypothesized that WUE is closely related to seasonal variation in plant stoichiometry, and then stable carbon isotope can be used to indicate the variation in future models. For this study, we investigated seasonal changes in WUE and 14 elements (C, N, P, S, K, Na, Ca, Mg, Al, Fe, Mn, Zn, Cu, and Ba) of Quercus variabilis in a warm temperate forest, Central China. The WUE gradually reduced from late spring until leaf senescence in fall. Leaf C and N initially increased and then decreased. Leaf P, S, and K generally decreased, whereas Ca, Ba, Al and Fe gradually accumulated throughout the growing season. Leaf C:N, C:P, and N:P were lowest in early season, and then typically increased. As expected, WUE was positively correlated with N, P, S, K, and Mg, while negatively with C, Ca, Al, and Fe as well as C:N, C:P, and N:P. WUE increased with higher temperatures but had no relationship with precipitation. Leaf N, P, S, and K increased, while C:N, C:P, and N:P decreased with higher temperatures. Our results suggested that seasonal stoichiometry and WUE was closely coupled with plant growth, and temperature may be the main dynamic driver of water and nutrients in forest ecosystems. As WUE was estimated by carbon isotope composition, our findings provide new insights toward integrating carbon isotope with Earth system models.

Biodiversity is considered to mitigate the adverse effects of changing precipitation patterns. However, our understanding of how tree diversity at the local neighbourhood scale modulates the water use and leaf physiology of individual trees remains unclear. We made use of a large-scale tree diversity experiment in subtropical China to study eight tree species along an experimentally manipulated gradient of local neighbourhood tree species richness. Twig wood carbon isotope composition (δ13Cwood) was used as an indicator for immediate leaf-level responses to water availability in relation to local neighbourhood conditions and a target tree's functional traits. Across species, a target tree's δ13Cwood signatures decreased progressively with increasing neighbourhood species richness, with effects being strongest at high neighbourhood shading intensity. Moreover, the δ13Cwood-shading relationship shifted from positive (thin-leaved species) or neutral (thick-leaved species) in conspecific to negative in heterospecific neighbourhoods, most likely owing to a lower interspecific competition for water and microclimate amelioration. This suggests that promoting tree species richness at the local neighbourhood scale may improve a tree's local water supply with potential effects for an optimized water-use efficiency of tree communities during drought. This assumption, however, requires validation by further studies that focus on mechanisms that regulate the water availability in mixtures. [ABSTRACT FROM AUTHOR]