Primary to post-depositional microbial controls on the stable and clumped isotope record of shoreline sediments at Fayetteville Green Lake.

Lacustrine carbonates are a powerful archive of paleoenvironmental information but are susceptible to post-depositional alteration. Microbial metabolisms can drive such alteration by changing carbonate saturation in situ, thereby driving dissolution or precipitation. The net impact these microbial processes have on the primary δ18O, δ13C, and Δ47 values of lacustrine carbonate is not fully known. We studied the evolution of microbial community structure and the porewater and sediment geochemistry in the upper ~30 cm of sediment from two shoreline sites at Green Lake, Fayetteville, NY over 2 years of seasonal sampling. We linked seasonal and depth-based changes of porewater carbonate chemistry to microbial community composition, in situ carbon cycling (using δ13C values of carbonate, dissolved inorganic carbon (DIC), and organic matter), and dominant allochems and facies. We interpret that microbial processes are a dominant control on carbon cycling within the sediment, affecting porewater DIC, aqueous carbon chemistry, and carbonate carbon and clumped isotope geochemistry. Across all seasons and sites, microbial organic matter remineralization lowers the δ13C of the porewater DIC. Elevated carbonate saturation states in the sediment porewaters (Ω > 3) were attributed to microbes from groups capable of sulfate reduction, which were abundant in the sediment below 5 cm depth. The nearshore carbonate sediments at Green Lake are mainly composed of microbialite intraclasts/oncoids, charophytes, larger calcite crystals, and authigenic micrite-each with a different origin. Authigenic micrite is interpreted to have precipitated in situ from the supersaturated porewaters from microbial metabolism. The stable carbon isotope values (δ13Ccarb) and clumped isotope values (Δ47) of bulk carbonate sediments from the same depth horizons and site varied depending on both the sampling season and the specific location within a site, indicating localized (µm to mm) controls on carbon and clumped isotope values. Our results suggest that biological processes are a dominant control on carbon chemistry within the sedimentary subsurface of the shorelines of Green Lake, from actively forming microbialites to pore space organic matter remineralization and micrite authigenesis. A combination of biological activity, hydrologic balance, and allochem composition of the sediments set the stable carbon, oxygen, and clumped isotope signals preserved by the Green Lake carbonate sediments.

Insights on long-term ecosystem changes from stable isotopes in historical squid beaks.

BACKGROUND: Assessing the historical dynamics of key food web components is crucial to understand how climate change impacts the structure of Arctic marine ecosystems. Most retrospective stable isotopic studies to date assessed potential ecosystem shifts in the Arctic using vertebrate top predators and filter-feeding invertebrates as proxies. However, due to long life histories and specific ecologies, ecosystem shifts are not always detectable when using these taxa. Moreover, there are currently no retrospective stable isotopic studies on various other ecological and taxonomic groups of Arctic biota. To test whether climate-driven shifts in marine ecosystems are reflected in the ecology of short-living mesopredators, ontogenetic changes in stable isotope signatures in chitinous hard body structures were analysed in two abundant squids (Gonatus fabricii and Todarodes sagittatus) from the low latitude Arctic and adjacent waters, collected between 1844 and 2023. RESULTS: We detected a temporal increase in diet and habitat-use generalism (= opportunistic choice rather than specialization), trophic position and niche width in G. fabricii from the low latitude Arctic waters. These shifts in trophic ecology matched with the Atlantification of the Arctic ecosystems, which includes increased generalization of food webs and higher primary production, and the influx of boreal species from the North Atlantic as a result of climate change. The Atlantification is especially marked since the late 1990s/early 2000s. The temporal patterns we found in G. fabricii's trophic ecology were largely unreported in previous Arctic retrospective isotopic ecology studies. Accordingly, T. sagittatus that occur nowadays in the high latitude North Atlantic have a more generalist diet than in the XIXth century. CONCLUSIONS: Our results suggest that abundant opportunistic mesopredators with short life cycles (such as squids) are good candidates for retrospective ecology studies in the marine ecosystems, and to identify ecosystem shifts driven by climate change. Enhanced generalization of Arctic food webs is reflected in increased diet generalism and niche width in squids, while increased abundance of boreal piscivorous fishes is reflected in squids' increased trophic position. These findings support opportunism and adaptability in squids, which renders them as potential winners of short-term shifts in Arctic ecosystems.

Not all soil carbon is created equal: Labile and stable pools under nitrogen input.

Anthropogenic activities have raised nitrogen (N) input worldwide with profound implications for soil carbon (C) cycling in ecosystems. The specific impacts of N input on soil organic matter (SOM) pools differing in microbial availability remain debatable. For the first time, we used a much-improved approach by effectively combining the 13C natural abundance in SOM with 21 years of C3-C4 vegetation conversion and long-term incubation. This allows to distinguish the impact of N input on SOM pools with various turnover times. We found that N input reduced the mineralization of all SOM pools, with labile pools having greater sensitivity to N than stable ones. The suppression in SOM mineralization was notably higher in the very labile pool (18%-52%) than the labile and stable (11%-47%) and the very stable pool (3%-21%) compared to that in the unfertilized control soil. The very labile C pool made a strong contribution (up to 60%) to total CO2 release and also contributed to 74%-96% of suppressed CO2 with N input. This suppression of SOM mineralization by N was initially attributed to the decreased microbial biomass and soil functions. Over the long-term, the shift in bacterial community toward Proteobacteria and reduction in functional genes for labile C degradation were the primary drivers. In conclusion, the higher the availability of the SOM pools, the stronger the suppression of their mineralization by N input. Labile SOM pools are highly sensitive to N availability and may hold a greater potential for C sequestration under N input at global scale.

Developing δ15N and δ13C isoscapes using whole blood from Magellanic penguins, Spheniscus magellanicus.

RATIONALE: Understanding the migration of marine animals is hindered by the limitations of traditional tracking methods. It is therefore crucial to develop alternative methods. Stable isotope-based tracking has proven useful for this task, although it requires detailed isoscapes in the focal area. Here, we present predator-based isoscapes of the coastal zone of the Patagonian Shelf Large Marine Ecosystem (PSLME), which offers a novel tool for geolocation. METHODS: Whole-blood samples from breeding Magellanic penguins nesting at 11 colonies were used to create δ15N and δ13C isoscapes. Isotopic values were assigned to random positions inside their corresponding foraging area. Spatial analysis and data interpolation resulted in δ15N and δ13C isoscapes for the coastal zone of the PSLME, which were validated through cross-validation. RESULTS: The isoscapes mean standard error ranged from 0.05 to 0.41 for δ15N and from 0.07 to 0.3 for δ13C, similar to the error range of the mass spectrometer used for measuring isotope ratios. Predictive surfaces reflected the latitudinal trends, with δ13C and δ15N values increasing northwards. δ13C values showed a strong latitudinal gradient, while δ15N values had two distinct domains, with higher values in the north. The error surface indicated the highest certainty within 130 km from the shore and within the reported Magellanic penguin foraging areas. CONCLUSIONS: Both isoscapes revealed strong spatial variation. The δ13C isoscape showed a latitudinal gradient, consistent with patterns in other oceans. The δ15N isoscape clearly separated northern and southern colonies, likely influenced by nitrogen sources. The error obtained fell within the measurement error ranges, adding credibility to the models.

Effect of calcium supplementation on reversing metformin-based inhibition of vitamin B12 bioavailability in healthy adults using a [13C] cyanocobalamin tracer - A pilot study.

BACKGROUND & AIMS: Metformin is a widely prescribed first line drug for the treatment of type 2 diabetes mellitus (DM). Studies have shown that the use of metformin is often associated with a decrease in vitamin B12 (B12) levels in patients with DM. Few studies have shown that this effect could be mitigated with calcium supplementation. In the present study, we quantified the effect of metformin, and metformin co-administered with calcium on B12 absorption using a novel stable isotope [13C] cyanocobalamin tracer. METHODS: A pilot crossover study was conducted to estimate the bioavailability of B12 in healthy subjects, using [13C] cyanocobalamin as a tracer. In the study, [13C] cyanocobalamin was administered orally to the participants followed by hourly venous sampling to measure the concentration of the tracer and estimate bioavailability. This protocol was followed for three experiment days, each separated by a one month wash out period. As part of the study, all participants received the tracer alone for the control day (C), metformin 850 mg along with the tracer for the metformin day (M) and metformin 850 mg with calcium 500 mg and the tracer for the metformin calcium day (MC). RESULTS: Seven participants completed all three experiment days. The mean B12 bioavailability (±SD, n = 7) was 42.6 ± 10.2% for the control day (C), 30.8 ± 15.3% for the metformin day (M) and 46.4 ± 8.6% for the metformin-calcium day (MC). Repeated measures ANOVA was done and the pairwise comparison showed a significant difference in the B12 bioavailability between control and metformin day (C vs M p = 0.010), and between the metformin and metformin with calcium day (M vs MC p = 0.003). CONCLUSION: B12 bioavailability reduced significantly from baseline (C) when metformin (M) was administered and this reduction was reversed when calcium was co-administered (MC) in healthy participants. In patients using metformin, calcium supplementation as a strategy to prevent B12 deficiency needs to be further studied.

Lipid extraction alters amino acid composition and bulk, but not amino acid, carbon and nitrogen isotope values.

RATIONALE: Concerns exist over observed shifts in value and variance of nitrogen isotopes following physicochemical extraction of lipids from organic matter. The mechanisms behind these apparent changes in bulk tissue δ15N values are not fully understood yet have major implications for analytical costs and integrity of data interpretations. METHODS: Changes in proximate analysis, amino acid composition, C:N ratios, bulk tissue and amino acid δ13C and δ15N values, and resulting isotope-based food web metrics were compared between lipid-intact and lipid-extracted muscle tissue of fishes spanning <1% to >20% muscle fat content to identify mechanisms of nitrogen isotope fractionation associated with physicochemical lipid extraction. RESULTS: Bulk δ13C and δ15N values increased and %N, C:N ratios and crude protein content decreased following lipid extraction. Resulting bulk isotope niche spacing and overlap varied significantly between lipid-intact and lipid-extracted tissues. While amino acid composition significantly changed during lipid extraction, particularly for lipid-associated amino acids (e.g., Glu, Lys, Ser), individual amino acid δ13C and δ15N values, and their associated compound-specific isotope analysis of amino acids (CSIA-AA)-based food web metrics, did not. CONCLUSIONS: Physicochemical lipid extraction caused significant tissue composition changes (e.g., leaching of amino acids and 15N-deplete nitrogenous waste) that affected δ13C and δ15N values and tissue %C and %N beyond simply removing lipids. However, lipid extraction did not alter individual amino acid δ13C or δ15N values or their associated CSIA-AA-based food web metrics.

Stable isotope analysis in soil prospection reveals the type of historic land-use under contemporary temperate forests in Europe.

The determination of δ13C and δ15N values is a common method in archaeological isotope analysis-in studying botanical and human remains, dietary practices, and less typically soils (to understand methods of agricultural cultivation, including fertilization). Stable isotope measurements are also commonly used in ecological studies to distinguish different ecosystems and to trace diachronic processes and biogeochemical mechanisms, however, the application of this method in geochemical prospection, for determining historic land-use impact, remains unexplored. The study at hand focuses on a deserted site of a Cistercian manor, dating from the thirteenth to fifteenth centuries. Isotopic measurements of anthropogenically influenced soils have been compared to approximately 400 archaeobotanical, soil, and sediment samples collected globally. The results reveal the potential of isotope measurements in soil to study the impact of past land use as isotope measurements identify specific types of agricultural activities, distinguishing crop production or grazing. δ13C and δ15N ratios also likely reflect fertilization practices and-in this case-the results indicate the presence of cereal cultivation (C3 cycle plants) and fertilization and that the site of the medieval manor was primarily used for grain production rather than animal husbandry.

Aromatic Characterisation of Moscato Giallo by GC-MS/MS and Validation of Stable Isotopic Ratio Analysis of the Major Volatile Compounds.

Among the Moscato grapes, Moscato Giallo is a winegrape variety characterised by a high content of free and glycosylated monoterpenoids, which gives wines very intense notes of ripe fruit and flowers. The aromatic bouquet of Moscato Giallo is strongly influenced by the high concentration of linalool, geraniol, linalool oxides, limonene, α-terpineol, citronellol, hotrienol, diendiols, trans/cis-8-hydroxy linalool, geranic acid and myrcene, that give citrus, rose, and peach notes. Except for quali-quantitative analysis, no investigations regarding the isotopic values of the target volatile compounds in grapes and wines are documented in the literature. Nevertheless, the analysis of the stable isotope ratio represents a modern and powerful tool used by the laboratories responsible for official consumer protection, for food quality and genuineness assessment. To this aim, the aromatic compounds extracted from grapes and wine were analysed both by GC-MS/MS, to define the aroma profiles, and by GC-C/Py-IRMS, for a preliminary isotope compound-specific investigation. Seventeen samples of Moscato Giallo grapes were collected during the harvest season in 2021 from two Italian regions renowned for the cultivation of this aromatic variety, Trentino Alto Adige and Veneto, and the corresponding wines were produced at micro-winery scale. The GC-MS/MS analysis confirmed the presence of the typical terpenoids both in glycosylated and free forms, responsible for the characteristic aroma of the Moscato Giallo variety, while the compound-specific isotope ratio analysis allowed us to determine the carbon (δ13C) and hydrogen (δ2H) isotopic signatures of the major volatile compounds for the first time.

Detection of early-stage NASH using non-invasive hyperpolarized 13C metabolic imaging.

Non-alcoholic steatohepatitis (NASH) is characterized from its early stages by a profound remodeling of the liver microenvironment, encompassing changes in the composition and activities of multiple cell types and associated gene expression patterns. Hyperpolarized (HP) 13C MRI provides a unique view of the metabolic microenvironment, with potential relevance for early diagnosis of liver disease. Previous studies have detected changes in HP 13C pyruvate to lactate conversion, catalyzed by lactate dehydrogenase (LDH), with experimental liver injury. HP ∝ -ketobutyrate ( ∝ KB) is a close molecular analog of pyruvate with modified specificity for LDH isoforms, specifically attenuated activity with their LDHA-expressed subunits that dominate liver parenchyma. Building on recent results with pyruvate, we investigated HP ∝ KB in methionine-choline deficient (MCD) diet as a model of early-stage NASH. Similarity of results between this new agent and pyruvate (~ 50% drop in cytoplasmic reducing capacity), interpreted together with gene expression data from the model, suggests that changes are mediated through broad effects on intermediary metabolism. Plausible mechanisms are depletion of the lactate pool by upregulation of gluconeogenesis (GNG) and pentose phosphate pathway (PPP) flux, and a possible shift toward increased lactate oxidation. These changes may reflect high levels of oxidative stress and/or shifting macrophage populations in NASH.

Shortened food chain length in a fished versus unfished coral reef.

Direct exploitation through fishing is driving dramatic declines of wildlife populations in ocean environments, particularly for predatory and large-bodied taxa. Despite wide recognition of this pattern and well-established consequences of such trophic downgrading on ecosystem function, there have been few empirical studies examining the effects of fishing on whole system trophic architecture. Understanding these kinds of structural impacts is especially important in coral reef ecosystems-often heavily fished and facing multiple stressors. Given the often high dietary flexibility and numerous functional redundancies in diverse ecosystems such as coral reefs, it is important to establish whether web architecture is strongly impacted by fishing pressure or whether it might be resilient, at least to moderate-intensity pressure. To examine this question, we used a combination of bulk and compound-specific stable isotope analyses measured across a range of predatory and low-trophic-level consumers between two coral reef ecosystems that differed with respect to fishing pressure but otherwise remained largely similar. We found that even in a high-diversity system with relatively modest fishing pressure, there were strong reductions in the trophic position (TP) of the three highest TP consumers examined in the fished system but no effects on the TP of lower-level consumers. We saw no evidence that this shortening of the affected food webs was being driven by changes in basal resource consumption, for example, through changes in the spatial location of foraging by consumers. Instead, this likely reflected internal changes in food web architecture, suggesting that even in diverse systems and with relatively modest pressure, human harvest causes significant compressions in food chain length. This observed shortening of these food webs may have many important emergent ecological consequences for the functioning of ecosystems impacted by fishing or hunting. Such important structural shifts may be widespread but unnoticed by traditional surveys. This insight may also be useful for applied ecosystem managers grappling with choices about the relative importance of protection for remote and pristine areas and the value of strict no-take areas to protect not just the raw constituents of systems affected by fishing and hunting but also the health and functionality of whole systems.

Solution-state methyl NMR spectroscopy of large non-deuterated proteins enabled by deep neural networks.

Methyl-TROSY nuclear magnetic resonance (NMR) spectroscopy is a powerful technique for characterising large biomolecules in solution. However, preparing samples for these experiments is demanding and entails deuteration, limiting its use. Here we demonstrate that NMR spectra recorded on protonated, uniformly 13C labelled samples can be processed using deep neural networks to yield spectra that are of similar quality to typical deuterated methyl-TROSY spectra, potentially providing information for proteins that cannot be produced in bacterial systems. We validate the methodology experimentally on three proteins with molecular weights in the range 42-360 kDa. We further demonstrate the applicability of our methodology to 3D NOESY spectra of Escherichia coli Malate Synthase G (81 kDa), where observed NOE cross-peaks are in good agreement with the available structure. The method represents an advance in the field of using deep learning to analyse complex magnetic resonance data and could have an impact on the study of large biomolecules in years to come.

[Differences and drivers of leaf stable carbon and nitrogen isotope in herbs under different vegetation types on the eastern Qinghai-Tibet Plateau]. / é’è—é«˜åŽŸä¸œç¼˜ä¸åŒæ¤è¢«ç±»åž‹ä¸‹è‰æœ¬æ¤ç‰©å¶ç‰‡ç¢³æ°®ç¨³å®šåŒä½ç´ å·®å¼‚åŠå ¶é©±åŠ¨å› ç´ .

The natural abundance of stable carbon and nitrogen isotopes (δ13C and δ15N) in leaves can provide comprehensive information on the physiological and ecological processes of plants and has been widely used in ecological research. However, recent studies on leaf δ13C and δ15N have focused mainly on woody species, few studies have been conducted on herbs in different vegetation types, and their differences and driving factors are still unclear. In this study, we focused on the herbs in subalpine coniferous forests, alpine shrublands, and alpine mea-dows on the eastern Qinghai-Tibet Plateau, and investigated the differences in leaf δ13C and δ15N of herbs and the driving factors. The results showed that there were significant differences in leaf δ13C and δ15N values of herbs among different vegetation types, with the highest δ13C and δ15N values in alpine meadows, followed by alpine shrublands, and the lowest in subalpine coniferous forests. Using variation partitioning analysis, we revealed that differences in leaf δ13C and δ15N of herbs among various vegetation types were driven by both leaf functional traits and climate factors, with the contribution of leaf functional traits being relatively higher than that of climate factors. Hierarchical partitioning results indicated that mean annual temperature (MAT), chlorophyll content index, leaf nitrogen content per unit area (Narea), and leaf mass per area were the main drivers of leaf δ13C variations of herbs across different vegetation types, while the relative importance of Narea and MAT for variation in leaf δ15N of herbs was much higher than those other variables. There was a strong coupling relationship between leaf δ13C and δ15N as indicated by the result of the ordinary least squares regression. Our findings could provide new insights into understanding the key drivers of leaf δ13C and δ15N variations in herbs across different vegetation types.

[Characterization of carbon and oxygen isotopes of plant on climate and plant physiology at the southeastern margin of Qinghai-Tibet Plateau, China]. / é’è—é«˜åŽŸä¸œå—ç¼˜æ¤ç‰©ç¢³æ°§åŒä½ç´ å¯¹æ°”å€™åŠæ¤ç‰©ç”Ÿç†çš„è¡¨å¾.

To investigate the correlation between carbon and oxygen isotope compositions of plant cellulose and climatic factors as well as plant physiological indices on the southeastern margin of the Qinghai-Tibet Plateau, we examined plant species in eight sampling sites with similar latitudes and different longitudes in this region. Through the characteristics of δ13C and δ18O values, fractionation values (Δ13C and Δ18O) in leaf cellulose, we discussed water use efficiency (WUE) and the environmental factors, the variation of carbon and oxygen isotopes in the southeastern margin of the Qinghai-Tibet Plateau with elevation and longitude, and revealed the indication degrees of isotopic signals to different environments and vegetation physiology. By using the semi-quantitative model of carbon and oxygen dual isotopes, we investigated the physiological adaptation mechanisms of plants to varying environmental conditions. The results demonstrated that both Δ13C and Δ18O of cellulose decreased with increasing elevation and longitude, and Δ13C was more influenced by longitude, while Δ18O was more susceptible to elevation variation. Additionally, Δ13C and Δ18O were significantly and positively correlated with temperature (TEM), precipitation (PRE), potential evapotranspiration (PET), and relative humidity (RH). PRE was the dominant meteorological factor driving the variation of Δ13C, while RH was the dominant meteorological factor influencing Δ18O variation. In contrast to Δ13C, WUE showed a stronger correlation with elevation than with longitude, which increased as elevation and longitude increased. According to the carbon-oxygen model, plant stomatal conductance (gs) and photosynthetic capacity (Amax) decreased with increasing precipitation and relative humidity, while the values increased with increasing elevation and longitude. The combined analysis of carbon and oxygen isotopes of organic matters would yield additional environmental and gas exchange information for studies on climate tracing and vegetation physiology studies on the southeastern margin of the Qinghai-Tibet Plateau.

[Effects of long-term positioning tillage on13C assimilate distribution and grain yield formation in wheat]. / 长期定位耕作模式对小麦13CåŒåŒ–ç‰©åˆ†é å’Œç±½ç²’äº§é‡å½¢æˆçš„å½±å“.

To provide a theoretical basis and technical support for the high-yield and high-efficiency production of wheat, we examined the effects of different tillage patterns on wheat grain yield of Jimai 22 and the physiological mechanisms in an experiment with three treatments: 14 years in rotary tillage (R), minimal and no tillage (S), and minimal and no tillage with a 2-year subsoiling interval (SS). We assessed the light interception by wheat plant canopy, the distribution of photosynthate transport, and grain yield for the three cultivation modes. The results showed that leaf area index was significantly higher for SS treatment than the other treatments at 14-28 days after anthesis. The interception rate and amount of photosynthetically active radiation in the upper and middle layers of wheat canopy were significantly higher for SS treatment than R and S treatments at 21 days after anthesis. The contribution rate of grain assimilation and the distribution proportion of 13C assimilated in grain, and the maximum and average filling rates, were the highest under SS treatment. The 1000-kernel weight for SS treatment increased by 8.7% and 9.6%, and the grain yield increased by 14.2% and 19.4% compared with R and S treatments, respectively. SS treatment significantly improved light energy utilization by wheat canopy, promoted the accumulation and transport of dry matter, increased the grain-filling rate, increased grain weight, which together contributed to the highest grain yield. Therefore, SS was the optimal tillage pattern under the conditions of this experiment.

[Effects of N, P, and K application rates on distribution of 13C assimilates, starch accumulation in grains and fertilizer utilization of wheat]. / 氮磷钾施用量对小麦旗叶13CåŒåŒ–ç‰©åˆ†é ã€ç±½ç²’æ·€ç²‰ç§¯ç´¯å’Œè‚¥æ–™åˆ©ç”¨çš„å½±å“.

Clarifying the appropriate application rates of N, P, and K fertilizers and the physiological mechanisms of wheat under water-saving recharge irrigation in the North China Plain would provide a theoretical basis for formulating reasonable fertilization plans for high-yield and high-efficiency wheat production. We established four treatments with different amounts of nitrogen (N), phosphorus (P2O5), and potassium (K2O) application: 0, 0, and 0 kg·hm-2 (F0), 180, 75, and 60 kg·hm-2 (F1), 225, 120, and 105 kg·hm-2 (F2), and 270, 165, and 150 kg·hm-2 (F3). During the jointing and anthesis stages of wheat, the relative water content of each treatment in the 0-40 cm soil layer was replenished to 70%, to investigate the differences in wheat flag leaf photosynthetic characteristics, distribution of 13C assimilates, grain starch accumulation, and fertilizer utilization. The results showed that the relative chlorophyll content of flag leaves, photosynthetic and chlorophyll fluorescence parameters, 13C assimilate allocation in each organ, enzyme activities involved in starch synthesis, and starch accumulation in the F1 treatment were significantly higher than that in F0 treatment, which was an important physiological basis for the 20.9% increase in grain yield. The above parameters and yield in the F2 and F3 treatments showed no significant increase compared to F1 treatment, while fertilizer productivity and agronomic efficiency of N, P, and K decreased by 17.5%-58.4% and 12.7%-50.7%, respectively. Therefore, F1 could promote flag leaf photosynthetic assimilate production and grain starch accumulation under water-saving supplementary irrigation conditions, resulting in higher grain yield and fertilizer utilization efficiency.

[Effects of phosphorus application rate on distribution of 13C assimilates and spike formation in different til-lers of wheat with supplementary irrigation]. / 补灌条件下施磷量对小麦不同茎蘖13CåŒåŒ–ç‰©åˆ†é åŠå ¶æˆç©—çš„å½±å“.

To clarify the appropriate rate of phosphorus application and physiological mechanism for promoting wheat tillering and efficient utilization of phosphorus fertilizer with supplementary irrigation, we used 'Jimai 22' wheat variety as the test material, to set up three phosphorus application treatments, including low (90 kg P2O5·hm-2, P1), medium (135 kg P2O5·hm-2, P2), and high (180 kg P2O5·hm-2, P3) application rates, with no phosphorus application as the control (P0). We increased the relative soil water content of each treatment at join-ting stage and anthesis stage to 70%, and measured the area of tiller node, the content of endogenous hormones, the number of tillers in each tiller position, photosynthetic parameters, the distribution of 13C assimilates in each stem and tiller, as well as the grain yield and partial productivity of phosphate fertilizer. The results showed that compared with P0 and P1 treatments, P2 significantly increased the area of tiller node and the trans-zeatin (tZ), the photosynthetic parameters of the uppermost expanded leaves of the main stem, the total tillers per plant, and the distribution of 13C assimilates in each tiller. The number of ears per plant was increased by 0.51 and 0.36, and grain yield was increased by 40.3% and 13.2%, respectively. In P3 treatment, the number of tillers increased, but the panicles per plant, and the grain yield and phosphate fertilizer partial productivity decreased. Our results suggested that the moderate phosphorus treatment (135 kg·hm-2) under supplementary irrigation was suitable for high yield and high efficiency of wheat.

Testing for effects of growth rate on isotope trophic discrimination factors and evaluating the performance of Bayesian stable isotope mixing models experimentally: A moment of truth?

Discerning assimilated diets of wild animals using stable isotopes is well established where potential dietary items in food webs are isotopically distinct. With the advent of mixing models, and Bayesian extensions of such models (Bayesian Stable Isotope Mixing Models, BSIMMs), statistical techniques available for these efforts have been rapidly increasing. The accuracy with which BSIMMs quantify diet, however, depends on several factors including uncertainty in tissue discrimination factors (TDFs; Δ) and identification of appropriate error structures. Whereas performance of BSIMMs has mostly been evaluated with simulations, here we test the efficacy of BSIMMs by raising domestic broiler chicks (Gallus gallus domesticus) on four isotopically distinct diets under controlled environmental conditions, ideal for evaluating factors that affect TDFs and testing how BSIMMs allocate individual birds to diets that vary in isotopic similarity. For both liver and feather tissues, δ13C and δ 15N values differed among dietary groups. Δ13C of liver, but not feather, was negatively related to the rate at which individuals gained body mass. For Δ15N, we identified effects of dietary group, sex, and tissue type, as well as an interaction between sex and tissue type, with females having higher liver Δ15N relative to males. For both tissues, BSIMMs allocated most chicks to correct dietary groups, especially for models using combined TDFs rather than diet-specific TDFs, and those applying a multiplicative error structure. These findings provide new information on how biological processes affect TDFs and confirm that adequately accounting for variability in consumer isotopes is necessary to optimize performance of BSIMMs. Moreover, results demonstrate experimentally that these models reliably characterize consumed diets when appropriately parameterized.

Agropastoral and dietary practices of the northern Levant facing Late Holocene climate and environmental change: Isotopic analysis of plants, animals and humans from Bronze to Iron Age Tell Tweini.

One of the largest isotopic datasets of the ancient Eastern Mediterranean region is evaluated, based on plants (n = 410), animals (n = 210) and humans (n = 16) from Tell Tweini (Syria). Diachronic analysis of plant and faunal specimens from four main periods of occupation: Early Bronze Age (2600-2000 BC), Middle Bronze Age (2000-1600 BC), Late Bronze Age (1600-1200 BC) and Iron Age (1200-333 BC) were investigated. Mean Δ13C results from seven plant species reveal emmer and free threshing wheat, olives, bitter vetch, rye grass and barley were adequately or well-watered during all periods of occupation. The grape Δ13C results suggest excellent growing conditions and particular care for its cultivation. The δ15N results indicate that especially the emmer and free threshing wheats received some manure inputs throughout the occupation sequence, while these were likely further increased during the Iron Age, encompassing also the olive groves and grape vineyards. Generally, domestic animals (cattle, sheep, goats) had C3 terrestrial diets and were kept together in similar environments. However, some animals consumed significant amounts of marine or C4 plants, possibly from disturbed habitats due to land use pressure or salt tolerant grasses and shrubs from wetland environments, which were recorded in the direct vicinity of the site. Middle Bronze Age humans consumed a C3 terrestrial diet with no measurable input from C4, freshwater or marine protein sources. Interestingly, the human diet was relatively low in animal protein and appears comparable to what is considered today a typical Mediterranean diet consisting of bread (wheat/barley), olives, grapes, pulses, dairy products and small amounts of meat. The combined isotopic analysis of plants, animals and humans from Tell Tweini represents unbroken links in the food chain which create unparalleled opportunities to enhance our current understanding of environmental conditions, climate change and lifeways in past populations from the Eastern Mediterranean.

The hidden oases: unveiling trophic dynamics in Namib's fog plant ecosystem.

The Namib Desert is a hyperarid coastal desert where fog is a major moisture source. We hypothesized that the fog-harvesting grass Stipagrostis sabulicola establishes an important ecological niche, termed the "Fog-Plant-Oases" (FPOs), and serves as the primary carbon source for the invertebrate community. To determine this, we measured the natural variations of the stable carbon and nitrogen isotopes (δ13C and δ15N) of invertebrates as well as that of plant biomass and belowground detritus and estimated the contributions of the fog plants in their diets. Our findings revealed a complex trophic structure and demonstrated that S. sabulicola fuels carbon flow from lower to higher trophic levels in the aboveground food web. The distinct δ13C values of bacterial- and fungal-feeding nematodes indicated however the separation of the aboveground niche, which is primarily sustained by S. sabulicola, from the belowground niche, where wind-blown sediments may serve as the main energy source for the soil biota. Our findings further accentuate the critical role of S. sabulicola FPOs in establishing complex trophic dynamics and a distinctive food web within the hyperarid Namib dunes.

Plastic ingestion and trace element contamination of Manx shearwaters Puffinus puffinus on the Faroe Islands.

Procellariiform seabirds can accumulate high levels of plastic in their gastrointestinal tracts, which can cause physical damage and potentially provides a contamination route for trace elements. We examined plastic ingestion and trace element contamination of fledgling Manx shearwaters Puffinus puffinus that were harvested for human consumption in 2003 and 2018 on Skúvoy, Faroe Islands (North Atlantic Ocean). Overall, 88% of fledglings contained plastic in their gastrointestinal tracts, with a mean (± SD) of 7.2 ± 6.6 items weighing 0.007 ± 0.016 g. Though the incidence was similar, fledglings ingested significantly more plastic in 2018 compared to 2003. Hepatic trace element concentrations were unrelated to plastic ingestion. Hepatic carbon (δ13C) and nitrogen (δ15N) stable isotope values were significantly lower in birds sampled in 2018 versus 2003, potentially reflecting further offshore feeding at lower trophic levels. Future research is needed to understand the extent of plastic ingestion by Faroe Islands seabirds.