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The nature of vegetation cover present in Beringia during the last glaciation remains unclear. Uncertainty rests partly with the limitations of conventional paleoecological methods. A lack of sufficient taxonomic resolution most notably associated with the grasses and sedges restricts the paleoecological inferences that can be made. Stable isotope measurements of subfossil plants are frequently used to enhance paleoenvironmental reconstructions. We present an investigation of the stable carbon isotope composition (δ13C) of modern and subfossil grasses and sedges (graminoids) from Eastern Beringia. Modern grasses from wet habitats had a mean d13C of 229.1% (standard deviation [SD] = 2.1%, n = 75), while those from dry habitats had a mean of 226.9% (SD = 1.19, n = 27). Sedges (n = ∼50) from dry, wet, marsh, and sand dune habitats had specific habitat ranges. Four modern C4 grasses had δ13C values typical of C4 plants. Analyses were also conducted using subfossil graminoid remains from several sedimentary paleoecological contexts (e.g., arctic ground squirrel nests, loess, permafrost, and paleosols) in Eastern Beringia. Results from these subfossil samples, ranging in age from >40,000 to ca. 11,000 cal. yr BP, illustrate that the δ13C of graminoid remains has altered during the past. The range of variation in the subfossil samples is within the range from modern graminoid specimens from dry and wet habitats. The results indicate that stable isotopes could contribute to a comprehensive and multiproxy reconstruction of Beringian paleoenvironments. [ABSTRACT FROM AUTHOR]

At northern high latitudes, biosphere responses to and interactions with climate warming are expected to be significant during the 21st century. Most predictions of climate-biosphere interactions rely on experiments and observations in contemporary landscapes, e.g., modem distributions of vegetation types and their structural features are used to delimit potential biosphere-atmosphere feedbacks. Paleorecords look beyond the present to examine vegetation configurations under climatic regimes that approximate future scenarios. To enhance the knowledge of arctic and subarctic ecosystems under varying climatic conditions, we analyzed pollen and macrofossil data from Beringia (northeast Siberia, Alaska, and northwest Canada; 130° E to 130° W) over the past 21 000 years, with a focus on structural and functional features of the vegetation. During the early Holocene (∼ 13 000- 10 000 cal yr BP), shrub tundra ecosystems responded to climate warming through a shift from shrub tundra to deciduous forest or woodland. Early-Holocene vegetation was structurally, and hence functionally, novel compared with today's dominant vegetation types. "Modern" boreal forest developed in the mid-Holocene (∼ 10 000-6000 cal yr BP), when evergreen conifers expanded in much of the region. The shift froth tundra to deciduous forest could have happened rapidly and in situ as the result of individual (phenotypic) and/ or population-scale responses to climate warming. Because the structural and functional properties of deciduous forest differ from those of evergreen coniferous forest and tundra, deciduous boreal forest should be included in the range of future scenarios used to assess the probable feedbacks of vegetation to the climatic system that result from global warming at northern high latitudes. [ABSTRACT FROM AUTHOR]

Beringia, far north-eastern Siberia and north-western North America, was largely unglaciated during the Pleistocene. Although this region has long been considered an ice-age refugium for arctic herbs and shrubs, little is known about its role as a refugium for boreal trees and shrubs during the last glacial maximum (LGM,c. 28,000–15,000 calibrated years before present). We examine mapped patterns of pollen percentages to infer whether six boreal tree and shrub taxa (Populus,Larix,Picea,Pinus,Betula,Alnus/Duschekia) survived the harsh glacial conditions within Beringia.Extensive networks of pollen records have the potential to reveal distinctive temporal–spatial patterns that discriminate between local- and long-distance sources of pollen. We assembled pollen records for 149 lake, peat and alluvial sites from the Palaeoenvironmental Arctic Sciences database, plotting pollen percentages at 1000-year time intervals from 21,000 to 6000 calibrated years before present. Pollen percentages are interpreted with an understanding of modern pollen representation and potential sources of long-distance pollen during the glacial maximum. Inferences from pollen data are supplemented by published radiocarbon dates of identified macrofossils, where available.Pollen maps for individual taxa show unique temporal-spatial patterns, but the data for each taxon argue more strongly for survival within Beringia than for immigration from outside regions. The first increase ofPopuluspollen percentages in the western Brooks Ranges is evidence thatPopulustrees survived the LGM in central Beringia. Both pollen and macrofossil evidence supportLarixsurvival in western Beringia (WB), but data forLarixin eastern Beringia (EB) are unclear. Given the similar distances of WB and EB to glacial-age boreal forests in temperate latitudes of Asia and North America, the widespread presence ofPiceapollen in EB andPinuspollen in WB indicates thatPiceaandPinussurvived within these respective regions.Betulapollen is broadly distributed but highly variable in glacial-maximum samples, suggesting thatBetulatrees or shrubs survived in restricted populations throughout Beringia.Alnus/Duschekiapercentages show complex patterns, but generally support a glacial refugium in WB.Our interpretations have several implications, including: (1) the rapid post-glacial migration rate reported forPiceain western Canada may be over estimated, (2) the expansion of trees and shrubs within Beringia should have been nearly contemporaneous with climatic change, (3) boreal trees and shrubs are capable of surviving long periods in relatively small populations (at the lower limit of detection in pollen data) and (4) long-distance migration may not have been the predominant mode of vegetation response to climatic change in Beringia. [ABSTRACT FROM AUTHOR]

Abstract: Chukotka is a key region for understanding both Quaternary environmental history and transcontinental migrations of flora and fauna during the Pleistocene as it lies at the far eastern edge of Asia bordering the Bering Sea. The now submerged land bridge is the least understood region of Beringia yet the most critical to understanding migrations between the Old and New Worlds. The insect fauna of the Main River Ledovy Obryv (Ice Bluff) section, which is late Pleistocene in age (MIS 3-2), is markedly different from coeval faunas of areas further to the west, as it is characterized by very few thermophilous steppe elements. From the fauna we reconstruct a steppe-tundra environment and relatively cold conditions; the reconstructed environment was moister than that of typical steppe-tundra described from further west. The data from this locality, if typical of the Chukotka Peninsula as a whole, may indicate that a barrier associated with the environments of the land bridge restricted trans-Beringian migrations, particularly the more thermophilous and xeric-adapted elements of the Beringian biota, supporting the hypothesis of a cool but moist land-bridge filter inferred from evidence from several other studies. [Copyright &y& Elsevier]

Abstract: Andrei Sher (1939–2008) was a key individual in Beringian studies who made substantial and original contributions, but also, importantly, built bridges between western and eastern Beringian scientists spanning some five decades of research. He is perhaps best known as a Quaternary palaeontologist, specializing in large mammals, and mammoths in particular, but his field of his scientific research was much broader, encompassing Quaternary geology, stratigraphy, geocryology, and paleoenvironmental reconstructions. He worked mainly in Siberia, in the Kolyma and Indigirka lowlands, and Chukotka, but also completed fieldwork in Alaska and Yukon through joint projects with American and Canadian scientists. Andrei was an active scientist until the last days of his life. He was involved in many different research projects ranging from mammoth evolution, fossil insects and environmental changes and ancient DNA. Without Andrei’s connections between researchers, many unique discoveries would likely be unknown. [Copyright &y& Elsevier]