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To document the occurrence of vertical displacements of vegetation in the high plateaus of the Venezuelan Guayana ( tepuis) over the last c. 6000 years, and to discuss their significance for the origin of their flora, especially the endemism patterns observed in their flat summits. Two hypotheses have been proposed for the origin of the summit flora. One (the Lost World hypothesis) proposes a long history of evolution in isolation from the surrounding plains, while the other (the Vertical Displacement hypothesis) suggests that vertical movements of vegetation during the Pleistocene glacial-interglacial cycles would have resulted in floristic mixing within the lowlands, and genetic interchange among plateau summits. This work has been conducted on the flat summit of the Churí-tepui, in the Chimantá massif, at 5°15′ Lat. N and 62°01′ Long. W, around 2250 m altitude. Pollen analysis and radiocarbon dating of two peat outcrops, using modern analogue technique and numerical methods for palaeoecological interpretation were used. The replacement of a high-altitude plant community (a paramoid Chimantaea shrubland) by a lower elevation (< 2300 m) Stegolepis meadow, occurred about 2500 years before present (yr bp). This vegetation change is inferred to have resulted from a regional climatic shift to higher temperature and moisture. A subsequent decrease in temperature and moisture led to the establishment of present conditions after about 1450 yr bp. The highland vegetation of the tepuis responded to climate shifts with vertical displacements, supporting the hypothesis of vertical mixing. However, a physiographical analysis shows that around half of the tepuis would never have been connected by lowlands. Therefore, both hypotheses are needed to explain the origins of the summit flora in the tepuis. [ABSTRACT FROM AUTHOR]

The UN's Paris Agreement goal of keeping global warming between 1.5 and 2°C is dangerously obsolete and needs to be replaced by a commitment to restore Earth's climate. We now know that continued use of fossil fuels associated with 1.5–2°C scenarios would result in hundreds of millions of pollution deaths and likely trigger multiple tipping elements in the Earth system. Unexpected advances in renewable power production and storage have radically expanded our climate response capacity. The cost of renewable technologies has plummeted at least 30‐year faster than projected, and renewables now dominate energy investment and growth. This renewable revolution creates an opportunity and responsibility to raise our climate ambitions. Rather than aiming for climate mitigation—making things less bad—we should commit to climate restoration—a rapid return to Holocene‐like climate conditions where we know humanity and life on Earth can thrive. Based on observed and projected energy system trends, we estimate that the global economy could reach zero emissions by 2040 and potentially return atmospheric CO2 to pre‐industrial levels by 2100–2150. However, this would require an intense and sustained rollout of renewable energy and negative emissions technologies on very large scales. We describe these clean electrification scenarios and outline technical and socioeconomic strategies that would increase the likelihood of restoring a Holocene‐like climate in the next 100 years. We invite researchers, policymakers, regulators, educators, and citizens in all countries to share and promote this positive message of climate restoration for human wellbeing and planetary stability. Plain Language Summary: New research in global ecology and public health shows that the consequences of burning fossil fuels are much more severe than previously understood. Current global warming targets are not enough to protect us from sea level rise, ecosystem collapse, and hundreds of millions of human deaths from fossil fuel pollution. Thankfully, the cost of renewable energy technologies has dropped below the cost of fossil fuels decades faster than predicted. This has triggered a renewable revolution that is transforming the global energy system. Our paper considers the feasibility of accelerating this transition through policy, investment, and strategic research. We conclude that there is a viable pathway to restoring Earth's climate through clean electrification and carbon capture. We call for a global commitment to restore pre‐industrial climate conditions within a century and describe what approaches would increase our chances of success. Accelerating the renewable revolution would move us toward a sustainable civilization by eliminating air pollution, stabilizing climate, reducing energy costs, and enhancing living standards worldwide. Because there is no safe level of climate disruption or pollution death, we believe it is our responsibility to restore a Holocene‐like climate, which we know can support human civilization and other life on Earth. Key Points: Goals of 1.5–2°C are not safe given current understanding of ecosystem climate sensitivity and high social costs of fossil fuel pollutionClimate restoration‐rapidly reestablishing Holocene‐like conditions‐has not been fully considered because of socioeconomic obstaclesStrategic financing and prioritization of clean electrification could create pathways back to the Holocene within a century [ABSTRACT FROM AUTHOR]

This paper develops a composite absolute paleointensity record for Holocene paleomagnetic secular variation (PSV) from central North America. Twelve full‐vector (inclination, declination, paleointensity) PSV records were assessed in order to build the composite record. Nine of the paleointensity records come from sediment paleomagnetic studies and are considered relative in intensity. Three of the paleointensity records come from absolute paleointensity measurements of archeological materials and lava flows. This paper develops a new method to normalize the sediment relative paleointensity records to the absolute intensity records. The final composite paleointensity record describes intensity variability over a region of Central North America delineated by 35°–48.6°N and 240.4–291.4°E (∼14° × 50°). This composite record shows a distinctive long‐duration (∼104 year) oscillation and a series of millennial‐scale intensity oscillations that are consistent over our study region. Plain Language Summary: This study develops a composite record of geomagnetic field intensity for the central North America for the last 8,000 years. This record is important for considering the total geomagnetic field variability I this region and its dynamo source(s). Key Points: We develop a new composite absolute paleointensity record for Holocene Central North AmericaWe develop a new renormalization technique to combine absolute paleointensity records and sediment relative paleointensity recordsThe final composite absolute paleointensity record has a distinctive long‐term trend and millennial‐scale variability [ABSTRACT FROM AUTHOR]

Recent climate and environment over the Tibetan Plateau (TP) have undergone significant changes, dominated by variations in the Westerlies and the Indian summer monsoon. However, long‐term shifts in atmospheric circulation during the transitional seasons are still lacking. Here we investigate the modern distribution of Tsuga pollen over the central‐western TP and confirm it as an indicator of variable atmospheric circulation in spring. By combining our Tsuga record from Taro Co with existing records in the Tsuga pollen source area, we suggest that a potential particle transport pathway from the southern slope of the Himalayas to the interior of the plateau appeared in the spring of the late Holocene. Our results show that the springtime atmospheric circulation over the southwestern TP during the early and late Holocene is closely related to the substantial remnants of ice sheets at northern high latitudes and the frequency of El Niño events, respectively. Plain Language Summary: The spring climate over the Tibetan Plateau (TP) is undergoing significant changes that yield profound impacts on environmental changes such as variations in vegetation phenology and alpine treeline. Knowledge of long‐term variations in atmospheric circulation during spring can improve the understanding of current climatic and environmental change and the projection of future variability. In this paper, we use an exotic pollen grain, which can be transported long distances in the air, as an indicator to trace the variability of spring atmospheric circulation over the TP. The results indicate that the spring meridional atmospheric circulation from the southern slope of the TP to its interior has been enhanced in the last four thousand years, which is mainly influenced by the frequency of El Niño events. Key Points: Spring atmospheric circulation change over the southwestern Tibetan Plateau (TP) during Holocene is reconstructedMeridional atmospheric circulation in spring over the southwestern TP is strengthened in the late HoloceneHigh‐(low‐) latitude forcing mainly influence the variations in spring atmospheric circulation during the early (late) Holocene [ABSTRACT FROM AUTHOR]

The Holocene history of the forest-alpine tundra ecotone in Central Sweden (Scandes Mountains) is inferred from radiocarbon analyses of subfossil wood remains. Pinus sylvestris was the dominant subalpine tree species during the early Holocene, when it ascended almost 200 m higher than currently. A short climatic episode (less than 100 years) is postulated to have triggered erosional processes around 6300 B.P., and extinguished the upper part of the subalpine pine woodland. Subsequently, a subalpine belt of Betula pubescens ssp. tortuosa and Alnus incana developed. A Holocene thermal optimum occurred around 6100 B.p., when the birch/alder belt flourished and the tree-limits probably reached their highest levels during the Holocene. Shortly after 6000 B.P., a long-term pine forest retrogression started and the birch/alder belt was disrupted by expanding snow-beds. Pine receded slightly at its tree-limit, but the uppermost belt of closed pine forest (presently dominated by birch) remained intact until c. 3300 B.p., when a severe climatic deterioration occurred. The present-day subalpine belt of pure birch forest developed successively and increased in vertical extent after c. 5300 B.P., when summer temperature declined. The evolution of the birch belt is postulated to have been ultimately a response to decreased seasonality, which favoured birch at the expense of pine. Because of the 'inertia' characterizing the highest pine forest, the birch belt was relatively narrow until a major thermal decline c. 3300 B.P., when it made a massive downslope expansion. The latest phase of pine recession was during the Little Ice Age, 800-300B.P. [ABSTRACT FROM AUTHOR]

The North American Monsoon (NAM) is a critical component of the hydrologic cycle in southwestern North America. However, our understanding of the long‐term evolution of this monsoon system is incomplete due to a paucity of long‐term paleoclimatic records from the core and periphery of the NAM domain. C. Routson et al. (2022, https://doi.org/10.1029/2022gl099772) leverage a new compilation of Holocene proxy records to generate a new composite index of NAM evolution over the Holocene. They identify a relationship between NAM strength and the latitudinal temperature gradient over the Holocene. The authors suggest that shifts in the strength of the westerlies altered NAM convection via ventilation, a process whereby the large‐scale circulation imports low moist entropy air into the monsoon domain. These results highlight the importance of paleoclimatic records, especially from past "warm" intervals, for generating new insights about the evolution of regional monsoons. Plain Language Summary: The North American Monsoon is a circulation that brings summer rain to regions of the US southwest and western Mexico. Despite the fact that this circulation provides a majority of the precipitation in many parts of the arid southwest, we do not fully understand the factors that govern long‐term changes in this monsoon. A new paper by C. Routson et al. (2022, https://doi.org/10.1029/2022gl099772) uses proxy indicators of past summer rainfall, stretching from Central America to Arizona, to reconstruct changes in the monsoon over the geologic epoch known as the Holocene, or the last 11,000 years of Earth history. The results of this study suggest that Holocene changes in the temperature difference between the equator to pole, known as the "latitudinal temperature gradient," exerted an important influence over monsoon strength in the southwest. This has implications for the future of the summer monsoon, especially as the high latitudes of the northern hemisphere are expected to warm in the future. Key Point: The strength North American Monsoon tracks changes in the position of the midlatitude westerlies over the Holocene [ABSTRACT FROM AUTHOR]

The englacial stratigraphic architecture of internal reflection horizons (IRHs) as imaged by ice‐penetrating radar (IPR) across ice sheets reflects the cumulative effects of surface mass balance, basal melt, and ice flow. IRHs, considered isochrones, have typically been traced in interior, slow‐flowing regions. Here, we identify three distinctive IRHs spanning the Institute and Möller catchments that cover 50% of West Antarctica's Weddell Sea Sector and are characterized by a complex system of ice stream tributaries. We place age constraints on IRHs through their intersections with previous geophysical surveys tied to Byrd Ice Core and by age‐depth modeling. We further show where the oldest ice likely exists within the region and that Holocene ice‐dynamic changes were limited to the catchment's lower reaches. The traced IRHs from this study have clear potential to nucleate a wider continental‐scale IRH database for validating ice sheet models. Plain Language Summary: Ice‐penetrating radar is widely used to measure the thickness of ice sheets, critical to assessments of global sea level rise potential. This technique also captures reflections from chemical contrasts within the ice sheet, caused by the atmospheric deposition of conductive impurities, known as "internal reflection horizons" (IRHs) that can be traced over large distances. As these deposits are laid down in distinct events, most IRHs are isochronous age tracers and contain valuable information on past ice sheet processes. In this paper we trace and place age constraints on stratigraphic horizons across a large portion of the West Antarctic Ice Sheet, including regions where fast ice flow has disrupted the ice sheet stratigraphy. The resulting data set allows us to identify where the oldest ice is buried in the study region and provides evidence that flow of the ice sheet interior has been stable during the Holocene. Our results can be used to test the performance of ice sheet models, which seek to simulate the response of ice sheets to long‐term environmental change. Key Points: We measure and date individual isochronal radar internal reflection horizons across the Weddell Sea sector of the West Antarctic Ice SheetHorizons dated to 1.9–3.2, 3.5–6.0, and 4.6–8.1 ka are widespread and linked to previous radar surveys of the Ross and Amundsen Sea sectorsThese form the basis for a wider database of ice sheet architecture for validating and calibrating ice sheet models of West Antarctica [ABSTRACT FROM AUTHOR]

Cyclic facies variations in shallow‐water carbonate platforms often show repetitive facies patterns that are frequently interpreted to reflect the sedimentary response to variations in sea‐level related to changes in climate linked to orbital variations, the Milankovitch frequencies. Whether these shallow‐marine carbonates represent a complete infill of accommodation space, or are subtidal cycles, has been discussed in numerous papers. The extent to which the thickness of a single depositional cycle is a direct measure of the amplitude of relative sea‐level change is not fully understood. New shallow seismic data from Great Bahama Bank reveal that accommodation space created during the Holocene sea‐level rise is not filled in a predictable way. Three seismic horizons were identified: the seabed, the Pleistocene top, and a horizon within the Pleistocene. Depth surface and thickness maps of the Holocene and Pleistocene layers were combined with 326 in situ water‐depth measurements to assess the upper limit of the present accommodation space. The analysis showed that accommodation space and Holocene sediment thickness, and water depth are not correlated. In addition, the actual water depth and inner platform facies distribution showed no straightforward link. The energy distribution across the shallow‐water platform appears to control the facies type rather than water depth. Mud‐dominated sediments prevail in shallow low‐energy areas protected by a topographic barrier, whereas mud‐free coarse‐grained sediments mainly occur in deeper areas with hydrodynamic energy induced by strong tidal currents, ocean water influx, and winds. Hence, the uneven energy distribution not only results in unpredictable differences in the carbonate‐cycle thickness on the platform but also to a water depth independent facies distribution pattern within the inner platform. Therefore, care should be taken when deducing sea‐level signals from inner platform facies distribution and sediment thickness patterns on ancient platforms. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of radiocarbon dating of shell mounds and middens in Blue Mud Bay, northern Australia. The aim is to investigate variability in use of the landscape and foraging activity through time. By considering both mounded and non-mounded shell deposits, results indicate that occupation and use of coastal landscapes during the Holocene in this region of northeast Arnhem Land was highly variable, with several overlapping phases of occupation and gaps in site formation, As in some other Australian regions, this implies a discontinuous or nonlinear pattern of occupation, one that suggests the late Holocene occupation of coastal Blue Mud Bay may be characterised by variability in the distribution and intensity of foraging behaviour through time and space. [ABSTRACT FROM AUTHOR]

Aim Projections of human impact on the environment and biodiversity patterns are crucial if we are to prevent their destruction. Such projections usually involve the assumption that the same human activities always affect biodiversity in the same way, either in geographically distant areas within the same time-scale or in the same areas in different periods. In this paper, plant and snail fossils from central Europe that cover the last 12,000 years provide evidence against this assumption. Location Central Europe. Methods We examined fossil data on central European plants and snails and extracted time-series of (1) local species richness (alpha diversity) at a scale of approximately 300 m × 300 m and decays of (2) the Jaccard index and (3) Simpson's beta with increasing distance (up to approximately 400 km) through time. Results We show that two vital biodiversity patterns follow neither oxygen-isotope nor borehole temperature proxies, but instead vary between archaeologically known periods, with the most noticeable and irreversible breaks (1) when arable agriculture was introduced into central Europe, (2) when the Roman Empire collapsed, and (3) during the event known as the 12th-century colonization in central Europe. The patterns computed from data across time sometimes contradicted the patterns computed across space. Main conclusions We therefore infer that people can, and sometimes have, contributed to temporal changes in ecological rules that are seemingly general across space. Our findings indicate that the changes in ecological rules are so substantial that efforts to project future biodiversity based on space-for-time substitution might fail, unless we gain knowledge about how these general rules are altered. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) is an important greenhouse gas which destroys the ozone in the stratosphere. Primary sources of atmospheric N2O are nitrification and denitrification in terrestrial soils and the ocean, and the main sink is photolysis in the stratosphere. Studies have mostly focused on the climate‐related response of N2O during glacial‐interglacial periods. However, its mechanism of variation during the Holocene remains unclear. We present a high‐resolution N2O record from the South Pole Ice (SPICE) core covering the Holocene epoch. The millennial‐scale N2O trend agrees with existing records. We constructed a Holocene composite consisting of the new N2O measurements in SPICE and existing records from other ice core sites. The N2O composite reveals four distinct periods of N2O variation during 11.5–10.0 ka, 10.0–6.2 ka, 6.2–2.2 ka, and 2.2–1.4 ka, including two maxima in 11.0–10.0 ka and 3.0–2.2 ka and minima in 8.8–6.2 ka and approximately 1.4 ka. Apart from these, our new high‐resolution record from SPICE shows a short‐term N2O decrease around 2.8 ka which is not observed in other records possibly due to lower sample resolution and/or higher age smoothing. Comparison of our new Holocene N2O composite with the paleo‐proxy records suggests the plausible linkage of major monsoon (Asian, North African, South and North American, and Australian‐Indonesian monsoon) and upwelling (Arabian Sea and Eastern Tropical South Pacific) regions in regulating the atmospheric N2O during the Holocene. Plain Language Summary: Nitrous oxide (N2O) is an important greenhouse and ozone‐depleting gas. The growing level of N2O in the atmosphere is of global concern, and records of past N2O variations can provide an essential context for understanding the links between N2O and climate change. In this study, we report a new, high‐quality N2O record covering the Holocene epoch using an ice core obtained from the South Pole. Our record shows four important periods of N2O variation during 11.5–10.0 ka, 10.0–6.2 ka, 6.2–2.2 ka, and 2.2–1.4 ka. These include two local N2O maxima in 11.0–10.0 ka and 3.0–2.2 ka and minima in 8.8–6.2 ka and approximately 1.4 ka. Comparison with climate records suggests that the variation in monsoon precipitation and ocean productivity contributed to centennial‐ to millennial‐scale N2O variations during the Holocene. Key Points: High‐resolution N2O record from the South Pole Ice core covering the Holocene epoch is investigated for N2O variationInsight into the key drivers of atmospheric N2O on millennial time scales during the Holocene is providedN2O exhibits two local maxima during 11.0–10.0 ka and 3.0–2.2 ka, and two local minima during 8.8–6.2 ka and at around 1.4 ka [ABSTRACT FROM AUTHOR]

This paper addresses the surface and Holocene aeolian deposits in the southeastern Mu Us Desert, N. China, systematically analysing the evolution of the geochemical characteristics of aeolian sand-palaeosol sequences and their environmental significance. Our results indicate that the geochemical components of the Holocene aeolian deposits and surface deposits had the similar material sources, sediment transport and deposition processes in the study region, which were dominated by SiO2, Al2O3, and Na2O. In the weathering process of the Jinjie (JJ) profile, the Na, K, and Si presented the slight leaching and migration in general, while the other elements were relatively accumulated. The Holocene aeolian deposits and surface deposits incurred weaker geochemical weathering under cold and dry conditions and were only weakly leached, which implies a relatively arid environment in the Holocene epoch and the modern era. The weathering degree was controlled by the regional temperature and precipitation, and was probably more sensitive to the precipitation changes. In the sedimentary profile, the geochemical parameters and migration of elements demonstrated that there have been several alternating warm-wet and cold-dry intervals in the Mu Us Desert in the Holocene epoch; there were relatively warm and wet conditions prior to 4.6 ka, and it has been cold and dry since then. Six millennial-scale dry events were recorded during the Holocene, which were not only accordant with the history of palaeoclimatic changes in the different latitudes and archives of the Northern Hemisphere, but also correspond to the millennial-scale variation of cosmic radiation and solar activity during that period. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Holocene evolutionary history of the Banni Plain in the Great Rann of the Kachchh Basin is reconstructed from a subsurface sediment core of ca 50 m. Detailed data on textural and lithofacies variations, grain‐size analysis, environmental magnetism and accelerator mass spectrometry 14C dates on seven samples were generated on the sediment core retrieved from the Banni Plain near Berada. A high‐resolution record extending back to 10 ka has been reconstructed from the top ca 40 m of the core section comprising shallow marine sediments. The core is divisible into five depositional units. The basal part is a fluvial depositional unit followed upward by estuarine, sub‐tidal, intertidal and supra‐tidal environments. The sediment accumulation rate is highest in the sub‐tidal to intertidal facies (1.9 cm year−1) and decreases towards the supra‐tidal facies to 0.09 cm year−1. Environmental magnetic analysis, χlf coupled with the S‐ratio, indicates high magnetic mineral concentrations during the Early Holocene, suggesting a wet period accompanied by high monsoon precipitation. This is followed by the onset of semi‐arid conditions in the Great Rann of the Kachchh Basin as indicated by the low values of the χlf and S‐ratios. A westward and northward shift in the shoreline towards the deeper part of the basin is suggested during the Late Holocene, which is coupled with aridity and reduced monsoonal conditions. The change in depositional pattern from the retrogradational deposit of fluvial (Unit 1) to estuarine sediment (Unit 2), progressing to sub‐tidal (Unit 3), is attributed to sea‐level transgression followed by regressive intertidal (Unit 4) to supra‐tidal deposition (Unit 5), culminating in complete withdrawal of the sea, aided by tectonic uplift, during the Late Holocene. The results reveal that the sediment accumulation rates and depositional environments changed over time in response to changes in sea level from minima to maxima and then eventually to the present level. [ABSTRACT FROM AUTHOR]

The interaction between climate change and disturbances affects forest composition and dynamics, but most of our empirical knowledge comes from short‐term studies of the past century. Pollen and charcoal analyses of lake sediment cores retrieved from three sites in Nova Scotia were used to produce a landscape‐level analysis of long‐term forest cover dynamics and fire disturbances of the past ~2500 years. The present‐day forests had been established by that time, although a long‐term increase in Picea at the expense of northern hardwoods was seen at all sites, consistent with other pollen records found across New England and Eastern Canada. The driving influences of forest change prior to European settlement were a combination of climate and disturbance, acting on site characteristics of each region. Fires were relatively infrequent in this region and did not have a major impact on the evolution of the forests of central Nova Scotia. Changes in the relative abundances of the tree taxa occurred in response to long‐term cooling during the past 3000 years and century‐scale climate variability such as the Little Ice Age (ce 1450–1850) and Medieval Warm Period (ce 800–1300). The impact of climate variability on the fire regime depends on the landscape and vegetation type. "Borealization" of the Acadian Forest, noted during the period of European colonization, has been occurring for millennia. [ABSTRACT FROM AUTHOR]

Aim This paper examines eight fossil pollen datasets from Romania with the aim of exploring regional and elevational patterns in site similarity throughout the Holocene. In particular, we aim to determine whether there are clear intervals of homogenization/differentiation and to ascertain the potential driving factors. Location Romania. Methods Qualitative (pollen diagrams) and numerical methods including principal components analysis and Bray-Curtis similarity analyses were used. Results We found strong variability in the past vegetation dynamics during the Holocene. Bray-Curtis similarity analyses show large fluctuations in vegetation similarity and distinct periods of homogenization and differentiation throughout the Holocene. The magnitude and length of these periods appear quite variable in time, but the significant ones can be delimited as follows: (1) differentiation between 11,250 and 11,000 cal. yr bp, 10,000 and 9750 cal. yr bp, 6000 and 5750 cal. yr bp, 2500 and 2250 cal. yr bp, and especially over the last 200 years; and (2) homogenization between 9750 and 9500 cal. yr bp, and 2750 and 2500 cal. yr bp, with more stable periods between 9000 and 7750 cal. yr bp, 4750 and 3500 cal. yr bp, and 2000 and 1000 cal. yr bp. Main conclusions First, periods of biotic homogenization that occurred before significant anthropogenic impact on vegetation demonstrate that not all homogenization is a product of anthropogenic change: it can also be driven by natural causes. In fact, recent human impact (over the last 200 years) appears to have resulted in increased regional differentiation and not in homogenization - a result that contradicts most studies based on more modern, short-term records. Second, both abiotic (climate and disturbance) and biotic factors are likely drivers of intervals of differentiation and homogenization. We suggest that differentiation may be triggered primarily by climate changes and disturbances (mostly natural pre-2500 cal. yr bp and human-induced thereafter), whereas homogenization may be driven predominantly by biotic interactions (e.g. immigration and interspecific competition). Third, this long-term study raises awareness that assessments of pattern in vegetation homogenization/differentiation may depend on the specific time period and length of investigation. Long-term investigations through multiple generations are likely to yield particularly useful information on the mechanisms and effects of biotic homogenization. [ABSTRACT FROM AUTHOR]

Late Quaternary sediments from Ocean Drilling Program (ODP) Hole 1055B, Carolina Slope, western North Atlantic (32°47.041′ N, 76°17.179′ W; 1798 m water depth) were examined for deep-sea ostracod taxonomy. A total of 13 933 specimens were picked from 207 samples and c. 120 species were identified. Among them, 87 species were included and illustrated in this paper. Twenty-eight new species are described. The new species are: Ambocythere sturgio, Argilloecia abba, Argilloecia caju, Argilloecia keigwini, Argilloecia robinwhatleyi, Aversovalva carolinensis, Bythoceratina willemvandenboldi, Bythocythere eugeneschornikovi, Chejudocythere tenuis, Cytheropteron aielloi, Cytheropteron demenocali, Cytheropteron didieae, Cytheropteron richarddinglei, Cytheropteron fugu, Cytheropteron guerneti, Cytheropteron richardbensoni, Eucytherura hazeli, Eucytherura mayressi, Eucytherura namericana, Eucytherura spinicorona, Posacythere hunti, Paracytherois bondi, Pedicythere atroposopetasi, Pedicythere kennettopetasi, Pedicythere klothopetasi, Pedicythere lachesisopetasi, Ruggieriella mcmanusi and Xestoleberis oppoae. Taxonomic revisions of several common species were made to reduce taxonomic uncertainty in the literature. This study provides a robust taxonomic baseline for application to palaeoceanographical reconstruction and biodiversity analyses in the deep and intermediate-depth environments of the North Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Aim The assumedly anomalous occurrence of savannas and forest–savanna mosaics in the Gran Sabana – a neotropical region under a climate more suitable for tropical rain forests – has been attributed to a variety of historical, climatic, and anthropogenic factors. This paper describes a previously undocumented shift in vegetation and climate that occurred during the early Holocene, and evaluates its significance for the understanding of the origin of the Gran Sabana vegetation. Location A treeless savanna locality of the Gran Sabana (4°30′–6°45′ N and 60°34′–62°50′ W), in the Venezuelan Guayana of northern South America, at the headwaters of the Caroní river, one of the major tributaries of the Orinoco river. Methods Pollen and charcoal analysis of a previously dated peat section spanning from about the Pleistocene/Holocene boundary until the present. Results Mesothermic cloud forests dominated by Catostemma (Bombacaceae) occupied the site around the Pleistocene/Holocene boundary. During the early Holocene, a progressive but relatively rapid trend towards savanna vegetation occurred, and eventually the former cloud forests were replaced by a treeless savanna. Some time after the establishment of savannas, a marked increase in charcoal particles indicates the occurrence of the first local fires. Main conclusions The occurrence of cloud forests at the Pleistocene/Holocene boundary contradicts the historical hypothesis according to which the Gran Sabana is a relict of the hypothetical widespread savannas that have been assumed to have dominated the region during the last glaciation. The first local fires recorded in the Holocene were on savanna vegetation, which is against the hypothesis of fire as the triggering factor for the establishment of these savannas. Climate change, in the form of global warming and a persistently drier climate, emerges as the most probable cause for the forest–savanna turnover. [ABSTRACT FROM AUTHOR]

This paper reports new dates for mid to late Holocene occupation of the lower Adelaide River in northern Australia. Earth mounds located on the margins of the floodplains provide a series of radiocarbon determinations that suggest continuous settlement from at least 4000 years BP until recently. During that time the floodplains have undergone a dramatic environmental evolution from extensive mangrove swamps in the mid Holocene, through a variable mosaic of estuarine and freshwater conditions c.3000 years ago, to the freshwater floodplains extant since 2000 BP. These results have implications for the chronology of earth mounds elsewhere in northern Australia. [ABSTRACT FROM AUTHOR]

This paper presents a probabilistic method of pollen spectra analysis. The method relies on a pollen taxon characterization using biotic and abiotic plant attribute modes, and their occurrence in a given pollen spectrum at a specific site. This type of analysis can provide an interpretation, which can lead to the reconstruction of the biome and, to an extent, of the abiotic conditions at the site.The analysis has been carried out at the European scale using data provided by the European Pollen Database for about 1000 sites. This dataset contains about 50,000 pollen spectra from the last 21 ka. In these spectra, each pollen taxon has been characterized by a set of 10 chosen attributes. These have been selected with regard to their relevance in biome reconstruction, but also on the basis of available literature. By using the probability of occurrence of each taxon in a given pollen spectrum, it is possible to calculate an affinity index for the spectrum to the attribute considered. To overcome difficulties caused by pollen identification in low diversified pollen spectra, a co-occurrence concept has been used to give more information.The method has been validated on a set of 1327 modern surface samples by comparing the results to the major climatic and environmental variables that control the distribution of the vegetation. A reconstruction exercise on various characteristics of the plants was then carried out on a 6-ka dataset. This confirmed previous studies by showing a strong dominance of deciduous forest over most of Europe, related to a milder climate than at present in the north and a wetter and colder climate than at present in the south. By analysing the change in pollen/seed dispersion strategies and the light requirement, we show that the history of vegetation dynamics in relation to human influences can be assessed using this method.Our results show that the probabilistic method is an objective tool for pollen assemblage analysis. It allows reconstruction of various characteristics of the vegetation at the continental and global scale for periods and sites with significantly different climate conditions. This method can also be used to compare maps of vegetation attributes for the validation of the new generalized dynamic ecosystems models. [ABSTRACT FROM AUTHOR]

The Holocene spread of Picea abies in Fennoscandia is well established from many sites and thus provides an opportunity for detailed study of the dynamics of tree spread and population expansion. Early- and mid-Holocene macrofossil evidence for presence of P. abies in Fennoscandia has questioned traditional interpretations of the timing and direction of its spread. This paper aims to determine when, from where and by which pathways P. abies spread into Fennoscandia. Understanding the character and dynamics of this spread may give insight into the general understanding of Holocene tree spread. The north-western distribution of P. abies in Europe, including Norway, Sweden, Finland, Estonia, Latvia, Lithuania, north-western Russia, parts of Byelorussia and Poland. Holocene pollen diagrams with independent dating control were collected from this region. The timing of the onset of the continuous curve, the timing of the rise of the curve, the first appearance of frequencies of 1%, 3%, 5%, and 10%, as well as timing and the maximum amount of P. abies pollen, was obtained from these pollen diagrams. A GIS analysis was used to display the data and interpolate ages over the area under investigation. Maps are presented showing a clear ESE to WNW trend in the spread of P. abies for all characters interpolated. The timing of the rise of the curve was difficult to use as sites east of the Baltic have slowly rising P. abies frequencies while the western sites often show a rapid rise. The spread of P. abies in Fennoscandia and adjacent areas can be separated into two phases: (i) A rapid early Holocene spread out of Byelorussia and northern Russia at low population density giving rise to small outpost populations, possibly as far west as the Scandes Mountains. (ii) A mid- to late Holocene front-like spread at high population densities moving from east to west into the Baltic Republics and Finland, into northern Scandinavia and then moving south and west towards its present-day distributional limits. [ABSTRACT FROM AUTHOR]

Aim This paper seeks to elucidate the first post-glacial arrival of tree species to high elevations in the Scandes. This enables testing of general theories concerning glacial refugia, immigration routes and palaeoclimate. Location The study site, 1360 m a.s.l., was close to the summit of Mt Åreskutan in the alpine region of the southern Swedish Scandes, 400–500 m above modern tree-limits. Methods Tree megafossils (trunks, roots, cones) were retrieved (and radiocarbon-dated) from the ground surface in the forefields of receding `perennial' snow-patches. This approach allows elevational range-margin reconstructions to be made with an accuracy not possible with any other method. Results and conclusions Megafossils were recovered substantially higher and earlier than previously recorded or inferred for tree growth in this part of Europe. The species were Betula pubescens Ehrh. ssp. tortuosa (Ledeb.) Nyman, Picea abies (L.) Karst. and Pinus sylvestris (L.). The oldest dates obtained are c . 14,000, 11,000 and 11,700 BP for these species, respectively. For the first time, explicit evidence of tree growth in the Late-Glacial (including the Younger Dryas stadial) is demonstrated for central/northern Scandinavia. The swift appearance of boreal tree species at high northern latitudes and altitudes on the western fringe of Scandinavia and near the most extended margin of the Weichselian ice sheet hypothetically suggests that the first immigration of the trees considered here was from the west. Glacial refugia for these species (other plants and animals as well) on the exposed continental shelf areas west and southwest of Norway is hypothesized. By extension, the results fit into a more general pattern, suggesting the presence of boreal and temperate trees quite close to the full glacial (Weichselian) ice margins in central Europe. Thus, the Quaternary forest and landscape history of Europe seems more complex than previously believed. [ABSTRACT FROM AUTHOR]

The desiccation (extreme drying) of rivers has important implications for the broader Earth System. However, the desiccation history and its linkage to climate are rarely known for numerous major river systems, primarily due to difficulties in recognizing desiccation events from available stratigraphic records. Here, using a combination of geochemical techniques (major and rare‐earth element geochemistry, detrital zircon geochronology, and optically stimulated luminescence dating), we demonstrate that the Yellow River, which maintains the highest sediment load on Earth, became desiccated during the Last Glacial Maximum at approximately 20 thousand years ago. This finding implies that transportation of sediments and dissolved constituents to the oceans via the Yellow River may have decreased substantially or ceased during glacials, which would have ramifications for ocean chemistry and biology. Furthermore, our work highlights the importance of desiccated riverbed sediments as potential dust sources during glacial periods, a finding that is different from what is observed today. Plain Language Summary: Understanding the characteristics of major rivers is important for better constraining changes in the Earth System. Based on new geochemical data, we find that during the period dominated by overall drier and colder climate conditions ∼20,000 years ago, water flow in the upper reaches of the Yellow River was reduced to the point that flow effectively ceased downstream of the Hetao Basin. In other words, the Yellow River was no longer a perennial river between the upper and middle‐low reaches until re‐integrating ∼10,000–5,000 years ago. Moreover, we demonstrate that surface processes related to the Yellow River system are substantially different between colder‐drier and warmer‐wetter intervals, at least for the last ∼40 thousand years, and we suggest caution when using modern observations to infer regional environments and geomorphology related to rivers during colder‐drier periods. Key Points: Provenance changes at the outlet of the Hetao Basin indicate the desiccation and re‐integration of the upper Yellow River over the last ∼40 kaPaleo‐lake shorelines and geochemical proxies confirm that the west Hetao Basin contained the terminal lake for the desiccated Yellow RiverClimate‐river feedbacks across glacial‐interglacial cycles have implications for constraining terrestrial‐marine source‐to‐sink processes [ABSTRACT FROM AUTHOR]

Studying the evolution history of the southwest summer monsoon (SSM) throughout geological time, particularly during its strongest period in the Holocene, can improve our understanding of its variation and driving mechanisms, and even help predict future climate changes, due to its significant social and economic implications. Here, we reconstructed the history of chemical weathering intensity since the Last Glacial Maximum (LGM) based on clay mineral proxies [(illite/smectite)/(illite + chlorite) and illite crystallinity] obtained from Qionghai Lake sediments and examined its response to paleoclimate and SSM. Our findings indicate that the intensity of chemical weathering generally aligned with changes in paleoclimate, exhibiting strong chemical weathering intensity during warm and humid climate conditions. In addition, the intensity of chemical weathering basically tracks the evolution of the SSM since the LGM. Our results support the view that the highest SSM intensity occurred during the early‐middle Holocene, followed by gradual weakening during the late Holocene, with Northern Hemisphere summer insolation being the primary driver of the SSM evolution. The variations of the SSM and the corresponding intensity of chemical weathering were also influenced by the cumulative effects of glacier boundary conditions, North Atlantic climate fluctuations, and Intertropical Convergence Zone migrations. Key Points: Clay minerals can effectively reflect regional chemical weathering intensityChemical weathering intensity was following the monsoon variabilityThe strongest southwest summer monsoon occurred in the early‐middle Holocene [ABSTRACT FROM AUTHOR]

Summary Aim The aim of this paper is to describe and interpret early Holocene floras and faunas. Location The floras and faunas come from various localities in North-east Greenland. Methods Sediment samples were wet sieved, and macrofossils picked out and dated by the AMS radiocarbon-dating method. Results Sediments, dated to the first centuries after the last glacial stage came to an abrupt end, contain a macroflora of bryophytes and a few herbs, and we suggest that these plant remains represent a pioneer vegetation entirely without woody plants. The named species of herbs are either confined to the northern parts of Greenland at present, or they become increasingly more important towards the north. Crowberry is the oldest woody plant recovered; it was present at 10.4 cal. ka BP, and it appears to have been common during the early Holocene in East Greenland. Main conclusions We suggest that the majority of the extant flora of vascular plants of East Greenland arrived by long distance dispersal during the Holocene. Some species may also have arrived during the late-glacial, and a few hardy species that are adapted to low summer temperatures may have survived the last glacial stage in nonglaciated areas. Some hardy animals may also have survived, but the majority of the fauna are considered Holocene immigrants. We suggest that migrating birds and storms, perhaps in combination, are under-appreciated dispersal vectors. [ABSTRACT FROM AUTHOR]

SummaryThe concept of biodiversity can operate at several different ecological levels from that of the Global ecosystem to the genetic diversity of a single species. This paper focuses on the beta-type diversity of vegetation communities at the intra and inter-regional scale, using five mid-Holocene (Neolithic) pollen diagrams from eastern Cumbria (c. 500 km2 centred on the Eden valley). The sites were selected in order to include the variation in both soil/rock type and altitude within the study area, ranging from the Eden valley and southern limestone plateau to the foothills and summits of the western edge of the Pennines. The local pollen component which is dominant in these small sites, is used to determine intra-regional vegetation diversity for a time-slice in the Neolithic. Simple statistical methods are used to compare sites and as a measure of intra-regional vegetation-type diversity. This is compared with estimates of the community diversity for the British Isles during the same period. The results suggest that the intra-regional vegetation diversity is comparable to that of Northern England, and it is related to variation in both altitude and soil type. There are some differences, for example the steepness of the western face of the Pennines is probably responsible for a lack of the pine dominated zone, and pedological constraints probably prevented the full development of woodland on the limestone plateau at the south of the study area. The open landscape of the limestone plateau acted as a refuge for late glacial herbaceous taxa prior to their re-expansion into the wider landscape after widespread deforestation and arable cultivation. The results have implications for both the mapping of past vegetation at the national scale and for landscape archaeology. [ABSTRACT FROM AUTHOR]

Three radiocarbon-dated pollen diagrams are presented from Holocene peat and lake deposits in Snowdonia, close to the Late Iron Age/Romano-British ironworking hill-fort of Bryn y Castell, Gwynedd, in upland north Wales. This paper discusses pollen, charcoal and peat-stratigraphic evidence for major local vegetation changes and for the development of the surrounding cultural landscape during the last 10000 radiocarbon yr. Pollen data from one of the sites (BYC 2) provided a vegetational record for most of the Holocene. The early part of the sequence suggests an oligotrophic lake in a landscape that is being colonized b birch-pine woodland; later, mixed deciduous woodland surrounds an infilling lake basin. Dating of peat deposits at two of the sites (BYC, BYC H) indicated that their pollen records commenced between 5500 and 5000 yr BP. By this time, the lake basin was fringed by alder carr. There followed a gradual and then, c. 2700 yr BP, a more abrupt decline in woodland, such that, by the end of the Bronze Age and with the basin largely terrestrialized, the local landscape became dominated by mire vegetation communities, which have persisted to the present. Human activity seems to have been a major factor in the loss of woodland cover. Although there is some circumstantial evidence for earlier phases of human disturbance at BYC 2, human activity becomes increasingly apparent from c. 5000 yr BP. During the mid Holocene, the impact of Neolithic and early- to mid-Bronze Age cultures appears to be characterized by temporary woodland clearances, for arabIe and pastoral agriculture. By c. 2700 yr BP the majority of woodland cover seems to have been permanently removed from the landscape, but as there is scant archaeological evidence for late Bronze Age cultures in this part of Snowdonia, other factors, especially climate change, could be implicated. During the late Holocene, especially during part of the late Iron Age and Romano-British period, remaining local stands of woodland seem to have been exploited for iron smelting, although the overall impact of ironworking was limited. [ABSTRACT FROM AUTHOR]

This paper gives a detailed outline of Swiss vegetation history during the last 18 000 years. For each pollen zone, a map is given showing vegetation development from the late Würmian to the present. A concise historical review of the Swiss pollen analytical research during the last 60 years is presented is followed by some discussion of the central European glacial refugia. Based on a selection of over 100 pollen-analytical]y investigated sites, the development of Swiss vegetation since the late Würmian can be presented as follows: 1. Oldest Dryas. After the Würm maximum the ice network melted back quickly to small mountain glaciers. At some localities, several types of an Artemisia-Chenopodiaceae-Juniperus-Ephedra-Helianthemum-Poaceae steppe/tundra have been recorded, representing an apparent uniformity over the whole Swiss area. 2. Bölling Interstadial. This first, late Würmian, warm phase is characterized by the occurrence of Betula, Hippopha&euml, Juniperus, Ephedra and Salix. 3. Older Dryas. Little evidence for this period has yet been found in Switzerland. 4. Alleröd Interstadial. This marked warm phase led to a typical late Würmian reforestation, with both Betula and Pinus up to about 1200-1600 m above sea level. 5. Younger Dryas. In the whole alpine area there is good evidence for this last, late Würmian climate deterioration, which led to renewed glacier activity and to an alpine timber-line depression of 200 300 m. 6. Preboreal. For the central Alps and the Prealps a wide occurrence of Pinus sylvestris/mugo, P. cembra, Larix and Betula has been recorded, whereas in southern Switzerland the first mixed oak forest developed. 7. Boreal. Corylus and mixed oak forest spread in some cases rapidly over a wide area, chiefly in the Prealps, the Plateau, the Jura and in southern Switzerland. In the high mountains Pinus sylvestris/mugo, P. cembra and Larix still dominated.8. Older Atlantic. In both the Plateau and the Prealps, Corylus and mixed oak forest dominated, whereas in the continental Alps Pinus slvestoris/mugo, P. cembra and Betula grew with some elements of mixed oak forest. In the Grisons the immigration of Picea from east to west has been identified; in the eastern Prealps abies spread. 9. Younger Atlantic. This period is characterized in' a first maximum of' the timber-line extension to an altitude of about 2300 m. The spread of Fagus from west to east is seen on both the montane and subalpine belt, first Abies and later Picea dominated. Picea immigration to the west continued. 10. Subboreal. Until 3000 yr B.P. forest achieved its optimum development with a distribution tip to 2000 in above sea level. In both the Plateau and the Jura the major spread of Fagus took place in this period. Piece;now reached southwestern jura and even the Lake Geneva region. 11 .Subatlantic, This period is characterized by man's influence on the vegetation .According to the evidence of both pollen anal sis and archaeology, the first anthropogenic influences on Swiss vegetation took place between 6000 and 4500 yr B.P. In the anthropogenic timber-line belt secondary forests of Betula, Allunus and Pinus formed. On the southern alpine border, the Romans introduced Castanea, whereas on the Plateau Picea, Abies and Pinus have been planted. [ABSTRACT FROM AUTHOR]