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How Plants survived the Ice Age

The views expressed are those of the author and are not necessarily those of Scientific American.


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No such hypothesis is sufficient to explain either the cataclysms or the glacial phenomena; and we need not hesitate to confess our ignorance of this strange, this mysterious, episode in the history of the globe….
BRISTOW, H.G. (1872): The world before the deluge by Louis Figuier – Newly edited and revised by H.W. Bristow. 2nd. edition – Cassel, Petter, Galpin & Co.

The published description of the resuscitated “32.000 year old Ice Age plant“, in fact a phenotyp variation of the extant Silene stenophylla, is an ulterior intriguing glimpse in the ancient ecosystem of the Ice Age steppe, an environment characterized by unusual climatic conditions and a particular plant community with species that today grow in very different environments.

Fig.1. The period of the Diluvium, or Ice Age, with a glacier invading the land, from UNGER, F. (1851): Ideal Views of the Primitive World, in its Geological and Palaeontological Phases. Taylor and Francis, London (image in public domain, from the U.S.G.S. library).

There are various methods to reconstruct the plant community of a past landscape. Flowering plants produce pollen grains composed by a chemically very stable substance named Sporopollenin, therefore pollen grains usually are well preserved in sediments (but as correctly noted in the comments not in soils). Identifying and counting the pollen deposited over time on the bottom of a lake or conserved in the layers of a bog we can infer the vegetation that once surrounded these sediment traps. In such sediments also plant detritus can be conserved.
Many animals transport and store plant detritus in their burrows. The conserved seeds of S. stenophylla were found in an ancient ground squirrel cache. Apart trying to grow the seeds, the fragments of leafs, blossoms, buds and seeds can often be identified to species-level and help to reconstruct the vegetation inside the range of activity of the former burrow-occupier.
Plant remains or pollen can also be found in the gut content of mummified animals or in fossilized dung, also referred as coprolithes (or dung-stones).
Based on such fossils a particular ice age plant community was reconstructed that is often referred as steppe, arctic-steppe, steppe-tundra, herb-tundra or mammoth steppe. Today the term steppe is applied to grassland or shrubland with a relative dry and temperate climate, meanwhile tundra applies to an environment where the growth of trees and shrubs is inhibited by the low temperatures and species of herbaceous plants or grass dominate. The words steppe-tundra or mammoth steppe seems therefore at first an odd combination of contradicting terms.

Studying the preserved content in the intestine of the mummified mammoth calf “Lyuba“, we can try to imagine the plant community that dominated the continents of Europe-Siberia and North America some 40.000 years ago.
The preserved material is dominated by species of two grass-families (Poaceae and Cyperaceae), indicating an open environment. Other plant groups identified are Artemisia, a group found today especially under dry or semi-dry conditions, the rushrose Helianthemum, also found under dry conditions, and the Jacob’s ladder Polemonium, native today to cool temperate and arctic regions. Unlike as in the modern treeless tundra there existed apparently spots of forest, indicated by the presence of pollen grains of Pine (Pinus), Spruce (Picea), Birch (Betula), Willow (Salix) and Alder (Alnus), all trees that can tolerate snow or low temperatures and grow in part under dry conditions (pine and spruce) and in part under humid conditions (birch, willow, alder). It is unlikely that all these plants grow directly on one spot, considering also that a mammoth herd moved from grazing spot to grazing spot and pollen grains could be transported by wind, however all these plants nevertheless existed in a relative restricted space. The term mammoth steppe is therefore not too inappropriate, as species of warm and dry habitats did coexist with species of cold and humid habitats, resulting in a plant community with a uniquely rich biodiversity.

To understand such a community it is important to note the climatic differences of the modern tundra and the ice age steppes. The overall cold temperatures in an ice age world reduced significantly the evaporation of water from the oceans, resulting in a drier atmosphere and lack of precipitation (snow or rain) on large areas of the continents. This caused dry conditions in the summer and also reduced snow cover during winter time; and snows inhibits photosynthesis and therefore limits plant growth.
The modern tundra is today found at a northern latitude of more than 65°, characterized by short summers with the sun reaching only a low altitude above the horizon in this season. During the ice age the mammoth steppe spread until 45° N. Here the sun climbs much higher above the horizon and the insolation is more intense, photosynthetic activity is more productive and plants can grow well despite cold temperatures.

The particular plant community of the mammoth steppe was an adaption to the particular combination of environmental factors during the ice age. Little is known about adaptions of the single plants to this environment. The described specimens of the ice age S. stenophylla produced more buds and the roots developed slower than modern specimens of the same species. In an environment with a short period of growth and limited availability of insects as pollinators investing in more flowers could be an advantage – the discovery of living tissue is therefore a unique opportunity to study possible physiological adaptations to the lost world of the mammoth steppe.

Bibliography:

CRAWFORD, R.M.M. (2008): Plants at the Margin – Ecological Limits and Climate Change. Cambridge University Press: 496
GAGLIOTI, B.V.; BARNES, B.M.; ZAZULA, G.D.; BEAUDOIN, A.B. & WOOLLER, J.M. (2011): Late Pleistocene paleoecology of arctic ground squirrel (Urocitellus parryii) caches and nests from Interior Alaska’s mammoth steppe ecosystem, USA. Quaternary Research 76: 373-382
GEEL, v.B.; FISHER, D.C.; ROUNTREY, A.N.; ARKEL, v.J.; DUIVENVOORDEN, J.F.; NIEMAN, A.M.; REENEN, B.A.v.; TIKHONOV, A.N.; BUIGUES, B. & GRAVENDEEL, B. (2011): Palaeo-environmental and dietary analysis of intestinal contents of a mammoth calf (Yamal Peninsula, northwest Siberia). Quaternary Science Reviews 30: 3935-3946
NAGY, L. & GRABHERR, G. (2009): The Biology of Alpine Habitats. Oxford University Press: 389

David Bressan About the Author: Freelance geologist dealing with quaternary outcrops interested in the history and the development of geological concepts through time. Follow on Twitter @David_Bressan.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Paleoecologist 4:52 pm 02/24/2012

    Nice post! I offer one small correction: pollen doesn’t preserve very well in soils, sadly. That Sporopollenin survives lots of very harsh chemicals that we paleoecologists use to digest the mud and sediments the pollen is preserved in, but there’s one thing it can’t take: oxidation. Very wet, anoxic conditions like lake bottoms or bogs are great places to preserve pollen, but soils are not.

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  2. 2. David_Bressan 3:48 pm 02/26/2012

    Thanks, corrected the sentence

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  3. 3. Jerzy New 9:39 am 02/27/2012

    Please forward it to climate activists who claim wildlife cannot adapt to climate very different than today.

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  4. 4. Jerzy New 9:46 am 02/27/2012

    BTW, closest equivalent for conditions of Ice Age is probably not tundra, but high mountains and especially cold, dry, high-altitude plateaus in moderate latitudes, like Tibetian Plateau.

    Here you have, for example, a bizarre compression of habitats: arctic conditions border warm steppe and pockets of forest in sheltered valleys.

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  5. 5. David_Bressan 8:34 am 03/4/2012

    There are some suggestions that on very sunny slopes in Siberia there are at least spots of steppe-tundra ice-age flora. The high-plateau on Tibet is influenced apparently too much by a continental climate: very strong climatic oscillations between dry-warm summer and very cold winter – in sum very dry conditions, as even in winter precipitation are rare there is a too great lack of water during spring snowmelt, unlike as in the tundra. I’m trying to get some species list, but is seems that high plateaus are – at least today – dominated much more by steppe-plants than even the dry “ice-age steppe”

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  6. 6. bdddriller 9:06 pm 07/19/2012

    As I am disabled and don’t really know where to put the information that I have posted I am relying on your knowlege as to what catagory to list my information on or if there is a place invented yet to do it so I need to know if you are going to help me out by putting the information where it belongs and if you believe that the freedom of speech apllys to everyone I am asking that after you post my comments you e-mail me and tell me where to look for other folks responces as I want to do the right thing and share where I got my information,and answer the questions as best I can.Regards,rik

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  7. 7. bdddriller 9:25 pm 07/19/2012

    As God has told me what man needs to do is core the sedimentry levels in a major river in the Northern Hemisphere looking for records of ice ages and how long they last as the only responce I got when I asked God,was a long time which means in his language from a few hundred years to a few thousand and they always start the same a elivated evaporation rate,like the melting of the north pole area making a cloud bank that will block and reflect the sun lowering the global temperature and as the 12,000 year ice age cycle is anouther 400-2,000 years away if we elivate the temporature more we may cuase a mini-ice age so we must be careful as if this happens the growing cycle for all plants is going to be comprimised and the summers will be to cold and the sunlight to dim to grow the foods we are used to,we might have to go into abandoned mines and rely on the earths heat to live,eating a combination of mushrooms and chickens for meat and eggs as this is the most effective use of space and the chickens can eat our table scaps.Their waste can be dealt with by venting their area right so the ammonia isn’t a problem.And musrooms need a cool dark place to grow so they can exist anywhere thats not freezing.Regards,rik P.S. Canada has the Canadian sheild to burrow into but what about the rest of humanity.

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  8. 8. bdddriller 11:04 pm 07/21/2012

    As I have said I know everything about SATAN and his plans for the earth becase about 3,000 years ago God came to me he had a problem,He knew from traveling up and down the time line that heaven was going to be destroyed and untill the Olimpics came to Vancover it was a mystery but I intercepted both races,one we knick named snake heads the other had red fire that came out of their eyes in a beam.As God and I are mentaly linked he knew right away that the irridium asteroid came from a differant solar system and hit the Gulf of Mexico freeing SATAN from the earth 76 million years ago.God made white light very painful to SATAN and thats why someone invented the light bulb He got bored only being abil to effect peaple in thier dreams.Those races that I mentioned attacking heaven made me volitier to let my spirit exist in HELL and as I volintairily was there SATAN protected my spirit from everything including his deamons and as God controls time he went back to where they came from and didn’t turn on thier suns so they and everything they ever did is erased from the time line.GThe ship that guided the aridium asteroid into impacting the Gulf of Mexico was one of Gods desighn so it was easy to recover,sorry.But you have to invent your own or trade a ballaed power cell out at the edge of the asteroid belt for a better class of starship then oil.As I have said every planet that is firery in creaton without a atmousphere makes the condinsation reaction that made all the water on earth.Of all the planets there is only one earth that has a hell so the core never cools and tat way wil always have a magnetic feild forever,I am asking you to let man evolve as the jumpers that were prisoner in Newfoundland are gone back to heaven and we have relocated somewhere in space you will find out when you are a little more advanced,think of the kind of planet that you got from your parents think of the future.Regards,rik

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