Paleoecological Implications of Plant/Animal Grazing Relations on the Mammoth Steppe of Eastern Beringia

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Nebraska Anthropologist Anthropology, Department of

1995

PALEOECOLOGICAL IMPLICATIONS OF PLANT/ANIMAL GRAZING RELATIONS ON THE MAMMOTH STEPPE OF EASTERN BERINGIA

Andre Antinori

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Antinori, Andre, "PALEOECOLOGICAL IMPLICATIONS OF PLANT/ANIMAL GRAZING RELATIONS ON THE MAMMOTH STEPPE OF EASTERN BERINGIA" (1995). Nebraska Anthropologist. 79. https://digitalcommons.unl.edu/nebanthro/79

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Andre Antinori

This paper reassesses the areal extent of Mammoth Steppe in Eastern Beringia and discusses some of the ways in which grazing and topography entered into the maintenance of the Mammoth Steppe. Large, generalist grazing mammals, by their grazing style, helped maintain the Mammoth Steppe by removing old-growth and by stimulating grass plants to reproduce vegetatively. These grazers also' promoted uniformity in growth-form and uniformity in plant biomass (phytomass) above and below the ground surface. During the late Pleistocene the58 large, generalist grazers were eliminated from interior Alaska by Paleolndian hunters and their predatory animal companions. The loss of these large, generalist grazers precipitated a change in the structure of the Mammoth Steppe grassland and this eventually led to the replacement of steppe grassland by herb tundra.

were not human habitat there would be Broadcast little reason for geographers or anthropologists to study it. burning by humans and naturally This paper is an attempt to occurring fire are two reasons classically describe the full-glacial vegetation of given for the formation and maintenance interior Alaska/Yukon and to explain the of grasslands. Grazing is another. This role of grazing and topography in the paper explores grazing in a human maintenance of Mammoth Steppe. The habitat. Habitat, nature and natural understanding of grazing relationships resource are categories that are defined not only benefits anthropologists and by people rather than objects defined by geographers who focus their attention on their own intrinsic qualities. Without humans in grassland settings but is also human definition habitats are no more of value to the archaeologist who deals than systems among systems within a with hunting and pastoral peoples before universe of systems. Mammoth Steppe and after the advent of livestock raiSing. was human habitat in Siberia before the Hopefully this paper will put human action human occupation of eastern Beringia in perspective by casting people as a (Powers 1973). It remained human proximate rather than the ultimate cause habitat until its disappearance from the of environmental change and provide Beringian landscape. If Mammoth Steppe

Andre Antlnorl, Geography, University of Nebraska-Lincoln 68588

The Nebraska Anthropologist Vol. 12, No.1, 1995-1996, pp. 75-88 75 Antinori TtE NEBRASKA ANlHROPOLOGIST another way of looking at human impact diversity of opinions have arisen about on grassland ecosystems. the nature of the Beringian landscape during the last full-glaciation (about Paleolndlans In Beringia 35,000 to 16,000 yrs BP). Consequently many of the Humans may have entered North scenarios, theories and models used to America as early as 50,000 years before describe and explain the past vegetation the present (yrs BP) as part of the of Beringia are highly speculative and do Siberian faunal assemblage that crossed not necessarily represent observable, the Bering Land Bridge (Fig. 1) during demonstrable facts nor even accepted that time (Kurten and Anderson 1980; opinions. Turner 1984). However this date is purely speculative. Actual dated material from Vegetation in Beringia Bluefish Caves in the Yukon place humans in eastern Beringia around Two major vegetation types (herb 24,800 yrs BP well within the time-frame tundra and grassland steppe) probably dealt with by this paper. At Bluefish existed in interior Alaska during the Caves Morlan concluded: period of the last glaciation. Boreal forest tree species were confined to isolated Human presence is inferred from a variety of flaked -refugia to the southwest (Hopkins 1972) stone tools, including burins, microblades, and a and east (Anderson 1985, 1988). The microcore, several kinds of bone tools, numerous butchering marks on bones, bone breakage general look of the summer landscape patterns, and selective representation of was green and treeless with shrubby anatomical parts (Morlan 1987:38) willows in situations favorable to their growth. A number of smaller The human artifacts were found in environments were found within the two association with thousands of well major vegetation types such as the sand preserved bones of local ice-age dunes and shallow fresh-water marshes, mammals. Prior to this time humans in ponds and bogs of the exposed Chukchi eastern Beringia may have chosen to use Sea shelf (Elias et aI. 1992). Familiar tools of expedience such as splintered Alaskan boreal forest tree species of animal bones. Tools of this type would today (spruce and fir) did not re-invade have left little or no artifactual record. interior Alaska and the Yukon until sometime during the most recent Paleoenvironmental Interpretation deglaciation (13,000 to 11,500 yrs BP) (Ritchie 1984). By its very nature fossil pollen data is usually biased toward woody species, exotic pollen influx and local taxa that either produce an overabundance of pollen or are locally abundant at the depositional site. As a result of this bias a

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Figure 1. The BerIng Land Bridge showing western (Asiatic) and eastern (American) BerIngia

Herb Tundra time eastern Hokkaido (today's northern island of Japan) and the exposed During the last full-glacial, the northwestern Pacific shelf was a refugium vegetation of northwestern Canada has for boreal forest and tundrattundra been reconstructed by Ritchie and parkland species. The climate there was Cwynar as sparse, discontinuous herb cold and wet (Heusser and Mortey 1985). tundra in uplands and continuous grass From 16,000 to 12,000 yrs BP herb sedge marshes with local willow thickets tundra gave way to willow tundra and in lowlands (Cwynar and Ritchie 1980; scattered dwarf birch. This vegetation Cwynar 1982; Ritchie 1984). The climate type dominated upland sites until about was cold and dry analogous to the 11,500 yrs BP. The modem analog modem-day mid-arctic climate of the climate for this vegetation are the northern portions of Banks and Victoria southern portions of Banks and Victoria Islands (July mean 2-6 degrees C) Islands where the July mean is 10-13 (Ritchie 1984). At approximately the same degrees C (Ritchie 1984). Dwarf birch, a

77 THE NEBRASKA ANlHROPOLOGIST familiar tundra shrub, spread across findings and her own field work, Anderson northcentral and northwestern Alaska later concluded that the vegetation of her during this period, However it was not fossil pollen sites was "perhaps more common in the region until 12,000 yrs BP similar" to mid-arctic tundra than to arctic or later (Anderson 1988). meadows (Anderson 1988:270). Both of Herb tundra (Fig. 2) occurred these interpretations are probably correct throughout eastern Beringia below the and her characterization of the herb zone mountain glaciers of the Brooks Range, as "a complex mosaic of tundra types with Alaska Range and Richardson Mountains no latitudinal or longitudinal pattern" and between these mountain ranges and seems reasonable (Anderson 1985:271). the grasslands of the Mammoth Steppe. According to Barnosky and associates Smaller Environments this vegetation was a drier tundra in northeastern Alaska and northwestern In the central Brooks Range, Canada and a wetter (more mesic) tundra Brubaker and associates found that both in northwestern Alaska (Barnosky et al. sparse, discontinuous herb tundra and 1987). The fossil pollen sites used to map meadow plant communities existed this vegetation type are Scattered simultaneously. She' proposed " ... that throughout interior Alaska and the Yukon both vegetation types existed under the (Barnosky et aI. 1987). . same regional climate, depending on The predominant taxa of the herb local soil-drainage conditions" (Brubaker tundra zone were various species of et al. 1983:206), thus lending support to sedge, grass, sage (Artemisia) and willow the mosaic-crafters of Alaskan and (Salix). The genus and species of Yukonan paleoecology such as Young individual grasses and sedges cannot be (1982). resolved by fossil pollen analysis. The The role of soil (edaphic) and presence of sage in this vegetation belt microclimatic factors of the environment may be alternatively interpreted as dry, to the success or failure of plants is well rocky upland habitats, river banks, known to geographers and ecologists. meadowy terraces or even areas of Climatic regimes vary over several levels disturbance (Cwynar 1982; Anderson of spatial resolution and soil varies in 1988; Paus 1988). "In neither the upland both structure and texture within relatively nor lowland setting, however," says small areas. Hinds found that Anderson, "is Artemisia, by itself, microclimatic factors produced a potential indicative of widespread steppe or for variation in seedling establishment in grassland" (Anderson 1988:271). cheatgrass (Hin~ 1975). Cwynar and Ritchie's reconstruction is supported by data from a number of authors who worked in interior Alaska south of the Brooks Range. These authors are summarized in Anderson (1985). Building on their

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figure 2. Herb Tundra vegetation In Alaska during the last full-glaclal period, noting fossil pollen sites.

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Zedler and Zedler found that differences 19th century European and Russian in soil texture influence germination paleontologists recognized that the late success and that soil texture may interact Pleistocene climate and vegetation was with smaller-scale features of a place to different than at present and more times produce small-scale variations in climate than not invoked the idea or the ideal of and runoff patterns (Zedler and Zedler steppe as a landscape that supported a 1969). Mott and McComb working in diversity of large mammals. western Australia found soil texture and microtopography produced variations in Steppes and Mammoth Steppe nutrient levels of the soil (Mott and McComb 1974). Schimel and associates Present-day grasslands can be found that the soil of low places (swales) categorized into climatic, successional, are frequently higher in organic matter and agricultural types. Climatic and mineral nutrients than are the soils of grasslands occur where the water uplands (catenas) (Schimel et al. 1985). balance is below the threshold for tree Guthrie claims that localized factors such growth (Daubenmire 1978). Successional as these (especially aridity) are the key to grasslands are maintained or moved understanding the Mammoth Steppe through various levels of succession by (Guthrie 1990). physical or biological factors of the environment. An agricultural grassland is Mammoth Steppe planted and maintained by humans for a particular cultural purpose such as Based on the occurrence of livestock grazing or outdoor recreation. numerous large, grazing mammals Apparently Mammoth Steppe was a (especially bison, horse, mammoth) and combination of climatic and successional. their predators (especially wolf, lion, It was developed under a climate regime bear) in late Pleistocene sediments near that was both regionally variable and Fairbanks, Alaska, Guthrie proposed the different from any modem-day high existence of a steppe/grassland that has latitude climate because of a change in come to be known by the name Mammoth landlsea/ice relationships brought about Steppe (Guthrie 1982). To Guthrie lithe by the lowering of sea level and resultant high percentage of grazers in the fossil exposure of a large part of the Bering community suggests that interior Alaska continental shelf (Hopkins 1972, 1982; was a grassland environment during the CLIMAP project members 1981; Ritchie late Pleistocene" (Guthrie 1968:353). 1984; Heusser and Morley 1985). Mammoth Steppe is frequently Based on several lines of evidence seen as an alternative to the Guthrie reconstructed the winter weather paleoecological interpretation of Cwynar of this region as cold, windy and dry and Ritchie (1980). It is, however, which kept the region relatively snow-free probably more realistically viewed as and provided the potential for year simply another vegetation type of the last around grazing (Guthrie 1984; Guthrie glacial maximum. As early as the late and Stoker 1990). After establishment

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Mammoth Steppe was probably Coughenour discussed how basal maintained at some given level of me riste rns, rapid growth, deciduous succession by heavy grazing by large, shoots, relatively small stature, high herbivorous mammals. shoot density, and below-ground nutrient Mammoth Steppe grassland (Fig. reserves allow grasses to evade, escape 3) occurred throughout interior Alaska in and endure dry conditions and tolerate areas that were not occupied by tundra or grazing (Coughenour 1985). Meristematic riverine associations. At present this cells are the source of all postembryonic vegetation type is replaced by boreal plant growth including vegetative forest and it is presently restricted to reproduction. refugia as was boreal forest during the Milchunas and associates suggest last full-glacial epoch. Today the remains that these structures are due to the fact of Mammoth Steppe can be found on that both water stress and stress from south-facing slopes, bluffs, and in grazing periodically result in the same isolated enclaves throughout American thing: loss of organs (Milchunas et al. and Asiatic Beringia (Yurtsev 1982; 1988). Tolerance to one necessarily Edwards and Armbruster 1989; Walker et includes tolerance to the other. Both al. 1991). drought and herbivory provide selective Guthrie sees Mammoth Steppe as pressure to minimize the impact of organ a diverse complex of herbaceous and loss. Because of these factors plants can woody steppe plants organized into a respond to grazing in ways that increase mosaic of vegetation associations which rather than decrease their competitive in turn supported a great diversity of success. grazing mammals and their predators (Guthrie 1984). It forms a complex of High Intensity I Low Frequency steppe habitats very similar to those Grazing found today in Wyoming and Montana where associations of cold- and warm- In the Serengeti of East Africa season grasses, evergreen and grazing, by large, generalist grazers such deciduous shrubslsemishrubs are as wildebeest, is beneficial to grasslands. punctuated by wooded bluffs and water Wildebeest heavily graze a specific unit courses. of ground for a short period of time and then move to the next unit. This grazing Grazing Relations: Adaptations to style is called high intensity / low Grazing frequency grazing. The term low frequency is relative. Units may be Grasses have one or more reg razed more frequently than expected adaptations to each of the limiting factors or other species may use the same unit of environment. Several of these soon after another. However, on a year to adaptations enhance survival under year basis, grazing remains low semiarid conditions and promote frequency. tolerance to grazing pressure.

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figure 3. Mammoth Steppe vegetation In AIa8ka during the last full-glacJal period.

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High intensity I low frequency grazing plains prickly pear (Opuntia po/yacantha) keeps grass plants palatable and and various other plant species nutritious by removing old-growth and (Milchunas and Lauenroth 1989; stimulates grass plants to produce new Milchunas et aI. 1989). Under heavy stems by tillering and spread vegetatively grazing by cattle, blue grama increased in by stolons and rhizomes (McNaughton basal cover on grazed swales. No 1976, 1983). Tillering refers to the significant difference between wet and movement of grass shoots above and dry years or between ungrazed swales or below the ground surface. Stolons are uplands was found during the ~udy. The usually above ground, rhizomes are density of grass was also greater on always below ground. Both are capable of grazed sites and grass was most reproduction by budding. abundant in grazed swales. Shrubs and High intensity I low frequency semishrubs were most abundant on grazing not only increases the net ungrazed sites, in swales and in the dry primary productivity of the grassland and years. Plains prickly pear was more facilitates grazing for other grazing abundant on uplands and increased species such as Thompson gazelle but it during dry years on uplands. It also also increases the competitive advantage obtained a slightly greater basal cover of the grazed species over potential under heavy grazing. Litter build-up was invader species (McNaughton 1983). evident on ungrazed sites and on swales In the central Great Plains, in the and on grazed sites during wet years. absence of grazing, the warm-season grass, blue grama, grows and dies. The Ecological Segregation result is a build-up of litter which shades and cools the soil. This leads to the The segregation of plant demise of this warm-season grass and populations with respect to topographic provides a window of opportunity for the factors was indicated by swale to swale establishment of cool-season grasses, similarity and upland to upland similarity. forbs, and eventually, even shrubs. With Population segregation and plant active grazing the warm-season grass is diversity were generally greater on maintained. ungrazed sites and plant communities on the grazed sites were very uniform. Grazing in a Shortgrass These conditions suggest that cattle tend Grassland to reduce plant diversity of a site when they graze it. Plant species diversity was In the Colorado shortgrass greatest on ungrazed swales in both wet grassland communities studied by and dry years. However wet and dry Milchunas and assOciates, blue grama years had little effect on the segregation (Bouts/oua graci/is) made up 90% of the of plant populations (Milchunas et al. basal cover recorded whereas the 1989). remaining 10% was divided between

83 THE NEBRASKA ANTHROPOLOGIST Root Phytomass and Grazing converted to the energy required for everyday life. In return grazers help I n addition to the uniform maintain the grassland by removing old distribution of above-ground plant parts growth and excess leaf production. These on grazed sites, Milchunas and benefits increase forage quality and Lauenroth (1989) found a greater quantity for all the grazers in the system. uniformity in the horizontal distribution of It is a reciprocal relationship which can below-ground plant parts as well. This not be changed without consequence. extended McNaughton's (1984) concept Sometime during the late of grazing lawns (the origin of uniform, Pleistocene certain large, generalist lawn-like growth form) to the subsurface grazers were eliminated from eastern dimension. Milchunas and Lauenroth Beringia. The loss of these grazers (1989) also discovered that 45-years of precipitated change in the grassland heavy grazing of surface plant parts had steppe and eventually led to the very little effect on shallow root encroachment of Mammoth Steppe by phytomass. The effect was similar on herb tundra. lightly grazed uplands and heavily grazed Although widely accepted in both swales. Grazing had only a small effect scientific and popular circles the on the vertical distribution of roots and existence of Mammoth Steppe remains the changes were different for swales and somewhat problematic. This paper has uplands. The largest effect of grazing on presented one mechanism by which root structure was in horizonal distribution Mammoth Steppe could have been of roots. The horizonal distribution of maintained under the conditions available roots on grazed sites was more uniform. in Beringia during the late glacial period. In terms of Grubb's (1977) concept It has also provided a reason for the of regeneration niche this means that elimination of Mammoth Steppe from favorable localities for establishment Beringia Future research must be broad would be less likely to occur where root based and expand its focus beyond density is uniform. This is one reason why archaeological and fossil pollen sites to the density of invader species and the habitats that made those sites species richness in general is less on possible. grazed sites. References Cited Conclusion Anderson, P. M. Of the many features of grasslands 1985 Late Quaternary none is more striking than their ability to VegeumonaiChangeinthe favorably respond to grazing by large, Kotzebue Sound Area, generalist grazers. Grasses provide Northwestern Alaska. grazers with relatively high quality feed Quaternary Research that can be used for growth and 24:307-321. maintenance or that can be readily

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1988 Late Quaternary Pollen Coughenour, M. B. Records from the Kobuk 1985 Graminoid Responses to and Noatak River Grazing by Large Drainages, Northwestern Herbivores: Adaptations, Alaska. Quaternary Exadaptations, and Research 29:263-276. Interading Processes. Annals Missouri Botanical Bamosky, C. W., P. M. Anderson, and P. Garden 72:852-863. J. Bartlein 1987 The Northwestern U.S. Cwynar, L. C. During Deglaciation: 1982 A Late-Quaternary Vegetational History and Vegetation History from Paleoclimatic Implications. Hanging Lake, Northern In North America and Yukon. Ecological Adjacent Oceans During Monographs 52(1 ):1-24. the Last DeglaCiation, edited by W. F. Cwynar, L. C. and J. C. Ritchie Ruddimann, and H. E. 1980 Ardic Steppe-Tundra: A Wright, Jr., pp. 289-321. Yukon Perspective. The Geology of North Science 208 (June):1375- America, Vol. K-3, 13n. Geological Society of America, Boulder. Daubenmire, R. 1978 Plant Geography with Brubaker, L. B., H. L. Garfinkel, and M. E. Special Reference to North Edwards America. Academic Press, 1983 A Late Wisconsin and New York. Holocene Vegetation History from the Central Edwards, M. E., and W. S. Armbruster Brooks Range: Implications 1989 A Tundra-Steppe Transition for Alaskan Paleoecology. on Kathul Mountain, Quaternary Research Alaska. U.S.A. Arctic and 20:194-214. Alpine Research 21 (3):296- 304. CLIMAP projed members 1981 Seasonal Reconstrudions of Elias, S. A, S. K. Short, and R. L. Phillips the Earth's Surface at the 1992 Paleoecology of Late-Glacial Last Glacial Maximum. Peats from the Bering Land GSA Map and Chart Series Bridge, Chukchi Sea Shelf 36. Geological Society of Region, Northwestern America, Boulder. Alaska. Quaternary Research 38:371-378.

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Grubb, P. J. Guthrie, R. D., and S. Stoker 19n The Maintenance of 1990 Paleoecological Significance Species-Richness in Plant of Mummified Remains of Communities: The Pleistocene Horses from Importance of the the North Slope of the Regeneration Niche. Brooks Range, Alaska. Biological Review 52:107- Arctic 43(3} :267-274. 145. Heusser, l. E., and J. J. Morley Guthrie, R. D. 1985 Pollen and Radiolarian 1968 Paleoecology of the Large Records from Deep-Sea Mammal Community in Core RC14-103: Climatic Interior Alaska During the Reconstructions of Late Pleistocene. American Northeast Japan and Midland Naturalist Northwest Pacific for the 79(2} :346-363. Last 90,000 Years. Quaternary Research 1982 Mammals of the Mammoth 24:60-72. Steppe as Pal eoe nvi ro n me ntal Hinds, W. T. Indicators. In Paleoecology 1975 Energy. and Carbon of Beringia, edited by D. M. Balances in Cheatgrass: An Hopkins, J. V. Matthews, Essay in Autecology. Jr., C. E. Schweger, and S. Ecological Monographs B. Young, pp. 307-328. 45:367-388. Academic Press, New York. Hopkins, D. M. 1984 Mosaics, Alleochemics and 1972 The Paleogeography and Nutrition: A Theory of Late Climatic History of Beringia Pleistocene . Megafaunal During Late Cenozoic Extinctions. In Quatemary Time. Intemord 12:121- Extinctions, edited by P. s. 150. Martin and R. G. Klein, pp. 259-298. University of 1982 Aspects of the Arizona Press, Tucson. Paleogeography of Beringia During the Late 1990 Frozen Fauna of Mammoth Pleistocene. In Steppe: The Story of Blue Paleoecology of Beringia, Babe. University of Chicago edited by D. M. Hopkins, J. Press, Chicago.

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