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Origin and cause of the mammoth steppe: A story of cloud cover, woolly mammal tooth pits, buckles, and inside-out Beringia
Abstract
To account for the vastness of the northern arid steppes during Glacial episodes, I propose the proximate key variable was simply frequent clear skies. This hitherto under-emphasized point is the hub which best explains many questions. Low maritime cloud cover best accounts for today's tundra, and in a related way, the cloudy Polar Front accounts for the whole of the taiga. Even during Glacial maxima, the proximity of the sea to the Bering isthmus created intermittent maritime cloud cover. This regional cloud cover produced an ecological interruption, or buckle, of the arid steppe belt. While this Beringian mesic buckle did not serve as an intercontinental ecological barrier to most steppe-adapted species, it does seem to have limited the distributions of woolly rhinos, camels, American kiangs, short-faced bears, badgers, and some others. At the beginning of the Holocene, this narrow refugium seems to have been a source of some mesic-adapted species which colonized westward into the now tundra vegetation of northern Asia and eastward into northern North America. This Holocene expansion from a limited and regional Pleistocene refugium created our present misconceptions about Beringia. The mid-strait mesic ecological conditions were the exception to the more extensive, arid-adapted, communities of the Mammoth Steppe.
... During the 1990s, the analysis of cores retrieved from the former surface of the land bridge indicated a mesic tundra, and Guthrie and others later proposed that the low-lying BLB supported a mesic tundra belt that acted as an ecological barrier to at least some of the steppe-adapted taxa (including invertebrates) on opposing sides of the Bering Strait [29][30][31]. Both the oceanic influence of the North Pacific on the southern land bridge and poor drainage conditions created by the lack of topographic relief on the BLB would have promoted a mesic tundra environment. ...
... Kolyma Basin) and the North Slope of Alaska. Schirrmeister et al. labelled this landscape the 'Great Arctic Plain' (GAP) [31,36,37]. ...
... The mammalian fauna, reconstructed from hundreds of radiocarbon-dated bones recovered from localities on the northeastern Siberian lowlands, arctic Alaska/Yukon and islands in the East Siberian Sea, included typical northern steppe dwellers, such as bison, horse and woolly rhinoceros, along with tundra species, such as reindeer and musk ox. Woolly mammoth, which enjoyed a wide dietary niche, was especially common and survived on island remnants of both the GAP and southern BLB into the mid Holocene [4,31,36,39]. ...
Did Beringian environments represent an ecological barrier to humans until <15,000 years ago or was access to the Americas controlled by the spatial-temporal distribution of North American ice sheets? Beringian environments varied with respect to climate and biota, especially in the two major areas of exposed continental shelf. The East Siberian Arctic Shelf (“Great Arctic Plain” [GAP]) supported a dry steppe-tundra biome inhabited by a diverse large-mammal community, while the southern Bering-Chukchi Platform (“Bering Land Bridge” [BLB]) supported mesic tundra and probably a lower large-mammal biomass. A human population with west Eurasian roots occupied the GAP before the Last Glacial Maximum (LGM) and may have accessed mid-latitude North America via an interior ice-free corridor. Re-opening of the corridor <14,000 years ago indicates that the primary ancestors of living First Peoples, who already had spread widely in the Americas at this time, probably dispersed from the NW Pacific coast. A genetic “arctic signal” in non-arctic First Peoples suggests that their parent population inhabited the GAP during the LGM, before their split from the former. We infer a shift from GAP terrestrial to a subarctic maritime economy on the southern BLB coast before dispersal in the Americas from the NW Pacific coast.
... The mammoth steppe ecosystem collapsed at the end of the Pleistocene (ca. 14,000 cal yr BP) as increasing effective moisture (precipitation minus evaporation) led to paludification, cooler soil conditions and shallower active layers that favoured the expansion of woody shrub taxa including Betula and Salix (Guthrie, 2001;Mann et al., 2013Mann et al., , 2015. These new conditions were largely inhospitable to both grazing megafauna, which relied upon the steppe-tundra vegetation, and burrowing mammals, such as the arctic ground squirrel (Urocitellys parryii), that require deep active layer depths (>0.9 m) for nest construction and hibernation (Guthrie, 1984(Guthrie, , 2001Zazula et al., 2005). ...
... 14,000 cal yr BP) as increasing effective moisture (precipitation minus evaporation) led to paludification, cooler soil conditions and shallower active layers that favoured the expansion of woody shrub taxa including Betula and Salix (Guthrie, 2001;Mann et al., 2013Mann et al., , 2015. These new conditions were largely inhospitable to both grazing megafauna, which relied upon the steppe-tundra vegetation, and burrowing mammals, such as the arctic ground squirrel (Urocitellys parryii), that require deep active layer depths (>0.9 m) for nest construction and hibernation (Guthrie, 1984(Guthrie, , 2001Zazula et al., 2005). In eastern Beringia, lakesediments provide the most common continuous palaeoecological records that span the transition from steppe-tundra to shrub tundra vegetation. ...
... To establish the age of pore-ice, some understanding of the paleo-active layer thickness and sedimentation rate are required (Porter and Opel, 2020). It is likely that during the last cold stage active layers were deeper than at present because sparse vegetation and reduced cloud cover promoted exposed, well drained mineral soils (Guthrie, 1990b(Guthrie, , 2001. In this study, we assume cold stage active layers to be 0.8 m (samples from Unit 1 beneath the prominent paleosol), which may be a conservative estimate. ...
In eastern Beringia (unglaciated Alaska and western Yukon), the Pleistocene-Holocene transition was characterised by rapid changes in plant, insect and mammal communities as the mammoth steppe ecosystem was replaced, first by shrub tundra and later boreal forest. These changes indicate a transition from well drained terrain with deep active layers to wetter, cooler soils, to which steppe-tundra vegetation was poorly adapted. The nature and precise timing of these events is not well resolved, particularly in central Yukon where regional climate may have been strongly affected by the retreating Cordilleran-Laurentide ice sheet complex. Resolving this uncertainty is not only important for understanding past ecosystems, but also provides a long-term perspective for contemporary environmental change and shrub expansion that affects large areas of northern high-latitudes today. Here, we report chronology (41 radiocarbon dates), stratigraphy, pore-ice δ²H/δ¹⁸O measurements, pollen data, megafauna remains and fossil insect assemblages from a permafrost-preserved loessal sequence in central Yukon, named Lucky Lady. The site spans the interval from ca. 17,000 to 8000 cal yr BP (calibrated years before C.E. 1950) and records the Pleistocene-Holocene transition in exceptional resolution. Full glacial environments (ca. 16,500 cal yr BP) supported elements of steppe-tundra vegetation and an insect fauna dominated by Connatichela artemisiae - an endemic weevil indicating warm soil temperatures. The collapse of the mammoth steppe ecosystem began with slowing of loess accumulation and development of paleosol ca. 13,480 cal yr BP. At this time, C. artemisiae remains become infrequent and Artemisia pollen decline to be replaced by Cyperaceae (ca. 13,220), before mesic, shrub taxa (likely dwarf Betula and Salix) becomes dominant ca. 13,210 cal yr BP. The establishment of shrub tundra is associated with rapid changes in δ²H/δ¹⁸O measurements, suggesting that ecological turnover coincided with a shift in atmospheric conditions and moisture availability. Finally, boreal vegetation communities became established ca. 10,680 cal yr BP. The replacement of steppe-tundra vegetation in central Yukon lagged other areas of eastern Beringia by as much as 1000 years and coincided with rapid deglaciation during the Bølling–Allerød time-period (14,600–12,900 cal yr BP). Turnover in insect and vegetation communities took place in ca. 40 years as shrub tundra became dominant. This rapid turnover has parallels with contemporary Arctic greening and re-emphasises the sensitivity of high-latitude environments to climate change.
... We cannot directly assess the validity of the various named Beringian horse species here but have uncovered evidence that there is separation by body mass that could be unrelated to phylogenetic position, though we cannot yet reject the coexistence of multiple species. In fact, the mammoth steppe ecosystem is considered to have been a highly productive environment capable of supporting many species of large herbivores (Guthrie 1982(Guthrie , 2001Zimov et al. 2012;Willerslev et al. 2014;Zhu et al. 2018), including species with overlapping niches (Bocherens 2003;Pires et al. 2015;Davis 2017), not unlike the African savannah. There are several species of modern equids that coexist in Africa with many other species of large herbivores (i.e., elephants, wildebeasts, antelope) by niche partitioning (e.g., Voeten and Prins 1999;Cromsigt and Olff 2006;Schulz and Kaiser 2013;Kartzinel et al. 2015;Mandlate et al. 2019) that is driven in part by differences in body mass among species (Kleynhans et al. 2011). ...
... There are several species of modern equids that coexist in Africa with many other species of large herbivores (i.e., elephants, wildebeasts, antelope) by niche partitioning (e.g., Voeten and Prins 1999;Cromsigt and Olff 2006;Schulz and Kaiser 2013;Kartzinel et al. 2015;Mandlate et al. 2019) that is driven in part by differences in body mass among species (Kleynhans et al. 2011). Beringian equids would have similarly co-existed with other megaherbivores such as mammoths, bison, and muskox (Harington and Clulow 1973;Harington 1980Harington , 1990Harington , 2011Hughes et al. 1981;Weber et al. 1981;Porter 1986), likely by some degree of niche partitioning behaviours (e.g., Guthrie 2001;Fox-Dobbs et al. 2008;Schwartz-Narbonne et al. 2019;Drucker 2022). Although palaeoecological research on Beringian equids is limited, they are thought to have been primarily grazers that occasionally consumed some browse vegetation (Guthrie 2001;Fox-Dobbs et al. 2008;Semprebon et al. 2016;Kelly et al. 2021). ...
... Beringian equids would have similarly co-existed with other megaherbivores such as mammoths, bison, and muskox (Harington and Clulow 1973;Harington 1980Harington , 1990Harington , 2011Hughes et al. 1981;Weber et al. 1981;Porter 1986), likely by some degree of niche partitioning behaviours (e.g., Guthrie 2001;Fox-Dobbs et al. 2008;Schwartz-Narbonne et al. 2019;Drucker 2022). Although palaeoecological research on Beringian equids is limited, they are thought to have been primarily grazers that occasionally consumed some browse vegetation (Guthrie 2001;Fox-Dobbs et al. 2008;Semprebon et al. 2016;Kelly et al. 2021). In other regions, ancient equids are believed to have partitioned resources based on their sizes; larger horses consumed tall, coarse grasses and more browse vegetation, while the smaller horses were predominantly grazing on shorter, softer grasses (Van Asperen 2010; Wolf et al. 2010;Saarinen et al. 2021). ...
Unlabelled:
The metapodials of extinct horses have long been regarded as one of the most useful skeletal elements to determine taxonomic identity. However, recent research on both extant and extinct horses has revealed the possibility for plasticity in metapodial morphology, leading to notable variability within taxa. This calls into question the reliability of metapodials in species identification, particularly for species identified from fragmentary remains. Here, we use ten measurements of metapodials from 203 specimens of four Pleistocene horse species from eastern Beringia to test whether there are significant differences in metapodial morphology that support the presence of multiple species. We then reconstruct the body masses for every specimen to assess the range in body size within each species and determine whether species differ significantly from one another in mean body mass. We find that that taxonomic groups are based largely on the overall size of the metapodial, and that all metapodial measurements are highly autocorrelated. We also find that mean body mass differs significantly among most, but not all, species. We suggest that metapodial measurements are unreliable taxonomic indicators for Beringian horses given evidence for plasticity in metapodial morphology and their clear reflection of differences in body mass. We recommend future studies use more reliable indicators of taxonomy to identify Beringian horse species, particularly from localities from which fossils of several species have been recovered.
Supplementary information:
The online version contains supplementary material available at 10.1007/s10914-022-09626-4.
... Besides the iconic woolly mammoth (Mammuthus primigenius), the occurrence of large-and very large-sized mammals with large cranial appendages such as antlers and horns is one of the striking traits of the Mammoth Steppe (Guthrie 1982). Their presence over large territories implied the existence of a rich and productive plant biomass and limited direct competition for food and habitat (e.g., Guthrie 1982, Vereshchagin & Baryshnikov 1991. ...
... Besides the iconic woolly mammoth (Mammuthus primigenius), the occurrence of large-and very large-sized mammals with large cranial appendages such as antlers and horns is one of the striking traits of the Mammoth Steppe (Guthrie 1982). Their presence over large territories implied the existence of a rich and productive plant biomass and limited direct competition for food and habitat (e.g., Guthrie 1982, Vereshchagin & Baryshnikov 1991. Vereshchagin & Baryshnikov (1991) compared the LGP faunal assemblage to the modern African ecosystems, arguing for a similarity in ecosystem structure and the specialization by herbivores on different plants and/or different growth stages. ...
... Vereshchagin & Baryshnikov (1991) compared the LGP faunal assemblage to the modern African ecosystems, arguing for a similarity in ecosystem structure and the specialization by herbivores on different plants and/or different growth stages. Guthrie (2001) studied the plant remains found in fossil maxillae and mandibles of museum specimens of the LGP Alaska and concluded that herbaceous plants (grasses, sedges, and forbs) dominated in the diet of most large herbivores. This conclusion was later confirmed by the examination of occlusal microwear, which showed the high density of scratches for the specimens of Fairbanks (e.g., Rivals et al. 2010) with the notable exception of the moose (Alces), a species more securely associated with the Holocene than the LGP (Guthrie 2006). ...
The Mammoth Steppe was the dominant terrestrial biome of the Northern Hemisphere during the late Pleistocene. It encompassed a nonanalog community of animals living in a cold and treeless steppe-tundra landscape. The high diversity of species, including megafauna, could be supported by a productive environment. The carbon-13 and nitrogen-15 abundances in bone collagen confirmed that the coexistence of the large herbivores was facilitated by a pronounced dietary niche partitioning, with some species relatively flexible in the exploitation of browse and graze, while others were more specialized. The isotopic abundances of carbon and nitrogen in carnivores confirm a dietary partitioning, probably based on the size of prey, with an increasingly generalist behavior emerging after the Last Glacial Maximum with notable exceptions. Isotopic investigation reveals dynamic processes of ecological displacement and replacement, shedding new light on the potential niche spectrum of extant species that are now present as relic populations. ▪ The Mammoth Steppe is an extinct nonanalog ecosystem with high productivity and biodiversity despite the cold and dry conditions of the Last Glacial Period. ▪ Stable isotopes reveal that niche partitioning among herbivores and carnivores is a dominant trait of the Mammoth Steppe. ▪ Switches in preferred prey and ecological replacement are observed among carnivores over time, with the few highly specialized predators going extinct. ▪ Warmer and more humid conditions preceding the Holocene impacted large herbivores in most regions of the Mammoth Steppe, driving some of the largest ones to extinction.
Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 50 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
... Prior to these events, herds of grazing megafauna occupied a biome termed the mammoth steppe (7-9) or steppe-tundra (10, 11), which has no widespread modern analog. This novel, dry environment supported diverse plant communities, dominated by grasses, sedges, Artemisia spp., and a range of other forbs (8,(12)(13)(14)(15)(16). Sometime between 16 ka and 13 ka, woody shrub species began to expand across eastern Beringia, coupled with the development of peatlands and organic soil horizons (14,17,18). ...
... The broad chronological overlap between the timing of shrub expansion and turnover in mammal populations has led numerous authors to hypothesize that habitat loss was a key driver of Late Pleistocene extinctions in eastern Beringia (8,(25)(26)(27). These authors argue that the Betulaand Salix-dominated shrub tundra was inhospitable to grazing megafauna because lowgrowing shrubs develop strong antiherbivory compounds, making them inedible or toxic to many mammals that lack a rumen to aid digestion (28). ...
... In records with high-resolution sampling [e.g., Birch Lake (19)], this difference is small; however, in most records, sampling resolution is ≤1 pollen spectrum every 10 cm, which may represent >500 y of sediment accumulation (SI Appendix, Table S1). With this approach, we aim to establish whether shrub expansion began prior to turnover in megafauna communities, as predicted by Guthrie (6,8), or after populations of keystone species collapsed, as suggested by Zimov et al. (2,29). As these hypotheses predict events in the opposite order, it allows us to assess whether the Late Pleistocene extinction of grazing megafauna species was a response to, or the cause of, steppe-tundra decline. ...
Significance
Megafauna strongly influence vegetation structure, and population declines can alter ecosystem functioning. Overhunting of grazing megafauna is argued to have driven the collapse of widespread, northern steppe-tundra and its replacement by woody vegetation at the end of the ice age. However, in Alaska and Yukon, mammoth and horse became extinct around the time that steppe-tundra was replaced by shrub tundra, leaving it unclear whether this vegetation change caused, or was caused by, reduced megafauna populations. Comparison of accurately dated pollen records with a radiocarbon-dated bone chronology shows that shrubs began expanding before grazer populations declined. This indicates that climate was the primary control of steppe-tundra persistence and that climate-driven vegetation change may pose threats to faunal diversity in the future.
... Our study also evidences the (Beck et al. 2016;Viñas et al. 2016) and both boreal and deciduous forest environments are also suggested by the presence of shrews (Rhodes et al. 2018. The periodic encroachment of arid steppe vegetation during the MP at Geißenklösterle and MP and early UP at Hohle Fels may indicate the presence of a more typical steppe-tundra landscape (Chytrý et al. 2019) akin to the well-known Mammoth Steppe (Guthrie 2001(Guthrie , 2013. However, the lack of a consistent signal for steppe vegetation in the Ach Valley throughout the period studied suggests this landscape may have differed from the classical description of the mammoth Steppe in the past. ...
... This is common in European Paleolithic rodent and large faunal records and may reflect the presence of non-analogous environments in the past (Stewart 2005). Claims that the OIS 3 ecology was non-analogue in nature are far from new (Guthrie 2001(Guthrie , 2013Stewart et al. 2003Stewart et al. , 2019Stewart 2005). Although the likelihood of non-analogous environments may increase with age (Stewart 2008), the QlBM and QnBM model has been successfully applied to wide number of archaeological assemblages ranging in age from OIS 7 to the Holocene (Socha, 2014;López-García et al. 2015, 2016, 2017a, 2017b, 2018a, 2018bPinero et al. 2016;Rey-Rodríguez et al. 2016;Discamps and Royer 2017;Berto et al. 2018Berto et al. , 2019Fagoaga et al. 2018). ...
... Still, boreal, deciduous, steppe and tundra ecozones were clearly present across southern Germany during this period, and this may reflect an ecotone not present in modern day environmental variability. C) Regional and/or local response to OIS 3 climate This hypothesis has been put forth based on previous qualitative paleoenvironmental reconstructions of the Ach Valley landscape ) and the fact that geographic features of Central Europe may have shaped the vegetative and faunal response to climatic changes (Guthrie 2001). Genetic studies of forest adapted plants (Kolář et al. 2016) and insects (Drees et al. 2016) suggest that the mountainous regions north of the Swiss Alps may have harbored cryptic temperate forest refugia (Stewart and Lister 2001) during interstadial periods. ...
Ensuring comparability between results is a key goal of all paleoecological reconstructions. Quantitative estimates of meteorological variables, as opposed to relative qualitative descriptions, provide the opportunity to compare local paleoenvironmental records against global estimates and incrementally build regional paleoclimatic records. The Bioclimatic Method provides quantitative and qualitative estimates of past landscape composition and climate along with measures of statistical accuracy by applying linear discriminant functions analysis and transfer functions to faunal taxonomic abundance data. By applying this method to the rodent data from Geißenklösterle and Hohle Fels, two Paleolithic cave sites located in the Ach Valley of southwestern Germany, we classify the regional vegetation according to Walters’ zonobiome model. We also present new estimates of meteorological variables including mean annual temperature, mean annual precipitation, and vegetative activity period of the Ach Valley for the period spanning ~ 60,000 to 35,000 cal BP. The results suggest the Ach Valley contained a non-analogous landscape of arctic tundra and temperate deciduous woodland with occasional arid steppe expansion. Meteorological estimates suggest the climate was significantly colder during the Middle and Upper Paleolithic than today, with higher annual precipitation and dramatic temperature shifts between seasons. These results fit well with climatic reconstructions from Switzerland and the Netherlands based on a variety of proxies. They also provide further evidence of a localized climatic response within southwestern Germany to the stadial-interstadial shifts preceding the Heinrich 4 event. Finally, these results reinforce our previous claims that climatic volatility was not a driving force in the loss of Neanderthal groups throughout the Swabian Jura during OIS 3.
... However, some coldand/or dry-adapted taxa (such as Artemisia and Poa) were replaced by forbs that were better adapted to warmer climates, and Salix was partially replaced by Betula and Alnus (Extended Data Fig. 3). The vegetation in this region persisted as a steppe-tundra mosaic through much of the Holocene, probably due to central Siberia's extreme climatic continentality caused by the Siberian anticyclone 19 , which created largely ice-free conditions during the LGM and fostered dry hydrogeological conditions in postglacial times that mitigated the effects of rising global temperatures on vegetation 11 . ...
... When each herbivore species is considered individually, the only climate variable that is consistently and positively associated with the presence of their eDNA is temperature seasonality (Fig. 3 and Extended Data Fig. 4a), consistent with expectations based on the continental climate associated with the Mammoth Steppe, a biome that is associated with extremely cold and dry conditions that supported abundant large mammal grazers 19 . The importance of climatic variables becomes more evident when herbivores are considered as a group. ...
... The importance of climatic variables becomes more evident when herbivores are considered as a group. Precipitation-in greater amounts and seasonality-is a principal negative factor in the distribution of Arctic herbivores (Fig. 3), presumably because increased snow cover during winter limited the food access of grazers, and a wetter substrate is more difficult for them to exploit, in contrast to the firm and dry ground of the steppe-tundra 7,19 . ...
During the last glacial–interglacial cycle, Arctic biotas experienced substantial climatic changes, yet the nature, extent and rate of their responses are not fully understood1–8. Here we report a large-scale environmental DNA metagenomic study of ancient plant and mammal communities, analysing 535 permafrost and lake sediment samples from across the Arctic spanning the past 50,000 years. Furthermore, we present 1,541 contemporary plant genome assemblies that were generated as reference sequences. Our study provides several insights into the long-term dynamics of the Arctic biota at the circumpolar and regional scales. Our key findings include: (1) a relatively homogeneous steppe–tundra flora dominated the Arctic during the Last Glacial Maximum, followed by regional divergence of vegetation during the Holocene epoch; (2) certain grazing animals consistently co-occurred in space and time; (3) humans appear to have been a minor factor in driving animal distributions; (4) higher effective precipitation, as well as an increase in the proportion of wetland plants, show negative effects on animal diversity; (5) the persistence of the steppe–tundra vegetation in northern Siberia enabled the late survival of several now-extinct megafauna species, including the woolly mammoth until 3.9 ± 0.2 thousand years ago (ka) and the woolly rhinoceros until 9.8 ± 0.2 ka; and (6) phylogenetic analysis of mammoth environmental DNA reveals a previously unsampled mitochondrial lineage. Our findings highlight the power of ancient environmental metagenomics analyses to advance understanding of population histories and long-term ecological dynamics.
... Hydrology is a less conspicuous aspect of Arctic paleoclimate than extreme temperature variations or circulation patterns. However, the hydrologic impacts of climate change are the proximate cause for shifts in ecosystem function in Alaska and the former subcontinent of Beringia (MacDonald et al. 2000;Guthrie, 2001;Mann et al., 2002). These regions are characterized by low amounts of precipitation in addition to low temperatures, which in combination determine the distribution of plant functional types (e.g. ...
... The current predominance of oversaturated soils during the ice-free season, which serves to maintain the region's modern state of 'waterlogged aridity' (Mann et al., 2001), is a result of the interplay of active layer thaw, permafrost-impeded drainage, and seasonal snow and ice melt that have fostered the development of vast peatlands. Broad changes in late Pleistocene moisture balance across Beringia, via increased or reduced precipitation, evaporation and/or cloud cover, have been proposed, modeled and explored with proxy data (Bartlein et al., 1991(Bartlein et al., , 2015Anderson and Brubaker, 1994;Elias et al., 1996; Barber and Finney, 2000;Guthrie, 2001;Mann et al., 2002;Abbott et al., 2010;Finkenbinder et al., 2015), but many specific mechanisms remain unexplored by paleoenvironmental proxy data. For example, a more complete understanding of precipitation seasonality, and subsequent factors contributing to water cycling such as evaporation and evapotranspiration and infiltration/flow/permafrost, are needed to understand the impacts of climate change on Arctic regionspast, present and future. ...
... The results of this study further highlight previous observations that the low Arctic is sensitive to changes in P-E, which had significant impacts on Beringian ecosystem evolution. Changes in vegetation are temporally associated with human occupation and migration ( Hoffecker and Elias, 2007) and the demise of megafauna (Guthrie, 2001;Mann et al., 2015). Yet threshold ecosystem responses to changes in paleohydrology remain relatively unexplored, and a better understanding of water cycling is needed. ...
A submillennial-resolution record of lake water oxygen isotope composition (δ¹⁸O) from chironomid head capsules is presented from Burial Lake, north-west Alaska. The record spans the Last Glacial Maximum (LGM; ~20–16k cal a bp) to the present and shows a series of large lake δ¹⁸O shifts (~5‰). Relatively low δ¹⁸O values occurred during a period covering the LGM, when the lake was a shallow, closed-basin pond. Higher values characterize deglaciation (~16–11.5k cal a bp) when the lake was still closed but lake levels were higher. A rapid decline between ~11 and 10.5k cal a bp indicates that lake levels rose to overflowing. Lake δ¹⁸O values are interpreted to reflect the combined effects of changes in lake hydrology, growing season temperature and meteoric source water as well as large-scale environmental changes impacting this site, including opening of the Bering Strait and shifts in atmospheric circulation patterns related to ice-sheet dynamics. The results indicate significant shifts in precipitation minus evaporation across the late Pleistocene to early Holocene transition, which are consistent with temporal patterns of vegetation change and paludification. This study provides new perspectives on the paleohydrology of eastern Beringia concomitant with human migration and major turnover in megafaunal assemblages.
... In the WFL laminated layers, poorly preserved faunal remains (NISP = 17) possibly associated with accumulation by hyenas, were recovered and consist mainly of a 'mammoth-steppe' fauna including dental and osseous remains of horse, woolly rhinoceros, bison, and mammoth (cf. Guthrie 1990Guthrie , 2001. Hyena and small carnivore faunal elements are also present in the assemblage (Bringmans 2006). ...
... Outside of peak interglacial periods, the faunal and vegetation evidence from Middle Palaeolithic occupations, though coarse in temporal and spatial resolution, indicate ecological settings probably similar to the 'mammoth-steppe' (e.g. Guthrie 1990, Guthrie 2001, Gamble and Roebroeks 1999, Gamble 1999, Roebroeks and Tuffreau 1999. ...
... Large mammal populations would have also adapted to this unstable climatic setting by changing in population size, density, ranging/ foraging patterns and physical morphology (e.g. Guthrie 1990, Guthrie 2001, Gamble and Roebroeks 1999, Gamble 1999. Grazing species populations also contribute to the persistence of open grasslands and the mosaic distribution of plant communities in both upland plains and lowland floodplain areas (e.g. ...
The Palaeolithic archaeological database of northwest Europe is biased towards evidence originating in caves, rockshelters, fluvial, and littoral settings. Theories of regional land use patterns are therefore based on samples of behavioral residues from only certain parts of the environment. In addition, abundant and often ignored evidence for Palaeolithic land use is found in surface lithic assemblages occurring on elevated terraces and plateaus in river catchments. Integrating technological data from these landforms is necessary to complement this unbalanced picture of land use. This dissertation presents the results of analysis of lithic assemblages from elevated surfaces in the region of Dutch and Belgian Limburg, and attempts to integrate these data with those from lower elevation parts of the landscape to test hypotheses on land use and mobility. It was necessary to address theoretical and substantive problems associated with the time averaged, palimpsest nature of surface assemblages. When scales of analysis and theoretical perspectives were adjusted to accommodate these problems, long-term patterns of regional land use behavior became identifiable. The research examines how lithic assemblages on elevated surfaces vary in terms of raw material procurement, inter-site fragmentation of core reduction sequences, and patterns of artifact discard; and how this variability relates to site occupational frequency, an indicator of differential land use. Detailed techno-typological analysis was applied to samples of lithic assemblages from 9 sites (n artifacts = 2885). Comparison among assemblages from high and low elevation settings was conducted using analyses of artifact class diversity in relation to sample size. The results of these efforts indicate differences in site occupational frequency that describe variability in site function. Over the long time span of the Middle Palaeolithic, stable elevated terraces and plateaus were frequently re-occupied for a variety of purposes, whereas lower elevation localities, often in fluvial settings, were occupied less frequently for specific tasks. Logistical mobility was probably more common than traditionally thought for Palaeolithic groups in the research area. This research demonstrates that systematic analysis of Palaeolithic upland surface assemblages yields valuable data that can be integrated with those from other parts of the landscape to investigate long-term regional land use.
... Better seen as a mosaic of diverse landscapes, this highly productive non-analogue biome was evidently characterised by nutrient-rich, grass-and forb-dominated vegetation growing on loess-fertilised soils, supporting an unusual association of animals (e.g. Guthrie, 2001). Much of the work on the nature of the mammoth steppe has focused on Beringia (e.g. ...
... Much of the work on the nature of the mammoth steppe has focused on Beringia (e.g. Guthrie, 2001;Walker et al., 2001;Zazula et al., 2007Zazula et al., , 2009Elias and Crocker, 2008;Fox-Dobbs et al., 2008;Rivals et al., 2010), including very recent results from mammoth skeletal isotope compositions indicating significant ecological variability on an eastewest axis (Szpak et al., 2010). The spatial and temporal variabilities of the westernmost sector of the mammoth steppe biome have received far less attention. ...
... This open steppe-tundra landscape (Dale Guthrie, 2001;Zimov et al., 2012) spanned much of unglaciated northern Eurasia and Beringia during the Late Pleistocene (Johnson, 2009 (Novgorodov et al., 2013) and agree well with previous ancient DNA data (Seersholm et al., 2020). ...
... Indeed, the megafauna taxa, by their trampling and sapling consumption, may, during milder climatic intervals, have suppressed colonization by trees, keeping the open vegetation largely intact (Bakker et al., 2016;Dale Guthrie, 2001), with the exception, perhaps of woodland patches in habitats with a favorable mesoclimate (Chytrý et al., 2019;Edwards et al., 2014 ...
Pronounced glacial and interglacial climate cycles characterized northern ecosystems during the Pleistocene. Our understanding of the resultant community transformations and past ecological interactions strongly depends on the taxa found in fossil assemblages. Here, we present a shotgun metagenomic analysis of sedimentary ancient DNA (sedaDNA) to infer past ecosystem-wide biotic composition (from viruses to megaherbivores) from the Middle and Late Pleistocene at the Batagay megaslump, East Siberia. The shotgun DNA records of past vegetation composition largely agree with pollen and plant metabarcoding data from the same samples. Interglacial ecosystems at Batagay attributed to Marine Isotope Stage (MIS) 17 and MIS 7 were characterized by forested vegetation (Pinus, Betula, Alnus) and open grassland. The microbial and fungal communities indicate strong activity related to soil decomposition, especially during MIS17. The local landscape likely featured more open, herb-dominated areas, and the vegetation mosaic supported birds and small omnivorous mammals. Parts of the area were intermittently/partially flooded as suggested by the presence of water-dependent taxa. During MIS 3, the sampled ecosystems are identified as cold-temperate, periodically flooded grassland. Diverse megafauna (Mammuthus, Equus, Coelodonta) coexisted with small mammals (rodents). The MIS 2 ecosystems existed under harsher conditions, as suggested by the presence of cold-adapted herbaceous taxa. Typical Pleistocene megafauna still inhabited the area. The new approach, in which shotgun sequencing is supported by metabarcoding and pollen data, enables the investigation of community composition changes across a broad range of taxonomic groups and inferences about trophic interactions and aspects of soil microbial ecology.
... The coevolution of herbivores and grassland plant species has taken place for millions of years, and both large and small mammalian herbivores are natural components of the steppe biome (Chytrý, Horsák, et al., 2019;Guthrie, 2001;Pavelková Řičánková et al., 2018;Zimov et al., 2012) (Archer & Detling, 1986;McNaughton, 1983;Hobbs, 1996;Hejcman et al., 2013) or the microclimate, which tends to become drier, warmer and less buffered against climatic extremes on grazed sites (De Frenne et al., 2019). In addition, biomass removal can weaken competition among plant species, particularly for light (Hairston et al., 1960;Hulme, 1996). ...
... The effects of grazing are often dynamic in time and space due to the seasonal migrations of herbivores and their preferences. In heterogeneous, semi-open landscape, such as forest-steppe, wild herbivores prefer to graze in open areas (Guthrie, 2001) and seek shelter in the shade of solitary trees, forestpatches or in depressions. This behaviour leads to systematic redeposition of nutrients (Hilder & Mottershead, 1963;McNaughton, 1983;Oesterheld et al., 1992), stronger pressure on tree recruits in open parts of the landscape, and thus stabilization of the forest-steppe habitat mosaic. ...
The occurrence and origin of dry grasslands and their rich biota in the moderately humid Central‐European climate have fascinated scientists for over a century. Modern palaeoecological and phylogeographical data support earlier hypotheses that these grasslands are late Pleistocene relicts and can therefore be considered part of the Eurasian forest–steppe biome. However, it is still unclear which factors fostered the maintenance of steppe patches in Central Europe throughout the Holocene. Here, we provide an overview of the main hypotheses, which stress, respectively, the effects of climate, edaphic conditions and disturbances. We then develop a general conceptual framework on how these three factors interact to form forest–steppe mosaics. We thereby emphasize the role of topography as a crucial control on forest–steppe patterns at the landscape scale. Topography is related to several mechanistic drivers that influence vegetation processes, such as near‐surface microclimate and soil formation. Consequently, topographic variation allows both forest and steppe patches to occur beyond their macroclimatic niche, favouring the development of forest–steppe mosaics. To illustrate our framework, we demonstrate the interactive effect of macroclimate and topography on the occurrence of steppe patches at 108 selected Central European forest–steppe sites. Although we developed our framework focusing on the current distribution of Central European forest–steppe, we suggest that it contributes to the understanding of similar transitions between temperate forest and steppe biomes in the past as well as elsewhere in the world.
... It is thought to have been the most extensive terrestrial biome on Earth during the late Pleistocene, stretching from the Iberian Peninsula eastward across Eurasia and into Canada 31,50-52 , although the extent and character of this ecosystem remains controversial for some 53 . This paradoxically productive 54,55 highlatitude mosaic biome supported a diverse abundance of large bodied fauna 31,50,52 , facilitating higher biotic productivity (energy and nutrient turnover) than many habitats existing at high latitudes today 23,56 . ...
... If Salix was substantially more abundant in the Beringian shrub expansion than Betula as our sedaDNA dataset suggests, this questions whether the rise of defensive vegetation was a major driver in the extirpations as Salix is the most preferred and palatable shrub among extant subarctic browsers 135,137 . While Bison and Equus are considered closer towards the obligate grazer end of dietary guilds 50,138 , both have been observed to exhibit variable grazing and even mixed feeding 139,140 . Mammuthus, Equus, and Bison coprolites suggest that these taxa had a diet variably rich in forbs and graminoids, with a smaller but notable proportion of woody shrubs/trees ( If mammalian sedaDNA abundances are rough indicators of palaeo-biomass (a correlation in need of further research), it is unclear why Mammuthus primigenius and Bison priscus (Fig. 2) relative sedaDNA signals decline prior to an expansion of woody shrubs during the Bølling-Allerød warming (Fig. 3). ...
The temporal and spatial coarseness of megafaunal fossil records complicates attempts to to disentangle the relative impacts of climate change, ecosystem restructuring, and human activities associated with the Late Quaternary extinctions. Advances in the extraction and identification of ancient DNA that was shed into the environment and preserved for millennia in sediment now provides a way to augment discontinuous palaeontological assemblages. Here, we present a 30,000-year sedimentary ancient DNA (sedaDNA) record derived from loessal permafrost silts in the Klondike region of Yukon, Canada. We observe a substantial turnover in ecosystem composition between 13,500 and 10,000 calendar years ago with the rise of woody shrubs and the disappearance of the mammoth-steppe (steppe-tundra) ecosystem. We also identify a lingering signal of Equus sp. (North American horse) and Mammuthus primigenius (woolly mammoth) at multiple sites persisting thousands of years after their supposed extinction from the fossil record.
... The RADs for Units 1-3 are dominated by a few taxa and are not statistically different (p-value < 0.05), indicating that the local, largebodied vertebrate assemblage did not change significantly prior to (Unit 1) or during the Last Glacial Maximum (Units 2 and 3). The primary perturbation(s) affecting this ecosystem at the base of the Big Horn Mountains is not known, but the trend in RADs at NTC does fit with the "Plaids and Stripes" hypothesis (Guthrie, 1984(Guthrie, , 2001Lister and Sher, 1995;Mann et al., 2018). This hypothesis predicts that the large, frequent, and rapid climatic fluctuations indicative of the Quaternary kept many terrestrial ecosystems from reaching equilibrium. ...
... world was in disequilibrium, with species' ranges shifting rapidly and repeatedly over time and space, and rarely reaching their physiological range limits before the climate changed again. The "Plaids and Stripes" hypothesis was first proposed by Guthrie (1984Guthrie ( , 2001 and expanded by Lister and Sher (1995) and Mann et al. (2018) to include millennial-scale climate fluctuations and environmental factors relevant to eco-physiological attributes of Late Pleistocene megafauna. If the local ecosystem surrounding NTC was going to reach or approach equilibrium, we would expect it to occur during the depositing of Unit 1, prior to the Last Glacial Maximum, or during the deposition of Unit 3, when sufficient time had passed for the vertebrate assemblage to adjust to the conditions of the Last Glacial Maximum, but neither occurs. ...
Natural Trap Cave (NTC) is a well-known fossil locality located in Wyoming that contains a discontinuous record of sediments from the early Sangamonian (∼150 ka) to the present and produces a diverse vertebrate assemblage from 2 to 9 and 23–47 cal ka BP. This study examines changes in the rank abundance distribution (RAD) of NTC's large-bodied (>8 kg) vertebrates, to assess the stability of the local ecosystem surrounding the cave across the Late Pleistocene-Holocene transition. RADs were generated based on 2208 skeletal elements from four stratigraphic units, collected by Gilbert and Martin from 1974 to 1979. All bones included in this study had: a north-west grid coordinate, a known depth below the sediment surface, were over 20% complete and taxonomically diagnostic. Isotaphonomy was assessed using multinomial regressions of %MAU against multiple taphonomic variables: size, shape, degree of abrasion and weathering, fracture type, percent complete, original bulk density, and surface area to volume ratio. Changes in RADs were analyzed using rank abundance curves (RACs), Wilcoxon Rank Sums test, and kurtosis. RADs were also fit to a suite of standard ecological models (i.e., geometric, log-series, zero-sum multinomial, & log-normal) using maximum likelihood and the Akaike Information Criterion corrected for small sample size (AICc). The four faunal assemblages show little variation in taphonomic biasing, so any changes in the RADs reflects changes in the ecosystem. The four RACs showed little change in their shape or faunal composition and are dominated by a few abundant taxa, representing an ecosystem that experienced perturbations (i.e., a concave RAC and a kurtosis value > 3). The Wilcoxon Rank Sums test found no statistical difference among the RADs from the lower three stratigraphic units. This means that the abundance structure of the large-bodied vertebrates did not change prior to (35.8–25.3 cal ka BP) or during the Last Glacial Maximum (25.3–17.2 cal ka BP) and the local ecosystem surrounding NTC never approached equilibrium. The uppermost stratigraphic unit represented a mixed Late Pleistocene and Early Holocene assemblage, so changes in ecosystem structure from the Last Glacial Maximum to the Holocene (10.5 cal ka BP – present) cannot be evaluated. Unfortunately, the ecological models used in this study provide little insight into the maturity or processes influencing the formation of the local ecosystem surrounding NTC because only three models produced a ΔAICc value between 4.4 and 6.7.
... The landscape was dominated by emblematic megafauna such as woolly mammoths and steppe bison, and in terms of biomass some authors have compared this period to the current African savannah (Zimov et al., 2012). Mammals had a major role in shaping vegetation community and structure by reducing vegetation density, enhancing nutrient turnover, dispersing seeds and reducing fire potential (Guthrie, 2001;Hester et al., 2006;Johnson, 2009). Reconstructing the species composition of this former plant community without a modern analogue, as well as the corresponding diets of the mammals that roamed it has been challenging. ...
... When many megafauna species disappeared at the end of the Pleistocene, the Holocene vegetation shifted significantly to become a more waterlogged environment with mossy and shrubdominated tundra and deciduous forests (Edwards et al., 2005;Guthrie, 2001). The habitats reconstructed for the Holocene horse and bison reflect this mesic environment. ...
The study of faecal samples to reconstruct the diets and habitats of extinct megafauna has traditionally relied on pollen and macrofossil analysis. DNA metabarcoding has emerged as a valuable tool to complement and refine these proxies. While published studies have compared the results of these three proxies for sediments, this comparison is currently lacking for permafrost preserved mammal faeces. Moreover, most metabarcoding studies have focused on a single plant-specific DNA marker region. In this study, we target both the commonly used chloroplast trnL P6 loop as well as nuclear ribosomal ITS (nrITS). The latter can increase taxonomic resolution of plant identifications but requires DNA to be relatively well preserved because of the target length (∼300–500 bp). We compare DNA results to pollen and macrofossil analyses from permafrost and ice-preserved faeces of Pleistocene and Holocene megafauna. Samples include woolly mammoth, horse, steppe bison as well as Holocene and extant caribou. Most plant identifications were found using DNA, likely because the studied faeces contained many vegetative remains that could not be identified using macrofossils or pollen. Several taxa were, however, identified to lower taxonomic levels uniquely with macrofossil and pollen analysis. The nrITS marker provides species level taxonomic resolution for commonly encountered plant families that are hard to distinguish using the other proxies (e.g. Asteraceae, Cyperaceae and Poaceae). Integrating the results from all proxies, we are able to accurately reconstruct known diets and habitats of the extant caribou. Applying this approach to the extinct mammals, we find that the Holocene horse and steppe bison were not strict grazers but mixed feeders living in a marshy wetland environment. The mammoths showed highly varying diets from different non-analogous habitats. This confirms the presence of a mosaic of habitats in the Pleistocene ‘mammoth steppe’ that mammoths could fully exploit due to their flexibility in food choice.
... Evolutionary trend of m1 enamel of the Pleistocene population of genus Arvicola in Central Europe (modified after Heinrich, 1990) typické tak pre obyvateľov tzv. mamutej stepi (termín používaný pre chladné stepné až lesostepné prostredie počas posledného glaciálu; Guthrie, 2001), ako aj pre zástupcov pohybujúcich sa v otvorenom lesnom až lesostepnom prostredí počas teplejšieho a vlhkejšieho obdobia (obr. 8). ...
Submitted article presents results of a new study of faunal fossil remians from the
Prepoštská Cave, the Middle Palaeolithic site from the Horná Nitra region. The faunal analysis is focused on the fossil record of Janšák´s collections from 1927 and Bárta´s collections from 1965 to 1967. The results document a Neanderthal hunting game during the Micoquian and palaeoenvironment of the surrounding region. The last datings by 14C method places the objective settlement to the period > 49 – 24,5 ka uncal BP. Based on the taxonomic determination of findings and the
isotopic analyses, determined taxa represent an interstadial assemblage, which lived in forest-steppe environment with the presence of water source in the vicinity, as well as a cold steppe assemblage. Marks of human activity and the activity of predators were found on the bones. Settlements of Neanderthals took a short-term period and the cave served probably as a hyena den during the man absence.
... Much of this area was represented by the exposed East Siberian Arctic Shelf (now submerged). Conditions of extreme aridity precluded extensive formation of peat deposits and created a high-latitude steppe-tundra biome populated by mammoth, horse, bison, reindeer, and other large mammals (e.g., Guthrie, 2001;Lindgren, Hugelius, & Kuhry, 2018;Mann et al., 2015;Sher, Kuzmina, Kuznetsov, & Sulerzhitsky, 2005). ...
Through biodistance analyses, anthropologists have used dental morphology to elucidate how people moved into and throughout the Americas. Here, we apply a method that focuses on individuals rather than sample frequencies through the application rASUDAS2, based on a naïve Bayes' algorithm. Using the database of C.G. Turner II, we calculated the probability that an individual could be assigned to one of seven biogeographic groups (American Arctic, North & South America, East Asia, Southeast Asia & Polynesia, Australo-Melanesia, Western Eurasia, & Sub-Saharan Africa). The frequency of classifications for each biogeographic group was determined for 1418 individuals from six regions across Asia and the Americas. Southeast Asians show mixed assignments but rarely to American Arctic or “American Indian.” East Asians are assigned to East Asia half the time while 30% are assigned as Native American. People from the American Arctic and North & South America are assigned to Arctic America or non-Arctic America 75-80% of the time, with 10-15% classified as East Asian. All Native American groups have a similar degree of affinity to East Asia, with 10-15% classified as East Asian. East Asians are classified as Native American in 30% of cases. Individuals in the Americas are decreasingly classified as Arctic the farther south they are located. Equivalent levels of classification as East Asian across all Native American groups suggests one divergence between East Asians and the population ancestral to all Native Americans. Non-arctic Native American groups are derived from an arctic population, which represents the Native American founder group.
... Mammoth fauna was the most productive and the largest continuous ecosystem on Earth in the Pleistocene, being represented by a community of large mammals adapted to cold (Kahlke, 2014). Such diversity and synthesis of elements of megafauna and flora cannot be found in modern high-latitude ecosystems (Guthrie, 1982(Guthrie, , 2001. Traditionally, the mammoth steppe has been compared to modern African savannah, both in ecological structure and in bioproductivity (Vereshchagin and Baryshnikov, 1992;Zimov et al., 2012). ...
... Despite the fact that herbivores graze these plants during the vegetation period, they also suppress the growth of trees and keep the habitat open for the survival of light-demanding herbaceous species (Bocherens, 2018). Accordingly, the Palaeolithic tundra grazed by woolly mammoth and other megafauna has been considered to be dependent on the low occurrence of clouds in the sky and thus on intense radiation (Guthrie, 2001). Marcescence may, therefore, have been important for the maintenance of grasslands in the ancient wilderness. ...
The plant economics spectrum (PES) drives nutrient cycling through effects on soil decomposers. However, dead phytomass may remain standing or unshed (marcescent), hardly accessible to decomposers and be photodegraded. In arid zones, the significant part of marcescent phytomass can be decomposed without touching the ground. In temperate zones, photodegradation of marcescent phytomass is low but prompts important chemical changes, which affect its subsequent decomposability in the soil and alters the surrounding environment. It is unknown, however, how common marcescence is among different taxa and in which habitats, and how it is coordinated by PES traits.
We sampled standing (marcescent) and lying (shed) dead phytomass from a broad spectrum of 127 herbaceous temperate species in a common garden experiment and related these parameters to PES traits, species ecological preferences and phylogeny.
Nearly all species (97%) kept their phytomass marcescent. Tall species with a small leaf area and high leaf carbon had a high level of marcescence. Marcescent species also preferred sites affected by severe (but not necessarily frequent) disturbance. The degree of marcescence was considerably conserved in phylogeny.
Synthesis. Marcescence extends PES trait effects on ecosystems, particularly in immature habitats, being a common but overlooked phenomenon of the temperate flora.
... Al der was also pres ent, sug gest ing suf fi cient hu mid ity and corre lat ing with data from Sokli, NE Fin land, where rel a tively moist cli ma tic con di tions have been in di cated at ~40-50 cal kyr BP (Helmens et al., 2007). Tra di tion ally the hab i tat of the woolly mam moth, the so-called "steppe mam moth", orig i nally de scribed as a cold-steppe biome (Guthrie, 1968), may have consisted of a mo saic of di verse land scapes (Guthrie, 2001). In gen eral, dis tinct vegetational and cli ma tic het er o ge ne ity has been noted in ana lys ing the ecol ogy of this megaherbivore in dif fer ent parts of Eu rope . ...
Palaeobiological data, supplemented by new 14C dates in conjungtion with palaeobotanical and lithological information, have allowed reconstruction of Middle Weichselian (MIS 3) environmental fluctuations in the southern Eastern Baltic region.
... Several studies show that mammoths mainly fed on forbs and graminoids, i.e. grasses and sedges, which tend to have higher δ 15 N values (Stewart et al., 2003;Wang and Wooller, 2006) compared with shrubs and lichen (Wang and Wooller, 2006;Finstad and Kielland, 2011;Kristensen et al., 2011). Moreover, remains of grasses and sedges were also found in the jaws of fossil mammoths from Beringia (Guthrie, 2001;Drucker, 2022). A similar diet can also be reconstructed for woolly rhinoceros and steppe bison, which show δ 15 N values partly similar to those of mammoths in the pre-LGM food web in our study (Fig. 4a) and may suggest a special dietary niche. ...
We investigated palaeofood web structures using stable isotope analyses on animal bone collagen from four Upper Palaeolithic sites dated to the Early Gravettian (Krems-Hundssteig and Krems-Wachtberg: 33-31k cal a BP, Langenlois: 31-29k cal a BP) and to the Early Epigravettian (Kammern-Grubgraben: 24-20k cal a BP). In both periods, δ 13 C values show niche partitioning between hare, horse and mammoth on one side, and reindeer and ibex on the other, indicating different diets and habitats between both herbivore groups. The δ 15 N differences between carnivores and herbivores suggest a difference of one trophic level during the pre-Last Glacial Maximum (pre-LGM) period at the Early Gravettian sites and a tendency towards secondary carnivores during the LGM at Kammern-Grubgraben. δ 15 N values of pre-LGM mammoths are elevated in relation to other herbivores but shifted to the level of other herbivores in the LGM. A general δ 15 N value shift in herbivores of 3.3‰ from the pre-LGM to the LGM is related to climatic deterioration. This may have led to the disappearance of certain ecological niches and to a shift from broader to overlapping ecological herbivore niches shortly before the LGM, as demonstrated by SIBER analyses.
... Loess and aeolian sand deposits dated to this period mantle the lowlands and upland hills (Dilley, 1998;Muhs et al., 2003;Reuther, 2013;Reuther et al., 2016). Although the middle Tanana Valley was surrounded by ice sheets and larger mountain glaciers, it remained unglaciated during the LGM and may have served as a refugium for plant and animal species (P ew e, 1975b;Guthrie, 1990Guthrie, , 2001. The lack of ice in this area has been explained by relatively warm and dry LGM climatic conditions, related to decreased cloudiness and subsequent lowering of planetary albedo, circulation changes forced by the Laurentide Ice Sheet, and a southward-shifted Pacific stormtrack (L€ ofverstr€ om and Liakka, 2016). ...
Aeolian deposits in the middle Tanana Valley of central Alaska offer a well-preserved record of paleoenvironmental change since the deglacial period (c. 16,000-11,000 cal yr BP). These deposits also contain some of North America's oldest archaeological occupations (c. 14,000-13,000 cal yr BP), making this
region critically important for understanding human migration into the high latitudes and the Americas. Major research questions involve assessing the magnitude of deglacial climatic change and the influence of climate on early human groups. This study uses branched glycerol dialkyl glycerol tetraethers (brGDGTs) from six loess-paleosol sequences to develop a quantitative paleotemperature record within terrestrial locations in the Tanana basin that are close to archaeological sites. BrGDGT-derived temperatures demonstrate a lack of cooler temperatures associated with deglacial conditions, making this region relatively “warm” compared to other parts of the globe. Additionally, our brGDGT record shows little coherent temperature change associated with deglacial climate variability (e.g., Bølling-Allerød, Younger Dryas), and Holocene temperatures are relatively stable as well, indicating that temperature fluctuation was not the main driver of environmental or archaeological change over time. We recommend averaging data across multiple terrestrial exposures to produce regional temperature reconstructions.
... The existence of the steppe-tundra or the mammoth steppe biomes in the Pleistocene was postulated based on the studies of mammal [26,27], insect [8,9,22,28], and plant [29] remains. The steppe-tundra is an extinct non-analogue landscape that served as the favorable habitat for mammals typical of tundra (e.g., caribou) and steppe (saiga, horse, bison). ...
Analysis of the database of Beringian subfossil insect assemblages showed a relatively low role of aquatic, riparian, and wetland species of insects with hard exoskeleton in the Pleistocene communities and an increase in their proportions and taxonomic diversity in the Holocene. Aquatic insects were represented in all types of geological deposits and in some paleosols, but their proportions varied in different depositional environments. Poor representation of aquatic insects and a lack of freshwater invertebrates in the Late Pleistocene ice-rich deposits of Beringia called Siberian Yedoma or Yukon Muck attest to the predominantly aeolian origin of this phenomenon.
... In a parallel extinction in Europe, the loss of species did not occur in a single definable event but was progressive and sporadic, with losses occurring during warm, wet events over 30,000 years (Cooper et al., 2015). In North America, where there is a relatively high abundance of megafaunal records (Barnosky et al., 2016) deglacial warming around 14 kcal BP seems to have triggered major population declines (Gill et al., 2009(Gill et al., , 2012Guthrie, 2001;Robinson et al., 2005). Humans clearly hunted some of the North American megafaunas (Halligan et al., 2016;Martin, 1967;Waters et al., 2011), though the importance of that hunting as a cause of actual extinction remains debated (Brook & Bowman, 2002;Grayson, 2001;Lima-Ribeiro & Diniz-Filho, 2013). ...
Aim
To determine the timing of megafaunal extinction in the high plains of Peru and also to determine if the timing was delayed in grasslands compared with previously published forested settings to dissociate the effects of succession from human or climatic impacts.
Location
The Junín Plateau, Peru.
Taxon
Flowering plants and Ascomycetes.
Methods
The sediments used in this analysis were collected from the edge of Lake Junín, Peru. Eleven ages derived from ¹⁴ C accelerator mass spectrometry provide a chronology. We provide a paleoecological reconstruction of past climate and vegetation change, fire history and megafaunal herbivore presence from c. 20,000–7000 years ago based on fossil pollen, charcoal and Sporormiella spores. Data were analysed using multivariate analysis and Bayesian change point analysis.
Results
Megafaunal populations appear to have been positively impacted by dry climatic oscillations until c. 15,200 years ago. A reduction in Sporormiella abundance between 13,000 and 12,300 years before the present coincides with increased charcoal abundance and is identified as the period of megafaunal population collapse leading to extinction. The timing of the extinction does not differ substantially from that observed in wooded Andean settings.
Main Conclusion
The timing of the collapse of megafaunal populations in high grasslands was very similar to that of lower, now‐forested settings. Upticks in fire activity, during what is generally seen to be a wet period, formed the backdrop to extinction and are strongly associated with human activity.
... This area has complex physiography that is also defined by glacial history. A large portion was unglaciated (the Beringian refugium) during the last continental glaciation due to the prevailing aridity that prevented ice formation (Guthrie, 2001). As a result, Beringia is considered an endemism hotspot in northern North America (Cook et al., 2016;Edwards et al., 2018). ...
Aim
Species are expected to disperse poleward in response to climate change. For species that are endemic to the high latitudes, this implies that many in the future would face a “no‐where‐to‐go” situation as they are currently occupying the northernmost portion of the continent. Further, because endemism may arise from a combination of physical barriers, climate and geological history, the persistence of many species may require spatial matching of multiple environmental factors within a limited dispersal space. Thus, it is not clear how endemic species might spatially adjust their distributions in response to climate change and whether there are future climate change refugia for these species.
Location
Northwest North America.
Taxa
Plants.
Time Period
Current and the future (2040).
Methods
We used ensemble bioclimatic models to evaluate drivers and directional patterns of future change in the distributions of 66 North American Beringian and amphi‐Beringian species currently occurring in Alaska and the Yukon. We explored the spatial pattern of species richness, losses and climate change refugia across the region.
Results
More than 80% of the species showed northward shifts in their latitudinal centroids under intermediate warming and are expected to shift their range northward by more than 140 km on average by 2040. Additionally, more than 60% were projected to experience range contractions and up to 20% of the species would have the potential to expand their ranges by more than 100%.
Main Conclusions
Suitable habitat for endemic species in northwest North America is expected to decline significantly, especially for species occupying the Arctic tundra. Although the models identified several potential refugia from future climate change, especially at high latitude and elevation, whether the species would be able to colonize new habitats on their own and/or capitalize sufficiently on in situ refugia remains a pertinent conservation question.
... Nevertheless, the Quaternary situation gives clues on this issue. The strong asymmetry is also observed in the Quaternary (Guthrie, 2001), when many carnivores and ungulates went across the Beringia corridor from Eurasia to North America, and only Equus went in the opposite direction. The discovery of many North American endemic groups in Alaska, e.g., giant shortfaced bear Arctodus simus, coyote Canis latrans, American badger Taxidea taxus, and American river otter Lontra canadensis suggest that these North American species can endure the cold environment, but just cannot get across the landbridge. ...
Mammals have high dispersal ability, and many lineages can spread across the continents when a landbridge appears. Here, we summarize the dispersal of mammals between the Old and New World at the end of the Miocene. Our analysis suggested that the three phases of dispersal represented the largest dispersal tide during the Neogene, and the direction of dispersal is dominated by being from the Old to New World. Judging from the components that crossed the dispersal corridor, the Arctic environment near the Beringia corridor in the first phase (∼7.5 Ma) is a mixed environment, and in the second phase (∼6.5 Ma) is an open environment, and in the third phase (∼5.8 Ma and continue to the Pliocene) is a wooded (closed) environment. A clear trend of eastern Asian humidification driven by Asian monsoon and the global C4 grassland expansion explain this dispersal pattern. The boost of mammalian dispersals is controlled by the heterogeneity of environmental changes in different continents.
... The surrounding biotic landscape would have been largely devoid of trees when late-glacial humans inhabited Nataeł Na', with the predominant ecosystem being an open shrub tundra (Ager, 1989;Ager and Sims, 1981) similar to reconstructions of much of Beringia at the time (Bigelow and Edwards, 2001;Edwards et al., 2000;Guthrie, 2001;Hoffecker and Elias, 2007;Hopkins et al., 1982). In this unique mosaic landscape wetlands and marshes, favoring the growth of ligneous plants such as willow, would doubtless have been a critical determinant in the procurement of firewood and potentially even plant foods by ancient populations. ...
After decades of debate, the homeland of the First Americans is now generally understood to be northeast Asia; however, the process of Late Pleistocene peopling remains unresolved. As more archaeological sites south of the continental ice sheets are discovered that predate the opening of the interior “ice-free” corridor, interest in a coastal Pacific dispersal route has grown, and previously overlooked regions proximal to the Pacific coast have become a central focus of exploration efforts. The Copper River basin of southern Alaska is one such region. Here we present the results of 2019 archaeological excavations at Nataeł Na’, a buried and stratified archaeological site situated along the upper Copper River. The site contains a robust occupation dating to the late Younger Dryas climate reversal as well as an earlier occupation dating to the late Allerød interstadial. This discovery demonstrates that Pleistocene hunter-gatherers inhabited the Pacific basin of southern Alaska during the same time Clovis peoples inhabited temperate North America. The occupations at Nataeł Na’ join a growing body of evidence suggesting that the early inhabitants of eastern Beringia were geographically more widely dispersed than previously documented.
... Le milieu dans lequel les sociétés ont vécu, était sans équivalent actuel ; il est qualifié de « steppe à mammouth » par D. Guthrie (1968Guthrie ( , 1982Guthrie ( , 1990Guthrie ( , 2001) et correspond à la zone de végétation de « steppe-toundra » identifiée pour la période 25 000 -15 000 cal BP ( fig. 2). Cet environnement témoigne des conditions climatiques et de l'extension de l'inlandsis (jusqu'à 44°N entre 26 000 et 19 000 cal BP) qui ont entraîné la migration d'un certain nombre d'espèces végétales et animales du Nord vers le Sud, l'Ouest et l'Est de l'Eurasie -comme à d'autres périodes bien plus anciennes. ...
... Examples can be found among plants (Brubaker et al., 2005), insects (Elias & Crocker, 2008), fish (Campbell et al., 2015), and mammals (Anijalg et al., 2018;Heintzman et al., 2016), including humans (Watson, 2017). Yet, habitat and climate heterogeneity across the BLB shaped species ranges and promoted population structure (Dale Guthrie, 2001;Elias & Crocker, 2008;Kuzmina et al., 2011;Vershinina et al., 2021). The decline in sea level that exposed the BLB also reshaped the coastline of Pacific Northwest North America, connecting several islands to the mainland (Baichtal, 2010;Shugar et al., 2014). ...
Glacial and interglacial periods throughout the Pleistocene have been substantial drivers of change in species distributions. Earlier analyses suggested that modern grey wolves (Canis lupus) trace their origin to a single Late Pleistocene Beringian population that expanded east and westwards, starting ca. 25,000 years ago (ya). Here, we examined the demographic and phylogeographic histories of extant populations around the Bering Strait with wolves from two inland regions of the Russian Far East (RFE) and one coastal and two inland regions of North‐western North America (NNA), genotyped for 91,327 single nucleotide polymorphisms. Our results indicated that RFE and NNA wolves had a common ancestry until ca. 34,400 ya, suggesting that these populations diverged before the previously proposed expansion out of Beringia. Coastal and inland NNA populations diverged ca. 16,000 ya, concordant with the minimum proposed date for the ecological viability of the migration route along the Pacific Northwest coast. Demographic reconstructions for inland RFE and NNA populations reveal spatial and temporal synchrony, with large historical effective population sizes that declined throughout the Pleistocene, possibly reflecting the influence of broad‐scale climatic changes across continents. In contrast, coastal NNA wolves displayed a consistently lower effective population size than the inland populations. Differences between the demographic history of inland and coastal wolves may have been driven by multiple ecological factors, including historical gene flow patterns, natural landscape fragmentation, and more recent anthropogenic disturbance.
... Преобладающими ландшафтами плоскогорий и низменностей Восточной Сибири на протяжении позднеледниковья являлись так называемые мамонтовые степи, которые характеризовались довольно плодородными почвами, богатыми карбонатами [Guthrie, 2001]. Практически двухкратное увеличение количества атмосферных осадков в течение теплых фаз, коррелирующих с бёллингом и аллерёдом, привело к интенсивному выщелачиванию растворимых компонентов из почв, в частности карбонатов. ...
The monograph contains a new data on the morphology, genesis and environmental conditions of secondary carbonate accumulations in surface soils and buried paleosols of the Baikal region. Key characteristics of the carbonate soil profile have been determined, its mostly relic nature and considerable stability under modern climatic conditions have been revealed. The classification of pedogenic carbonate accumulations is carried out based on their morphology, elemental, mineral, isotopic composition. The effect of carbonate parent rocks on the formation of carbonate pedofeatures is estimated. The role of soil freezing in the accumulation of secondary carbonates in the sharply continental conditions of the Baikal region is revealed. The first data were obtained on the age and main stages of soil carbonates formation. The conditions of their formation were reconstructed and correlated with the climatic changes in the Baikal region and adjacent areas.
The book is designed for specialists dealing with problems of soil genesis and evolution,
paleopedology, Quaternary geology, paleogeography.
В монографии приводятся новые данные о морфологии, генезисе и условиях формирования аккумуляций вторичных карбонатов в дневных и погребенных почвах Байкальского региона. Определены основные характеристики карбонатного профиля почв, установлена его реликтовая природа и стабильность при современных климатических условиях. Проведена типизация карбонатных новообразований, основанная на их морфологии, элементном, минеральном, изотопном составе. Оценено влияние карбонатных почвообразующих пород на
формирование новообразований. Выявлена роль промерзания почв в аккумуляции вторичных карбонатов в резко континентальных условиях Байкальского региона. Получены первые данные о возрасте и основных этапах формирования карбонатных новообразований. Проведена реконструкция условий их формирования и корреляция с общим ходом климатических изменений в Байкальском регионе и на прилегающих территориях.
Книга рассчитана на специалистов, занимающихся проблемами почвоведения, палеопочвоведения, четвертичной геологии, палеогеографии.
... While primarily occupying continental Asia, pollen and macrofossil evidence of drought-adapted Artemisia and numerous Amaranthaceae representatives is found from north-western America as well (Yurtsev, 2001;Zimov et al., 2012). These two continents were connected via the Bering land bridge, which, due to extensive Pleistocene decrease of cloud cover, allowed arid-and cold-adapted vegetation to persist in this region during interglacial cycles (Dale Guthrie, 2001). Such a disjunct distribution pattern is known also from another Amaranthaceae species Krascheninnikovia ceratoides (Heklau and Röser, 2008;Seidl et al., 2021), further supporting our view. ...
Atriplex is the most species-rich genus of Amaranthaceae and one of the largest C4 clades in eudicots. Distributed predominantly in the arid subtropical and temperate regions worldwide, many Atriplex species dominate the plant communities of harsh and inhospitable inland and coastal habitats. Current threats of aridification and salinisation increase the ecological and economic value of this highly stress tolerant xerophytic genus. We compiled sequence data of approximately 80% (208 spp.) of all currently recognised species and carried out a phylogenetic reconstruction using nuclear-encoded internal and external transcribed spacers. In addition, time divergence estimation analysis and ancestral area reconstruction were carried out to reconstruct the worldwide spread of Atriplex. Our results show that Atriplex originated in continental Asia during the Oligocene and dispersed from there across the world, often via long-distance dispersal from the Aralo-Caspian and the Pontic regions, or the floristic province of Turkestan. The highest alpha diversity was retrieved from arid habitats of Australia and the New World resulting from extensive radiation events of the Late Miocene and Pliocene. Most dispersal events took place into the Mediterranean region. Atriplex invaded most continents several times independently from different regions throughout the continuous cooling trend of the Neogene and the Quaternary. Despite limited resolution power of the used molecular markers, this study allows for a more comprehensive understanding of the evolutionary history of Atriplex and lays the foundation for future evolutionary studies of saltbushes.
... Guthrie also postulated that mammoths would not have been able to penetrate snow cover, as striations on the tusks do not indicate snow shovelling and mammoths would therefore have been limited to wind-blown winter ranges. It has since been suggested, however, that the mammoth steppe was rather arid with thin snow cover in winter (Guthrie, 2001;Kienast et al., 2005;Pitulko et al., 2007;Schirrmeister et al., 2002). Soffer (1985) also believed that the movement of woolly mammoths in Eastern Europe would have been regulated by vegetation availability. ...
The ecology and behaviour of woolly and Columbian mammoths and mastodons have been extensively studied. Despite this, their patterns of mobility, and particularly the question of whether or not they migrated habitually, remains unclear. This paper summarises the current state of knowledge regarding mobility in these species, reviewing comparative datasets from extant elephant populations as well as isotopic data measured directly on the ancient animals themselves.
Seasonal migration is not common in modern elephants and varies between years. Nonetheless, non-migratory elephants can still have considerable home ranges, whose size is affected mainly by habitat, seasonal availability of water and food, and biological sex. Strontium isotope analyses of woolly mammoths, Columbian mammoths, and mastodons demonstrate plasticity in their migratory behaviour as well, probably in response to spatio-temporal variations in ecological conditions. However, biological sex is difficult to establish for most proboscidean fossils and its influence on the results of Sr analyses can therefore not be assessed. Advances in intra-tooth sampling and analytical methods for strontium isotope analysis have enabled research on intra-annual movement, revealing nomadic behaviour in all three species. Sulfur isotopes have been analysed from woolly mammoth remains numerous times, but its methodology is not yet developed well enough to inform on past proboscidean mobility in as much detail as strontium studies.
The inter- and intra-individual variation in migratory behaviour in mammoths and mastodons implies that their role in the subsistence strategies of Palaeolithic people may have fluctuated as well. Further assessment of hominin-proboscidean predator-prey interactions will require a more detailed understanding of proboscidean habitual mobility in specific contexts and places. Strontium isotope studies based on multi-year enamel sequences from multiple individuals have the potential to provide this insight.
... Paleoenvironmental proxies from Pleistocene deposits in the region illustrate a complex mosaic of steppe-tundra vegetation that has no modern analogue (Blinnikov et al., 2011;Hoffecker and Elias, 2007;Pavlova and Pitulko, 2020;Zazula, 2003;Zazula et al., 2006a). At the height of the last glaciation, mesic tundra vegetation with small trees and shrubs persisted in lowland regions (e.g., central Beringia) creating a refugium for multiple floral and faunal species (Brubaker et al., 2005;Elias and Crocker, 2008;Guthrie, 2001;Hoffecker et al., 2016;Hoffecker et al., 2014;Meiri et al., 2014;Zazula et al., 2006b). Paleoclimate reconstructions suggest that mean annual temperatures in eastern Beringia during the Last Glacial were drier and about 3 cooler than today (Viau et al., 2008) but more mesic conditions (Izumi and Bartlein, 2016) and warmer-than-modern winter temperatures (Bartlein et al., 2011;Elias, 2001) have also been proposed. ...
Genetic data suggest that the Native American founder population diverged from its Asian parent population about 25,000 years ago and was geographically isolated during the Last Glacial Maximum (LGM, ca. 21,000 years BP) before dispersing into North and South America as the ice sheets retreated. Archaeological evidence in eastern Siberia and Beringia is scarce, however. Although stone tools and cutmarks on bones dated to the LGM are reported at Bluefish Caves (Yukon Territory, Canada), the stratigraphic integrity of the site and the interpretation of the bone modifications have long been questioned by the scientific community. Here, we describe the results of a zooarchaeological study of the faunal assemblages from Pleistocene loess deposits of Bluefish Caves 1 and 2. Taphonomic analyses indicate that humans hunted a variety of prey at the site, including the Beringian horse (E. lambei), as early as 23,500 years BP. We discuss the significance of the site in debates about the timing of the initial peopling of North America and the role of human-hunters in megafaunal extinctions.
... The higher latitudes are extremely sensitive to even subtle climatic oscillations; and Svalbard, a high Arctic region, provides good natural archives to study such changes. Though, there are good climatic records for the Arctic region from the marine deposits (Stroeve et al., 2008;Polyak et al., 2010;Stranne et al., 2014), robust data from the terrestrial realm are still somewhat lacking (Schweger, 1982;Anderson, 1985;Guthrie, 2001). A comparison of past climate change data, from both the marine and terrestrial archives, can provide a better understanding of the recent climatic conditions, and could possibly help in simulations for future climate change predictions. ...
One of the projects under the India Arctic Programme was to study the past climatic and environmental changes around Ny-Ålesund, Svalbard. In this endeavor, we adopted a multiproxy approach involving palynology, quartz grain microtexture, and magnetic susceptibility. The archives for the studies mainly include surface and subsurface sediments; besides, airborne pollen and polleniferous material from the flowers were also used. An attempt was made to interpret the pollen-vegetation relation in the area and to develop the modern analogues for the better interpretation of fossil pollen assemblages. For past climatic studies, subsurface sediments from a 1-m trench were analyzed. Pollen yield was found to be inadequate for reconstructing the past vegetation and concomitant climatic changes. Nonetheless, quartz grain microtexture and magnetic susceptibility were found to help reconstruct the past climatic changes in the region. The changes in the climate and environment around Ny-Ålesund, Svalbard, over the last 19,000 years are discussed in the present communication.
... Over larger time-spans and geographical areas, observations have already been made of underlying relationships between horses' body mass and environmental factors, diet and behaviour. The growth of a large body mass has been suggested to be associated with seasonally highly-productive and high-quality plant communities [119][120][121], or with environments that have a seasonal shortage of dietary resources [109,121,122]. Also, a large body mass can be related to small group size and population densities [18,118,123]. ...
Equus is a very sensitive genus which has expanded over a large area and lived in Europe despite the climatic instability of the Pleistocene. Its persistence and abundance are helpful in understanding and describing environmental and climatic regional parameters. In this study, we present the result of dental mesowear and microwear analysis and post-cranial skeleton biometry on Equus populations located in two regions in the South of France from ten sites, corresponding to twelve assemblages dated from MIS 12 to MIS 5. The areas refer to two major climatic zones: the oceanic or subcontinental climate for the South West of France, and the Mediterranean for the South East. The first objective of this study is to integrate and compare biometric data, dental wear, and other already-published environmental proxies. The goal is to discuss the validity of horse body shape adaptations on a small geographical scale. The second objective is to describe the impact of environmental features on the horse population through time in the two regions. We observe that the Equus diet was quite diverse, according to microwear analysis which shows adaptations according to seasonal variations. However, they remained mostly grazers over a long period of time. Estimated body mass of Equus in the localities studied here varies from a mean of 468 up to a mean of 570 kg, but these variations failed to be correlated with the diet, the climatic period, or the geographical position of the horse population, probably because of the sample size or the restricted time-span or geographical scale. However, the conformation of the metapodials and the width of the third phalanges may have been linked with environmental and behavioural parameters. The width of the third phalange may be correlated with the recurrence of the snow cover, while the robustness of the metapodial co-occurs with a humid climate. Also, diet may influence the conformation of the bones, since the tall and slender horses seem to be preferentially grazers all year long and seasonally browser horses are tall and robust. Seasonally mixed-feeder horses, all coming from the Mediterranean area, were found to be smaller, perhaps in relation to a less productive environment. The correspondence of the dietary and morphometrical data could suggest high pressure on the horse population, which caused rapid body adaptation. Thus, the combination of these different proxies allows us to suggest more accurate large mammal paleoenvironmental reconstructions.
The significant extinctions in Earth history have largely been unpredictable in terms of what species perish and what traits make species susceptible. The extinctions occurring during the late Pleistocene are unusual in this regard, because they were strongly size-selective and targeted exclusively large-bodied animals (i.e., megafauna, >1 ton) and disproportionately, large-bodied herbivores. Because these animals are also at particular risk today, the aftermath of the late Pleistocene extinctions can provide insights into how the loss or decline of contemporary large-bodied animals may influence ecosystems. Here, we review the ecological consequences of the late Pleistocene extinctions on major aspects of the environment, on communities and ecosystems, as well as on the diet, distribution and behavior of surviving mammals. We find the consequences of the loss of megafauna were pervasive and left legacies detectable in all parts of the Earth system. Furthermore, we find that the ecological roles that extinct and modern megafauna play in the Earth system are not replicated by smaller-bodied animals. Our review highlights the important perspectives that paleoecology can provide for modern conservation efforts.
Starting roughly 50,000 years ago, the Arctic region of East Siberia remained continuously populated by groups of anatomically modern humans including the most uncomfortable episodes in the development of the late Quaternary environment; for some of them, human presence in the area became ephemeral. At present, archaeological fossil records allow for distinguishing three main stages in human occupation of the area: Early (~50 to ~29 ka, MIS 3), middle (~29 to ~11.7 ka, MIS 2), and late (from 11.7 to ~8 ka). For most of the time, they the populated open landscapes of the Mammoth Steppe, which declined at the onset of the Holocene. Human settlement of the Arctic was driven by various abiotic and biotic factors and thus archaeologically visible cardinal cultural and technological changes correspond to the most important paleoclimatic and habitat changes in the late Pleistocene and early Holocene. Successful peopling of the Arctic was largely facilitated by the adoption of critically important innovations such as sewing technology based on the use of the eyed bone needle and the manufacture of long shafts and pointed implements made of mammoth tusks. Mammoth exploitation is seen in mass accumulations of mammoths formed by hunting. An obvious connection between archaeological materials and such accumulations is observed in the archaeological record. In the lithic technology, the early stage is presented by archaic-looking flake industries. Starting the LGM, the wedge-core based-microblade technology known as the Beringian microblade tradition spread widely following the shrinkage of the mammoth range. At the late stage, starting at the Holocene boundary, microprismatic blade technology occurs. In all stages, the complex social behavior of the ancient Arctic settlers is revealed. The long-distance transport of products, knowledge, and genes occurs due to the introduction of the land transportation system. Initial human settlement of this region is associated with carriers of the West Eurasian genome who became replaced by the population with East Asian ancestry constantly moving North under the pressure of climate change.
ABSTRACT
The western North America leech distributions was studied to assess this aquatic fauna diversity in widely dispersed and arid habitats during the last 10 Ka (thousand years). The leech distributions today may also reflect habitats some 10 Ma (million years) ago, with different drainages, climate, and topography, lacking precise geological events for leech barrier crossings, and correlated with other aquatic fauna distributions.
Western North America fish species have been extensively studied to determine aquatic connectivity among these dispersed habitats. The recession of the last continental glacier (10 – 15 Ka) revealed colonization from the southern Mississippi River to the mouth of the Mackenzie River and from the Columbia River and the Mackenzie River to British Columbia coastal drainages. The leeches, as fish, illustrate similar colonization of these same post-glacial habitats. Each regional section discusses the regions geology, the geological effects on aquatic fauna, and the geological effects on the leech distributions.
This study examines the geological processes to understand more ancient distributions as applied to mollusks and fish. The most classic is the Pliocene and Miocene “Fish hook” distribution between Bonneville Basin and Snake River and the western Great Basin and Pacific Coast drainages. Equally old as the “Fish hook”distributions, the southern route includes the western Great Plains, Rio Grande River and northern Mexico through southern Arizona to southern California. The Bonneville Basin, Snake River, and upper Green River was intertwined with aquatic colonization by fish with selective barriers for the fish host with mussel glochidia. The leech distributions are similar to the fish and mollusk distributions, with different sets of selectivity. Within the late Miocene time, the upper Colorado River adjoined the Gulf of California through the Grand Canyon, the upper Green and the lower Green through the Uinta Range, and the Snake adjoined the Columbia River.
With purported leech fossils found in Jurassic Europe and Silurian North America, one can suggest that leeches at one time or another have been on every continent, their distribution is a result of continental drift. Sister taxa have distributions with genetic based clade distributions on Euro-North American (Erpobdellidae) and South-North America (Helobdella) continents, suggesting isolation by continental separations. The present leech populations and distributions are a result of geological and climatic changes, with widespread abundant populations, widespread and restrictive populations, and populations isolates with possible extinctions.
The leech distributions will be discussed within these geological patterns. Leech taxonomy and Nearctic continental distributions are discussed in Section I. Postglacial mobility of the leeches to high elevations (Section II) and into northwest North America (Section III) are discussed. Section IV describes the western United States drainage basins distributions: the United States Pacific Coast and Columbia-Snake Rivers drainages (Section IVA), the Great Basin (Section IVB), the Colorado River basin (Section IVC), and the western Great Plains (Section IVD). Each section will have a discussion of the how geography and geology has affected aquatic fauna distribution. A summary discussion (Section V) of western United States leeches concludes this paper, illustrating the different distributional patterns within a geological frame.
Key Words: Hirudinida, leeches, western North America, paleogeography, drainage basin distributions, aquatic fauna
What causes Ice Ages? How did we learn about them? What were their affects on the social history of humanity? Allan Mazur's book tells the appealing history of the scientific 'discovery' of Ice Ages. How we learned that much of the Earth was repeatedly covered by huge ice sheets, why that occurred, and how the waning of the last Ice Age paved the way for agrarian civilization and, ultimately, our present social structures. The book discusses implications for the current 'controversies' over anthropogenic climate change, public understanding of science, and (lack of) 'trust in experts'. In parallel to the history and science of Ice Ages, sociologist Mazur highlights why this is especially relevant right now for humanity. Ice Ages: Their Social and Natural History is an engrossing combination of natural science and social history: glaciology and sociology writ large.
This chapter presents the chronological, cultural and palaeoenvironmental context as well as the species studied (Rangifer tarandus) and the object of the study (archaeological faunal remains). In Sect. 2.1 the notion of culture, based for the Palaeolithic on lithic industries, is criticised, before explaining why it is nevertheless referred to, for want of an alternative. Section 2.2 presents the chrono-environmental framework of the study area through a critical perspective of multidisciplinary data and underlines the important differences between the environment of the present-day Far North and that of the Upper Pleniglacial and Tardiglacial period in France. Section 2.3 summarises the main characteristics of the reindeer from the anatomical, physiological and ethological points of view, as well as its annual cycle and the history of its settlement in Europe. The corpus of study selected is specified in Sect. 2.4. It is composed of 256 archaeological assemblages from 117 French sites, occupied between the beginning of the Gravettian and the end of the Upper Magdalenian periods, classified into seven chrono-cultural periods and 10 geographical zones in order to allow comparisons.
This chapter presents, as an introduction, the intellectual framework of the author’s approach, based on a systemic approach to the status of the reindeer in Upper Palaeolithic societies and thus on the study of the global exploitation of the animal, while considering the role of the animal in the symbolic system. The way of conceiving and studying the economic system and the annual cycle of the hunter-gatherers is presented in detail, as well as the need to reconstruct the environments of Pleniglacial and Tardiglacial in France in a perspective that corresponds to the study of these societies. The author proposes to discuss the existence of a “Reindeer system” in Western Europe between 30,000 and 15,000 cal BP through a multi-proxy approach to the data. She thus questions the mobility of human groups, which is still considered as great since their main game, the reindeer, was itself reputed to carry out long-distance migrations. The plan of the book and the contents of the chapters are presented at the end of this first chapter.KeywordsIssuesMethodologyChronological contextEnvironmentHunter-gatherers societiesUpper PalaeolithicFranceEconomic systemReindeer
This chapter provides a discussion based on the data and assumptions made in the previous chapters. In Sect. 5.1, the author discusses the particularities of the environment of France (in the Upper Pleniglacial and Tardiglacial), which was located at the western end of the Mammoth steppe and thus explains the particular development of reindeer populations in this region of Europe. The existence of different ecosystems in distinct regions is then detailed for the period considered in France. The economic system of the societies that lived in France between 28,000 and 14,600 cal BP is discussed in Sect. 5.2 and the author defends, on the basis of the data analysed in the previous chapters, the hypothesis of a single system (reindeer system) based on the exploitation of reindeer (the animal and its antlers), a game that was not very mobile in most regions.KeywordsEcosystemsMammoth steppeZoocenosisAnimal populationsEcological nicheVegetationReindeer systemEconomic systemAnnual nomadic cycle
p>Using radiocarbon-dated sedimentary records with the temporal focus on two key vegetative transitions (deciduous- Picea and Picea-Pinus) and a climatic transition (cold and dry to moister), high resolution time series of charcoal-peak frequencies form lake sediments are used as a proxy of the local fire regime.
The regional vegetation transition from deciduous- to coniferous-dominated forest at ~10ka BP displays a clear sequence where the climate shift precedes the alteration in vegetation composition, to which the fire regime responds. The deciduous vegetation experienced low levels of burning, with a lower fire frequency than when Picea became dominant on the landscape, suggesting that Picea was excluded from the landscape due to moisture limitations rather than high fire return frequencies.
In the Yukon Territory, Pinus contorta (lodgepole pine) is migrating northwards and westwards towards Alaska, and is considered a potential invasive species to the northern boreal forest of Alaska under global warming. Lodgepole pine is a fire-dependent species that appears to thrive and spread when fires are intense and frequent. Analysis of stomata reveals lodgepole pine was present in the Southern Yukon forests, at least in low numbers, by ~6 ka BP, much earlier than conventional pollen records suggest. The main population expansion (represented by increased Pinus pollen from <5 to >15%) was regionally asynchronous, and occurred over 3 ka after the first appearance of Pinus. Contrary to expectations derived from flammability estimates and modern observations that pine stands burn particularly frequently, there is no clear, sustained increase in charcoal peak frequency in the late-Holocene Pinus zone; Pinus-Picea forests appear to have burned under a regime similar to that of the preceding Picea -dominated forests.</p
Bears exhibit marked evolution for Pleistocene Europe. Both lineages are thought to have arisen from etruscan bear U. etruscus in the Early Pleistocene, however their high degree of polymorphism has prevented the establishment of an accepted evolutionary scenario. Isotopic analysis and tooth morphology of fossil brown bear U. arctos suggests that it was an omnivorous opportunist. The deningeri bear U. deningeri represents the spelaean bear of the Middle Pleistocene, sharing certain morphological affinities with brown bear U. arctos (frontal bulge and face; occlusal surface of jugular teeth). Within U. deningeri, several subspecies have been distinguished as evolutionary stages leading to the speciation of the cave bear U. spelaeus, the typical spelaean bear of the Late Pleistocene, which dominates cave fossil deposits. The speloïd lineage might serve as a good chronological marker for Pleistocene stratigraphic levels. There are several morphologically distinct lineages within U. spelaeus "sensu lato", of controversial taxonomic status. Herbivorous feeding habits for U. spelaeus "s.l." have been inferred from morphology (tooth, skull, jaw), demographics, and stable isotope analysis. This dietary difference between brown bears and cave bears shows that ecological competition was probably limited between both types. Paleo-genetic studies suggest that cave bears gradually lowered their reproductive rate (between 52,800 and 27,800 y BP) which led to their extinction at the onset of the last glacial maximum. Climatic changes are the main suggested causes responsible for the extinction of U. spelaeus.
Les ours présentent une évolution marquée pour l'Europe du Pléistocène. On pense que les deux lignées sont issues de l'ours étrusque U. etruscus au Pléistocène inférieur, mais leur degré élevé de polymorphisme a empêché l'établissement d'un scénario évolutif accepté. L'analyse isotopique et la morphologie des dents de l'ours brun fossile U. arctos suggèrent qu'il s'agissait d'un omnivore opportuniste. L'ours de Deninger U. deningeri représente l'ours spéléen du Pléistocène moyen, partageant certaines affi-nités morphologiques avec l'ours brun U. arctos (renflement frontal et face; surface occlusale des dents jugales). Au sein d'Ursus deningeri, plusieurs sous-espèces ont été distinguées comme des stades évolutifs conduisant à la spéciation de l'ours des cavernes U. spelaeus, l'ours spéléen typique du Pléistocène supérieur, qui domine les dépôts fossiles des cavernes. La lignée spéloïde pourrait servir de bon marqueur chronologique pour les niveaux stratigraphiques du Pléistocène. Il existe plusieurs lignées morphologique-ment distinctes au sein de U. spelaeus «sensu lato», de statut taxonomique controversé. Des habitudes alimentaires herbivores de l'U. spelaeus «s.l.» ont été déduits par la morphologie (dent, crâne, mâchoire), la démographie et l'analyse des isotopes stables. Cette différence alimentaire entre les ours bruns et les ours des cavernes montre que la concurrence écologique était probablement limitée entre les deux types. Des études paléogénétiques suggèrent que les ours des cavernes ont progressivement abaissé leur taux de reproduction (entre 52800 et 27800 ans BP), ce qui a conduit à leur extinction au début du dernier maximum glaciaire. Il est suggéré que les changements climatiques sont les causes principales de l'extinction de l'U. spelaeus.
A previously unknown evolutionary stage of true lemmings, Lemmini, is recorded in the lower upper Pliocene (early Villanyian, MN16a) of West Siberia. Tobienia fejfari, sp. nov. represents a more advanced evolutionary stage than the previously known European Tobienia kretzoii (late Ruscinian, MN15b), combining rhizodont molar teeth with extreme hypsodonty, crown cement, and occlusal morphology resembling the earliest lemming with rootless molars, Plioctomys, of
later Late Pliocene age (MN16b). The new discovery contributes to our knowledge of early stages in the formation of the high latitude mammalian fauna of Eurasia.
Long-chain n-alkanes are measured in sediment cores (Cores U1341C and UMK-3A) collected from the Bering Sea to evaluate the paleoclimatic utility of n-alkanes in high northern latitude marine sediments. The variations in concentration and molecular composition of long-chain n-alkanes since the end of the last glacial period (the past 18 kyr) have been reconstructed. Sedimentary records of molecular distributions of n-alkanes in Cores U1341C and UMK-3A indicate that they primarily originate from terrestrial vascular plants. The results indicate that concentrations of odd number C25–C31 n-alkanes increased in the last glacial and Younger Dryas (YD) cold periods for Core U1341C, while those in Core UMK-3A increased during the warm Bølling–Allerød period and the cold YD period. These findings suggest that the source and transport pathways differ between the two sites. However, the n-alkanes chain length distribution in Cores U1341C and UMK-3A exhibits a low and a high during the cold and warm periods, respectively. These millennial-scale variability patterns remarkably resemble those of the sea surface temperature records in the proximal sites. This similarity suggests that the sedimentary record of n-alkane chain length distribution reflects surface temperature changes rather than changes in vegetation in the high northern latitudes (including in the Beringia). This study shows that n-alkanes are useful for reconstructing climate change in the high northern latitudes where applicable paleoclimate proxies are limited.
An analysis of the morphology and ecology of the late Pleistocene mammoth fauna of arctic Eurasia indicates that they lived in a cold, dry climate in steppe and steppe-tundra biotopes and landscapes characterized by hard, frozen ground. The decimation of the mammoth fauna came as a result of temperature increases during interstades within the Valdai (i.e., Wurmian of Europe, Wisconsin of North America) cold interval and the establishment of taiga and tundra vegetation at the end of this interval. The animals surviving the ecological catastrophe at the end of the Pleistocene (e.g., reindeer, arctic fox, marmot, souslik ground squirrel, and lemming) were able to persist in the severe conditions of present-day tundra as a result, in some cases, of their capacity for long migrations and, in others, of physiological adaptations that enabled them to cope with deep snow and occasional winter thaws. (Abstract by V.C.S.)
Many mammoth remains have been radiocarbon-dated. We present here more than 360 14C dates on bones, tusks, molars and soft tissues of mammoths and discuss some issues connected with the evolution of mammoths and their environment: the problem of the last mammoth; mammoth taphonomy; the plant remains and stable isotope records accompanying mammoth fossils; paleoclimate during the time of the mammoths and dating of host sediments. The temporal distribution of the 14C dates of fossils from the northern Eurasian territory is even for the entire period from 40 to 10 ka BP.
Successional theory has emphasized either interactions among plants that facilitate or inhibit establishment of late successional species (Whittaker 1975, Connell and Slayter 1977) or the changes in nutrient cycling during succession (Odum 1969, Vitousek and Reiners 1975, Van Cleve and Viereck 1981). However, the role of herbivory in succession has been largely overlooked (Connell and Slayter 1977) despite its clear importance in marine succession (Sousa 1979). In this chapter, we discuss the role of browsing by mammals upon recruitment of trees and shrubs during plant succession in boreal forests. Radiation, soil temperature, and nutrient availability decline sharply through succession in Alaska, and they are probably the primary factors responsible for successional change (Van Cleve and Viereck 1981). However, these changes in environment influence: (1) patterns of selective feeding by browsing mammals through allocation of carbon-to-plant secondary metabolites; and (2) the capacity of woody plants to replace tissue eaten by browsing mammals through compensatory growth. The interplay of these two factors determines the role of browsing upon plants during boreal forest succession. Moreover, plant secondary metabolites that evolved to defend the plant against herbivores may also affect nutrient cycling in boreal forests by altering litter quality. In short, succession in boreal forests may be characterized by a feedback loop.
This technical comment responds to an article on absorption of radiation by clouds. Measurement of atmospheric absorption is difficult, requiring measurement of all radiation flowing into and from a volumn. In measurement from aircraft the volume is ill defined and measurement of fluxes on its boundaries is limited to a few locations. In the sited study the cloud flux data derive from satellite observations where as the surface measurement are obtained from either a single radiometer or a network of 11 radiometers. This analysis is supposed to account for large space and time scale variability and accomodate undersampled boundary fluxes. However, the commentor contends that the report contains neither an error analysis or evidence to support the assumption. 24 refs., 2 figs.
UNDERSTANDING the environment of the Bering land bridge and determining
the timing of late Wisconsin inundation are important for several areas
of study. These include: (1) the timing of the re-establishment of
circulation between Pacific and Atlantic Oceans; (2) the timing of
development of a northern biotic refugium and the closing of the bridge
to species immigration; (3) Palaeoindian migration routes; and (4)
palaeotopographic data for atmospheric general circulation
models1. Late Wisconsin palaeobotanical and fossil insect
data from the central and northern sectors of the Bering land bridge
indicate widespread mesic shrub tundra environments even during the last
glacial maximum. Contrary to previous hypotheses, we found no evidence
of steppe tundra on the land bridge. New accelerator mass spectrometer
14C dates show much of the land bridge was above sea level
and thus available for human and animal migration until 11,000 yr BP.
Insect evidence suggests that summer temperatures at that time were
substantially warmer than now.
This paper originally appeared in the Izvestiya of the All-Union Geographic Society (Tomirdiaro, 1975), and was translated for this volume by Dorothy Vitaliano. Because much of Dr. Tomirdiaro's argument and interpretation represents a controversial view in the Soviet Union, it is useful to point the reader to his more recent work, which provides much new and concrete data relevant to the paper published here. Useful photographs and extensive supporting data on sedimentary structures, granulometry, mineralogy, geochemistry, palynology, and geochronology may be found in Tomirdiaro (1978 and 1980, see especially pp. 5–73 of the 1980 paper).
Large and small tracts of steppe and tundra-steppe vegetation are scattered widely in the more continental parts of northeastern Siberia. Soils in these steppe and tundra-steppe areas share common features, including base saturation, lime-accumulation horizons, and a humic horizon involving saturation with plant roots rather than accumulation of surficial peat. A study of the character and distribution of these arctic steppe tracts provides insight into the former character of Beringian vegetation during late Pleistocene cold intervals when glaciers were expanded and sea level was at its lowest.
Steppe vegetation covers large areas in the Yana and Indigirka drainage basins. In the most arid and continental part of this region, larch forests are restricted to north slopes and especially moist sites with other exposures. Steppe vegetation commonly replaces burned-over larch woodlands, suggesting that climatic conditions may have been more optimal for woodlands at some past time in the Holocene.
Steppe patches diminish in size and abundance eastward, but nevertheless, steppe and tundra-steppe vegetation are found on many sunny, well-drained sites in the Kolyma and Anadyr River basins and in an arctic belt extending eastward through the Anyui Mountains and northern Chukotka. The surprising presence of islets of steppe vegetation on favorable sites amidst the hypoarctic tundra of northern Chukotka may reflect the absence of larch and stone pine, which otherwise might be expected to colonize these drier, warmer sites. Several endemic species of very local distribution and several spectacular range disjunctions suggest that the small steppe patches of Chukotka may have expanded recently from even more restricted areas during an earlier, more mesic part of the Holocene.
Especially significant are large tracts of tundra-steppe on Wrangel Island, a large island on the continental shelf well north of the northeast Siberian mainland. The interior and the southwestern parts of the island are covered largely by a mosaic of tundra-steppe and cryophytic meadow steppe with low willow thickets in the valleys. A recent pollen spectrum from one of the steppe-tundra tracts resembles the herb zone spectra encountered in pollen sequences that extend back to late Pleistocene levels. The vegetation of Wrangel Island may be the closest living analog to the sort of vegetation that clothed northern Beringia during Pleistocene time (abstract by D. M. Hopkins).
Sediments exposed at Epiguruk, a large cutbank on the Kobuk River about 170 km inland from Kotzebue Sound, record multiple episodes of glacial-age alluviation followed by interstadial downcutting and formation of paleosols. Vertebrate remains from Epiguruk include mammoth, bison, caribou, an equid, a canid, arctic ground squirrel, lemmings, and voles. Radiocarbon ages of bone validated by concordant ages of peat and wood span the interval between about 37,000 and 14,000 yr B.P. The late Pleistocene pollen record is dominated by Cyperaceae, with Artemisia, Salix, Betula, and Gramineae also generally abundant. The fossil record from Epiguruk indicates that the Kobuk River valley supported tundra vegetation with abundant riparian willows during middle and late Wisconsin time. Large herbivores were present during the height of late Wisconsin glaciation as well as during its waning stage and the preceding interstadial interval. The Kobuk River valley would have been a favorable refugium for plants, animals, and possibly humans throughout the last glaciation.
Presents current knowledge on the effects of periglaciation on the British landscape. The book is in 4 parts, the first of which provides an introduction to periglaciation and the Quaternary environment and chronology. The second part deals with the periglaciation of lowland Britain (below 400m asl), including chapters on ice wedge casts, pingos, mass wasting and landscape modification. The third part looks at the periglaciation of upland Britain, which generally is underlain by more resistant rocks, and includes topics on frost weathering, patterned ground, solifluction, talus slopes and related landforms. The final part of the book examines the periglacial enviroments of three contrasting periods: the Dimlington Stadial; the Loch Lomond Stadial and the present day environment in upland Britian. An extensive reference list is provided. -R.Gower
The cave paintings and other preserved remnants of Paleolithic peoples shed light on a world little known to us, one so deeply embedded in time that information about it seems unrecoverable. While art historians have wrestled with these images and objects, very few scientists ha ve weighed in on Paleolithic art as artifacts of a complex, living society. R. Dale Guthrie is one of the first to do so, and his monumental volume The Nature of Paleolithic Art is a landmark study that will change the shape of our understanding of these marvelous images. With a natural historians keen eye for observation, and as one who has spent a lifetime using bones and other excavated materials to piece together past human behavior and environments, Guthrie demonstrates that Paleolithic art is a mode of expression we can comprehend to a remarkable degree and that the perspective of natural history is integral to that comprehension. He employs a mix of ethology, evolutionary biology, and human universals to access these distant cultures and their art and artifacts. Guthrie uses innovative forensic techniques to reveal new information; estimating, for example, the ages and sexes of some of the artists, he establishes that Paleolithic art was not just the creation of male shamans. With more than 3,000 images, The Nature of Paleolithic Art offers the most comprehensive representation of Paleolithic art ever published and a radical (and controversial) new way of interpreting it. The variety and content of these images—most of which have never been available or easily accessible to nonspecialists or even researchers —will astonish you. This wonderfully written work of natural history, of observation and evidence, tells the great story of our deepest past.
The primary observed ecological effects of dust are: 1) early snowmelt in roadside areas due to lower albedos, resulting in a snow-free band of vegetation within 30-100 m of the road in early spring, which is used by waterfowl and numerous other species of wildlife; 2) decrease in Sphagnum and other acidophilous mosses near the road; 3) increase in many minerotrophic mosses; 4) decrease in soil lichens, particularly species of Cladina, Peltigera and Stereocaulon; 5) elimination of corticolous lichens near the road in areas of particularly high dust fall; 6) a general opening of the ground cover near the road and a consequent colonization of these barren surfaces by many taxa that are common on mineral-rich soils; 7) few effects on vascular plant abundance except in areas of very high dust, where ericaceous taxa and conifers are affected; 8) increased depth of thaw within 10 m of the road, possibly due to decreased plant cover and earlier initiation of thaw; and 9) contribution to thermokarst in roadside areas. -from Authors
In order to identify the effects of mountains upon the general circulation of the atmosphere, a set of numerical experiments is performed by use of a general circulation model developed at the Geophysical Fluid Dynamics Laboratory of NOAA. The numerical time integrations of the model are performed with and without the effects of mountains. By comparing the structure of the model atmospheres that emerged from these two numerical experiments, it is possible to discuss the role of mountains in maintaining the stationary and transient disturbances in the atmosphere. The model adopted for this study has a global computational domain and covers both the troposphere and stratosphere. The results of the analysis reveal many important effects of mountains. For example, the probability of cyclogenesis in the model atmosphere increases significantly on the lee side of major mountain ranges where the core of the westerly jet is located. Also, mountains affect the hydrologic processes in the model atmosphere by modifying the field of three-dimensional advection of moisture, and alter the global distribution of precipitation very significantly. In general, the distribution of the model with mountains is less zonal and more realistic than that of the model without mountains.
The most puzzling feature of the mammoth steppe is its great diversity of large mammals. The reasons for their diversity, their dietary specializations and their gigantism are examined here, in conjunction with other information, as clues to an investigation of the general paleoenvironment.
The mammalian evidence suggests a specific vegetational mosaic with certain seasonal characteristics. Mammalian growth patterns indicate a long growing season, requiring diets high in available energy and nutrients. These features would require a seasonally rich Pleistocene vegetation in comparatively fertile soil that utilizes antiherbivory defenses quite different from those used by the dominant plant forms now present in the North.
The annual seasonal cycle reconstructed here is characterized by cold, but perhaps variable, winters with very little snowfall. Most of the annual moisture would have fallen during spring and little to none during summer. Summer soils generally were warm, dry, and had a deep thaw. This intraannual variability in the growth season produced hydric, mesic, and xeric plants within the same local communities. Windy conditions were most common.
A new model is presented to explain the high species diversity of Pleistocene mammals, their large social organs and gigantism, as well as the converse: Holocene dwarfing, shrinking social organs, range contractions and extinction with the demise of the mammoth steppe.
Dated geological sections, exposed along river valleys of eastern Beringia (Alaska-Yukon), have yielded late Pleistocene geological and paleoecological records. Pollen analyses of five of these sections are presented as relative percentage diagrams. Epiguruk, Kobuk River, Alaska, provides pollen records representing lowland and upland vegetation. These records dominated by Cyperaceae, Gramineae, and Artemisia indicate a birchshrub tundra during the middle Wisconsin, Itkillik/Walker Lake nonglacial interval. Three sections in the Koyukuk River valley, Alaska, have also yielded pollen profiles. Section EIII represents part of either the early Wisconsin Itkillik Glaciation or the middle Wisconsin nonglacial interval. Sections EII and EIV date from 29,000 to 13,000 years BP, clearly spanning the late Pleistocene Walker Lake Glaciation. The three pollen records are dominated by Cyperaceae, include lesser amounts of Gramineae and Artemisia, and display a large variety of herbs. These records indicate a sedge-dominated tundra vegetation with local Salix stands. The minor elements strongly suggest meadow-type vegetation. It is concluded that these pollen records represent a variety of floodplain communities. They compare favorably to modern floodplain surface samples from Banks Island, arctic Canada; the comparison indicates the extent to which alluvial pollen records represent the local pollen component.
Beringian vegetation was a complex mosaic reflecting a number of biotic and abiotic factors, water and elevation being the two most important influences. Pollen records suggest a vegetation continuum from lowland-mesic and wet-meadow floodplain vegetation to fell field at higher elevations, extending upslope to polar-desert vegetation. The Pleistocene herbifauna probably relied heavily upon the higher production values of floodplain vegetation.
The nature of the late Pleistocene environment of Beringia is a topic of current debate. Some have concluded that it was a large arctic-steppe biome which supported an ungulate fauna as diverse as that of certain temperate grasslands. Others argue that the late Wisconsin vegetation of much of East Beringia was similar to present arctic and alpine fell field. They claim that the evidence for either large numbers or diversity of ungulates during late Wisconsin time is deficient or nonexistent.
Although comparisons with the fauna of the African plains are inappropriate, several lines of evidence do show that the number of large-mammal species existing together in East Beringia during the late Pleistocene was several times larger than that of the existing tundra fauna. Prominent were Mammuthus primigenius, Bison priscus, Equus, several types of musk ox, and Rangifer. In spite of the apparent low pollen production in late Pleistocene plant communities, sufficient forage must have existed to support this unique ungulate community.
Herb-dominated pollen spectra representing the height of the late Wisconsin have attributes, such as high percentages of Artemisia and dominance of grass over sedge, that set them apart from the majority of lowland tundra surface samples; consequently, these herb-zone fossil spectra are thought to indicate an environment different from that of present tundra.
Macrofossils of plants and insects add dimension to this picture. They show that late Pleistocene treeless environments contained species and probably whole communities not found in East Beringia today. Many of the plant and insect fossils imply prevalence of steppe-like conditions.
When all evidence pertaining to Beringian environments is collated, the most probable reconstruction is of a treeless region composed of a mosaic of communities, among which were large tracts that can only be termed steppe-like. It is probable that both alpine fell field and some of the rare steppe sites in present day Alaska-Yukon harbor species which formerly occupied these steppe areas.
The late Wisconsin has been viewed as the last time when presently disjunct steppe species in the U.S.S.R. and East Beringia had continuous ranges. But if the land bridge itself acted to promote increased continentality in Beringia, then the exchange of steppe taxa may have occurred during the mid-Wisconsin or even earlier. Certainly, it is becoming clearer that the land bridge acted as a filter for certain steppe organisms during late Wisconsin time.
Recent investigations of fossil insect assemblages from 11 late Quaternary sites in the southwestern Alaska region of Eastern Beringia demonstrate the survival of an abundant mesic to hygrophilous beetle fauna in this refugium before, during, and after the last glacial interval. These faunas contrast sharply with late Quaternary fossil insect assemblages described from interior and northern sites in Eastern Beringia, where xeric and steppe-tundra species dominated regional faunas. Proximity of southwestern Alaskan to maritime sources of moisture may have played a role in the development of a refugium for mesic and hygrophilous species by maintaining wet habitats even through the last glaciation.
This study of the paleoecology of four fossil assemblages of large mammals from the late Pleistocene sediments near Fairbanks, Alaska, emphasizes the structure, composition, habitat, and the pattern of subsequent extinction of the community. All four faunas were composed predominantly of grazers. Bison, horse, and mammoth were the most common species. Many component species of this complex community of large mammals became extinct near the close of the Wisconsin glaciation, leaving the comparatively depauperate community that exists in Alaska today. The high percentage of grazers in the fossil community suggests that interior Alaska was a grassland environment during the late Pleistocene.
Studied the vegetation at Kathul Mountain, where continuous treeless vegetation occurs from low elevation to alpine tundra. Results from vegetation plots placed along an elevational gradient from 290-910 m suggest a gradual transition from steppe to tundra. Species responded individualistically to changing elevation, and steppe and tundra taxa were intermixed over a broad zone of intermediate elevation. Two important steppe taxa, Agropyron spicatum and Artemisia frigida, were consistently present to elevations >800 m. Both the interaction of slope and aspect and elevation were important factors controlling vegetation composition. Assuming that changes in elevation, slope, and aspect cause a change in temperature and growing-season length, some steppe taxa could have survived full-glacial conditions, at least on lower-elevation slopes with a S-facing aspect. -from Authors
Introduces the 'mammoth steppe', an ecological assemblage with no modern analogue. This large, complex, grassland existed in Alaska and NE Canada stretching across most of northern and central Asia and much of Europe. Responses available to large mammals under changing climatic regimes are analysed, eg ruminant limitations in the face of plant defense mechanisms. The complexity of plant/animal relationships are explained, as are the associated implications for body-size and survival. The appearance of man is coincidental with these ecological changes, and although hunting is included as an environmental stress, it is seen as primarily an additional feature to the pattern of extinctions, not a cause. -T.M.Kennard
Pleistocene periglacial eolian sediments are widespread in the Nushagak, Holitna, and Upper Kuskokwim lowlands of southwestern Alaska. These sediments comprise mainly sand-sheet deposits and sand-loess intergrades, with subordinate sand-dune deposits and loess. Sand-sheet deposits range from 1) sharply defined, parallel, low-angle laminae by migrating wind ripples to 2) irregular subhorizontal strata which reflect migration of poorly segregated wind ripples, accumulation on a sparsely vegetated surface, adhesion on a quasi-planar bed, and/or niveo-eolian deposition. Sand-loess intergrades represent alternating bed-load and suspension deposition related mainly to the stochastic and seasonal variability of former wind systems. The dominance of sand-sheet deposits over deposits of well-formed dunes in the Pleistocene eolian record of southwestern Alaska reflects the limited availability of loose, dry sand in this former periglacial environment. Immobilization of sand after deposition as low-relief sheets resulted from a seasonally variable combination of ice cementation, sparse vegetation, high water tables, and snow cover. -Author
In the Southern Vosges Mountains, Northeastern France, the Grande Pile peat bog (47° 44′ N, 6°30′14″ E, 330-m altitude, about 20 m deep) gives a continuous pollen sequence for the last 140,000 years, contrary to others in Northwestern and Central Europe which are all truncated. For the first time, in a region close to the type locatity for the Eem deposits and close to the Würm and Riss stratotypes, palynology demonstrates a complete “glacial-interglacial cycle” offering the possibility of studying the rapid degradation of vegetation at the end of the Last Interglacial, perhaps in sufficient detail to be useful soon in long-term global climate forecasting. The Grande Pile pollen sequence shows, between the classical Eemian Interglacial and the Last (Würm) Glaciation, two temperate intervals interpreted as interglacials (palynological definition): St. Germain I and St. Germain II. These are separated by two very cold phases, probably glacial: Melisey I and Melisey II. This sequence, not easily correlated with the classical European chronology of Woldstedt, agrees well with Frenzel's chronology and, therefore, makes the synchrony of the Alpine glaciations with those of Northern Germany questionable. An attempt is made to correlate the Grande Pile pollen sequence with other chronologies (e.g., deep sea curves based on foraminiferal fauna, oxygen isotopes, and carbonate content, Barbados sea levels, Rocky Mountains sequence) that span the period between 140,000 and 70,000 years BP.
The concept of stability of plant communities inevitably enters discussions of forest succession. Succession following disturbance often leads to restoration of the original community, which is seen as the equilibrium community for the site. In this context, succession can be viewed as a mechanism maintaining stability.
A substantial literature is reviewed which indicates that compensatory growth upon tissue damage by herbivory is a major component of plant adaptation to herbivores. Experiments in Tanzania's Serengeti National Park showed that net above-ground primary productivity of grasslands was strongly regulated by grazing intensity in wet-season concentration areas of the large ungulate fauna. Moderate grazing stimulated productivity up to twice the levels in ungrazed control plots, depending upon soil moisture availability. Productivity was maintained at control values even under very intense grazing, suggesting that conventional definitions of overgrazing may be inapplicable to these native plant-herbivore systems. A laboratory clipping experiment with a sedge abundant in one of the most intensely utilized regions resulted in a maximum net above-ground productivity of 11.6 g/m2 · day when clipped daily at a height of 4 cm. Few plant species have been reported with the ability to maintain a significant level of pr...