Neanderthals of Central-Eastern Europe are well documented by a wealth of archaeological sites, but thus far they remain poorly represented by both fossil and genetic data.1,2,3 At Stajnia Cave (Poland), nine Neanderthal teeth have now been integrated into a single high-resolution study combining morphological assessment, radiocarbon dating, and complete mitochondrial (mt) genome sequencing. We report eight new mitogenomes, including from four never-before-analyzed teeth, that resolve a minimum of seven, and possibly eight individuals. Three of the specimens share identical mitochondrial DNA (mtDNA), indicating that they are either from the same or maternally related individuals. Molecular branch shortening estimates place all samples in marine isotopic stage (MIS) 5, with point estimates of ∼119,700-92,498 years ago, making this the oldest multi-individual Neanderthal genetic assemblage yet characterized in Central Europe. Other Neanderthals with similar haplotypes were present in southeastern France, Iberia, and the Caucasus, suggesting this mt lineage might have been widespread across Europe before being replaced with the mtDNA of the "late Neanderthal type." Our analysis of the Stajnia fossils positions Central-Eastern Europe not as a peripheral fringe, but as a pivotal area for tracing Neanderthal geographic distribution.

Soil carbon dioxide (CO2) efflux constitutes a major carbon (C) transfer from terrestrial ecosystems to the atmosphere, driven by numerous metabolic and allocation processes in the plant-soil system. Land use affects key components of C cycling pathways through vegetation type, C allocation, abiotic conditions, and management impacts on soil organic matter (SOM). However, systematic comparisons of these pathways among land uses remain scarce. In two contrasting seasons, we measured respiration rates and C isotopic signatures (C-14, C-13) of in situ soil-respired CO2 and its autotrophic and heterotrophic sources derived from incubations at 16 sites across Switzerland, covering temperate and alpine grasslands, forests, croplands, and managed peatlands. Our findings revealed significant differences in the rates, ages, and sources of soil-respired CO2 between land-use types, reflecting variations in C cycling dynamics. We propose that respiration rates and ages of soil-respired CO2 serve as comprehensive indicators to categorize C cycling into: High-throughput systems (temperate grasslands) where high respiration rates of young (<10 years) CO2 reveal rapid C cycling. Temperature-constrained retarding systems (alpine grasslands) where the respiration of decadal- to centennial-old CO2 reveals slow C cycling mainly due to cooler climatic conditions. Input-constrained retarding systems (forests) where decadal-old CO2 reflects a delayed C transfer of assimilates back to the atmosphere through soil respiration. C-depleted systems (croplands) where reduced C inputs and tillage lead to C depletion and to respiratory losses of centennial-old C. Hotspots of C release (managed peatlands) where ancient C is lost through respiration due to disturbances in natural C cycling by drainage. Our results suggest that the relationship between rates and ages of soil-respired CO2 can serve as a robust indicator of C retention and loss along the trajectory from natural to anthropogenically disturbed systems on a global scale.

[This corrects the article DOI: 10.1371/journal.pone.0280598.].

Climate change is intensifying the frequency and severity of droughts, with profound implications for carbon (C) cycling in forest ecosystems. While progress has been made in understanding how drought alters plant and microbial ecophysiology, it remains unclear how these changes affect the overall magnitude and pace of C cycling within the plant-soil continuum. In this study, we examined the effects of 22 years of experimental irrigation in a naturally drought-prone Scots pine forest. We integrated long-term measurements of C inputs (i.e., litterfall) and outputs (i.e., soil respiration) with radiocarbon (¹⁴C) analysis of soil organic carbon, fine roots, and CO₂ from in situ soil respiration and its autotrophic and heterotrophic components. Our study demonstrates that long-term shifts in water availability enhance both C inputs and outputs, reshaping C cycling within the plant-soil system. Radiocarbon ( 14 C) analysis revealed that irrigation accelerated C cycling within plants and the organic layer, reducing the time that assimilated C remained in the ecosystem before being respired back to the atmosphere. The observed increase in soil respiration under irrigation was largely driven by enhanced autotrophic activity, associated with greater fine root biomass. Concurrently, the decomposition of labile, young organic matter intensified under irrigation, potentially contributing to a net C loss from the organic layer. Despite this increased respiration under irrigation, ¹⁴C contents in bulk SOC indicated greater inputs of young C to the mineral soil and enhanced downward translocation of C from the organic layer to the mineral phase, possibly through rhizodeposition and soil faunal activity. The enhanced input to the mineral soil under irrigation results in net C gains and may promote C stabilization through organo-mineral interactions and aggregate formation. Our findings also indicate that drought conditions limit both the magnitude and rate of C cycling within the plant-soil continuum and potentially reduce long-term C sequestration in mineral soils.

[This corrects the article DOI: 10.1371/journal.pone.0324911.].

The ongoing rapid glacier melting in the European Alps due to anthropogenic climate warming has led to the discovery of previously buried tree remnants at the retreating ice margins proving long-lasting Holocene glacier minima as analogous to the recent state of glaciation. Since 2018, remnants of multi-centennial-aged trees have become accessible at the retreating terminus of the Morteratsch Glacier, Swiss Alps. Some tree remnants prove multi-centennial glacier minima before c. 6.50 and 3.88 ka. However, the majority of the findings represent the oldest Holocene woods found to date on a glacier forefield in the European Alps. They demonstrate a distinct and previously unknown glacier minimum lasting at least 430 years, between c. 10.78 and 10.35 ka, during which the glacier was consistently smaller than c. 2020 CE. This earliest Holocene glacier minimum during the latePreboreal was terminated by an advance of the Morteratsch Glacier c. 10.35 ka (i.e. 8349 +/- 14 cal BCE) proven by several tree remnants with killing dates. The culmination of this glacier advance towards the end of the Preboreal is documented at few Alpine glaciers through moraines located slightly outside the later Little Ice Age limits and cosmogenic dated to around 10.2 ka. In a hemispheric comparison, the onset of the glacier minimum at Morteratsch Glacier corresponds with the oldest dates available for glacier extents as today, namely in western North America, and the dating of the late-Preboreal glacier culmination also corresponds with culmination ages in Scandinavia as well as in north-eastern North America and Greenland.

Reconstructing environmental changes near ice margins that have deglaciated since the Last Glacial Maximum (LGM) is essential for understanding future changes of the Antarctic Ice Sheet. Here, we conducted a multiproxy reconstruction of the Holocene environmental history of Cranton Bay, a small, bathymetrically enclosed, biologically productive embayment north of Pine Island Bay in the Amundsen Sea Embayment (ASE), West Antarctica. We present a detailed analysis of sediment core NBP20-02 KC72, which provides a record of environmental changes in the bay. We analyzed sediment grain size, magnetic susceptibility, computed tomography scans, stable carbon isotopes on bulk sediments, total diatom abundance and assemblages, and radiocarbon-dated calcareous benthic foraminifera. Our findings suggest that an ice canopy covered Cranton Bay early in the Holocene, evidenced by low primary productivity. During the mid-Holocene, the bay was seasonally sea-ice covered, as documented by the increase in total diatom abundance and the presence of diatom taxa with sea-ice affinity. The appearance of the offshore diatom Fragilariopsis kerguelensis during the mid-Holocene may suggest the advection of modified Circumpolar Deep Water (mCDW) into Cranton Bay. This implies that mCDW delivery across the ASE during the Holocene was spatially and/or temporally variable, possibly due to boundary conditions (e.g., bathymetry). Primary productivity increased during the latest Holocene, consistent with longer seasonally open-marine conditions. Absolute diatom abundances in Cranton Bay are among the highest within the ASE. Understanding past environments and drivers of glacial retreat since the LGM will help contextualize recent West Antarctic Ice Sheet changes.

Carbon exchange between biosphere and rhizosphere is an important component of the global carbon cycle. Photosynthetic products being sequestered into soils have been intensively studied, yet the reverse pathway from rhizosphere to biosphere is poorly known. In the present study, we determined the radiocarbon content (Delta 14C) of the bulk leaves of the deciduous Quercus oak and of chlorophyll a (Chl a) extracted from the same leaves collected in Switzerland during the 1950s and 2000s. Our results demonstrate that old soil-derived carbon significantly contributes to the synthesis of Chl a, an essential molecule for photoautotrophs. The Delta 14C values of Chl a were consistently lower than those of bulk leaves which closely tracked bomb-derived Delta 14C signals in the atmosphere. The results cannot be explained without invoking an additional carbon source with a turnover time exceeding 100 years. A two-pool mixing model assuming atmosphere and rhizosphere as two endmembers indicates that contributions of the soil carbon to Chl a are 17 +/- 2 % (n=4), and turnover time of such soil carbon is no shorter than 1000 years. We suggest that hydrophilic compounds such as amino acids or phytol are transferred into plant roots from soils through mycorrhizal symbionts, and Chl a is one of the destinations of such 14C-depleted carbon in vascular plants.

The independent evidence of radiocarbon wiggle-matching suggests that the dating of American oak timbers found in English building by ring-width dendrochronology is robust. The offset between contemporaneous same-laboratory pairs of measurements on American and European tree-rings is 5.9 +/- 3.8 BP (American wood older), which is not statistically significant.

Antarctic ice core evidence indicates that atmospheric CO2 levels increased during Heinrich Stadial (HS) 1 and the Younger Dryas (YD) during the last deglaciation. A substantial fraction of this carbon is believed to have stemmed from the ocean interior, released, in part, through enhanced wind-driven upwelling and air-sea CO2 exchange in the Southern Ocean. This was highlighted by two deglacial opal flux peaks identified in sediment core TN057-13-PC4 (53.17 °S, 5.13 °E, 2818 m water depth) from the Atlantic Southern Ocean south of the Polar Front, proximal to the Antarctic Divergence Zone (Anderson et al., 2009). However, there is limited information on changes in deep-ocean 14C ventilation and surface ocean hydrography in the Atlantic Antarctic Divergence, and their role in atmospheric CO2 variations during these two periods of deglacial CO2 rise. Here, we provide a new set of 12 mixed-benthic and 63 planktonic foraminiferal (i.e., Neogloboquadrina pachyderma) 14C ages obtained with a MIni-CArbon-DAting-System (MICADAS) in sediment core TN057-13-PC4, along with high-resolution multi-proxy (sub-)sea surface temperature reconstructions for the same site (N. pachyderma Mg/Ca ratios, TEX86, diatom assemblages). Our data help better constrain the nature, timing, and impacts of deep-ocean upwelling on surface ocean hydrography and on atmospheric CO2 exchange near the Antarctic Divergence of the Southern Ocean. Our data show strong (sub-)surface warming in the Antarctic Divergence during HS1 and YD that is accompanied by a rapid decline in benthic-minus-planktic 14C ages towards mean Holocene values at the onset of the deglaciation. We also observe millennial-scale increases in seawater d18O (paired N. pachyderma Mg/Ca-d18O analyses), hence local surface salinity and marked variations in 14C surface ocean reservoir ages that parallel changes in Antarctic sea ice extent. This corroborates previous evidence indicating increased upwelling of Circumpolar Deep Water in the Atlantic Antarctic Divergence during HS1 and YD, yet suggests an onset of strong Southern Ocean ventilation earlier than what is expected from increases in opal fluxes alone. Our data support a fundamental role of upwelling and CO2 outgassing in the Antarctic Divergence of the Southern Ocean in the two-step atmospheric CO2 rise during the last deglaciation, and further suggest that possible variations in CO2 solubility and sea-ice retreat amplified the effects of physical circulation changes on Southern Ocean air-sea CO2 exchange.References: Anderson, R.F., Ali, S., Bradtmiller, L.I., Nielsen, S.H.H., Fleisher, M.Q., Anderson, B., Burckle, L.H., 2009. Wind-driven upwelling in the Southern Ocean and the deglacial rise in atmospheric CO2. Science 323, 1443–1448. doi: 10.1126/science.116744

Research on Holocene climate variability and human history greatly benefits from annually resolved and absolutely dated tree-ring chronologies. The quality and quantity of such records, however, decline back in time, with little tree-ring evidence available for the Early and Middle Holocene. Here, we present a tree-ring width (TRW) chronology from 100 subfossil yews ( Taxus baccata L.) excavated from peat-rich soils in the Fenland region of eastern England. To precisely date the record, we measured stable oxygen (δ 18 O) isotopic ratios of over 1500 tree rings from a subset of 12 disc samples and used an absolutely dated oak ( Quercus spp.) δ 18 O chronology from the same region for cross-dating. Statistically significant isotopic agreement between the two species precisely dates the yew TRW chronology from 2668 to 2213 years BCE ( r = 0.4, t -value = 7.9, probability of error > 10 6 , Isolation Factor > 10 3 ). This 456-year period in the mid-Holocene marks the Neolithic-to-Bronze Age transition, coincides with the spread of the Bell Beaker culture across the British Isles, and precedes the still debated 4.2 ka climate anomaly. Emphasizing the advantages of tree-ring stable isotopes, our absolutely dated yew record offers new opportunities for archaeological interpretations and palaeoclimatological reconstructions in eastern England and beyond. We further expect our results to help dating the Icelandic eruptions of Katla and Hekla 4 and refining the next radiocarbon calibration curve.

Soil organic carbon (SOC) can persist from days to millennia but remains vulnerable to carbon (C) loss upon disturbances, depending on environmental conditions and mode of stabilization. Understanding drivers of persistence and vulnerability is crucial to assess soil C sequestration as well as potential SOC losses due to changes in climate and land use. Here, we investigate SOC persistence and vulnerability in five land-use types by combining radiocarbon-derived estimates of SOC age (system age) and age of respired CO2 (transit time) with indicators of biological (SOC decomposability) and thermal stability (residual oxidisable carbon content, ROC). Based on this, we developed a vulnerability index for SOC and applied it across soil profiles from 19 sites representing temperate and alpine grasslands, forests, croplands, and managed peatlands. Transit times and system ages ranged from 2 years in the organic layer of forests to 5760 years in subsoils of managed peatlands and varied significantly across land-use types and soil depth. Transit times were generally shorter than system ages, indicating that soil-respired CO2 is dominated by more recent inputs, while bulk SOC contains more persistent C. In forests, temperate grasslands, and croplands, system ages were positively linked to thermal stability and mineral reactivity, indicating higher SOC persistence through organo-mineral stabilization. In contrast, alpine grasslands and managed peatlands showed centennial to millennial system ages despite low thermal stability (< 10%-ROC), reflecting inhibited microbial decomposition due to cold and/or anaerobic conditions in these ecosystems. In combination with high SOC stocks (> 90 kg m(-2) in managed peatlands), this implies a high vulnerability of these soils to environmental disturbances that alleviate these constraints. Our findings demonstrate that combining metrics of biological and thermal stability with radiocarbon data provides a powerful framework to assess SOC vulnerability to disturbances induced by environmental change.

Cement production currently emits approximately 8 % of global CO2. However, the fossil content of these emissions can vary significantly due to methods used to reduce fossil emissions, such as the increased use of alternative fuels. Here, we investigated three CO2 sampling methods used to analyse 14CO2 and estimate the fossil fraction (in terms of F14C) of emissions from three Swiss cement factories. First, direct stack exhaust gas sampling was conducted at a main study site over 6 months and 14CO2 measurements were compared with 14C values from producer fuel use data. A positive offset in F14C was observed with theoretical values compared to the measurements. This could be reduced by adjusting the assumed 14C content of some fuels, particularly shredded wood waste. Second, repeated downwind CO2 emission plume sampling campaigns were carried out at all sites, allowing for a remote estimation and comparison of their F14C signatures. These measurements yielded realistic average values but also demonstrated sensitivity to local wind conditions, i.e. wind speed and direction. Lastly, we analysed the bulk 14C content of tree leaves collected around each site to assess their long-term atmospheric fossil CO2 exposure. Although the observed 14C depletion and fossil fraction were generally small (close to uncertainty ranges), trees near the factories consistently showed lower F14C values than background trees. Direct stack exhaust gas sampling proved to be the most reliable approach for quantifying fossil CO2 emissions from cement production. Crucially, adjustments made to fuel 14C contents to match measurements suggested an underestimation of fossil CO2 emissions from the producer at our main site by more than 2 %.

While the sun, as the primary source of energy on earth, is considered to have a constant energy output, small fluctuations can be observed over time. Historical records of solar activity (e.g., sunspot numbers) are however scarce, and only available over the last 400 years. Cosmogenic nuclides stored in tree rings (14C) or ice cores (10Be, 36Cl) can be used as proxies for solar activity and allow solar reconstructions reaching much further back in time1,2. However, only recently the presence of the eleven-year solar cycle could be revealed in an annually resolved 14C record from tree-rings covering the past 1000 years. The amplitude of this so called Schwabe cycles is found to correlate with the general level of the solar activity with high amplitudes during periods of strong solar activity and vice versa3.Here, we present the solar activity, and specifically the 11-year cycles, reconstructed from 14C in tree-rings covering two grand solar minima, one around 400 BCE and another one around 3400 BCE. The results will be compared with the two previously analysed grand solar minima (Spörer and Maunder) of the last millennia, coinciding with the Little Ice Age. 1 Bard, E. et al. (2000) Solar irradiance during the last 1200 years based on cosmogenic nuclides. Tellus Series B-Chemical and Physical Meteorology 52, 985-992.2 Muscheler, R. et al. (2007) Solar activity during the last 1000 yr inferred from radionuclide records. Quaternary Science Reviews 26, 82-97.3 Brehm N. et al. (2021) Eleven-year solar cycles over the last millennium revealed by radiocarbon in tree rings. Nature Geoscience. 14(1), 10-15.

The Sun drives Earth's energy systems, influencing weather, ocean currents, and agricultural productivity. Understanding solar variability is critical, but direct observations are limited to 400 years of sunspot records. To extend this timeline, cosmic ray-produced radionuclides like 14C in tree-rings provide invaluable insights. However, few records have the resolution or temporal span required to thoroughly investigate important short-term solar phenomena, such as the 11-year solar cycle, or 14C production spikes most likely linked to solar energetic particle (SEP) events. Here we present a continuous, annually resolved atmospheric 14C record from tree-rings spanning the first millennium BCE, confirming no new SEP's and clearly defining the 11-year solar cycle, with a mean period of 10.5 years, and amplitude of approximately 0.4‰ in 14C concentration. This dataset offers unprecedented detail on solar behavior over long timescales, providing insights for climatic research and solar hazard mitigation, while also offering enhanced radiocarbon calibration and dating accuracy.

Beginning with the Early Aurignacian, Homo sapiens demonstrated an enhanced symbolic capacity, expanding artistic expressions from body decoration to portable art and aesthetically refined tools. These artistic endeavors, often intertwined with utilitarian purposes, have sparked debates regarding their symbolic versus functional roles. Among these remarkable artifacts is a complete mammoth tusk boomerang from Layer VIII of Obłazowa Cave, Poland, found in association with a human phalanx. Determining its precise chronology and cultural context is critical for understanding the emergence and variability of symbolic behaviors among early Homo sapiens groups in Europe. This study refines the chronology of the Early Upper Paleolithic occupation of Layer VIII at Obłazowa Cave through radiocarbon dating of several bones and the human fossil found near the ivory boomerang. Bayesian modeling places the site’s main occupation phase between 42,810−38,550 cal BP (95,4% probability). The mammoth-ivory boomerang, calibrated to 42,290−39,280 cal BP with a 95.4% probability, emerges as one of Europe’s oldest known examples of this complex tool, exemplifying technological and symbolic innovation at Obłazowa Cave. This multi-disciplinary research underscores the importance of integrating advanced methodologies to explore cultural practices during the Upper Paleolithic. The findings not only deepen our understanding of Homo sapiens ’ adaptive strategies but also highlight the nuanced interplay of technology, symbolism, and environmental interaction during the earliest phases of human dispersals in Central Europe.

We introduce a novel high-precision method for oxygen-isotope analysis of iron (oxyhydr)oxides using high-temperature conversion isotope ratio mass spectrometry (HTC-IRMS). In this approach, a finely ground mixture of iron (oxyhydr)oxide and graphite is heated at 1450 °C in a helium flow environment, converting oxygen to CO gas with nearly 100% yield. Continuous-flow IRMS analysis of the liberated CO yields a precision of ±0.15‰ (1σ, n = 28) and shows excellent agreement with (and improved precision over) traditional fluorination methods. This practical and safe technique expands access to oxygen-isotope measurements of iron oxides, thereby enhancing their utility in Earth and environmental sciences.

Radiocarbon (14C) measurements on dissolved inorganic carbon (DIC) are a powerful tool to trace water masses and carbon cycling in the ocean. Existing methodologies to determine the 14C content of seawater DIC requires large volumes of sample (usually >100 mL) and specialized graphitization techniques to achieve the accuracy and precision needed for meaningful data interpretation. The advancement of the CO2 gas ionization accelerator mass spectrometry (AMS) technique today allows routine 14C measurements on small samples (<100 gC) and may thus permit reducing the sample volumes needed to determine 14C content of seawater DIC to similar to 2 mL. The proposed method utilizes the carbonate handling system (CHS), gas interface system (GIS) and MICADAS AMS, and provides good accuracy but reduced precision compared to established methods. Good accuracy is shown by comparing results for a marine in-house DIC standard and a DIC seawater profile from Antarctica between the proposed CHS-GIS-MICADAS approach and reference measurements conducted on the same material at established laboratories (ETH and NOSAMS). Further, two sedimentary porewater profiles from a fjord system in Svalbard are presented. Despite good agreement, the precision of the CHS-GIS-MICADAS approach is reduced, potentially limiting possible interpretations on seawater DIC. Nonetheless, the reduction of sample volumes proves particularly helpful to analyze porewater DIC from sediment cores, where sample material is notoriously limited, reduces the required amounts of toxic HgCl2 and simplifies expedition logistics.

AbstractProtection by metal (hydr) oxides is one of the key mechanisms for the long‐term stabilization of soil organic carbon (SOC). However, the source and turnover of (metal‐) bound organic carbon (OC) in soils are poorly constrained. Here we present the first large‐scale study on the 13C and 14C characteristics of bound OC in 15 wetland and upland soil profiles. We find that bound OC has similar δ13C as SOC, suggesting no preference for plant‐ or microbe‐derived carbon. However, bound OC Δ14C is more negative than SOC in wetland but not upland mineral soils, and decreases with increasing reactive minerals. Hence, in contrast to the conventional assumption, bound OC is better preserved relative to SOC in wetlands with high contents of reactive metals. Our finding highlights the dynamic exchange of bound OC with SOC in upland soils and calls for a better recognition of reactive metals in stabilizing OC in wetlands.

This article presents the development and application of a microsublimation apparatus aimed at improving the purity of ultra-small samples for compound-specific radiocarbon analysis. Accurate radiocarbon (14C) measurements require the effective isolation of biomarkers, yet procedural steps, such as chromatography and sample transfer, introduce contamination risks that can skew results. Here, we present a novel approach to remove contamination resulting from chromatographic isolation. The apparatus, constructed primarily from aluminum, allows solvent-free sublimation of multiple samples under vacuum. A constant contamination assessment showed a blank mass of 1.35 µg of carbon with a F14C of 0.33, indicating minimal contamination with 14C-depleted carbon. The apparatus demonstrated high efficacy for compounds with higher melting points, such as amino acids and dyes, while compounds like alkanes showed lower recovery rates. These findings confirm the potential of microsublimation to enhance post-chromatography sample purity and improve the accuracy of 14C measurements, though challenges remain for certain compound classes.