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Environmental changes have had an enormous impact on prehistoric hunter-gatherers as they affect the biotic landscape and availability of resources such as freshwater, edible plants, game and fish. To assess whether various innovations that took place in hunter-gatherer communities during the Boreal may be attributed to changes in the vegetation, a high-resolution pollen and macrofossil analysis of a well-AMS-dated Early Holocene peat record from the Grote Nete valley in the Belgian Campine was carried out. Shifts in the pollen assemblages indicate a change from a birch-pine woodland in the late Preboreal to pine-dominated forests in the Boreal. After the initial expansion of hazel, followed by oak and elm from the early Boreal onward, a prominent and abrupt reduction of the pollen concentration, by up to 95% over several spectra, is observed during the second half of the Boreal. This sharp decline affects all taxa and coincides with a decrease in pollen percentages of thermophilous trees and an increase of the cold-tolerant pine. This shift in pollen concentration and vegetation composition likely reflects a climatic cooling at 9.3 ka which is evident in the stable oxygen isotopic record of the Greenland ice cores. On the one hand, the vegetation dynamics are discussed in the light of the Boreal vegetation history in general and this temporary cooling more specifically. On the other hand, we discuss how these changes may have affected past hunter-gatherer communities.

The Holocene has always been considered a crucial epoch where the major cultural steps of humankind took place. Understanding past Holocene climatic variability, shifts in vegetation, and faunal communities are among crucial challenges in predicting the upcoming changes of the natural environment. In Central Europe, the Krakow-Czestochowa Upland is one of the best study areas for detecting faunal, environmental, and climate shifts. For that reason, we choose to study the small vertebrate and mollusc communities of three archaeological sites with Holocene horizons: Sąspowska Zachodnia Cave, Ciasna Cave, and Male Rockshelter. We analysed the faunal community shifts, and we compared our results with the major Holocene sites in the area with the correspondence and cluster analyses. The environment and climate were reconstructed through Habitat Weighting, Quantified Ecology, malacological spectra and Bioclimatic methods. Environment and climate values showed a temporary replacement of the Late Glacial tundra and grasslands with boreal forest mixed with open wetlands during the Preboreal and then stable landscapes dominated by temperate forests. Models based on rodent data show that temperature and precipitation generally increased, starting from the Boreal, to reach values near, or sometimes overwhelm, the current climate values of the area during the Atlantic and Subboreal. The climate values obtained from herpetofaunal analyses show very slight changes between the Preboreal and the Atlantic (Ciasna Cave layers 3 and 4), except for the winter temperatures, whereas results obtained for Sąspowska Zachodnia Cave are probably biased by a very low number of recovered remains. Among rodents, a major negative oscillation detected in layers related to the edge of Early Holocene was related to the Preboreal Oscillation or long-lasting effect of the Younger Dryas.

The aim of the present study was to estimate the range of climate variability in Central Poland during the Eemian Interglacial (MIS 5e). High resolution pollen records are available for all seven RPAZs typical of this interglacial in Central Europe. These pollen records were used to estimate total annual precipitation and mean annual temperature, as well as the mean temperatures of the warmest and the coldest months based on the plant indicator method and the modern analogue technique. The reconstructions indicate that the combination of these two methods provides a much clearer insight into the climate changes of the Eemian optimum. The results confirmed no drastic drop in temperature in the Middle Eemian, with high total precipitation in the hazel phase, and that this was followed by a decrease in temperature in the Late Eemian (fir-spruce and pine phases). A drop in precipitation occurred during the youngest part of the Carpinus phase, while coincided with a marked lowering of the water level in lakes and their transformation into peatbogs. The last part of the Eemian is characterized by decreasing temperature, particularly during the coldest month, rising water levels due to a combination of lower evaporation and higher air humidity, and a transition to glacial conditions. Principal Component Analysis found all investigated sites to follow the same pattern of changes. Mean winter temperature, annual temperature and precipitation were found to have a strong positive correlation with the occurrence of thermophilus temperate broadleaved trees (hazel, linden, and ash) typical for the mid-Eemian optimum. These three factors also have a negative correlation with the presence of cold tolerant boreal trees (birch and pine) and open land taxa characteristic of the beginning and end of the interglacial. Mean July temperature was found to be positively correlated with the occurrence of temperate broadleaved trees (oak, ash and elm) typical for early stages of the Eemian and negatively with that of coniferous trees (fir and spruce) characteristic for later stages of the interglacial.

The paper presents new data on the subfossil insects and molluscs, as well a new radiocarbon date for the Gornovo site in the Southern Fore-Urals. As a result, the stratigraphic interpretation of the sediments of the lower part of the first above floodplain terrace of the Belaya River is corrected and they are assigned to the Tabulda Horizon (MIS 3) of the Upper Pleistocene in the regional scheme of the Fore-Urals Quaternary. The malacofauna of the locality is represented by 27 species of terrestrial and freshwater molluscs. The composition of molluscs in the deposits of MIS 3 indicates the succession of deposit accumulation in the river valley from the stage of reservoirs that periodically connecting with the river to the stage of the overgrown oxbow lake. Single occurrence of mollusc shells in the loams of MIS 2 is a result of sharp climate change. New insect material includes 136 species of Coleoptera from 17 families, as well as Heteroptera and Hymenoptera representatives. 29 species of beetles (Carabidae, Histeridae, Scarabaeidae, Elateridae, Tenebrionidae, Chrysomelidae, Brentidae and Curculionidae) are recorded for the Pleistocene for the first time. The insect assemblages from Gornovo site are assigned to periglacial and humid boreal faunal types. The entomofauna of the periglacial type has no analogues in the recent fauna; it corresponds to the deposits assigned to the middle of MIS 3. This entomofauna is characteristic to the MIS 2 and MIS 3 insect assemblages from the south of West Siberian Plain. Based on entomological data, the climate of the middle of MIS 3 of the Southern Fore-Urals is reconstructed as dry and cold, extracontinental, with mean July temperature not exceeding +15 °C. Steppe landscapes likely prevailed in open areas and coniferous forests were restricted to river valleys. Beetles from deposits dated to end of MIS 3 are assigned to the fauna of the boreal humid type. These insect assemblages are significantly poorer in diversity than periglacial type assemblages and are represented mainly by near water and forest Coleoptera. Based on these species, meadow and forest landscapes were reconstructed. The reconstructed mean air temperature of July ranged from +16 to +19 °C. This suggests a trend towards more mild conditions in the region connected to the climate warming at the end of MIS 3. It is likely that humidification during this period was regional, determined by the proximity of the site to the Southern Urals Mountains.

Pseudamussium peslutrae has a geographical range from southern Iceland and Norway southwards to the western Mediterranean Sea and North Africa. In this study, its biometrics were examined from two collections at mean depths of 353 and 517m from the Rockall continental slope, with only four scallops obtained at depths to 810m. Growth was based on the formation of shell rings, with one specimen having seventeen rings. Associates fouling the shells were classified according to nine taxa.

In this study we analyzed turbulent heat fluxes over a seasonal ice cover on a boreal lake located in southern Finland. Eddy covariance (EC) flux measurements of sensible (H) and latent heat (LE) from four ice-on seasons between 2014 and 2019 are compared to three different bulk transfer models: one with a constant transfer coefficient and two with stability-adjusted transfer coefficients: the Lake Heat Flux Analyzer and SEA-ICE. All three models correlate well with the EC results in general while typically underestimating the magnitude and the standard deviation of the flux in comparison to the EC observations. Differences between the models are small, with the constant transfer coefficient model performing slightly better than the stability-adjusted models. Small difference in temperature and humidity between surface and air results in low correlation between models and EC. During melting periods (surface temperature T0>0 ∘C), the model performance for LE decreases when compared to the freezing periods (T0 ∘C), while the opposite is true for H. At low wind speed, EC shows relatively high fluxes (±20 W m−2) for H and LE due to non-local effects that the bulk models are not able to reproduce. The complex topography of the lake surroundings creates local violations of the Monin–Obukhov similarity theory, which helps explain this counterintuitive result. Finally, the uncertainty in the estimation of the surface temperature and humidity affects the bulk heat fluxes, especially when the differences between surface and air values are small.

Integrating tracking technology and molecular approaches provides a comprehensive picture of contemporary and evolutionary mechanisms promoting connectivity. We used mitochondrial DNA and double digest restriction-site associated DNA (ddRAD) sequencing combined with satellite telemetry to investigate the connectivity of geographically disparate breeding populations of a declining boreal shorebird, the lesser yellowlegs (Tringa flavipes). We were able to track 33 individuals on their round-trip migrations to Central and South America and back to the boreal wetlands of North America. Nearly all (93%) adults captured on the breeding grounds returned to within 5 km of the original capture site, with a median dispersal distance of 629 m. While our telemetry data revealed limited breeding dispersal in adults, genetic data uncovered significant interconnectedness across the species’ range. Very little genetic structure was estimated at ddRAD autosomal (ΦST = 0.001), Z-linked (ΦST = 0.001), and mtDNA loci (ΦST = 0.020), and maximum likelihood-based clustering methods placed all individuals in a single cluster regardless of capture location, indicating the species is panmictic. Our data indicate that large-scale juvenile dispersal is the main mechanism maintaining connectivity in this species, resulting in the absence of genomic structure.

Several studies have investigated new particle formation (NPF) events from various sites ranging from pristine locations, including forest sites, to urban areas. However, there is still a dearth of studies investigating NPF processes and subsequent aerosol growth in coastal yet semi-urban sites, where the tropospheric layer is a concoction of biogenic and anthropogenic gases and particles. The investigation of factors leading to NPF becomes extremely complex due to the highly dynamic meteorological conditions at the coastline especially when combined with both continental and oceanic weather conditions. Herein, we engage in a comprehensive study of particle number size distributions and aerosol-forming precursor vapors at the coastal semi-urban site in Helsinki, Finland. The measurement period, 25 June–18 August 2019, was timed with the recurring cyanobacterial summer bloom in the Baltic Sea region and coastal regions of Finland. Our study recorded several regional/local NPF and aerosol burst events during this period. Although the overall anthropogenic influence on sulfuric acid (SA) concentrations was low during the measurement period, we observed that the regional or local NPF events, characterized by SA concentrations on the order of 107 molec.cm-3, occurred mostly when the air mass traveled over the land areas. Interestingly, when the air mass traveled over the Baltic Sea, an area enriched with algae and cyanobacterial blooms, high iodic acid (IA) concentration coincided with an aerosol burst or a spike event at the measurement site. Further, SA-rich bursts were seen when the air mass traveled over the Gulf of Bothnia, enriched with cyanobacterial blooms. The two most important factors affecting aerosol precursor vapor concentrations, and thus the aerosol formation, were speculated to be (1) the type of phytoplankton species and intensity of bloom present in the coastal regions of Finland and the Baltic Sea and (2) the wind direction. During the events, most of the growth of sub-3 nm particles was probably due to SA, rather than IA or methane sulfonic acid (MSA); however much of the particle growth remained unexplained indicative of the strong role of organics in the growth of particles, especially in the 3–7 nm particle size range. Further studies are needed to explore the role of organics in NPF events and the potential influence of cyanobacterial blooms in coastal locations.

Using observations and numerical simulations, this study examines the intraseasonal variability of the surface zonal current (u ISV) over the equatorial Indian Ocean, highlighting the seasonal and spatial differences, and the causes of the differences. Large-amplitude u ISV occurs in the eastern basin at around 80°–90°E and near the western boundary at 45°–55°E. In the eastern basin, the u ISV is mainly caused by the atmospheric intraseasonal oscillations (ISOs), which explains 91% of the standard deviation of the total u ISV. Further analysis suggests that it takes less than ten days for the intraseasonal zonal wind stress to generate the u ISV through the directly forced Kelvin and Rossby waves. Driven by the stronger zonal wind stress associated with the Indian summer monsoon ISO (MISO), the eastern u ISV in boreal summer (May to October) is about 1.5 times larger than that in boreal winter (November to April). In the western basin, both the atmospheric ISOs and the oceanic internal instabilities contribute substantially to the u ISV, and induce stronger u ISV in boreal summer. Energy budget analysis suggests that the mean flow converts energy to the intraseasonal current mainly through barotropic instabilities.

The Bathurst caribou (Rangifer tarandus groenlandicus (Borowski, 1780)) herd declined from ∼349 000 animals in 1996 to ∼8200 in 2018. Climate-driven changes to tundra and boreal vegetation is one hypothesis for the decline. We modelled and mapped annual productivity and phenology across the herd’s range using enhanced vegetation index (EVI) data derived from a Moderate Resolution Imaging Spectroradiometer (MODIS) time series spanning 2000–2017. Maximum annual EVI, growing season length, and time-integrated EVI increased significantly on 16%, 18%, and 49% of the core annual range, respectively. Trends toward longer growing seasons were driven entirely by earlier spring green-up and, along with time-integrated EVI, were most prevalent in tundra regions. Trends in forested regions were overwhelmingly related to the influence of forest fires, which burned more than half of the range below the forest–tundra ecotone since 1965. These trends suggest that climate-driven changes in production and phenology have occurred in the tundra and forest–tundra portions of the range and could have contributed to the recent herd decline. However, the trends may also be a result of herd decline itself, given the loss of this large herbivore from the landscape. Elucidating cause and effect will require comprehensive analysis of interactions between climatic variables, herd dynamics, and vegetation change, complemented by targeted field investigations.

The wildfire regime in Canada’s boreal region is changing; extended fire seasons are characterized by more frequent large fires (≥200 ha) burning greater areas of land, whilst climate-mediated drying is increasing the vulnerability of peatlands to deep burning. Proactive management strategies, such as fuel modification treatments, are necessary to reduce fire danger at the wildland–human interface (WHI). Novel approaches to fuel management are especially needed in peatlands where deep smouldering combustion is a challenge to suppression efforts and releases harmful emissions. Here, we integrate surface compression within conventional stand treatments to examine the potential for reducing smouldering of near-surface moss and peat. A linear model (adj. R2 = 0.62, p = 2.2e−16) revealed that ground cover (F[2,101] = 60.97, p < 0.001) and compression (F[1,101] = 56.46, p < 0.001) had the greatest effects on smouldering potential, while stand treatment did not have a significant effect (F[3,101] = 0.44, p = 0.727). On average, compressed Sphagnum and feather moss plots showed 57.1% and 58.7% lower smouldering potential, respectively, when compared to uncompressed analogs. While practical evaluation is warranted to better understand the evolving effectiveness of this strategy, these findings demonstrate that a compression treatment can be successfully incorporated within both managed and unmanaged peatlands to reduce fire danger at the WHI.

Urban green areas are becoming increasingly recognized for their biodiversity potential. However, little is known about how urbanization shapes cryptic species communities, such as those residing in deadwood. In this study, we investigated downed Norway spruce trunks at intermediate stages of decay, in urban and semi-natural forests in southern Finland. To understand the interconnections between landscape context, deadwood characteristics and wood-inhabiting fungal communities, we studied structural characteristics, surface epiphyte cover and internal moisture and temperature conditions of the tree trunks, and fungal communities residing in the wood. Our findings showed that urban tree trunks had less epiphyte cover and lower moisture than trunks in semi-natural forests. Overall, urban forests provide less favourable habitats for a majority of the dominant wood-inhabiting fungal species and for red-listed species as a group. Yet, 33% of urban trunks hosted at least one red-listed species. While these landscape-scale effects may be driven by local climatic conditions as well as contingencies related to available species pools, our results also highlight the significance of substrate-scale variability of deadwood in shaping wood-inhabiting fungal communities. We show that epiphyte cover is a significant driver or indicator of these small-scale dynamic processes in deadwood.

The daily evolution of the Equatorial Ionization Anomaly (EIA) and the Equatorial Electrojet (EEJ) exhibits phase difference, which reflects the response time of the F-region equatorial plasma fountain to the E-region electric field variation. Studies on this response time contribute to clarifying the relative importance of different influence factors on the low-latitude E- and F-region coupling process. However, the solar-cycle, seasonal and longitudinal dependence of this response time has not yet been comprehensively revealed. In this paper, the occurrence time of the daytime most developed northern EIA crest (TEIA), the occurrence time of the daytime strongest EEJ (TEEJ), and their time delay (δT = TEIA-TEEJ) during 2008 to 2018 are derived from total electron content and magnetometer data, and the seasonal and solar-cycle variations of these parameters are analyzed and compared between the eastern Asian and American sectors. Main results are as follows. (1) TEIA and δT share similar seasonal and solar-cycle variation patterns, which are different from TEEJ. (2) The prevailing seasonal variation pattern of TEIA is generally consistent in the two sectors, which is earlier (later) in the boreal winter (summer). This feature is not determined by the variations of TEEJ or EEJ strength. (3) The solar-cycle variation pattern of TEIA is different between the eastern Asian and American sectors, but the 11-yr averaged TEIA is nearly the same in the two sectors. The solar-cycle and longitudinal dependencies are probably due to the combined effect of electric field, meridional wind, and local geomagnetic field configuration.

Soil organic carbon (SOC) is the largest carbon pool in terrestrial ecosystems, which plays an important role in climate change by regulating atmospheric carbon dioxide. Sweden’s forest management has led to a decrease in old growth forests. This change in land use can affect SOC levels in these forests. This report quantified SOC stocks among different wetness classes in 10 old growth forests across multiple regional environmental gradients in Sweden. I tested for the effects of some different environmental factors on SOC: temperature, precipitation, altitude, stem basal area, latitude, and normalized difference vegetation index. Soil measurements were taken from three different horizons: the O-, E-, and B-horizon. The results showed that the mean SOC stock in old growth forests (5.25 ± 0.60 kg m-2) is a bit higher than the regional average (4.1 ± 0.5 kg m-2) and that local variation within forests, mainly due to hydrology, appears to drive variation that is often as big or larger than regional variations. There were no significant differences between the different forests, but there were significant differences found between the different wetness classes. There were several correlations found between the different regional environmental factors and SOC stocks. The most prominent relationship was a positive link between the O-horizons’ SOC stocks and temperature (R2adj = 0.58). Overall, these results indicate that SOC stocks in old growth forests are affected by both soil wetness at a local scale and air temperature at a regional scale; and that they might contain a slightly larger amount of SOC than managed forests.

High latitude and altitude ecosystems are currently undergoing rapid and unprecedented warming in response to anthropogenically induced climate change. Subarctic, alpine regions are particularly vulnerable to increases in air temperature and changing precipitation regimes, which have caused cascading hydrological and ecological impacts. In addition to changing flow regimes, thawing permafrost, and declining glaciers, widespread changes in vegetation composition, density and distribution have been observed across northern regions. Specifically, treeline is advancing with increasing latitude and altitude and shrubs are increasing in height, extent, and density. Despite widespread documentation of this northern greening, few field-based studies have evaluated the hydrological implications of these changes. Quantification of total evapotranspiration (ET) across a range of vegetation gradients is essential for predicting water yield, yet challenging in cold alpine catchments due to heterogeneous land cover. Direct field-level measurements of transpiration (T) and evaporative partitioning across subarctic, alpine ecosystems and species are rare, yet essential to assess sensitivities and hydrological response to changing climate drivers. This thesis presents six years of surface energy balance components and ET dynamics and two years of sap flux measurements and critical zone stable water isotope sampling at three sites along an elevational gradient in a subarctic, alpine catchment near Whitehorse, Yukon Territory, Canada. These sites span a gradient of thermal and vegetation regimes, providing a space-for-time comparison for future ecosystem shifts: 1) a low-elevation boreal white spruce forest (~12-20 m), 2) a mid-elevation subalpine taiga comprised of tall, dense willow (Salix) and birch (Betula) shrubs (~1-3 m) and 3) a high-elevation subalpine taiga with short, sparse shrub cover (< 0.75 m) and moss, lichen, and bare rock. We utilize both mass flux measurements and stable water isotopes to evaluate the timing, magnitude, sensitivities, and sources of plant water uptake across these vegetation covers. Total ET decreased and interannual variability increased with elevation, with mean May to September ET totals of 349 (±3) mm at the forest, 249 (±10) mm at the tall, dense shrub site, and 240 (± 26) mm at the short, sparse shrub site. The shrub sites exhibited similar ET losses over 6 years despite differences in shrub height and abundance, although daily rates were higher at the tall shrub site in the peak growing season. From May to September, ET:R ratios were the highest and most variable at the forest (2.19 ± 0.37) and similar at the tall, dense shrub (1.22 ± 0.09) and short, sparse shrub (1.14 ± 0.05) sites. In the mid-growing season, mean T rates were greater at the dense shrub site (2.0 ± 0.75 mm d-1) than the forest (1.47 ± 0.52 mm d-1). During this time, T:ET was lower at the forest (0.48) than at the tall, dense shrub site (0.80). During the growing season between the two years, 2020 was considerably wetter and cooler than 2019. At the tall shrub site, during the mid-growing season (July 1-Aug 15), T dropped considerably in 2020 (-26%), as T was suppressed during the short, wet growing season. In contrast, T at the forest was only moderately suppressed (-3%) between years in this same period. Evapotranspiration was more strongly controlled by air temperature during the early and late season at the forest, while ET at the shrub site was more sensitive to warmer temperatures in the mid-growing season. At the shrub sites, ET was energy limited with no observed soil moisture limitation on T. While 2H and 18O of volume weighted precipitation became more depleted with elevation, the opposite was true in xylem water, where 2H and 18O became more enriched with elevation. Plant water uptake was more reflective of snow water at the forest site than both shrub sites, particularly early in the year and during dry periods. Near-surface bulk soil water had more negative lc-excess at the forest throughout the season and with depth, highlighting increased contributions from soil evaporation. This study combined direct measurements of sap flux, ET, and critical zone isotopes to provide new details on multi-year plant-soil-water dynamics, critical zone water cycling, and species-specific plant water uptake patterns in seasonally frozen soils, which have not previously been reported in cold regions. Our results suggest that advances in treeline will increase overall ET and lower interannual variability; however, the large growing season water deficit and stable water isotope signature at the forest indicates strong reliance on soil moisture from late fall and snowmelt recharge and the potential for plant water stress. Differences between the shrub species were apparent in the sap flux and stable isotope measurements, highlighting the need to further evaluate species specific responses and feedbacks when predicting hydrological fluxes across subarctic ecosystems. Overall, our results suggest that predicted changes in vegetation type and structure in northern regions will have a considerable impact on water partitioning and will vary in a complex way in response to changing precipitation timing, phase and magnitude. Thesis Candidate in Philosophy

Many modelling approaches have been developed to project climate change impacts on forests. By analysing 'comparable' yet distinct variables (e.g. productivity, growth, dominance, biomass, etc.) through different structures, parameterizations and assumptions, models can yield different outcomes to rather similar initial questions. This variability can lead to some confusion for forest managers when developing strategies to adapt forest management to climate change. In this study, we standardized results from seven different models (Habitat suitability, trGam, StandLEAP, Quebec Landscape Dynamics, PICUS, LANDIS-II and LPJ-LMfire) to provide a simple and comprehensive assessment of the uncertainty and consensus in future performance (decline, status quo, improvement) for six tree species in Quebec under two radiative forcing scenarios (RCP 4.5 and RCP 8.5). Despite a large diversity of model types, we found a high level of agreement (73.1%) in projected species' performance across species, regions, scenarios and time periods. Low agreements in model outcomes resulted from small dissensions among models. Model agreement was much higher for cold-tolerant species (up to 99.9%), especially in southernmost forest regions and under RCP 8.5, indicating that these species are especially sensitive to increased climate forcing in the southern part of their distribution range. Lower agreement was found for thermophilous species (sugar maple, yellow birch) in boreal regions under RCP 8.5 mostly as a result of the way the different models are handling natural disturbances (e.g. wildfires) and lags in the response of populations (forest inertia or migration capability) to climate change. Agreement was slightly higher under high anthropogenic climate forcing, suggesting that important thresholds in species-specific performance might be crossed if radiative forcing reach values as high as those projected under RCP 8.5. We expect that strong agreement among models despite their different assumptions, predictors and structure should inspire the development of forest management strategies to be better adapted to climate change.

Baseline data on the boreal jack pine associated chanterelle (Cantharellus cibarius Fr.) and pine mushrooms (Tricholoma magnivelare (Peck) Redhead) in the Boreal Plain Ecozone of Saskatchewan were collected in five ecosites of productive mushroom areas. It investigated hourly weather parameters correlated with daily purchase volumes over 4 yrs; yield data over 5 yrs; and varying age, tree density, and species for presence of mushrooms in over 100 stands. All plots fell within the lichen jack pine (jP) ecosite with an overstory entirely of jack pine. The understory was dominated by reindeer lichen, bearberry, and blueberry. Plots were well- to rapidly drained, subxeric to submesic, with low nutrient regime. Both chanterelle and pine mushrooms were present in jack pine stands of −1. Chanterelle cap diameter was a good predictor of fresh weight and proxy for yield. Pine mushroom was −1 over 4 yrs based on 5 days picking. With future climate predictions of warmer and moister conditions, timing of fruiting body appearance is anticipated to advance.

The Intraseasonal Oscillation (ISO) is the cornerstone for 2–8-week subseasonal prediction. Understanding the decadal variation of the ISO is important for improving subseasonal prediction; however, there is still a gap in our knowledge of ISO dynamics. Here, we presented a method, an Empirical Orthogonal Function (EOF) analysis of 11-year-sliding ISO evolution, to objectively detect decadal variation of the ISO originated from the equatorial Indian Ocean (EIO) during 1979–2016. The results show that the properties of ISO have a notable decadal change since 1998 for both boreal summer and boreal winter seasons, mainly in its evolution rather than in its intensity at origin. During the pre-1998 epoch, the boreal summer intraseasonal oscillation (BSISO), was confined to the Indian Ocean; since 1998, however, it propagated northeastward across the Maritime Continent (MC) and the intraseasonal variability over the western North Pacific was significant enhanced. On the other hand, the boreal-winter ISO, usually known as Madden-Julian Oscillation (MJO) shows minor changes in MC ‘barrier effect’ between the two epochs, and continuously propagates eastward across the MC. The MJO only shows suppressed activity over the central equatorial Pacific in the post-1998 epoch. These decadal changes are related to the eastern Pacific cooling during the ‘global warming hiatus’ period rather than to the four-decade global warming. Results here provide a set of potential precursors for foreseeing ISO propagation under different mean states.

This paper presents new field and laboratory data combined with previously published materials on interglacial sediments underlying two upper tills of northern European Russia and West Siberia. The emphasis is on the structure and chronometric data of marine strata with shells of boreal molluscs of Cyrtodaria genus indicative of the Atlantic marine invasion into these sedimentary basins during the late Middle Pleistocene. Another line of evidence for this time span is inferred from inter-till terrestrial sequences in the European Northeast with forest pollen spectra suggesting a climate much warmer than today. The decisive correlation signal is provided by optically stimulated luminescence and electron-spin resonance dates, indicating MIS 7 time, and by the geological position of two interglacial formations between the first, second and third from the surface glacial complexes. The collected evidence disagrees with the model of the unique boreal transgression and confirms that saline Atlantic water at least twice invaded northern Russia during the last 250 kyears. The sedimentary formations of the penultimate interglaciation can serve as a new intra-regional stratigraphic marker for the northern Pleistocene.

The thickest section of Early Jurassic strata known from onshore Ireland (total Jurassic thickness 566 m) is reported from the Ballinlea-1 well (Rathlin Basin) situated on the north coast of Northern Ireland. A biostratigraphical and palaeoenvironmental assessment is presented for this section largely based on calcareous benthic microfossils (foraminifera and ostracods). The Early Jurassic Waterloo Mudstone Formation (Lias Group) of Northern Ireland has previously received little micropalaeontological attention, therefore this work provides an opportunity to enhance palaeogeographic and palaeoenvironmental understanding for the Early Jurassic of the province, and this paper illustrates the key microfossil taxa of this age from Ireland for the first time. The records, based on ditch-cuttings samples, demonstrate a stratigraphical range from Hettangian to Early Pliensbachian, consistent with other wells and boreholes in this basin. The assemblage compositions are comparable to those elsewhere in the European boreal Atlantic realm. Hettangian to earliest Sinemurian microfossil assemblages are generally of low diversity and are numerically dominated by metacopid ostracods with occasional influxes of foraminifera. Gradually, foraminiferal abundance (often dominated by species of the Lagenida) come to exceed those of the ostracods in the Early Sinemurian reaching their greatest diversity in the Late Sinemurian. The sediments are considered to represent an inner to mid-shelf environment throughout while the record thickness for this region indicates ongoing syn-sedimentary fault movement along the basin margins within this period.

Methane emissions in Canada have both anthropogenic and natural sources. Anthropogenic emissions are estimated to be 4.1 Tg a−1 from 2010–2015 in the National Inventory Report submitted to the United Nation's Framework Convention on Climate Change (UNFCCC). Natural emissions, which are mostly due to boreal wetlands, are the largest methane source in Canada and highly uncertain, on the order of ∼ 20 Tg a−1 in biosphere process models. Aircraft studies over the last several years have provided “snapshot” emissions that conflict with inventory estimates. Here we use surface data from the Environment and Climate Change Canada (ECCC) in situ network and space-borne data from the Greenhouse Gases Observing Satellite (GOSAT) to determine 2010–2015 anthropogenic and natural methane emissions in Canada in a Bayesian inverse modelling framework. We use GEOS-Chem to simulate anthropogenic emissions comparable to the National Inventory and wetlands emissions using an ensemble of WetCHARTS v1.0 scenarios in addition to other minor natural sources. We conduct a comparative analysis of the monthly natural emissions and yearly anthropogenic emissions optimized by surface and satellite data independently. Mean 2010–2015 posterior emissions using ECCC surface data are 6.0 ± 0.4 Tg a−1 for total anthropogenic and 11.6 ± 1.2 Tg a−1 for total natural emissions. These results agree with our posterior emissions of 6.5 ± 0.7 Tg a−1 for total anthropogenic and 11.7 ± 1.2 Tg a−1 for total natural emissions using GOSAT data. The seasonal pattern of posterior natural emissions using either dataset shows slower to start emissions in the spring and a less intense peak in the summer compared to the mean of WetCHARTS scenarios. We combine ECCC and GOSAT data to characterize limitations towards sectoral and provincial-level inversions. We estimate energy + agriculture emissions to be 5.1 ± 1.0 Tg a−1, which is 59 % higher than the national inventory. We attribute 39 % higher anthropogenic emissions to Western Canada than the prior. Natural emissions are lower across Canada. Inversion results are verified against independent aircraft data and surface data, which show better agreement with posterior emissions. This study shows a readjustment of the Canadian methane budget is necessary to better match atmospheric observations with lower natural emissions partially offset by higher anthropogenic emissions.

Peatlands are globally significant C storage because waterlogged conditions slow down organic matter (OM) decomposition. Changes in the water table (WT) because of global warming or drainage, consecutive vegetation succession, and enhanced root exudation causing priming may transform peatlands from C sinks to sources. We studied how glucose addition, WT, and forest harvesting affect the chemical composition of peat and decomposition rate by incubating peat columns collected from drained clear-cut (CC) and forested (FD) peatlands. Columns were divided into high or low WT, and half were labeled with C-13 to study the priming effect on peat decomposition and peat chemical quality. We measured CO2 fluxes, peat OM, and water quality. There was no detectable priming effect after glucose addition. Lowering of the WT led to increased CO2 efflux, which during the measurements averaged between 39 and 291 mu g m(-2) s(-1). Low WT also decreased the proportion of water-soluble OM in CC areas but not in FD areas. The proportion of recalcitrant OM in surface peat was higher in forest than in clear cut. Forest management also affected the quality of dissolved OM in soil water, with CC showing higher concentrations of recalcitrant compounds. Decomposition and OM quality were governed by forest management practices and WT manipulation. In the future, the C sink capacity of forested peatlands will be regulated by changes in WT level, forest management, and quality of OM.

Climate warming is causing asynchronies between animal phenology and environments. Mismatched traits, like coat color change mismatched with snow, can decrease survival. However, coat change does not serve a singular adaptive benefit of camouflage, and alternate coat change functions may confer advantages that supersede mismatch costs. We found that mismatch reduced rather than increased, autumn mortality risk of snowshoe hares in Yukon by 86.5 %. We suggest that the increased coat insulation and lower metabolic rates of winter acclimatized hares confer energetic advantages to white mismatched hares that reduce their mortality risk. We found that white mismatched hares forage 17-77 minutes less per day than matched brown hares between 0 and -10 °C, thus lowering their predation risk and increasing survival. We found no effect of mismatch on spring mortality risk, where mismatch occurred at warmer temperatures, suggesting a potential temperature limit where the costs of conspicuousness outweigh energetic benefits.

There exists a need to document details related to the spatiotemporal climatology of precipitation over the Arabian Peninsula (Arabia) based on a sound assessment. Areal precipitation was calculated for Arabia, subtropical Arabia (STA), and tropical Arabia (TA) using a weighting scheme to adjust for latitudinal changes in grid-cell areas and extract statistics that have geographical/spatial interpretation based on a quality-controlled spatially-distributed precipitation dataset (1980–2019). Areal annual precipitation mean over Arabia (STA/TA) is 88.61 mm (85.72/92.79). While boreal winter and spring seasons are the wet seasons over Arabia (29, 40%) and STA (36, 40%), boreal spring and summer are the wet seasons over TA (41, 25%). Only 25% of Arabia (STA/TA) receives more than 110.73 (108.48/113.73) mm of precipitation annually. Spatiotemporal trends were explored using the Mann–Kendall test, applied to trend free pre-whitened data, and the Theil-Sen estimator. Average areal precipitation over Arabia and STA is decreasing during the boreal winter and spring seasons at varying rates. On the other hand, boreal summer and fall precipitation is increasing over Arabia, STA, and TA with only that of TA summer being statistically significant. An elongated region extending from southwest to northeast has a statistically significant negative trend in annual, spring, and winter precipitation. The southern part of Arabia is dominated by positive trends in annual, summer, and fall precipitation with only isolated areas being statistically significant. The statistically significant decreasing trend in wet season precipitation over Arabia calls for more conservative water resource management strategies and bold adaptation measures.

A grave of an individual of the Maglemosian Culture, discovered in 2013 during the excavation of the Bolkow site in Western Pomerania, is discussed in this article. The grave was dug into geological strata dated by the radiocarbon method and palynological analysis to the beginning of the Boreal period. Culturally and chronologically, the grave is associated with a vast Mesolithic campsite located in the vicinity. It is analyzed in terms of its burial form, and the religious beliefs and funerary rituals practiced by the members of this community, including a broadly understood cultural tradition. The feature was also compared with similar finds of Mesolithic date from other territories.

Interactions between soil nitrogen (N) availability, fungal community composition, and soil organic matter (SOM) regulate soil carbon (C) dynamics in many forest ecosystems, but context dependency in these relationships has precluded general predictive theory. We found that ectomycorrhizal (ECM) fungi with peroxidases decreased with increasing inorganic N availability across a natural inorganic N gradient in northern temperate forests, whereas ligninolytic fungal saprotrophs exhibited no response. Lignin-derived SOM and soil C were negatively correlated with ECM fungi with peroxidases and were positively correlated with inorganic N availability, suggesting decay of lignin-derived SOM by these ECM fungi reduced soil C storage. The correlations we observed link SOM decay in temperate forests to tradeoffs in tree N nutrition and ECM composition, and we propose SOM varies along a single continuum across temperate and boreal ecosystems depending upon how tree allocation to functionally distinct ECM taxa and environmental stress covary with soil N availability.

Satellite-based observations of atmospheric carbon dioxide (CO 2 ) provide measurements in remote regions, such as the biologically sensitive but undersampled northern high latitudes, and are progressing toward true global data coverage. Recent improvements in satellite retrievals of total column-averaged dry air mole fractions of CO 2 ( X CO 2 ) from the NASA Orbiting Carbon Observatory 2 (OCO-2) have allowed for unprecedented data coverage of northern high-latitude regions, while maintaining acceptable accuracy and consistency relative to ground-based observations, and finally providing sufficient data in spring and autumn for analysis of satellite-observed X CO 2 seasonal cycles across a majority of terrestrial northern high-latitude regions. Here, we present an analysis of X CO 2 seasonal cycles calculated from OCO-2 data for temperate, boreal, and tundra regions, subdivided into 5 ∘ latitude by 20 ∘ longitude zones. We quantify the seasonal cycle amplitudes (SCAs) and the annual half drawdown day (HDD). OCO-2 SCAs are in good agreement with ground-based observations at five high-latitude sites, and OCO-2 SCAs show very close agreement with SCAs calculated for model estimates of X CO 2 from the Copernicus Atmosphere Monitoring Services (CAMS) global inversion-optimized greenhouse gas flux model v19r1 and the CarbonTracker2019 model (CT2019B). Model estimates of X CO 2 from the GEOS-Chem CO 2 simulation version 12.7.2 with underlying biospheric fluxes from CarbonTracker2019 (GC-CT2019) yield SCAs of larger magnitude and spread over a larger range than those from CAMS, CT2019B, or OCO-2; however, GC-CT2019 SCAs still exhibit a very similar spatial distribution across northern high-latitude regions to that from CAMS, CT2019B, and OCO-2. Zones in the Asian boreal forest were found to have exceptionally large SCA and early HDD, and both OCO-2 data and model estimates yield a distinct longitudinal gradient of increasing SCA from west to east across the Eurasian continent. In northern high-latitude regions, spanning latitudes from 47 to 72 ∘ N, longitudinal gradients in both SCA and HDD are at least as pronounced as latitudinal gradients, suggesting a role for global atmospheric transport patterns in defining spatial distributions of X CO 2 seasonality across these regions. GEOS-Chem surface contact tracers show that the largest X CO 2 SCAs occur in areas with the greatest contact with land surfaces, integrated over 15–30 d. The correlation of X CO 2 SCA with these land surface contact tracers is stronger than the correlation of X CO 2 SCA with the SCA of CO 2 fluxes or the total annual CO 2 flux within each 5 ∘ latitude by 20 ∘ longitude zone. This indicates that accumulation of terrestrial CO 2 flux during atmospheric transport is a major driver of regional variations in X CO 2 SCA.

In this article, we employ statistical bias-correction to examine the changing climate of the latest 18 Coupled Model Intercomparison Project Phase 6 (CMIP6) over Southeast Asia under the medium-emission (SSP2-4.5) and high-emission (SSP5-8.5) scenarios. The “Variance scaling” and “Empirical quantile mapping” methods are used for temperature and precipitation, respectively. The bias-corrected dataset was evaluated against the observations obtained from inter-comparison among several observation grid datasets. Significant improvements are found over most areas in SEA, except the Maritime Continent such as high topography of Kalimantan, Sulawesi, and east Papua islands. The CMIP6 multi-model ensemble mean (MME) projects a warming (wetting) 1.99–4.29 °C (9.62–18.43%) in the twenty-first century. The model performance in simulating precipitation is generally lower than in simulating temperature. The MME model displays larger rainfall increases during the boreal summer rather than boreal winter. Overall, there are robust increases in Southwest Monsoon (14.54–19.69%), and Northeast Monsoon (1.68–6.61%) rainfall throughout the twenty-first century with larger values is found under SSP5-8.5 than SSP2-4.5. The climate stabilization is shown to flatten the curve of temperature and precipitation under SSP2-4.5 later in the century. All these findings can be an input for policymakers to develop adaptation strategies in response to the projected climate change impacts.

Climate change leads to a more frequent occurrence of hot days (HDs) and hot nights (HNs). The consecutive occurrence of HDs and HNs (COHs) is often used as a measure of the persistence of an extremely hot spell. Nonetheless, the combined effect of air temperature and relative humidity on the changing COHs has never been studied. In this paper, we use an ensemble of global climate models and multiple thermal indices to robustly examine the combined effect of air temperature and relative humidity on COHs globally on an hourly basis. Our findings reveal that COHs show an increasing trend in the future and a strong latitudinal gradient increasing from high latitudes to the equator. Compared to COHs based on air temperature, the frequency of COHs based on perceived temperature is amplified by the combined effects of high temperature and humidity for both boreal and austral summers. To investigate the underlying mechanisms, we examine two different diurnal temperature ranges (DTRs), derived from air temperature and perceived temperature, for their corresponding types of COHs. Both DTRs are projected to increase in the future relative to the historical period from 1980 to 2004, but the DTR changes derived from perceived temperature are consistently larger than those derived from air temperature. Due to the nonlinearity in thermal indices, the perceived temperature in HDs and HNs rising faster than air temperature leads to a larger increase in perceived COHs. The COHs are further amplified by the increasing number of HNs and HDs that occur consecutively under wet conditions.

Background and aimsWildfire is a primary driver of ecosystem functioning, and the fire-induced changes in the cycling and balance of multiple nutrients may influence the response of plant growth to burning. However, the relationships between total and available soil stoichiometry and stoichiometric effects on the growth of fine roots following fire in forests remain unclear.MethodsWe measured the total and available soil C, N and P concentrations, their ratios and fine root biomass (FRB) at an unburned control, 1-year-postfire and 11-year-postfire sites in a Chinese boreal larch forest. The relationships between soil stoichiometry and FRB were analyzed.ResultsWildfire significantly reduced the total and available soil C:N:P ratios and FRB immediately postfire. Eleven years postfire, most indicators recovered to the pre-fire levels except total soil C:P and N:P ratios, and available C:N ratio. Wildfire immediately increased the correlations between total and available soil C:N:P ratios, as well as between FRB and soil C:N:P ratios, but reduced the correlations between FRB and soil nutrient supply. These effects became weaker over time.ConclusionsThe effects of wildfire on biogeochemical processes in boreal ecosystems extend to the relationships between total and available soil stoichiometry. Wildfire strengthens the linkage between fine roots and soil stoichiometry, but weakens the effects of soil nutrient supply in the Great Xing’an Mountains. Therefore, the effects of wildfire on the coupling of soil C, N and P cycling can produce a more complex soil-plant interaction in the postfire early succession stage of boreal larch forest.

Hygrocybe calciphila, an uncommon species of the genus was found for the first time in Southeastern Europe in forests of Pinus heldreichii in Bulgaria. Description and illustrations of the finding are presented. The European distribution of the species is summarized and briefly discussed, with emphasis on the scarce previous findings in Southern Europe.

During transit from soils to the ocean, microbial communities are modified and re-assembled, generating complex patterns of ecological succession. The potential effect of upstream assembly on downstream microbial community composition is seldom considered within aquatic networks. Here, we reconstructed the microbial succession along a land-freshwater-estuary continuum within La Romaine river watershed in Northeastern Canada. We captured hydrological seasonality and differentiated the total and reactive community by sequencing both 16 S rRNA genes and transcripts. By examining how DNA- and RNA-based assemblages diverge and converge along the continuum, we inferred temporal shifts in the relative importance of assembly processes, with mass effects dominant in spring, and species selection becoming stronger in summer. The location of strongest selection within the network differed between seasons, suggesting that selection hotspots shift depending on hydrological conditions. The unreactive fraction (no/minor RNA contribution) was composed of taxa with diverse potential origins along the whole aquatic network, while the majority of the reactive pool (major RNA contribution) could be traced to soil/soilwater-derived taxa, which were distributed along the entire rank-abundance curve. Overall, our findings highlight the importance of considering upstream history, hydrological seasonality and the reactive microbial fraction to fully understand microbial community assembly on a network scale.

Linear disturbances from geological exploration (i.e., seismic lines) have an extensive footprint across much of Canada’s western boreal forest; however, how seismic lines interact with subsequent wildfire remains poorly understood. We assessed whether wildfires effectively mitigate the footprint of seismic lines by promoting forest recovery. We evaluated the forest structure of legacy seismic lines burned in 2001 and 2002 by comparing them against adjacent unburned control plots, using metrics derived from airborne laser scanning (ALS) data collected between 2007 and 2009. ALS metrics identified persistent differences in vegetation height and structure between seismic lines and adjacent forest controls, 7–9 years post-fire. Median canopy height was 2.90 m lower on upland seismic lines and 1.94 m lower on lowland seismic lines than on adjacent controls, corresponding to a 21% and 25% height reduction, respectively. Field surveys revealed greater graminoid and nonvascular plant cover, and lower tall-tree cover and dead vegetative matter, on seismic lines, in comparison with controls. Our results show that tree recovery remains significantly delayed on most upland and lowland burned seismic lines in our study area, and that additional management efforts or longer timescales may be required to restore these fragmented landscapes.

The exploration of the trend in stratospheric sudden warmings (SSWs) is conducive to predict SSWs in the future. Utilizing the National Centre for Environmental Prediction Reanalysis (NCEP) (1948–2020) and Japanese 55-year Reanalysis (JRA55) (1958–2020), we investigated the duration and strength of SSWs in the Northern Hemisphere occurred in the boreal winter (December–February). We found the duration of SSWs tends to increase and the strength of SSWs tends to strengthen from 1948 to 2003. After 2003, these trends did not continue. We utilized the observed cloudiness from the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) to find that the convective activities in the tropical Central Pacific were enhanced during 1948–2003, and the enhancement of the convective activities did not continue after 2003. The circulation anomalies caused by the enhanced convective activities propagate to the high latitudes through wave trains. The anomalies of circulation and the climatological circulation at high latitudes interfere with each other and superimpose, which has a significant impact on planetary wave 1 (PW1). As a result, the PW1 also showed an increasing trend from 1948 to 2003 and a decreasing trend after 2003. After the stratosphere filters out the planetary wave with a large wavenumber, PW1 accounts for more proportion of planetary waves, which causes the trend in SSWs to change.

The climate is described by the predominant atmospheric conditions in a particular region and influences several human activities. In agriculture, water availability defines the growth and yield of crops and can be obtained by the water balance. The climate classification also aids to identify suitable areas for agricultural crops. Thus, the aim of this work was to elaborate the water balance and perform the climate classification through the method of Thornthwaite and Mather (1955) for six weather stations (Bohicon, Cotonou-Airport, Kandi-Airport, Natitingou, Parakou-Airport and Savè) located in Benin, Western Africa. For the execution of this work, monthly series of precipitation and potential evapotranspiration from 1970 to 2015 were used. Once the monthly water balance of the six seasons was elaborated, it was observed that the rainy (dry) period decreases (increases) from the coast (Cotonou-Airport) to the north of Benin (Kandi-Airport) and, coincides with Boreal summer and part of autumn (Boreal winter and part of spring). Regarding the climate classification, the Cotonou-Airport station was characterized as Subhumid Megathermal climate with moderate winter deficit (C2wA’a’); the stations of Bohicon and Savè presented similar climate classification with Subhumid Dry Megathermal climate with low or without water surplus (C1dA’a’); Natitingou with Subhumid Dry climate Megathermal with large summer surplus (C1s2A’a’); Parakou-Airport with Subhumid climate Dry Megathermic with moderate summer surplus (C1sA’a’) and, Kandi-Airport presented Semi-arid Megathermal climate with moderate summer surplus (DsA’a’). In Benin, subsistence and rainfed farming showed greater risk in the north of the country due to the decrease in the rainy season and the water surplus from the coast (south) to the north of the country, with the increase in aridity.

The article analyzes the zonal landscape distribution and the structure of the diurnal lepidoptera ranges on the territory of the Udmurt Republic. The zonal indicators of the dynamics of the species richness of lepidoptera in the region have the following form: the southern taiga - 100 species, the subtaiga as a whole-122 species, including the northern band of the subtaiga-107 species, the southern band of the subtaiga-119 species. The zonal trend is based on the significant participation of the regional fauna of the regional representatives. The general indicators of the numerical participation of structural and arealographic groups in the fauna are as follows: 46 species are located within the generalized part of the area in the region; 22 species are located near the periphery of the area; 42 species are located on the border of the area; 13 species are located on the periphery of the area. The main share of lepidoptera located in the marginal parts of their ranges is made up of southern subboreal (steppe and non-morale) and subboreal-subtropical representatives (72 species). The proportion of such species among the northern geographical groups - the Hypo-Arctic and boreal (16 species) is significantly lower. The most important biochorological units that determine the conditions for the distribution and localization of bulavous are uplands, forest landscapes on the sands, as well as the valleys of large and medium-sized rivers in the southern part of the region.

Northern aapa mire complexes are characterized by patterned fens with flarks (wet fen surfaces) and bog zone margins with Sphagnum moss cover. Evidence exists of a recent increase in Sphagnum over fens that can alter ecosystem functions. Contrast between flarks and Sphagnum moss cover may enable remote sensing of these changes with satellite proxies. We explored recent changes in hydro-morphological patterns and vegetation in a south-boreal aapa mire in Finland and tested the performance of Landsat bands and indices in detecting Sphagnum increase in aapa mires. We combined aerial image analysis and vegetation survey, repeated after 60 years, to support Landsat satellite image analysis. Aerial image analysis revealed a decrease in flark area by 46% between 1947 and 2019. Repeated survey showed increase in Sphagnum mosses (S. pulchrum, S. papillosum) and deep-rooted vascular plants (Menyanthes trifoliata, Carex rostrata). A supervised classification of high-resolution UAV image recognized the legacy of infilled flarks in the patterning of Sphagnum carpets. Among Landsat variables, all separate spectral bands, the Green Difference Vegetation Index (GDVI), and the Automated Water Extraction Index (AWEI) correlated with the flark area. Between 1985 and 2020, near-infrared (NIR) and GDVI increased in the central flark area, and AWEI decreased throughout the mire area. In aapa mire complexes, flark fen and Sphagnum bog zones have contrasting Landsat NIR reflectance, and NIR band is suggested for monitoring changes in flarks. The observed increase in Sphagnum mosses supports the interpretation of ongoing fen–bog transitions in Northern European aapa mires, indicating significant ecosystem-scale changes.

Temporal patterns in stream chemistry provide integrated signals describing the hydrological and ecological state of whole catchments. However, stream chemistry integrates multi-scale signals of processes occurring in both the catchment and stream. Deconvoluting these signals could identify mechanisms of solute transport and transformation and provide a basis for monitoring ecosystem change. We applied trend analysis, wavelet decomposition, multivariate autoregressive state-space modeling, and analysis of concentration–discharge relationships to assess temporal patterns in high-frequency (15 min) stream chemistry from permafrost-influenced boreal catchments in Interior Alaska at diel, storm, and seasonal time scales. We compared catchments that varied in spatial extent of permafrost to identify characteristic biogeochemical signals. Catchments with higher spatial extents of permafrost were characterized by increasing nitrate concentration through the thaw season, an abrupt increase in nitrate and fluorescent dissolved organic matter (fDOM) and declining conductivity in late summer, and flushing of nitrate and fDOM during summer rainstorms. In contrast, these patterns were absent, of lower magnitude, or reversed in catchments with lower permafrost extent. Solute dynamics revealed a positive influence of permafrost on fDOM export and the role of shallow, seasonally dynamic flowpaths in delivering solutes from high-permafrost catchments to streams. Lower spatial extent of permafrost resulted in static delivery of nitrate and limited transport of fDOM to streams. Shifts in concentration–discharge relationships and seasonal trends in stream chemistry toward less temporally dynamic patterns might therefore indicate reorganized catchment hydrology and biogeochemistry due to permafrost thaw.

Phytocoenotic behaviour of 11 species of boreal vascular plants and mosses is analyzed within the broadleaved-forest zone in comparison with that in different subzones of the boreal-forest zone, based upon the set of 1417 relevés made in European Russia in 1996–2017. The significance of differences in species cover is estimated by means of the one-way ANOVA. The cover of species like Vaccinium myrtillus, V. vitis-idaea, andHylocomium splendens in broadleaved / spruce forests of zonal types is constantly decreasing southwards. On the contrary, the cover of Luzula pilosain Scots pine forests and Pleurozium schreberi and Dicranum polysetum in paludified Norway spruce forests is subject to southward increase. Finally, Oxalis acetosella and Equisetum sylvaticum demonstrate maximae of their cover in forests of zonal types in the southern-boreal and hemiboreal subzones. The dark-coniferous boreal forest “cortege” of species is breaking down into several different floristic elements in the broadleaved-forest zone. These are: “vaccinietal” species p. p. sensu Yu. D. Kleopov (like Vaccinium myrtillus), “quasi-boreal” species sensu V. B. Sochava (Oxalis acetosella, Maianthemum bifolium, Trientalis europaea), hygromesophytes with aged areas (Equisetum sylvaticum), associated species with European-Ancient-Mediterranean nemoral (Luzula pilosa) or East-Asian boreal-montane (Rubus saxatilis) origins. Phytocoenotical behaviour of species is not always different in the intrazonal and the zonal community types but is rather similar in many cases like those of Vaccinium vitis-idaea and Equisetum sylvaticum. The more distinct differences in species positions are found in the extrazonal communities. The statistically proved differences are lacking in phytocoenotical behaviour of Maianthemum bifolium and Trientalis europaea in different zones and subzones due to either florogenetical, or purely methodical reasons, the latter connected with low abundance but high constancy of these species. Disintegration of vegetation “corteges” and individualization of coenotic patterns of species previously growing together are usually observed at the climatically determined (zonal / subzonal or altitudinal) distribution limits.

Arctic cyclones are one of the important synoptic-scale systems that affect weather variability over the Arctic and can cause intense weather phenomena and disasters. Thus, research on the assessment of the climate characteristics, activity laws, and variability trends of Arctic cyclones using climate models has practical significance. On the basis of the fifth-generation European Center for Medium-Range Weather Forecasts reanalysis (ERA5) data, the spatiotemporal variations of Arctic cyclones during 1981–2014 are analyzed by detecting and tracking cyclones using the Lagrangian method. Then, the simulation results of 14 global climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP5) are compared with the results of ERA5. Both the individual models and their ensemble mean can simulate the spatial distribution of the density of cyclone tracks with reasonable capability, the correlation coefficients of track density are approximately 0.6. Furthermore, in boreal winter, the Atlantic zonal negative bias of track density is stronger than that in summer. By contrast, in boreal summer, the negative bias over the Arctic Ocean region is stronger than that in winter. Moreover, the simulations of density -field-related variables (i.e., cyclolysis, cyclogenesis, track, and lowest center pressure densities) of Arctic cyclones are generally better in winter than in summer, and the models can simulate well that the number of external Arctic cyclones entering the Arctic region from the midlatitudes is more than the internal Arctic cyclones generated inside the Arctic region (60°‒90°N). Furthermore, we show that the capability of models to capture Arctic cyclones with a short lifespan (

Background Understanding how warming influence above-ground biomass in the world’s forests is necessary for quantifying future global carbon budgets. A climate-driven decrease in future carbon stocks could dangerously strengthen climate change. Empirical methods for studying the temperature response of forests have important limitations, and modelling is needed to provide another perspective. Here we evaluate the impact of rising air temperature on the future above-ground biomass of old-growth forests using a model that explains well the observed current variation in the above-ground biomass over the humid lowland areas of the world based on monthly air temperature. Results Applying this model to the monthly air temperature data for 1970–2000 and monthly air temperature projections for 2081–2100, we found that the above-ground biomass of old-growth forests is expected to decrease everywhere in the humid lowland areas except boreal regions. The temperature-driven decrease is estimated at 41% in the tropics and at 29% globally. Conclusions Our findings suggest that rising temperatures impact the above-ground biomass of old-growth forests dramatically. However, this impact could be mitigated by fertilization effects of increasing carbon dioxide concentration in the atmosphere and nitrogen deposition.

The Kungur forest-steppe is the northernmost outpost of European forest-steppe, located in the western pre-Urals within the boreal climatic zone. The co-existence of boreal, nemoral and steppe species with relicts and endemics results in a high plant diversity, making it an important biodiversity hotspot. Under current climate change and strong agricultural impacts, the Kungur forest-steppe is rapidly degrading. In order to develop sustainable management strategies, we studied the vegetation history over the last 3500 years in the natural reserve area Spasskaya Gora. Palynological data indicate that the territory of Spasskaya Gora was largely covered by hemiboreal forests with high proportion of elm during the late Holocene. An opening of the vegetation strongly correlates with erosion, both indicating anthropogenic activities such as lumbering, agriculture, grazing and hay making. The modern Pinus and Betula dominated forests combined with large areas dominated by grasses and herbs appear in the last 300 years and caused by human activity. The data support the ‘anthropogenic’ hypothesis of the Kungur forest-steppe development, suggesting that Pleistocene steppe was replaced by hemiboreal forests during the Holocene. Steppe elements survived on exposed rocks. The recent forest-steppe landscapes dominated by pioneer birch and poplar were formed due to anthropogenic deforestation. With respect to nature conservation, our data demonstrate that prohibition of any anthropogenic activities at Spasskaya Gora will lead to loss of diversity of steppe assemblages over the mid-term. We emphasize that conservation of the high plant diversity of the Kungur forest-steppe must include disturbance factors in the form of selective lumbering, prescribed burning, moderate grazing or traditional mowing.

Актуальность исследования обусловлена интенсивным развитием горнодобывающей промышленности на территории Западной Якутии в последний 70-летний период. В результате чего происходит загрязнение окружающей среды химическими веществами в условиях распространения многолетнемерзлых пород. В первую очередь это загрязнение почв поллютантами, которые образуются в техногенных отложениях при извлечении горных масс из недр земли при отработке коренных месторождений алмазов и остаются в почве в течение многих лет даже после ремедиации техногенно-трансформированных территорий. Настоящее исследование позволяет выявить геохимическую специфику мерзлотных почв с разной геолого-геохимической обстановкой и ее трансформацию при техногенном воздействии. Цель: изучение элементного состава и его вертикального распределения в профиле мерзлотных почв Северо-Западной Якутии, подверженных техногенному воздействию при проведении алмазодобычных работ. Объекты: криоземы – мерзлотные почвы северо-таежных ландшафтов Северо-Западной Якутии. Объекты и методы. Статья представляет результаты выполненных работ за период с 1994 по 2019 гг. на территории Далдынского кимберлитового поля, где разрабатываются открытым способом кимберлитовые трубки Удачная и Зарница и где находится Удачнинский горно-обогатительный комбинат АК «Алроса» (ПАО). Объектом изучения являлись мерзлотные почвы северо-таежных ландшафтов Северо-Западной Якутии. Почвы данного района отражают общие закономерности формирования почвенного покрова на территории исследования и входят в состав Восточно-Сибирской мерзлотно-северотаежной области бореального пояса почв России. В ходе полевых наблюдений был применен профильный подход, предполагающий сбор образцов из почвенных генетических горизонтов до границы сезонно-талого слоя. Определены знаковые содержания 23 химических элементов методом спектрального полуколичественного анализа. Результаты геохимических исследований мерзлотных почв приведены с учетом геохимии почвообразующих пород Далдыно-Алакитского горнопромышленного района. Для выявления геохимических характеристик рассчитаны коэффициенты концентрации (Кс) и коэффициенты накопления (K0–К3) исследуемых элементов в системе породы–почвы. Построены накопительные ряды, отражающие геохимическую специфику доминирующих типов почв территории исследования. Каждый из исследованных типов почв характеризуется своеобразием микроэлементного спектра. Полиэлементные ассоциации создаются в результате геохимического влияния почвообразующего субстрата. Выявлено, что территория Далдыно-Алакитского района отличается повышенными концентрациями в почвах Cr, Ni, Co, V, Сu, Pb, Li, Sr.

Whilst the Arctic and boreal bumblebee fauna is increasingly studied worldwide, information is missing about the genetic connections between circum-boreal populations of some widespread species, especially those living in remote regions like North-East Siberia and Alaska. Here, we study one of the most common boreal bumblebee species, Bombus (Pyrobombus) jonellus (Kirby, 1802), as a model to investigate current circum-boreal genetic connections and relations with relictual populations in its post-glacial refugia in Southern Europe. Our haplotype network analysis based on a fragment of the cytochrome oxidase 1 gene reveals two main conspecific lineages, one in Europe including the Southern relictual populations from the Pyrenees and the second comprising Eastern Palearctic and Nearctic populations. However, West-Siberian populations of Bombus jonellus share haplotypes with the two distinct lineages. These results could indicate a postglacial, multidirectional and circum-boreal recolonization both in Europe and East-Palearctic from refugia in Siberia, in addition to other recolonization ways from Southern European refugia and Beringia. These findings highlight that a priori distant and isolated conspecific populations of B. jonellus could presently remain connected or have only presented a recent break in gene flow.

According to baroclinic adjustment theory, the isentropic slope maintains its marginal state for baroclinic instability. However, the recent trend of Arctic warming raises the possibility that there could have been a systematic change in the extratropical isentropic slope. In this study, global reanalysis data are used to investigate this possibility. The result shows that tropospheric isentropes north of 50°N have been flattening significantly during winter for the recent 25 years. This trend pattern fluctuates at intraseasonal time scales. An examination of the temporal evolution indicates that it is the planetary-scale (zonal wavenumbers-1–3) eddy heat fluxes, not the synoptic-scale eddy heat fluxes, that flatten the isentropes; synoptic-scale eddy heat fluxes instead respond to the subsequent changes in isentropic slope. This extratropical planetary-scale wave growth is preceded by an enhanced zonal asymmetry of tropical heating and poleward wave activity vectors. A numerical model is used to test if the observed latent heating can generate the observed isentropic slope anomalies. The result shows that the tropical heating indeed contributes to the isentropic slope trend. The agreement between the model solution and the observation improves substantially if extratropical latent heating is also included in the forcing. The model temperature response shows a pattern resembling the warm-Arctic–cold-continent pattern. From these results, it is concluded that the recent flattening trend of isentropic slope north of 50°N is mostly caused by planetary-scale eddy activities generated from latent heating, and that this change is accompanied by a warm-Arctic–cold-continent pattern that permeates the entire troposphere.

The transition zone between the northern boreal forest and the Arctic tundra, known as the tundra–taiga ecotone (TTE) has undergone rapid warming in recent decades. In response to this warming, tree density, growth, and stand productivity are expected to increase. Increases in tree density have the potential to negate the positive impacts of warming on tree growth through a reduction in the active layer and an increase in competitive interactions. We assessed the effects of tree density on tree growth and climate–growth responses of Cajander larch (Larix cajanderi Mayr.) and on trends in the normalized difference vegetation index (NDVI) in the TTE of Northeast Siberia. We examined 19 mature forest stands that all established after a fire in 1940 and ranged in tree density from 300 to 37 000 stems·ha−1. High-density stands with shallow active layers had lower tree growth, higher stand productivity, and more negative growth responses to growing season temperatures compared with low-density stands with deep active layers. Variation in stand productivity across the density gradient was not captured by Landsat-derived NDVI, but NDVI did capture annual variations in stand productivity. Our results suggest that the expected increases in tree density following fires at the TTE may effectively limit tree growth and that NDVI is unlikely to capture increasing productivity associated with changes in tree density.

To reconstruct the climatic fluctuations that occurred in the middle latitudes of the Northern Hemisphere in the Atlantic Ocean in the Campanian Age, the systematic composition of the shells of planktonic foraminifera was studied from core samples from seven deep-water drilling holes. The identified foraminiferal assemblages are assigned to two types (boreal and intermediate) and one subtype (warm boreal) thanatocenosis. On the basis of their spatial distribution, the position of climatic zones for sections of the early, middle, beginning and end of the late Campanian was determined. Different climatic zones were characterized by different types of water masses. Within the studied water area, during most of the studied age interval, two climatic zones were developed: intermediate and boreal. In the Early and Middle Campanian, the boundary between them was in the southern part of the region under consideration. At the beginning of the late Campanian, this border sharply shifted to the north. A short-term Late Campanian warming began. At the end of the late Campanian, the temperature dropped sharply. An intermediate type of thanatocenosis has not been identified. Even in the southernmost part of the water area, the warmboreal subzone prevailed. The obtained reconstructions are confirmed by our own and published data of oxygen isotope analysis.