Modern Samples Research Articles

Geometric morphometric analysis of Pleuronectiformes vertebrae: A new tool to identify archaeological fish remains?

Flatfish (Pleuronectiformes) vertebrae are difficult to identify to species due to the lack of diagnostic features. This has resulted in a lack of understanding of the species abundances across archaeological sites, hindering interpretations of historical fisheries in the North Sea area. We use a new approach, utilising a combined 2D landmark-based geometric morphometric analysis as an objective and non-destructive method for species identification of flatfish vertebrae from the North Sea area. Modern specimens were used as a reference to describe the morphological variation between taxa using principal component analysis (PCA) and to trial an automated classification using linear discriminant analysis. Although there is limited distinction between taxa using PCAs, the classification shows high accuracies, indicating that flatfish species identifications using geometric morphometrics are possible. Bone samples (n = 105) from two archaeological sites in the United Kingdom and France were analysed using this approach and their identifications were verified using collagen peptide mass fingerprinting. The success rate of species identification was usually less than 50%, indicating that this technique has limited applicability due to preservation/fragmentation of archaeological fish bone. Nonetheless, this could prove a valuable tool for modern and non-fragmented samples. Furthermore, the technique applied in this study can be easily adapted to work on other landmark datasets.

Spatial influence of the Asian Summer Monsoon on pollen assemblages of the Tibetan Plateau and its potential implication for the interpretation of fossil pollen records

The direction and intensity of Asian Summer Monsoon (ASM) circulation in the Tibetan Plateau (TP) region strongly influence pollen dispersal patterns; however, this spatial effect has been rarely quantified. In this paper, we explore the relative importance of this directional spatial effect. Specifically, we construct a wind connectivity diagram for modern pollen sample sites according to the prevailing monsoon direction, and extract latent spatial variables representing the directional process of the ASM, using the method of asymmetric eigenvector maps. We fit redundancy analysis models using both spatial variables and local climate factors, and conduct variation partitioning to quantify the effect of directional spatial effect by the ASM. Taking into account the joint effect with local climate, the directional spatial process induced by the ASM significantly explains the variation of pollen assemblages on the TP. The effect is detected in pollen groups with contrasting functional types and dispersal modes; for example, the composition of arboreal pollen and non-arboreal pollen are both significantly affected by the ASM, yet best explained by models assuming different monsoon directions. Anemophilous pollen shows a higher percentage of variation explained by the ASM than non-anemophilous pollen. Our results indicate that directional processes induced by the monsoon is an important influence on pollen assemblages in the TP and support the idea that deposition patterns of pollen, especially arboreal pollen is a useful proxy for studying monsoon evolution. A similar approach can also be applied to paleomonsoon simulations using fossil pollen records. The role of directional dispersal in affecting fossil pollen composition and abundance by prevailing winds deserves further investigation when undertaking Quaternary paleoenvironmental reconstructions using pollen.

Parameters and Modes of Operation of Modern Technical Means for Deep Tillage

The parameters of modern samples of chisel plows and subsoilers tested at MIS are presented; the modes and functional indicators of their work as part of machine and tractor units are given; an analysis of the rationality of aggregation has been completed.

Representation and biases: Pollen–vegetation relationships and their contribution to the study of fossil pollen records in SW Iberia

In order to provide a better framework for the interpretation of fossil pollen records, a set of 49 modern pollen samples collected across different habitats of SW Iberia, categorised by context and sample type (soil vs moss), were selected to explore pollen–vegetation relationships by multivariate analysis and identify possible biases in pollen representativeness. The distribution of both samples and pollen taxa in the plots is successfully explained according to specific environmental variables in some clusters (A, B and E) in which plant communities depend on certain environmental conditions. On the other hand, other clusters (C, D and F) are better explained by opposition to some variables and suggest a wider range of adaptability of their floristic communities. The classification of samples by context consistently explains their differences in vegetal and environmental terms. However, some discrepancies seem to be better explained by sample type (soil vs moss), which raises some questions on how taphonomic factors may cause biases in both modern and fossil pollen samples.

Historic trophic decline in New England's coastal marine ecosystem.

Overfishing is a worldwide occurrence that simplifies marine food webs, changes trophic patterns, and alters community structure, affecting not only the density of harvested species but also their trophic function. The northwestern Atlantic has a history of heavy fishing, and over the past century has also experienced destructive bottom fishing and harmful mobile fishing gear. After confirming that preservation solvent did not alter the nitrogen stable isotopes of preserved samples, we used museum specimens and modern samples to analyze nitrogen stable isotopes in tissues of two common demersal fishes pre-1950 (1850 to 1950) compared to 2021 to assess changes in trophic positions of coastal New England consumers over this time period. Both the mesopredator Centropristis striata (black sea bass) and the benthivore Stenotomus chrysops (scup) experienced significant declines in trophic position during this time. C. striata declined almost a full trophic level, S. chrysops declined half a trophic level, and these species are now occupying almost the same trophic position. Heavy fishing activities potentially shorten food chains, simplify trophic complexity, lessen the separation of trophic niches, and generally flatten food webs. The consequences of these within-species shifts are poorly investigated but could generate underappreciated cascading impacts on community structure and function. Archived natural-history collections are an invaluable resource for investigating ecological changes in natural communities through time. The evaluation of changing trophic positions via stable isotope analysis may allow fisheries managers to quantify large-scale effects of fishing on ecosystems and food webs over time.

Museomics and phylogenomics of lovebirds (Psittaciformes, Psittaculidae, Agapornis) using low-coverage whole-genome sequencing

Natural history collections contain specimens that provide important insights into studies of ecology and evolution. With the advancement of high-throughput sequencing, historical DNA (hDNA) from museum specimens has become a valuable source of genomic data to study the evolutionary history of organisms. Low-coverage whole genome sequencing (WGS) has been increasingly applied to museum specimens for analyzing organelle genomes, but is still uncommon for genotyping the nuclear DNA fraction. In this study, we applied low-coverage WGS to phylogenomic analyses of parrots in the genus Agapornis by including both modern samples and historical specimens of ∼100-year-old. Agapornis are small-sized African and Malagasy parrots with diverse characters. Earlier phylogenetic studies failed to resolve the positions of some key lineages, prohibiting a robust interpretation of the biogeography and evolution of these African parrots. Here, we demonstrated the use of low-coverage WGS for generating both mitochondrial and nuclear genomic data, and evaluated data quality differences between modern and historical samples. Our resolved Agapornis phylogeny indicates the ancestor of Agapornis likely colonized Madagascar from Australasia by trans-oceanic dispersal events before dispersing to the African continent. Genome-wide SNPs also allowed us to identify the parental origins of hybrid Agapornis individuals. This study demonstrates the potential of applying low-coverage WGS to phylogenomics and population genomics analyses and illustrates how including historical museum specimens can address outstanding questions regarding the evolutionary history of contemporary lineages.

Declining autozygosity over time: An exploration in over 1 million individuals from three diverse cohorts

Previous studies have hypothesized that autozygosity is decreasing over generational time. However, these studies were limited to relatively small samples (n<11,000) lacking in diversity, which may limit the generalizability of their findings. We present data that partially support this hypothesis from three large cohorts of diverse ancestries, two from the US (All of Us, n= 82,474; the Million Veteran Program, n= 622,497) and one from the UK (UK Biobank, n= 380,899). Our results from a mixed-effect meta-analysis demonstrate an overall trend of decreasing autozygosity over generational time (meta-analyzed slope= -0.029, SE= 0.009, p= 6.03e-4). On the basis of our estimates, we would predict FROH to decline 0.29% for every 20-year increase in birth year. We determined that a model including an ancestry-by-country interaction term fit the data best, indicating that ancestry differences in this trend differ by country. We found further evidence to suggest a difference between the US and UK cohorts by meta-analyzing within country, observing a significant negative estimate in the US cohorts (meta-analyzed slope= -0.058, SE= 0.015, p= 1.50e-4) but a non-significant estimate in the UK (meta-analyzed slope= -0.001, SE= 0.008, p= 0.945). The association between autozygosity and birth year was substantially attenuated when accounting for educational attainment and income (meta-analyzed slope= -0.011, SE= 0.008, p= 0.167), suggesting they may partially account for decreasing autozygosity over time. Overall, we demonstrate decreasing autozygosity over time in a large, modern sample and speculate that this trend can be attributed to increases in urbanization and panmixia and differences in sociodemographic processes lead to country-specific differences in the rate of decline.

Hydrologic Controls on Individual Ostracode Stable Isotopes in a Desert Lake: A Modern Baseline for Lake Turkana

AbstractStable carbon (δ13C) and oxygen (δ18O) isotope measurements in lacustrine ostracodes are widely used as paleolimnological indicators of past climate change. Previous work has used individual ostracode valves to resolve seasonal and subdecadal paleohydrological signals, yet replicated assessments of co‐occurring specimens from modern samples are rare. Here we focus on ostracodes from sediments collected in 1979 from Lake Turkana, an alkaline desert lake in tropical eastern Africa. Sourced from the Ethiopian highlands, the Omo River is the dominant inflow into this lake. We present individual ostracode valve analyses (IOVA) of δ13C and δ18O measurements (n = 329) of the extant benthic ostracode Sclerocypris clavularis from 17 sites spanning the entire lake (navg = ∼19 specimens/site). We demonstrate that the pooled statistics of individual valve measurements at each site are shaped by lake hydrology, superimposed over inter‐individual isotopic variations. Within‐site variance in IOVA‐δ13C is larger (∼60%) than that of IOVA‐δ18O. Yet, site‐based averages exhibit a systematic pattern, with higher δ values toward the southern part of the lake, away from Omo River inflow. We suggest that the latitudinal δ13C gradient may arise from low riverine δ13C and low organic matter δ13C as a productivity response to nutrient‐rich Omo River inflow toward the north. The δ18O pattern may be explained by the diminishing influence of Omo River inflows and more evaporation driving higher IOVA‐δ18O values toward the windier, southern basin. We conclude that pooled IOVA statistics in Omo‐Turkana sediments can aid interpretations of past regional paleohydrology and its variability in this basin.

High-resolution mass spectrometry identification of dye compounds and their degradation products in American cochineal from a historic shipping cargo

Cochineal dyes constitute paradigmatic organic compounds that guide in the elucidation of historic cultural and economical exchanges. This study combines liquid chromatography and high-resolution tandem mass spectrometry to assess the degradation products of the organic dyes of American cochineal collected from the cargo of a 16th century sunken wreck. The identification of biological materials of historical and archeological origin is often challenging due to molecular degradation. In this scenario, the mapping of the chemical routes underlying the fate of the organic and biochemical compounds employed as taxonomic biomarkers becomes of crucial importance. This work shows that, under harsh environmental conditions, the original carminic and (flavo)kermesic acid structures of cochineal dyes are prone to chemical transformation, typically losing the carboxylic acid and glucoside groups. The anthraquinone core is preserved in the majority of degradation products identified in this study, with eventual side chains reminiscent of a partial degradation of the glucoside moiety. The comparison of these observations with the analysis of modern cochineal samples allows us to lay out an updated chart of dye compounds and degradation products which should constitute a seminal benchmark for future biomolecular analysis of historic and archeological dye materials.

Paleoenvironments and climate at Nahal Me'arot (Mount Carmel, Israel) during the Middle and Late Pleistocene: The herpetofauna of Tabun Cave and el-Wad Terrace

The Paleolithic record of the Levant encompasses several key changes in human population dynamics and human biological and cultural evolution. These processes are frequently linked to climatic shifts, but high-resolution and long-term paleoenvironmental and paleoclimatic records often come from off-site sources, hindering the correlation with human developments observed in the archaeological sites. This paper aims to reconstruct the long-term paleoenvironmental and paleoclimatic records of the Middle and Late Pleistocene Nahal Me'arot, Mount Carmel, Israel, using the archaeological herpetofauna assemblages from the Middle Paleolithic (MP) of Tabun Cave (layers C and B; using 18 stratigraphically ordered beds in total) and the Early Natufian of el-Wad Terrace (EWT), and employing the habitat weighting and mutual climate range methods. To strengthen our control of the correlation between the observed variation and the changing environment we also add a modern sample from the same location. We provide a systematic description of the finds and employ taphonomic and taxonomic analyses, which enabled us to identify three major accumulation agents that differentially affected the various samples: raptor predation predominantly in Tabun C, natural entrapment and death in Tabun B, and human consumption in Natufian EWT.The studied Tabun sequence exhibits changes in temperature and humidity. These are more apparent in the lower part (Tabun C), where the driest spell of our sequence also occurred, than in its upper part (Tabun B), and potentially coincide with the succession of two different hominin populations in the site. The correlation with regional off-site records remains challenging. Yet, given the available dates for the layers immediately underlying our driest sample, this dry fluctuation can be cautiously correlated with one of the dry phases apparent in the isotope records at the end of MIS 6. In the Terminal Pleistocene, the Early Natufian EWT reconstruction shows a wetter and cooler climate than the present day, with favorable Eastern Mediterranean vegetation, possibly enabling the long-term sedentary habitation that is suggested for this phase. Finally, our results testify to the general resilience of amphibian and reptile communities through the sequence but also to the rising impact of human activities on the reptile community during the Natufian.

Developing a new testate amoeba hydrological transfer function for permafrost peatlands of NW Siberia

The vast areas of permafrost peatlands in the West Siberian Lowland (WSL) hold a significant amount of carbon currently at risk due to human-caused global warming. The rapid thawing of about 20–60% of the frozen soils of Western Siberia adds to the destruction of the region's signature palsa landscape and the development of thermokarst lakes or fens. Due to the complex interactions between climate and the ecosystem that shape its formation and degradation, permafrost reacts in different ways to environmental changes. Understanding recent changes in Western Siberia requires knowledge of previous environmental transitions, which needs to be enhanced further. This study, aimed to create a hydrological testate amoebae (TA) transfer function (TF) from the Khanymei area in the WSL to reconstruct past hydrological conditions in permafrost peatlands. In addition, this research intended to examine the influence of TA communities living in lichens (genus Cladonia) on the performance of TF by integrating these data with a calibration data set. In the summer of 2019, 76 modern samples of Sphagnum, Cladonia, and vascular plants from permafrost and non-permafrost sites were collected. Moreover, one peat core was extracted from the same area to reconstruct the depth to water table (DWT) quantitatively. The Shannon's diversity index, a quantitative measure of species richness, was calculated for each sample to estimate the TA species diversity in a community. Non-metric multidimensional scaling ordination was applied to the dataset to explore the similarities in TA communities between samples and determine whether the DWT controls the TA community structure. Results showed that the typical transition of TA species along the microtopographic (wet–dry) gradient is influenced by the presence of lichens on the surface of the peatland. Statistical analysis confirmed that TA communities in Cladonia are less affected by DWT. Therefore, the TF was constructed on the entire dataset (n = 75) and the dataset with Cladonia excluded (n = 55). Both these TFs showed satisfactory results. Even though the TF constructed on the entire dataset showed fewer predictive abilities, it provided a complete picture of the current vegetation conditions of Khanymei peatlands, where lichens are an essential element of the ecosystem. Therefore, it is assumed that TF with local environment traits may be more suitable for quantitative reconstruction, particularly in the newly explored permafrost area of Western Siberia.

Reconstructing the Paleo‐Ecological Diet of Snow Petrels (Pagodroma nivea) From Modern Samples and Fossil Deposits: Implications for Southern Ocean Paleoenvironmental Reconstructions

AbstractSnow petrels (Pagodroma nivea), which are endemic to the Antarctic region, produce proventricular stomach oil from ingested food for feeding purposes but also spit the oil in the immediate surrounds of the nests, where it forms encrustations over time (Antarctic mumiyo). These deposits provide a unique opportunity to understand the paleo‐ecological diet of snow petrels and because the seabirds forage in the ocean, they potentially provide an archive of past marine environmental conditions in the Southern Ocean. For validating methods for reconstructions we use compositional data obtained on modern stomach oils and DNA data from fecal samples of snow petrels. We find that the distribution of carboxylic acid compounds in modern stomach oils and in the fossil deposits are consistent with variable contributions of fish and krill, which are the main constituents of modern snow petrel diet, and allows inference of past changes in snow petrel diet from the fossil record. Analyses of mumiyo deposits from six regions in East Antarctica reveal systematic differences in the isotopic composition of organic matter (δ13C and δ15N) and carboxylic acid patterns. This may suggest regional and/or temporal variability in the composition of snow petrels diet, likely differing in response to the prevailing environmental conditions in the foraging range of the birds, such as sea‐ice variability, polynya activity and primary productivity. Our study provides confidence for using these approaches for broader scale paleo‐studies in the future and for an assessment of the temporal changes and regional variability in snow petrel diet.

Personal chapter in the popular biobibliographic essays

The article deals with the features of the structure of the personal chapter (chapters-personalities) in modern popular bio-bibliographic essays. Prospects for further practical work on the creation of modern heads-personalities are outlined. It is told about the bibliographic manual of the modern sample which is currently being worked on. The research is based on more than half a century of recommendatory bibliographic activity of the Russian State Library. The material used for the study was the bibliographic production of this library, dedicated to fiction and first of all to the domestic literature.

Influence of common palynological extraction treatments on ultraviolet absorbing compounds (UACs) in sub-fossil pollen and spores observed in FTIR spectra

IntroductionBiological life, atmospheric circulation and the Earth’s climate may be influenced by UV-B radiation. In plants, Ultraviolet Absorbing Compounds (UACs) are an indicator of UV-B exposure, and the abundance of UACs in pollen and spores of embryophytes is measurable using Fourier Transform Infrared (FTIR) micro-Spectroscopy. However, understanding the influence of common chemical pre-treatments on sub-fossil pollen and spores with a view to UV-B reconstruction still requires investigation.MethodsHere, peat samples collected from a Late Holocene raised bog were treated with different chemicals (HCl, KOH, and acetolysis) for varying treatment times (up to 210 min). Pollen or spores of three common taxa (Alnus, Calluna and Sphagnum) were isolated and FTIR spectra obtained on individual grains. The spectra were compared to modern pollen and spore samples collected nearby.ResultsSpectra of modern and sub-fossil samples show several visible differences related to lipid and protoplast contents. The results of chemical treatments on sub-fossil pollen and spores reveal that HCl produced limited changes, while KOH and acetolysis altered several peaks, including the UAC-related aromatic peak at 1516 cm−1. We observe that all treatments modify the FTIR spectra to some degree, from weakest (HCl) to strongest (acetolysis). With respect to reduction of UAC peak area and treatment time, we observe in some cases a significant log-decay relationship, notably for KOH treatment on Calluna pollen and acetolysis on Sphagnum spores. Compared to untreated control samples, UAC peak area in Alnus, Calluna and Sphagnum reduced by 68%, 69% and 60% respectively, after only 3 min of acetolysis treatment. After 60 minutes of acetolysis treatment UAC peaks were reduced by 77%, 84% and 88%.DiscussionDue to the potential for taxon-specific effects and significant reductions in UAC peak area even within short treatment times, our recommendation for future applications in palaeoecological studies on palynomorph chemistry is to avoid chemical digestions in the pollen extraction process in favour of separation methods including micro-sieving and density separation.

The oxygen isotope value of whole wood, α-cellulose, and holocellulose in modern and fossil wood

The oxygen isotope value (δ18O) of α-cellulose extracted from modern and fossil wood has been used widely to reconstruct climate throughout the Quaternary and deep-time. Substantial effort has been made towards developing more efficient and cost-effective methods for obtaining α-cellulose from whole wood, though some research groups advocate for measuring δ18O directly on whole wood due to a constant offset between the δ18O of whole wood and α-cellulose. The utility of alternative substrates to α-cellulose (e.g., whole wood or holocellulose) for paleoclimate reconstruction using fossil wood, however, has not been evaluated. Here we present 48 new δ18O measurements on mummified (subfossil) wood ranging in age from Eocene to Miocene. Whereas the δ18O value of whole wood and α-cellulose is only weakly related in these subfossils, there is a strong linear correlation between the δ18O value of α-cellulose and holocellulose. We augmented this dataset with 1546 new and published oxygen isotope pairs on whole wood, α-cellulose, and holocellulose from modern wood (Quaternary to present) to compare with our pre-Quaternary fossil samples. In contrast to the fossil wood, we found strong correlations between α-cellulose and whole wood and α-cellulose and holocellulose in modern samples. This finding suggests that all three substrates (whole wood, cellulose and holocellulose) derive oxygen isotopes from a common source (i.e., meteoric water) on a global scale, and that processing of α-cellulose may not be required for modern wood in some settings. Because average holocellulose yields in fossil wood were approximately double that of α-cellulose (22.2 ± 12.8% versus 11.6 ± 10.3%), δ18O analysis on holocellulose rather than α-cellulose should produce reliable environmental data while reducing time and sample material required.

The endocast from Dana Aoule North (DAN5/P1): A 1.5 million year-old human braincase from Gona, Afar, Ethiopia.

The nearly complete cranium DAN5/P1 was found at Gona (Afar, Ethiopia), dated to 1.5-1.6Ma, and assigned to the species Homo erectus. Its size is, nonetheless, particularly small for the known range of variation of this taxon, and the cranial capacity has been estimated as 598 cc. In this study, we analyzed a reconstruction of its endocranial cast, to investigate its paleoneurological features. The main anatomical traits of the endocast were described, and its morphology was compared with other fossil and modern human samples. The endocast shows most of the traits associated with less encephalized human taxa, like narrow frontal lobes and a simple meningeal vascular network with posterior parietal branches. The parietal region is relatively tall and rounded, although not especially large. Based on our set of measures, the general endocranial proportions are within the range of fossils included in the species Homo habilis or in the genus Australopithecus. Similarities with the genus Homo include a more posterior position of the frontal lobe relative to the cranial bones, and the general endocranial length and width when size is taken into account. This new specimen extends the known brain size variability of Homo ergaster/erectus, while suggesting that differences in gross brain proportions among early human species, or even between early humans and australopiths, were absent or subtle.

Cenozoic topographic evolution of the Southern Central Andes foreland as revealed by hydrogen stable isotopes in hydrated volcanic glass

We use the “isotope-paleotopography” method to resolve the topographic evolution of the Southern Central Andes and adjacent foreland to the east, at the latitude of 35°S. Our analysis is based on δ2H measurements from hydrated volcanic glass from 107 samples collected from a 55 to 10 Ma stratigraphic section in the Malargüe basin, and from an additional 11 samples of Quaternary tuffs. The results are supported by an analysis of a large dataset of modern meteoric water samples (n=197), which are used to characterize the relationship between orographic lifting and precipitation isotopes in the modern. Our interpretations are guided by the Orographic Precipitation and Isotopes (OPI) programs, which provide a full simulation of the flow of moist air over a specified 3D topography and the resulting condensation and fall out of rain and snow, and the isotopic fractionation associated with these processes. The OPI model is fit, in a least-squares sense, to the modern isotope data, which provides a way to test for moisture sources and to calculate how precipitation isotopes would be influenced by variations in climate.There are three important conclusions from these data: 1) OPI modeling of modern water isotopes shows that precipitation at the Malargüe study area is derived solely from the moist northeasterly winds. The isotopic fractionation along this wind path occurs by lifting over the Córdoba and San Luis basement highs, and during the initial rise up the east side of the range. Westerly moist air is able to pass over the range, but downslope flow over the east side means that this source becomes strongly undersaturated, so precipitation from this source is suppressed in this area. 2) Our volcanic glass data indicate that the hydrogen isotopic composition of precipitation, δ2H, has been strongly depleted, by −50 to −90 per mil, since 55 Ma to present. The only way to produce this depletion is by upslope flow of moist winds and associated precipitation over the eastern side of the range. The amount of isotopic fractionation remains fairly constant and similar to modern for the interval from 55 to 15 Ma, which indicates that the topography to the east of Malargüe has been fairly steady during that time interval. 3) Our δ2H record indicates that between 15 and 10 Ma, the topography upwind of Malargüe decreased by about 50%, and then increased by the same amount between 10 and 0 Ma. This subsidence event coincides with the Paranense marine transgression, and is also predicted by numerical modeling of mantle flow and dynamic topography associated with subduction of the Nazca plate.

Novel luminescence diagnosis of storm deposition across intertidal environments

Salt marshes provide valuable nature-based, low-cost defences protecting against coastal flooding and erosion. Storm sedimentation can improve the resilience of salt marshes to accelerating rates of sea-level rise, which poses a threat to salt marsh survival worldwide. It is therefore important to be able to accurately detect the frequency of storm activity in longer-term sediment records to quantify how storms contribute to salt marsh resilience. Luminescence is able to infer how long mineral grains were exposed to sunlight prior to burial (e.g., the presence or absence of sediment processing). This study used sediment cores collected from the Ribble Estuary, North West England, to show that luminescence properties of sand-sized K-feldspar grains can diagnose the differential modes of deposition across intertidal settings (i.e., sandflat, mudflat and salt marsh) in longer-term sediment records by detecting the variability in sediment bleaching potential between settings (i.e., sediment exposure to sunlight), thus establishing a framework for the interpretation of luminescence properties of intertidal sediments. It then used modern sediment samples collected before and after a storm event to show how such properties can diagnose changes in sediment processing (i.e., bleaching potential) of mudflat sediments caused by storm activity, despite no changes in sediment composition being recorded by geochemical and particle size distribution analyses. This new luminescence approach can be applied to longer-term sediment records to reveal (and date) changes in the environment of deposition and/or depositional dynamics where there is no obvious stratigraphic evidence of such.

Quantitative tree cover reconstruction during the past 2000 years in the central–northern parts of the Daxing'an Mountains, northeast China

Reconstructing the history of tree cover and exploring the relationship between forest growth and environmental factors are of great significance for predicting future vegetation changes and guiding ecosystem restoration and protection. On the basis of pollen data of two lake cores and three peat profiles in the central–northern parts of the Daxing'an Mountains and using multiple methods, we quantitatively reconstructed the tree cover of the past 2000 years. We found that the reconstruction results of the different methods are quite similar. Among all these methods, random forest had the highest prediction accuracy for modern pollen samples. Therefore, the random forest reconstruction results can better reflect changes in regional tree cover, which was approximately 38%–42% during 2000–200 Cal yr BP. It then obviously increased from a low value of approximately 40% to a modern level of approximately 45%. The precipitation and carbon dioxide (CO2) concentration were the main drivers for the tree cover before and after 200 Cal yr BP, respectively. This indicates that environments with elevated CO2 level in the near future will benefit the growth of vegetation in the central–northern parts of the Daxing'an Mountains.

Experiences in the commissioning of the first radiocarbon dating laboratory based on the carbosorb method in Tehran

In this paper, the experiences in the commissioning of the first radiocarbon dating laboratory based on the carbosorb method in Tehran are presented and described. Its purpose is to: (a) validate the predefined procedures, (b) introduce the relevant commissioning equipment, and (c) report on significant experiences in the sample preparation. The procedure of sample preparation for the carbosorb method including acid-base degreasing, carbonization, oxidizing, and refinement of CO2 gas, followed by chemical conversion to a compound suitable for C-14 dating was achieved in this work. Using a Liquid Scintillation Counter (LSC), the measurements of the prepared standard, blank, and of a modern sample were carried out and the results were discussed. The similar radiocarbon activities of blank and marble samples confirmed the minimum absorption of environmental CO2 gas during sample preparation and the measured specific activity of the wood sample proved the absorption of radiocarbon in the cocktail.