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As the Anthropocene advances, there are few parts of Earth that have not been impacted by human influence. Humans have had a long-sustained interaction with grassy ecosystems, but they are becoming severely impacted by direct and indirect impacts as the Anthropocene advances. Grassy ecosystems are easy to clear and cultivate, poorly protected, and poorly defined due to legacies of colonial narratives that can describe them as deforested, wastelands, or derived. Climate change, land conversion, and the erosion of the processes that have shaped grassy ecosystems for millennia have had cascading and cumulative impacts on grassy ecosystem extent and integrity. We examine how these changes are impacting grassy ecosystems, more specifically, those that fall into ecosystem uncertain space—a climate envelope where vegetation is not at equilibrium with climate and either grassy or forest ecosystems can occur. It is within this space that climate, CO2, and disturbances (fire, herbivores) interact to determine the presence of grassy ecosystems. Changes to any of these components reduce the integrity of grassyecosystems. The loss of these ancient biodiverse ecosystems means loss of an array of ecosystem services fundamental to the lives of more than 1 billion people alongside Earth-system impacts of altered albedo, carbon, and hydrological cycles.

Human activity has fundamentally altered wildfire on Earth, creating serious consequences for human health, global biodiversity, and climate change. However, it remains difficult to predict fire interactions with land use, management, and climate change, representing a serious knowledge gap and vulnerability. We used expert assessment to combine opinions about past and future fire regimes from 98 wildfire researchers. We asked for quantitative and qualitative assessments of the frequency, type, and implications of fire regime change from the beginning of the Holocene through the year 2300. Respondents indicated that direct human activity was already influencing wildfires locally since at least ~12,000 years BP, though natural climate variability remained the dominant driver of fire regime until around 5000 years BP. Responses showed a ten-fold increase in the rate of wildfire regime change during the last 250 years compared with the rest of the Holocene, corresponding first with the intensification and extensification of land use and later with anthropogenic climate change. Looking to the future, fire regimes were predicted to intensify, with increases in fire frequency, severity, and/or size in all biomes except grassland ecosystems. Fire regime showed quite different climate sensitivities across biomes, but the likelihood of fire regime change increased with higher greenhouse gas emission scenarios for all biomes. Biodiversity, carbon storage, and other ecosystem services were predicted to decrease for most biomes under higher emission scenarios. We present recommendations for adaptation and mitigation under emerging fire regimes, concluding that management options are seriously constrained under higher emission scenarios.Competing Interest StatementThe authors have declared no competing interest. Introduction Methods and materials Results and discussion Timing and type of future fire regime change Consequences of fire regime change Our capacity to prevent, control, or adapt to future fire regimes Charting a course in a world of uncertainty Expert assessment application in fire management

Northern peatlands store globally-important amounts of carbon in the form of partly decomposed plant detritus. Drying associated with climate and land-use change may lead to increased fire frequency and severity in peatlands and the rapid loss of carbon to the atmosphere. However, our understanding of the patterns and drivers of peatland burning on an appropriate decadal to millennial timescale relies heavily on individual site-based reconstructions. For the first time, we synthesise peatland macrocharcoal re-cords from across North America, Europe, and Patagonia to reveal regional variation in peatland burning during the Holocene. We used an existing database of proximal sedimentary charcoal to represent regional burning trends in the wider landscape for each region. Long-term trends in peatland burning appear to be largely climate driven, with human activities likely having an increasing influence in the late Holocene. Warmer conditions during the Holocene Thermal Maximum (similar to 9e6 cal. ka BP) were associated with greater peatland burning in North America's Atlantic coast, southern Scandinavia and the Baltics, and Patagonia. Since the Little Ice Age, peatland burning has declined across North America and in some areas of Europe. This decline is mirrored by a decrease in wider landscape burning in some, but not all sub-regions, linked to fire-suppression policies, and landscape fragmentation caused by agricultural expansion. Peatlands demonstrate lower susceptibility to burning than the wider landscape in several instances, probably because of autogenic processes that maintain high levels of near-surface wetness even during drought. Nonetheless, widespread drying and degradation of peatlands, particularly in Europe, has likely increased their vulnerability to burning in recent centuries. Consequently, peatland restoration efforts are important to mitigate the risk of peatland fire under a changing climate. Finally, we make recommendations for future research to improve our understanding of the controls on peatland fires.(c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

This research has been supported by the Leverhulme Trust (grant no. RC-2018-023), the European Research Council (grant no. 694481), the German Research Foundation (grant no. FE-1096/6-1), the Swiss Government Excellence Postdoctoral Scholarships (grant no. FIRECO 2016.0310), the National Science Centre of Poland (grant no. 2015/17/B/ST10/01656), the SCIEX Scholarship Fund (grant no. PSPB-013/2010), and the Estonian Research Council (grant no. MOBJD313)., Sedimentary charcoal records are widely used to reconstruct regional changes in fire regimes through time in the geological past. Existing global compilations are not geographically comprehensive and do not provide consistent metadata for all sites. Furthermore, the age models provided for these records are not harmonised and many are based on older calibrations of the radiocarbon ages. These issues limit the use of existing compilations for research into past fire regimes. Here, we present an expanded database of charcoal records, accompanied by new age models based on recalibration of radiocarbon ages using IntCal20 and Bayesian age-modelling software. We document the structure and contents of the database, the construction of the age models, and the quality control measures applied. We also record the expansion of geographical coverage relative to previous charcoal compilations and the expansion of metadata that can be used to inform analyses. This first version of the Reading Palaeofire Database contains 1676 records (entities) from 1480 sites worldwide. The database (RPDv1b – Harrison et al., 2021) is available at https://doi.org/10.17864/1947.000345., Leverhulme Trust RC-2018-023, European Research Council (ERC) European Commission 694481, German Research Foundation (DFG) FE-1096/6-1, Swiss Government Excellence Postdoctoral Scholarships FIRECO 2016.0310, SCIEX Scholarship Fund PSPB-013/2010, Estonian Research Council MOBJD313

Quantitative reconstructions of past land cover are necessary to determine the processes involved in climate-human-land-cover interactions. We present the first temporally continuous and most spatially extensive pollen-based land-cover reconstruction for Europe over the Holocene (last 11g€¯700g€¯calg€¯yrg€¯BP). We describe how vegetation cover has been quantified from pollen records at a 11 spatial scale using the "Regional Estimates of VEgetation Abundance from Large Sites"(REVEALS) model. REVEALS calculates estimates of past regional vegetation cover in proportions or percentages. REVEALS has been applied to 1128 pollen records across Europe and part of the eastern Mediterranean-Black Sea-Caspian corridor (30-75° N, 25° W-50° E) to reconstruct the percentage cover of 31 plant taxa assigned to 12 plant functional types (PFTs) and 3 land-cover types (LCTs). A new synthesis of relative pollen productivities (RPPs) for European plant taxa was performed for this reconstruction. It includes multiple RPP values (≥2 values) for 39 taxa and single values for 15 taxa (total of 54 taxa). To illustrate this, we present distribution maps for five taxa (Calluna vulgaris, Cerealia type (t)., Picea abies, deciduous Quercus t. and evergreen Quercus t.) and three land-cover types (open land, OL; evergreen trees, ETs; and summer-green trees, STs) for eight selected time windows. The reliability of the REVEALS reconstructions and issues related to the interpretation of the results in terms of landscape openness and human-induced vegetation change are discussed. This is followed by a review of the current use of this reconstruction and its future potential utility and development. REVEALS data quality are primarily determined by pollen count data (pollen count and sample, pollen identification, and chronology) and site type and number (lake or bog, large or small, one site vs. multiple sites) used for REVEALS analysis (for each grid cell). A large number of sites with high-quality pollen count data will produce more reliable land-cover estimates with lower standard errors compared to a low number of sites with lower-quality pollen count data. The REVEALS data presented here can be downloaded from https://doi.org/10.1594/PANGAEA.937075 (Fyfe et al., 2022). © 2022 Esther Githumbi et al.

Wildfire is the most common disturbance type in boreal forests and can trigger significant changes in forest composition. Waterlogging in peatlands determines the degree of tree cover and the depth of the burning horizon associated with wildfires. However, interactions between peatland moisture, vegetation composition and flammability, and fire regime in forested peatland in Eurasia remain largely unexplored, despite their huge extent in boreal regions. To address this knowledge gap, we reconstructed the Holocene fire regime, vegetation composition, and peatland hydrology at two sites in Western Siberia near Tomsk Oblast, Russia. The palaeoecological records originate from forested peatland areas in predominantly light taiga (Pinus-Betula) with the increase in dark taiga communities (Pinus sibirica, Picea obovata, Abies sibirica) towards the east. We found that the past water level fluctuated between 8 and 30 cm below the peat surface. Wet peatland conditions promoted broadleaf trees (Betula), whereas dry peatland conditions favoured conifers and a greater forest density (dark-to-light-taiga ratio). The frequency and severity of fire increased with a declining water table that enhanced fuel dryness and flammability and at an intermediate forest density. We found that the probability of intensification in fire severity increased when the water level declined below 20 cm suggesting a tipping point in peatland hydrology at which wildfire regime intensifies. On a Holocene scale, we found two scenarios of moisture-vegetation-fire interactions. In the first, severe fires were recorded between 7.5 and 4.5 ka BP with lower water levels and an increased proportion of dark taiga and fire avoiders (Pinus sibirica at Rybanya and Abies sibirica at Ulukh Chayakh) mixed into the dominantly light taiga and fire-resister community of Pinus sylvestris. The second occurred over the last 1.5 ka and was associated with fluctuating water tables, a declining abundance of fire avoiders, and an expansion of fire invaders (Betula). These findings suggest that frequent high-severity fires can lead to compositional and structural changes in forests when trees fail to reach reproductive maturity between fire events or where extensive forest gaps limit seed dispersal. This study also shows prolonged periods of synchronous fire activity across the sites, particularly during the early to mid-Holocene, suggesting a regional imprint of centennial to millennial-scale Holocene climate variability on wildfire activity. Increasing human presence in the region of the Ulukh-Chayakh Mire near Teguldet over the last four centuries drastically enhanced ignitions compared to natural background levels. Frequent warm and dry spells predicted for the future in Siberia by climate change scenarios will enhance peatland drying and may convey a competitive advantage to conifer taxa. However, dry conditions, particularly a water table decline below the threshold of 20 cm, will probably exacerbate the frequency and severity of wildfire, disrupt conifers’ successional pathway and accelerate shifts towards more fire-adapted broadleaf tree cover. Furthermore, climate-disturbance-fire feedbacks will accelerate changes in the carbon balance of forested boreal peatlands and affect their overall future resilience to climate change.

Sedimentary charcoal records are widely used to reconstruct regional changes in fire regimes through time in the geological past. Existing global compilations are not geographically comprehensive and do not provide consistent metadata for all sites. Furthermore, the age models provided for these records are not harmonised and many are based on older calibrations of the radiocarbon ages. These issues limit the use of existing compilations for research into past fire regimes. Here, we present an expanded database of charcoal records, accompanied by new age models based on recalibration of radiocarbon ages using INTCAL2020 and Bayesian age-modelling software. We document the structure and contents of the database, the construction of the age models, and the quality control measures applied. We also record the expansion of geographical coverage relative to previous charcoal compilations and the expansion of metadata that can be used to inform analyses. This first version of the Reading Palaeofire Database contains 1681 records (entities) from 1477 sites worldwide. The database (DOI: 10.17864/1947.319) is available from https://researchdata.reading.ac.uk/id/eprint/319.

Grasslands are globally extensive, but the processes governing their ecology and evolution remain unclear. The role of fire for the expansion of ancestral C3 grasslands is particularly poorly understood. Here we present the first biomass combustion record based on late Miocene to Pleistocene (~10–1.9 Ma) charcoal morphologies (grass, herbs, wood) from the Black Sea, and test the extent of fire events and their role in the rise of open grassy habitats in eastern Eurasia. We show that a mixed regime of surface and crown fires under progressively colder and, at times, drier climates from the late Miocene to Pliocene (8.5–4.6 Ma) accelerated the forest to open woodland transition and sustained a more flammable ecosystem. A tipping point in the fire regime occurred at 4.3 Ma (mid-Pliocene), when increasingly cold and dry conditions led to the dominance of grasslands, and surface, litter fires of low intensity. We provide alternative mechanisms of C3 plant evolution by highlighting that fire has been a significant ecological agent for Eurasian grasslands. This study opens a new direction of research into grassland evolutionary histories that can be tested with fossil records of fire alongside climate and vegetation as well as with dynamic vegetation modells.

Forest steppes are dynamic ecosystems, highly susceptible to changes in climate and land use. Here we examine the Holocene history of the European forest steppe ecotone in the Lower Danube Plain to better understand its sensitivity to climate fluctuations and human impact, and the timing of its transition into a cultural forest steppe. We used multi-proxy analyses (pollen, n-alkane, coprophilous fungi, charcoal, and geochemistry) of a 6000-year sequence from Lake Oltina (SE Romania), combined with a REVEALS model of quantitative vegetation cover. We found the greatest tree cover, composed of xerothermic (Carpinus orientalis and Quercus) and temperate (Carpinus betulus, Tilia, Ulmus and Fraxinus) tree taxa between 6000 and 2500 cal yr BP. Maximum tree cover (~ 50 %) occurred between 4200 and 2500 cal yr BP at a time of wetter climatic conditions. Compared to other European forest steppe areas, the dominance of Carpinus orientalis represents the most distinct feature of the woodland's composition during that time. Forest loss was under way by 2500 yr BP (Iron Age) with REVEALS estimates indicating a fall to ~ 20 % tree cover from the mid-Holocene forest maximum linked to clearance for agriculture, while climate conditions remained wet. Biomass burning increased markedly at 2500 cal yr BP suggesting that fire was regularly used as a management tool until 1000 cal yr BP when woody vegetation became scarce. A sparse tree cover, with only weak signs of forest recovery, then became a permanent characteristic of the Lower Danube Plain, highlighting recurring anthropogenic pressure. The timing of anthropogenic ecosystem transformation here (2500 cal yr BP) was in between that in central eastern (between 3700 and 3000 cal yr BP) and eastern (after 2000 cal yr BP) Europe. Our study is the first quantitative land cover estimate at the forest steppe ecotone in south eastern Europe spanning 6000 years and provides critical empirical evidence that the present-day forest steppe/woodlands reflects the potential natural vegetation in this region under current climate conditions. This study also highlights the potential of n-alkane indices for vegetation reconstruction, particularly in dry regions where pollen is poorly preserved.

The analysis of charcoal fragments in peat and lake sediments is the most widely used approach to reconstruct past biomass burning. With a few exceptions, this method typically relies on the quantification of the total charcoal content of the sediment. To enhance charcoal analyses for the reconstruction of past fire regimes, and to make the method more relevant to studies of both plant evolution and fire management, more information must be extracted from charcoal particles. Here, I burned in the laboratory seven fuel types comprising 17 species from boreal Siberia, and build on published schemes to develop morphometric and finer diagnostic classifications of the experimentally charred particles. As most of the species used in this study are common to Northern Hemisphere forests and peatlands, these results can be directly applicable over a broad geographical scale. Results show that the effect of temperature on charcoal production is fuel dependent. Graminoids and Sphagnum, and wood (trunk) lose the most mass at low burn temperatures, whereas heathland shrub leaves, brown moss, and ferns retain the most mass at high burn temperatures. In contrast to the wood of trunk, the wood of twigs retained their mass at intermediate temperature. This suggests that species with low mass retention at hotter burning temperatures might be underrepresented in the fossil charcoal record. Charred particle aspect ratio (L / W) appeared to be the strongest indicator of the fuel type burnt. Graminoid charcoals are more elongate than those of all other fuel types, leaf charcoals are the shortest and bulkiest, and twig and wood charcoals are intermediate. Finer diagnostic features were the most useful in distinguishing between wood, graminoid, and leaf particles, but further distinctions within these fuel types are difficult. High-aspect-ratio particles dominated by graminoid and Sphagnum morphologies are robust indicators of cooler surface fires. Contrastingly, abundant wood and leaf morphologies and low-aspect-ratio particles likely indicate higher-temperature fires. However, the overlapping morphologies of leaves and wood from trees and shrubs make it hard to distinguish between high-intensity surface fires combusting living shrubs and dead wood and leaves or high-intensity crown fires combusting living trees. Despite these limitations, the combined use of charred-particle aspect ratios and fuel morphotypes can aid in more robustly interpreting changes in fuel source and fire type, thereby substantially refining histories of past wildfires. Further fields of investigation to improve the interpretation of the fossil charcoal records will require: i) More in-depth knowledge of plant anatomy for a better determination of fuel sources; ii) Relate the proportion of particular charcoal morphotypes to the quantity of biomass; iii) Link the chemical composition of fuels, combustion temperature, and charcoal production. The advanced use of image-recognition software to collect data on other charcoal features could also aid in extracting fire temperatures as well as a change in particles morphology and morphometry during particles transportation.

A comprehensive database of paleoclimate records is needed to place recent warming into the longer-term context of natural climate variability. We present a global compilation of quality-controlled, published, temperature-sensitive proxy records extending back 12,000 years through the Holocene. Data were compiled from 679 sites where time series cover at least 4000 years, are resolved at sub-millennial scale (median spacing of 400 years or finer) and have at least one age control point every 3000 years, with cut-off values slackened in data-sparse regions. The data derive from lake sediment (51%), marine sediment (31%), peat (11%), glacier ice (3%), and other natural archives. The database contains 1319 records, including 157 from the Southern Hemisphere. The multi-proxy database comprises paleotemperature time series based on ecological assemblages, as well as biophysical and geochemical indicators that reflect mean annual or seasonal temperatures, as encoded in the database. This database can be used to reconstruct the spatiotemporal evolution of Holocene temperature at global to regional scales, and is publicly available in Linked Paleo Data (LiPD) format. Fil: Kaufman, Darrell. Northern Arizona University.; Estados Unidos Fil: McKay, Nicholas. Northern Arizona University.; Estados Unidos Fil: Routson, Cody. Northern Arizona University.; Estados Unidos Fil: Erb, Michael. Northern Arizona University.; Estados Unidos Fil: Davis, Basil. University Of Lausanne; Suiza Fil: Heiri, Oliver. University Of Basel; Suiza Fil: Jaccard, Samuel. University Of Bern; Suiza Fil: Tierney, Jessica. University of Arizona; Estados Unidos Fil: Dätwyler, Christoph. University Of Bern; Suiza Fil: Axford, Yarrow. Northwestern University; Estados Unidos Fil: Brussel, Thomas. University of Utah; Estados Unidos Fil: Cartapanis, Olivier. University Of Bern; Suiza Fil: Chase, Brian. Universite de Montpellier; Francia Fil: Dawson, Andria. Mount Royal University; Canadá Fil: de Vernal, Anne. Université du Québec a Montreal; Canadá Fil: Engels, Stefan. University of London; Reino Unido Fil: Jonkers, Lukas. University Of Bremen; Alemania Fil: Marsicek, Jeremiah. University of Wisconsin-Madison; Estados Unidos Fil: Moffa Sánchez, Paola. University of Durham; Reino Unido Fil: Morrill, Carrie. University of Colorado; Estados Unidos Fil: Orsi, Anais. Université Paris-Saclay; Francia Fil: Rehfeld, Kira. Heidelberg University; Alemania Fil: Saunders, Krystyna. Australian Nuclear Science And Technology Organisation; Australia Fil: Sommer, Philipp. University Of Lausanne; Suiza Fil: Thomas, Elizabeth. University At Buffalo; Estados Unidos Fil: Tonello, Marcela Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Tóth, Mónika. Balaton Limnological Institute; Hungría Fil: Vachula, Richard. Brown University; Estados Unidos Fil: Andreev, Andrei. Alfred Wegener Institut Helmholtz Centre for Polar and Marine Research; Alemania Fil: Bertrand, Sebastien. Ghent University; Bélgica Fil: Massaferro, Julieta. Administración de Parques Nacionales. Parque Nacional "Nahuel Huapi"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

A comprehensive database of paleoclimate records is needed to place recent warming into the longer-term context of natural climate variability. We present a global compilation of quality-controlled, published, temperature-sensitive proxy records extending back 12,000 years through the Holocene. Data were compiled from 679 sites where time series cover at least 4000 years, are resolved at sub-millennial scale (median spacing of 400 years or finer) and have at least one age control point every 3000 years, with cut-off values slackened in data-sparse regions. The data derive from lake sediment (51%), marine sediment (31%), peat (11%), glacier ice (3%), and other natural archives. The database contains 1319 records, including 157 from the Southern Hemisphere. The multi-proxy database comprises paleotemperature time series based on ecological assemblages, as well as biophysical and geochemical indicators that reflect mean annual or seasonal temperatures, as encoded in the database. This database can be used to reconstruct the spatiotemporal evolution of Holocene temperature at global to regional scales, and is publicly available in Linked Paleo Data (LiPD) format., Measurement(s)climateTechnology Type(s)digital curationFactor Type(s)temporal interval • geographic location • proxy typeSample Characteristic - Environmentclimate systemSample Characteristic - LocationEarth (planet) Machine-accessible metadata file describing the reported data: https://www.ncdc.noaa.gov/paleo/study/27330

Peatlands cover 3% of the land, occur in 169 countries, and have—by sequestering 600 Gt of carbon—cooled the global climate by 0.6 °C. After a general review about peatlands worldwide, this paper describes the importance of the Great Vasyugan Mire and presents suggestions about its protection and future research. The World’s largest peatland, the Great Vasyugan Mire in West-Siberia, forms the border between the Taiga and the Forest-Steppe biomes and harbours rare species and mire types and globally unique self-organizing patterns. Current oil and gas exploitation may arguably be largely phased out by 2050, which will pave the way for a stronger focus on the mire’s role in buffering climate change, maintaining ecosystem diversity, and providing other ecosystem services. Relevant new research lines will benefit from the extensive data sets that earlier studies have gathered for other purposes. Its globally unique character as the ‘largest life form on land’ qualifies the Great Vasyugan Mire in its entirety to be designated as a UNESCO World Heritage Site and a Ramsar Wetland of International Importance.

Over the past few decades, mean summer temperatures within the Carpathian Mountains have increased by as much as 2 °C leading to a projected increased forest fire risk. Currently, there are no paleofire records from the Western Carpathians that provide the long-term range of natural variability to contextualise the response of upper-montane forests to future environmental change and disturbance regimes. We present the first high-resolution Holocene fire history record from the upper-montane ecotone from the High Tatra Mountains, Slovakia, as well as provide a regional synthesis of pan-Carpathian drivers of biomass burning in upper-montane forests. Our results illustrate that forest composition and density both greatly influence biomass burning, creating two different climate-fuel feedbacks. First, warmer conditions in the early Holocene, coupled with generally higher abundances of Pinus sp., either P. cembra and/or P. mugo/sylvestris, created a positive climate-fuel relationship that resulted in higher amounts of biomass burning. Second, cooler and wetter late Holocene conditions led to denser Picea abies upper-montane forests, creating a negative climate-fuel feedback that reduced biomass burning in upper-montane forests across the Carpathians. Given that warmer and drier conditions are expected across the entire Carpathian region in the future, our results illustrate how future climate change could potentially create a positive climate-fuel relationship within upper-montane forests dominated by Picea abies and Pinus cembra and/or P. mugo/sylvestris.

The Eurasian (née European) Modern Pollen Database (EMPD) was established in 2013 to provide a public database of high-quality modern pollen surface samples to help support studies of past climate, land cover, and land use using fossil pollen. The EMPD is part of, and complementary to, the European Pollen Database (EPD) which contains data on fossil pollen found in Late Quaternary sedimentary archives throughout the Eurasian region. The EPD is in turn part of the rapidly growing Neotoma database, which is now the primary home for global palaeoecological data. This paper describes version 2 of the EMPD in which the number of samples held in the database has been increased by 60% from 4826 to 8134. Much of the improvement in data coverage has come from northern Asia, and the database has consequently been renamed the Eurasian Modern Pollen Database to reflect this geographical enlargement. The EMPD can be viewed online using a dedicated map-based viewer at https://empd2.github.io and downloaded in a variety of file formats at https: //doi.pangaea.de/10.1594/PANGAEA.909130 (Chevalier et al., 2019)., Swiss National Science Foundation (SNSF) 200021_169598, University of Lausanne

Worldwide accelerated forest loss and the associated environmental impacts are important environmental concerns. In this study we integrate evidence from historical maps and a Landsat-derived time series of catchment scale forest cover changes with a multi-proxy, palaeolimnological reconstruction spanning the last 150 years from Red Lake (Eastern Carpathians, Romania) to better understand the impact of long-term forest changes on catchment erosion and sediment accumulation. We are able to consider two time windows. Firstly, we show that during the traditional (1840–1948) and socialist (1948–1989) periods, catchment changes and sediment responses, as reflected in the sediment accumulation rate, detrital input and grain size were moderate and likely reflect the combined result of known periods of excessive precipitation and local-scale forest disturbances. Secondly, and in contrast, rapid responses in catchment-scale geomorphological processes to forest loss are evident during the post-socialist land use period (1987-2010). We found that the first land restitution period (1987-1999) and the first part of the second land restitution period (2000-2002) had a greater impact on forest loss and subsequent catchment processes with sediment accumulation rates increasing from 0.5 cm/yr-1 to 1.2 cm/yr-1. Finally, environmental impacts of forest changes were strongly dependent on the size of the area deforested, its location within the catchment, susceptibility to erosion and geomorphological thresholds. In a region noted for accelerated recent forest loss, our study highlights the potential of combining historical maps, satellite images and sediment proxies for documenting such changes and highlights the need for more strategic and sustainable environmental management planning.

High-resolution plant macrofossil records were examined alongside pollen, micro- and macro-charcoal, and testate amoeba data to elucidate the dynamics of two permafrost peatlands in the northern foothills of the Brooks Range, Alaskan Arctic. The vegetation dynamics of these two peatlands were driven by autogenic processes reflecting the development trajectory of the peatlands towards ombrotrophic status, and allogenic climate change. We observe an increase in shrub pollen and macrofossils (e.g. Ericaceae, Betula nana) during two Late Holocene warm episodes and in recent decades. Pollen data suggest that regional forest cover also responded to temperature increase since ca. 1950 CE. An increase of Picea pollen (up to 13%) in the upper part of peat profile is probably associated with long distance pollen transport from populations of Picea mariana and Picea glauca located at the southern foothills of the Brooks Range. Relatively small amount of micro- and macrocharcoal in the two profiles indicates little fire activity around the sampling sites over the last ca. 2000 years, which is in agreement with regional findings. The lack of surface and groundwater influence under prolonged warmer/drier condition can allow Sphagnum to expand in Arctic peatlands. Cold climatic conditions might have been detrimental to Sphagnum populations, that were replaced by Carex spp. and other vascular plants owing to wetter conditions in the peatland.

As natural and anthropogenic ecosystems are dependent on the local water availability, understanding past changes in hydroclimate represents a priority in research concerning past climate variability. Here, we used testate amoebae (TA) and chironomid analysis on a radiocarbon dated complex of small pond and peat bog sediment profiles from an ombrotrophic bog (Taul Muced, northern Carpathians, Romania) to quantitatively determine major hydrological changes and July air temperature over the last 7500 years. Wet mire surface conditions with a pH between 2.3 and 4.5 were inferred for the periods 4500–2700 and 1300–400 cal yr BP by the occurrence of Archerella flavum , Amphitrema wrightianum and Hyalosphenia papilio . Dry phases in mire surface conditions and a pH between 2.5 and 5 were inferred for 7550–4500, 2750–1300 and 0 cal yr BP–present by the dominance of Nebela militaris , Difflugia pulex and Phryganella acropodia . The quantitative reconstruction of mean July temperature based on the chironomid communities suggests low summer temperatures for the periods 6550–5600, 4500–3150 and 1550–600 cal yr BP, while periods of slightly higher summer temperatures were observed for 5600–4500, 3150–1550 and 100 cal yr BP–present. There is a generally good agreement between drier phases of the peat surface conditions with higher July temperature, suggesting that temperature may have been a controlling factor for water table fluctuation. Our quantitative reconstructions, among the first for central eastern Europe, show a relatively good agreement with other palaeohydrological studies from central eastern Europe, but contrast with others estimates from north-west Europe. Another important aspect of our study is that it provides valuable information on changes in local hydrology and the potential effect of the mean summer temperature over these changes.

Here, for the first time in SE Poland, we document the long-term development of a rich fen and assess its sensitivity to climate change and human impacts over the last ca. 3500 years. Our results are based on a high-resolution, continuous plant macrofossil remains, mollusc and pollen record, complemented by geochemical, mineral magnetic and physical characterisation, and radiocarbon dating from Bagno Serebryskie rich fen located in SE Poland. Based on the palaeoecological data we distinguished five stages of wet habitat conditions: 5000–3300, 2800–2150, 1600–1100, 750–230, 150–10 cal yr BP and five dry periods at ca. 3300–2800, 2150–1600, 1100–750, 230–150, 10 to − 64 cal yr BP. The pollen and geochemistry records, particularly Pb, show that the first human activity in the study area occurred ca. 3200 cal yr BP and increased markedly from 500 cal yr BP affecting local plant development including the population size of Cladium mariscus. Our study has shown that despite human impact (drainage, fire), Bagno Serebryskie peatland has hosted rare, presently protected species, such as Cladium mariscus for hundreds of years. We conclude that, in common with ombrotrophic bogs, rich fen ecosystems can provide a reliable source of palaeoclimatic and palaeohydrological data. Our study also shows that a large peatland (376 ha) can be as sensitive a palaeohydrological archive as smaller mires.

Climate warming and human impacts are thought to be causing peatlands to dry,\ud potentially converting them from sinks to sources of carbon. However, it is unclear\ud whether the hydrological status of peatlands has moved beyond their natural envelope.\ud Here we show that European peatlands have undergone substantial, widespread drying\ud during the last ~300 years. We analyse testate amoeba-derived hydrological\ud reconstructions from 31 peatlands across Britain, Ireland, Scandinavia and continental\ud Europe to examine changes in peatland surface wetness during the last 2000 years.\ud 60% of our study sites were drier during the period CE 1800-2000 than they have been\ud for the last 600 years; 40% of sites were drier than they have been for 1000 years; and\ud 24% of sites were drier than they have been for 2000 years. This marked recent\ud transition in the hydrology of European peatlands is concurrent with compound\ud pressures including climatic drying, warming and direct human impacts on peatlands,\ud although these factors vary between regions and individual sites. Our results suggest\ud that the wetness of many European peatlands may now be moving away from natural\ud baselines. Our findings highlight the need for effective management and restoration of\ud European peatlands.

Wildfire occurrence is influenced by climate, vegetation and human activities. A key challenge for understanding fire-climate-vegetation interactions is to quantify the effect vegetation has in mediating fire regime. Here, we explore the relative importance of Holocene land cover and dominant functional forest type, and climate dynamics on biomass burned in temperate and boreo-nemoral regions of Central and Eastern Europe over the past 12 ka BP years. We used an extensive data set of Holocene pollen and sedimentary charcoal records, in combination with climate simulations and novel statistical modelling. Biomass burned was highest during the early Holocene and lowest during the mid Holocene in all three ecoregions, but diverged more markedly over the past 3–4 ka BP. Although the climate was an important driver of fire hazard during the warm and dry early Holocene, tree cover was consistently the strongest predictor of past biomass burning. In temperate forests, biomass burned was high at ~ 45 % tree cover and decreased strongly towards 60 % tree cover. In needleleaf dominated forests, biomass burned was highest at ~ 60–65 % tree cover and abruptly declined at > 65 % tree cover. Biomass burned also increased when arable lands and grasslands reached ~ 15–20 %, although this relationship was highly dynamic depending on land use intensity throughout ignition and fuel type and availability. Our observations cover the full range of Holocene climate variability and land cover changes and illustrates that percentages of land cover is a key predictor of the probability of fire occurrence over timescales of centuries to millennia. We suggest that long-term fire risk may be effectively reduced through land cover management, given that land cover has controlled fire regimes under the dynamic climates of the Holocene.

Fire is a natural component of global biogeochemical cycles and closely related to changes in human land use. Whereas climate-fuel relationships seem to drive both global and subcontinental fire regimes, human-induced fires are prominent mainly on a local scale. Furthermore, the basic assumption that relates humans and fire regimes in terms of population densities, suggesting that few human-induced fires should occur in periods and areas of low population density, is currently debated. Here, we analyze human-fire relationships throughout the Holocene and discuss how and to what extent human-driven fires affected the landscape transformation in the Central European Lowlands (CEL). We present sedimentary charcoal composites on three spatial scales and compare them with climate model output and land cover reconstructions from pollen records. Our findings indicate that widespread natural fires only occurred during the early Holocene. Natural conditions (climate and vegetation) limited the extent of wildfires beginning 8500 cal. BP, and diverging subregional charcoal composites suggest that Mesolithic hunter-gatherers maintained a culturally diverse use of fire. Divergence in regional charcoal composites marks the spread of sedentary cultures in the western and eastern CEL. The intensification of human land use during the last millennium drove an increase in fire activity to early-Holocene levels across the CEL. Hence, humans have significantly affected natural fire regimes beyond the local scale – even in periods of low population densities – depending on diverse cultural land-use strategies. We find that humans have strongly affected land-cover- and biogeochemical cycles since Mesolithic times.

Traditional farming landscapes in the temperate zone that have persisted for millennia can be exceptionally species-rich and are therefore key conservation targets. In contrast to Europe’s West, Eastern Europe harbours widespread traditional farming landscapes, but drastic socio-economic and political changes in the twentieth century are likely to have impacted these landscapes profoundly. We reconstructed long-term land-use/cover and biodiversity changes over the last 150 years in a traditional farming landscape of outstanding species diversity in Transylvania. We used the Regional Estimates of Vegetation Abundance from Large Sites model applied to a pollen record from the Transylvanian Plain and a suite of historical and satellite-based maps. We documented widespread changes in the extent and location of grassland and cropland, a loss of wood pastures as well as a gradual increase in forest extent. Land management in the socialist period (1947–1989) led to grassland expansion, but grassland diversity decreased due to intensive production. Land-use intensity has declined since the collapse of socialism in 1989, resulting in widespread cropland abandonment and conversion to grassland. However, these trends may be temporary due to both ongoing woody encroachment as well as grassland management intensification in productive areas. Remarkably, only 8% of all grasslands existed throughout the entire time period (1860–2010), highlighting the importance of land-use history when identifying target areas for conservation, given that old-growth grasslands are most valuable in terms of biodiversity. Combining datasets from different disciplines can yield important additional insights into dynamic landscape and biodiversity changes, informing conservation actions to maintain these species-rich landscapes in the longer term.

We present the paleoecological development of a rich fen located in the dune area on the SE Baltic coast, during the last 7500 years. The Apsuciems Mire hosts rare and endangered plant communities in Europe, such as Schoenus ferrugineus and Cladium mariscus. Analysis at high-resolution of plant macroremains in two peat cores was carried out to reconstruct local vegetation succession and fluctuations in moisture availability on the peatland, while a pollen record was developed to reconstruct plant succession, moisture variability and human activity at the regional scale. Based on the presence or the absence of macroremains of plants that occur in wet habitat e.g. Cladium mariscus, Schoenoplectus tabernaemontani, Alisma plantago-aquatica and Botrycoccocus we distinguished four wet periods ca. 6000, 2000, 1750–1550, 1200–150 cal yr. BP and four dry periods (ca. 7000, 4600–4200, 1800–1750, 1550–1200 cal yr. BP) in the peatland’s development. A water level increase at 1200 cal yr. BP triggered the development of plant communities containing Chara sp., Schoenoplectus tabernaemontani, then Cladium mariscus. Our study shows a link between climate change at the regional scale and vegetation development in Apsuciems Mire. We showed that changes in vegetation structure during last 150 years was caused by drainage and human activity.

We present a high-resolution, continuous plant macrofossil remains record complemented by a pollen sequence from Taul Muced bog, in the Eastern Carpathian Mountains (Romania). The record spans the last 9000 years and we test whether peatland development in the Eastern Carpathians is linked to climate change or to autogenic succession. We find that Sphagnum magellanicum was the dominant peat-forming species for ca. 8000 years but we also identify ten phases of increased representation of Eriophorum vaginatum at approximately 8100, 7550, 6850, 6650, 5900, 4650, 3150, 1950, 1450, and 750 cal yr BP. Visual inspection and wavelet analysis show that the episodic increases in the relative abundances of Eriophorum vaginatum were simultaneous with decreased abundances of Sphagnum magellanicum and Sphagnum angustifolium. Comparison with published palaeoclimatic records in this region suggests that these cyclical successions of S. magellanicum and E. vaginatum appear to be primarily a result of climate changes, with E. vaginatum developing mainly during dry phases and S. magellanicum during wetter periods. We therefore suggest that the development of this peatland was largely influenced by changing climatic conditions, although the role of autogenic plant succession cannot be excluded. Our results show the value of ombrotrophic peat deposits as archives of past climate change.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Worldwide reforestation has been recommended as a landscape restoration strategy to mitigate climate change in areas where the climate can sustain forest. This approach may threaten grassland ecosystems of unique biodiversity as such policies are based on the false assumption that most grasslands are man-made. Here, we use multiple lines of evidence (palaeoecological, pedological, phylogenetic, palaeontological) from Central Eastern Europe and show that various types of grasslands have persisted in this area throughout the postglacial i.e., the past 11,700 years. A warm and dry climate, frequent fires, herbivore pressure and early Neolithic settlements kept forests open until widespread forest clearance beginning 4000 to 3000 years ago. Closed forest cover has been the exception for the last two million years. This long-term persistence has likely contributed to the high biodiversity of these grasslands. Consequently, we call for a more cautious prioritisation of the protection of what may be erroneously considered natural, i.e. forests, by many environmental specialists and managers. Instead we provide a new framework for a better understanding of the evolution and persistence of different grassland types and their biodiversity, so that grasslands can be better understood, valued and conserved.

International audience

Climate changes and anthropogenic activities are projected to have a significant impact on mountain environments. This is because of their ecosystems’ sensitivity and increased response to the extreme weather events and natural catastrophes (Beniston, 2000). The modification of climatic conditions can therefore impact heavily on mountain ecosystems. Furthermore, human impact has been shown to modify environmental response to climatic stressors (Beniston, 2003; Jones & Mann, 2004). This holds particularly true because mountain regions are usually at the border of conflicting interests between economic development and environmental conservation (IPCC, 1996). Deciphering the relation between local mountain environment, climate variability and human components therefore becomes of great importance for both regional climate study and local socio-economies.

Extensive proxy data and modeling suggest that the environmental response to climate forcing varied both spatially and temporarily even during the current interglacial (Davis et al., 2003; Davis and Brewer, 2009). The drivers of these short-term shifts in climate are of multiple origins, ranging from solar irradiance, periodic shifts in the regional expression of atmospheric circulation(e.g., NAO phases) to the episodic cold-water forcing of North Atlantic surface waters. Recently Magny et al. (2013) provided a comprehensive overview of regional climate change during the Holocene and its reflection in local hydrological data and water levels. Although these studiessuggest a degree of regionalism in the climate signal, which might be expected, the most intriguing hypothesis is the so-called seesaw gradient, expressed as latitudinal and longitudinal differences in climate over relatively short distances (Davis et al., 2003; Davis and Brewer, 2009).In central-eastern Europe it is likely that the distribution of mountain ranges contributed even further to this climate fragmentation, therefore a regional scale perspective of the temporal development of climatic conditions and phase-relationships requires an increasing spatial resolution in proxy record (Dragusin et al., 2014)

An understanding of contemporary and likely future biodiversity requires knowledge of how past human societies have shaped diversity patterns. Here, we use long-term pollen data sets extending from lowlands to subalpine environment in the Carpathian region (Romania) with the aim of exploring the relationship between landscape openness, anthropogenic disturbance, elevation and vegetation richness over the Holocene. We found that landscape openness represents a significant driver of pollen richness: The more open sites from mid (440–750 m) and high elevations (1550–1850 m) showed on average greater diversity than more forested upland sites (1050–1360 m). For the first time, our results show pollen richness patterns along elevation gradients that remain constant over the Holocene. Although significant only over the last 3000 cal. yr BP, these elevational patterns become accentuated with stronger evidence of anthropogenic impact. We also found a strong link between diversity change and major land use strategies of prehistoric societies, demonstrating the potential of pollen richness to be used as a tool to depict the ecological impact of human disturbance on diversity. Most distinct episodes of enhanced floristic richness are evident during the Roman Period (2000 cal. yr BP), and over the last 500 cal. yr BP. Recent anthropogenic activity negatively impacted diversity in mountainous areas mainly through plantations; the lack of sites in agriculture landscapes however limits our inference for this type of setting. The maintenance of habitat diversity is key to maintaining high levels of diversity. While there is temporal consistency in the diversity pattern in records from similar climate and vegetation settings, comparison of diversity from different vegetation assemblages and levels landscapes openness should be interpreted cautiously. ispartof: The Holocene vol:23 issue:6 pages:869-881 status: published

Romania has for a long time been lacking good palaeoenvironmental records, particularly for the Late Quaternary. A chronological framework had been nearly absent and the vegetation development had been reconstructed entirely from pollen data. Data sets from this part of Europe are important for assessing the spatial variability of past vegetation and climatic changes and to reconstruct tree migration routes at the end of the last glacial period. New palaeobotanical evidence has enabled us to address this gap and to provide a more comprehensive picture of the Lateglacial and early Holocene continental environment. This paper reviews results from radiocarbon dated sequences in Romania with the aim to place them in a larger perspective with regard to glacial refugia and tree immigration, and to asses the vegetation response to climatic oscillation from the end of the Last Glacial Maximum (LGM) to the early Holocene. This study documents that some coniferous and broad-leaved trees were present prior to 14,700 cal. yr BP in Romania, and thus it appears that this region may have been a refugial area for some tree species. During the Lateglacial, the vegetation shows a distinct response to climatic oscillations at all elevations, although the response is stronger at mid altitude (800-1100 m. a.s.l) than at high altitudes. Moreover, smaller climatic oscillations are only recorded at sites situated at mid altitudes, probably because these areas were located close to the tree line ecotone. © 2007 Elsevier B.V. All rights reserved.

The forest ecosystem of the Apuseni National Park (ANP) in NW Romania is recognized for its high species and genetic diversity and is protected through various conservation measures. As ANP is the most populated natural park in Romania, the focus is on the need for communities to manage, sustain and prosper by using, exploring and sustaining the natural resources. But what activities are the most appropriate for the conservation of a highly diverse natural forest? This paper presents results from a long-term ecological study using fossil pollen, microscopic and macroscopic charcoal and AMS 14 C dating on a site in the ANP in order to examine how the interaction between climate change, human activities and other disturbances have shaped the present protected landscapes over the last 5700 years in this part of the reserve. Results from this study show that the landscape in this region has been continuously forested over the last 5700 years BP, but the forest composition and structure have been dynamic throughout much of the time. In particular, distinct changes in forest composition have occurred over the last 700 years of the record. Fagus sylvatica was the major taxon between 5200 and 200 years BP and its dominance is associated with the highest forest stability. The formation of the current Picea abies forests started 400 years ago and spruce became the dominant forest species during the last two centuries as a result of selective forest clearance, intensive grazing, and more recently, plantations. This led to a large reduction in forest diversity, decline of F. sylvatica and local extinction of several species including Abies alba, Ulmus, Tilia, and Acer. Our results show the high conservation values of A. alba and F. sylvatica in the ANP. Current management practices that allow the anthropogenic activities of timber production and fast tree regeneration, usually involving the plantation of P. abies in this part of the ANP are not in keeping with the NATURA 2000 objectives of ensuring the persistence of the most vulnerable species and habitats.

It is assumed that the south-eastern Europe and especially the Romanian Carpathians were important regions for surface and underground invertebrates survival during glacial periods and acted as a source of post-glacial colonization processes. We analyzed data from 233 georeferenced records for 164 species of groundwater copepods and ostracods from Romania and used a comparative approach to recognize the determinants of the regional-scale richness, endemism, and distribution patterns, with a primary focus on species from the Carpathian Mountains. In addition, we examined the driving forces for the observed pattern of distribution and richness linked to contemporary (groundwater habitat fragmentation and heterogeneity, climate, vegetation) and historical (past climate and vegetation) environmental conditions. Our analyses showed that: (1) species richness was high, irrespective of habitat heterogeneity, in karst and non-karst areas; (2) the main driver accounting for high species richness in the karst landscape was the rainfall regime (> 1350 mm per year), whereas, in non-karst areas, it was woodland vegetation; and (3) there was significant species richness and richness of phyletic lineages in hypothetical forest glacial refugia of the Carpathian arc. The combination of the distribution pattern, diversification, and evolution of stygobite lineages provides reliable evidence for species persistence in the Romanian groundwater during Pleistocene.

Fire is recognized as a critical process with significant impacts on biota and the atmosphere. In this study, 11 micro- and macrocharcoal sedimentary records extracted from peat bogs and lakes at different elevations in the Carpathian region (in Hungary and Romania) were used to explore the patterns and the potential underlying mechanisms in biomass burning in this region during the last 15,000 years. Results from micro-charcoal and macro-charcoal data show similar trends in biomass burning and suggest that the major signal of both charcoal size-fragments relates mainly to local fires. Fire activity was low during the lateglacial, attained maximum values in the early Holocene (11,700-8000 cal. yr BP), become lower than present during the mid-late Holocene (8000-1000 cal yr BP), and increased again over the last 1000 years. The reconstructed spatial trends in biomass burning display different degrees of heterogeneity through time. Generally, there was more spatial similarity in fire activity across the study region during the lateglacial and early Holocene (15,000-8000 cal yr BP), followed by increased spatial heterogeneity from ca 8000 cal yr BP onwards. Biomass burning appears to have been primarily modulated by climate during both the lateglacial and Holocene, through its effect on vegetation productivity and therefore fuel availability (lateglacial), and fuel structure, moisture and flammability (the Holocene). Onsite human activities are likely to have provided an extra ignition source already in the early Holocene. However, evidence suggest that anthropogenic activities have markedly altered the natural trends in biomass burning from about 5500 yr BP (lowlands) and over the last 2000-1000 years (in the mountain environments), by either removing the biomass (in the lowlands) or igniting fire where it seldom occurs naturally (i.e., in the mountain environments). On the other hand, burning activity also appears coincident with significant changes in tree species compositions, indicating that fire has likely acted as a driving factor in forest dynamics. Results also suggest that peat deposits provide a more localized fire record than lakes, and that trends and patterns of change can be different even for sites situated close to each other. © 2012 Elsevier Ltd.