PALEOBIOMES AND PALEOPASTURES INITIATIVE
An international, cross-hemispheric, research project
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Project Summary The Paleobiomes and Paleopastures Initiative (PPI) aims to reconstruct patterns of vegetation since the Last Glacial Maximum (21,000 cal years BP) in south-central North America and Southern Africa. PPI attempts to introduce four new innovative aspects to research in paleovegetation reconstruction: (1) the combined use of opaline phytoliths, fungal spores, microscopic charcoal, and carbon isotopes from organic matter in modern and ancient soils; (2) reconstruction of herbivore and fire influence in the shaping of vegetation biomes, in addition to climatic and orbital changes; (3) analysis of parallel climatic and vegetation histories in two hemispheres and two continents, and (4) the fostering of collaboration between Quaternary paleoecologists and conservation scientists via the comparative study of ancient and modern ecosystems in parks and reserves. The main question that PPI attempts to answer relates to the short and long-term effects of large herbivore grazing and browsing and fire in vegetation structure. One of the secondary questions that PPI addresses is the role of vegetation change in the habitats of extinct large mammals, particularly Proboscideans in North America, through a closer look to contemporary elephant habitats. For this reason, in its early stages, PPI has focused on modern elephant habitats in Africa and their relation to vegetation structure, fire, and climate variables. PPI is now in its embryonic phase, which consists of preliminary and exploratory sampling of surface soils in locations with native herbivores and controlled fires. The data collected in this phase will be utilized to strengthen a grant proposal to the US National Science Foundation for a large-scale project. PPI will also expand collaboration and cross-experience between American and South African paleoecologists, ecologists, and conservation scientists. |
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To read more about PPI, scroll down or click on the subheadings below
1. What motivated the creation of the Paleobiomes and Paleopastures Initiative? 22. Why grass-dominated ecosystems? 3. South-central North America and Southern Africa as focus regions 4. PPI and the habitats of large extinct Ice Age mammals? 5. Paleoenvironmental records used in PPI 6. Opaline phytoliths for reconstructing past vegetation structure 7. The frequency of past fires and the effects of herbivores on vegetation 8. Research phases of this project 9. Why are parks and reserves so important in the early phases of PPI research? 10. What areas have been sampled thus far? 11. Who is involved in PPI?
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1. What motivated the creation of the Paleobiomes and Paleopastures Initiative? The context in which PPI was created was shaped by a series of research questions. However, the most important of such questions appeared in 2005, when a group of ecologists published a controversial article in Nature (1). The article proposed a plant to re-wild North America with animals lost at the end of the Pleistocene. The proposal included the formation of reserves and parks where living relatives of the Ice Age extinct mammals would be introduced. Soon afterwards, articles and notes bearing different points of criticism appeared in Nature and other scientific journals. Most critics agreed that North American ecosystems have changed considerably since the time of mass extinctions and that the project poses serious to the modern ecosystems of North America.(2) However, the proposal revived many of the old research questions concerning the extinctions of Pleistocene fauna, particularly the different hypotheses involving climate change and overkill by the groups of hunters that had arrived from Asia at the end of the Pleistocene (3) and most recently the effects of an extraterrestrial(4). It is for this reason that PPI attempts now not only to take on some of these questions, but also investigate more about habitat change of surviving large mammals (e.g., bison), as well as the combination of aspects inherent to the pre-European landscapes of North America (e.g., fires). In view of this controversy, PPI has the objective of comparing modern and Pleistocene vegetation-grazing-fire trilogy in south-central North America, as a way to assess the background of a possible re-wilding process. (1) Donlan, J., H.W. Greene, C.E. Bock, J.E. Bock, D.A. Burney, J.A. Estes, P. Martin, D. Foreman, G.W. Roemer, F.A. Smith, and M.E. Soulé. 2005. Re-wilding North America. Nature 436: 913-914. (2) For details on this aspect see: Rubenstein, D.R., D.I. Rubenstein, P.W. Sherman, and T.A. Gavin. 2006. Pleistocene Park: Does re-wilding North America represent sound conservation for the 21st century? Conservation Biology 132: 232-238. (3) Martin, P. 2005. Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of America. Berkeley: University of California Press. (4) Firestone, R.B. and a list of authors. 2007. Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling. Proceedings of the National Academy of Sciences, 104(41): 16016-16021. |
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2. Why grass-dominated ecosystems? Grasslands and other grass-dominated ecosystems (savannas and parklands) are emphasized in this research because these ecosystems dominate in the two study areas: south central United States (e.g., the Great Plains) and the Republic of South Africa. PPI is investigating opaline phytoliths produced by graminoids (grasses and grass-like plants) and a number of non-graminoid species, particularly woody plants. This approach will facilitate the reconstruction of changes in the proportion of woody plants and grasses in the past ecosystems, which in turn will be correlated with the proxy records for grazing, fire, and climate change. |
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3. South-central North America and Southern Africa as focus regions Primary considerations for the selection of these two world regions include latitudinal, environmental, and climatological components. The south and central part of the North American Great Plains, which is occupied by grasslands and shrublands lies between latitudes 27° and 32° N. The Grassland, Savanna, Karoo, and Albany Thickets approximately occupy about the same latitude in the southern hemisphere. Both straddle a gradient between desert and woods and between summer and bimodal rain seasons, and both areas have rainfall influences from two oceans. The grasslands of both regions face encroachment by thorny shrubs and trees. In North America the southern grasslands are being encroached upon by shrubs of the Chihuahuan Desert, a region that bears a remarkable ecological similarity to the Karoo of South Africa. In general, the two research regions represent excellent northern and southern parallels to study the relationships between large herbivores, vegetation, and climate change since the Last Ice Age. |
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4. PPI and the habitats of large extinct Ice Age mammals? Regardless of the causes of faunal extinctions at the end of the Pleistocene (overkill, climate change, and the effects of extraterrestrial impacts), animal habitat change before and after the extinctions is poorly known. PPI offers a look into vegetation structure as conditions for grazers and browsers through remains of phytoliths and palynomorphs in the soil. Although this approach implies local change, the project aims at comparing this information with local faunal assemblages. The sites spotted for this research are often found in or near paleontological localities. In addition, to responding to the Pleistocene Re-Wilding of North America, PPI attempts to answer numerous questions regarding the extinctions: Why certain large mammals disappear (mammoths, camels, and horses) and others remained (bison, moose, and elk)? Why animals that today seem to occupy different environments were sharing the same ecosystem? What effects did extinction of large herbivores left in vegetation structure? |
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5. Paleoenvironmental records used in PPI
PPI is using palynomorphs (microscopic particles such as phytoliths, pollen, spores, and charcoal) obtained from buried soils (paleosols). The combination of palynomorph types helps reconstruct the local vegetation types and the grazing and fire regimes over time (Figures 1 and 2).
Figure 1. Conceptual and methodological framework of the project
Figure 2. Selection of palynomorphs from a modern soil.
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6. Opaline phytoliths for reconstructing past vegetation structure Traditionally, paleovegetation reconstruction has been based on fossil pollen obtained from lake sediments. However, lakes are rare in extensive areas of North America, particularly on the Great Plains, and in most of Southern Africa. Often when lakes exist in these areas pollen is poorly preserved. This leaves large spatial voids of unknown vegetation on maps portraying floral communities in the past. Additionally, pollen records from lakes illustrate regional rather than local patterns of past vegetation, merely because most pollen grains are wind-blown. Furthermore, certain pollen grains are invisible in the palynological record, because of their poor production and/or dispersal capabilities. Pollen also does not provide taxonomic resolution to grasses. Opaline phytoliths are microscopic fragments of silica formed in the tissues and cells of plants. When plants die and decay, phytoliths remain in the soil, becoming a testimony of plants supported by that soil. Although only a few are taxonomic, they can be a very good indicator of plant groups (e.g., grasses, certain groups of non-graminoid and woody plants). Because they are well preserved in soils, they represent a wealth of information for local, rather than regional, vegetation change. Opaline phytoliths also provide higher taxonomic resolution for grasses, allowing for the division of cool and warm season grasses, as well as subfamilies with more or less palatable grasses. Through PPI research, data obtained from opaline phytoliths will be combined with carbon stable isotopes to reconstruct vegetation structure. Therefore, a clear idea of the ratio between herbaceous and woody vegetation will be clear, pointing mainly to the role of grasses in the ecosystem. This information will require a link to two important non-climatic factors: fire and herbivory. |
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7. The frequency of past fires and the effects of herbivores on vegetation PPI uses frequencies of burned grass phytoliths and microscopic pieces of charcoal stored in soils and ancient soils (paleosols). For this purpose, a study is necessary in areas with modern controlled burning will be conducted. For example, grassland patches with year-to-year burning should have more burnt phytoliths than areas with lower frequency. Microscopic charcoal is used as a proxy for burning of woody material (Fig. 3).
Figure 3. Assemblage of phytoliths and charcoal from a Holocene paleosol. (a) charcoal, b)dicot phytolith, c,d,e) grass short cell phytoltihs, e)burnt grass phytolith.
The use of fungal spores, particularly Sporormiella, will be used as a proxy for the presence of ungulates. Sporpormiella spores are abundant in dung, and found in relatively high frequencies in areas grazed by large herbivores. Studies by Owen Davies (U. of Arizona) show that the content or Sporormiella spores in areas with high stocking rates of cattle are high. In fact, the frequencies of this spore in pollen diagrams are an indicative of the European period in the American Southwest.(5) Additionally, Davies found that the Late Pleistocene sediments contain high amount of Sporormiella spores, due probably to the high density of large grazers, some of which are extinct of vanished from the region. This pattern of fungal spore distribution in paleosols seems to be consistent with our sections in the Great Plains. It is particularly this aspect of fire and herbifory effects of grass dominated ecosystems that PPI will look into with more detail. A typical profile in the PPI database will consist of several sets of data. A summary of information from a palesosol sequence is portrayed on the example form an undisclosed locality in west Kansas (Fig. 4). (5) Davies, O.K., and D.S. Shafer, 2006. Sporormiella fungal spores, a palynological means of detecting herbivore density. Palaeogeography, Palaeoclimatology, Palaeoclimatology 237: 40-50.
Figure 4. Example of section and paleodata produced by PPI. |
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8. Research phases of this project The number of tasks involved in acquiring raw data and processing in PPI is complex. However, three distinct phases of research are thought to facilitate the flow of research and the achievement of objectives and goals (Fig. 5). Phase I and Phase II are aimed at obtaining data from modern environments and stratigraphic sections, respectively. Phase III will involve quantitative research, mapping and spatial analysis of data produced in the two phases. The objective of Phase III is to display data in a chronological and spatial way. This objective also aims at comparing information of biomes and pasture conditions with those of faunal distribution maps such as the FAUNMAP. (6) (6) FAUNMAP Working Group 1994. FAUNMAP a database documenting the distributions of mammal species in the United States. Illinois State Museum Scientific Papers 25. Illinois State Museum: Springfield, IL.
Figure 5. Research phases in PPI.
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9. Why are parks and reserves so important in the early phases of PPI research? Parks and reserves often seek to recreate and/or protect landscapes that resemble pre-agricultural wild environments. Therefore, they can be an excellent reference to pre-historic landscapes. PPI hopes to provide paleoecological data that will be useful to contriving restoration and re-wilding projects in parks and nature reserves. In these areas PPI is not looking for modern analogs, but references to the presence, absence, and proportions of plant forms and their representation in phytolith assemblages and carbon isotopic data. In these locales, stocking rates of native and domesticated ungulates vary considerably. Therefore, their variability is studied through the remains of phytoliths, spores, and other palynomorphs. In general, as suggested on Fig. 5, this information will be crucial for the reconstruction of ecosystems and habitats (Phases II and III). |
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10. What areas have been sampled thus far? The North American part of Phase I, namely the sampling modern locales, has almost been completed (Figure 6). The sites sampled include from national andvprovincial parks, wildlife management areas, nature reserves, as well as private and tribal land reserves. This work was carried out during 2006 and the first half of 2007. The South African part began in July 2007. Thus far the areas sampled include a transect along a climatic gradient, from the grasslands of the Highveld to the Atlantic coast, encompassing parts of 5 of the regions biomes (Grassland, Savanna, Nama Karoo, Succulent Karoo, and Desert) (Figure 7). The transect was also meant to straddle the areas of summer and winter season precipitation. This strategy allows not only the recovery of phytolith references for plants and soils representative of each biome, but also of phytolith forms of warm season (C4) and cool season (C3) grasses.
Figure 6. Modern sample localities in North America (as of October, 2007).
Two game reserves in the savanna biome were sampled (Madikwe Game Reserve and Pilansberg National Park). The main reason for sampling in them was to obtain data of areas grazed by elephants and areas where elephants are excluded. This strategy will allow us analyze palynomorphs and phytoliths in soils of areas where a relative of the extinct mammoths, and an animal of similar size and probably similar behavior interact with vegetation. Modern phytoliths sampling in Pilansberg National Park included elephant teeth for extraction of phytoliths from tartar. The phytolith assemblages will be used to create a protocol for a similar study on mammoth teeth. See the similarities of Columbian mammoth and the African elephant teeth collected (Fig.8). Actualistic research on African elephants shows a great potential for comparing animal-environment relations between living and extinct proboscideans. (7) PPI wants to exploit this idea for a better understanding of mammoth and mastodont environments in Pleistocene North America and Eurasia.
Figure 7. Modern sample localities in South Africa (as of October, 2007).
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In 2008 more elephant parks and reserves will be sampled in South Africa. Another transect encompassing other biomes will be laid during the second phase of modern sampling. Phase II, or the collection of data from stratigraphic sections, has been much slower. At present, only four sections in Kansas and Oklahoma have been studied. But more funds will imply a faster development of this phase. (7) Haynes, G. 1991. Mammoths, mastodonts, and elephants. Biology, behavior, and the fossil record. New York: Cambridge University Press
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11. Who is funding PPI? At the moment, PPI is working with small funds from the College of Arts and Sciences of Oklahoma State University, the National Endowment for the Humanities and the American Center of Oriental Research, and contributions from other sources. The budget is limited, but it has permitted collection of control data for the project. In 2008 a proposal for a large grant will be submitted to the National Science Foundation, a US federal grant, through their Geography, Archaeology, and Geosciences programs. An estimated cost of approximately US$170,000.00 for three years of research is expected to be requested in this proposal. Further developments and funding will allow expanding this research to neighboring countries such as Mexico, in North America, and Namibia, Lesotho, Botswana and Swaziland in Southern Africa.
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Principal Investigator: Carlos E. Cordova, Oklahoma State University, USA Co-investigators: William Johnson, University of Kansas, USA Louis Scott, University of the Free State, Bloemfontein, South Africa James Brink and Lloyd Roussouw, National Museum, Bloemfontein, South Africa Lindsey Gillson, University of Cape Town, South Africa Elna van der Linde, Plant Protection Research Institute, Pretoria, South Africa
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Last Updated: 6 October 2007
Oklahoma State University
Department of Geography
Stillwater, OK 74078