“This is one of the best examples of a spring marsh I have yet seen. . . ” wrote State Geologist Charles White about this Marion, Iowa fen in the course of his critical statewide survey of Iowa’s wetlands in the fall of 1867 (White, 1867). However, White didn’t come to admire the flora.  The future of the State rested upon what he could learn here about turning this peatland into an urgently needed fuel source.

Coming largely from the forested eastern U.S., Iowa’s early settlers were the first to encounter vast expanses of prairie, and face the bleak prospect of developing an economy without a ready supply of wood.  The soil was incomparable and opportunities boundless–limited only the fuel shortage.  Timber was in desperately short supply, especially in the north and west, and disappearing rapidly everywhere.   Once it became evident Iowa’s coal deposits were limited to the southern counties, hopes coalesced around peat as a source of energy. . . at least as a stopgap until new forests could be grown.  White wrote (1868):

Our peat “. . .  will soon become invaluable. . . for (it) lies wholly beyond the limits of the coal-field, and the timber, although enough for the present inhabitants, can not supply a tithe of the fuel which the prospective population of a region so fertile and inviting, will soon demand. Peat has there a local value which can not be questioned.”

Mention peat today, and potting soil or fertilizer probably springs to mind—not so for earlier generations. Dwindling timber supplies had stirred some limited commercial fuel ventures in New England early in the century (Hawes, 1912), but few native-born Americans had any direct experience with burning peat.  Cultural roots and memories run deep though, and many Iowa families were of northern European stock, with a long tradition of burning peat.  Some British and Irish immigrants, coming here to farm or build railroads, found themselves overseeing peat operations instead (Cedar Falls Gazette, 1867).

Half the peat harvested in the world today is used for fuel (Turetsky and St. Louis, 2006).  The European Union has 125 peat-fired power plants, mostly in Finland and Estonia, with more being announced every year (International Peat Society, 2010).  Some of the new plants are 100% peat-fired, but many older coal-fired plants are converting to co-burn peat, reducing their average mercury and sulfur emissions and significantly extending their service lives.

Good dry peat is a light clean fuel.  It is easily kindled and burns with a hot red flame leaving little smoke, soot or ash.  Unlike coal, though, there is no clinker or slag; low sulfur means no acid rain either.  There’s a pungent odor to burning peat that some people find objectionable, but others liken to Scotch whisky.   Pound for pound, plain dry peat has about the same heating value as pine (Savage, 1905), but owing to its lower density, needs twice the storage space—8-18X more than coal (Davis, 1907).

 Peat is the partially decayed remains of plants.  It is the permanent saturation by water keeping dissolved oxygen low that retards decomposition and distinguishes a peat-bog or fen from a marsh (which dries out occasionally, speeding decomposition).  The types of plants, the degree of decay and chemical composition of peat vary widely.  It may be a light and fibrous sponge, or a dense black muck with no visible structure–changing by depth and location in the bed.  The usual sequence of a deposit is a tough fibrous mat overlaying a progressively denser and darker muck, but depending on the hydrology of the site, this sequence can be reversed, or repeated, with sediment inter-layered.   Given enough time, heat and pressure, a deposit of peat will be transformed into a more uniform bed of coal, but at this stage it’s a highly variable natural living raw material.

Peat is more than just a sodden compost heap of leaves and stems. The aerated top layer of a peat bed is interwoven with the roots and rhizomes of living plants.  Most store their food and overwinter here.  Nutriments like this made wetlands an attractive destination for hunter-gatherers, especially in the spring after a hungry winter, before the uplands had much to offer. Native Americans had the tools needed to access this underground bounty–few animals do, however, except for moose maybe. . .  and ground sloths.   More than a few of the Megalonyx skeletons found in situ, including our Tarkio trio, have been recovered from bottomlands—three of the more complete specifically from peat bogs like this one (McDonald, 1998).

Still, peatlands are relatively barren of wildlife compared to other ecosystems.  The living conditions that make life hard for plants, affect animals too (e.g. high water, low oxygen (for the burrowers), etc. ). Small mammals stick to the hummocks and the trails left by deer and other visitors.  Travel is difficult, unless you’re a bird, and dangerous besides, judging from the many bison bines uncovered here and elsewhere (Toennies, 2003).  Generally, visitors find what they need, and leave.  It may not be food or water drawing sloths and bison here though–some of these plants may offer trace elements the animals need.   Caribou retreat to boreal bogs for calving to avoid wolves (Rettie and Messier, 2000) . . . our “baby” is older than that though.

Sphagnum and Hypnum mosses make up the bulk of boreal peat-bog deposits but sedges predominate in Iowa’s beds (Pammel, 1909).  Trees and shrubs are an important component of some northern bogs but they were less common here–only likely to invade after drainage and intense grazing or other disturbance (Middleton, 2002).  From an energy perspective, the specific plants that make up peat are less important than the impurities.  Contamination like loess, silt and sand, the shells of mollusks, and the bones of the occasional mammal that falls in, are unburnable and leave ash—too much (>25%) and the peat is worthless as a fuel.

In Europe, peat was traditionally harvested by hand—cut into blocks or turves with special peat-spades (“slanes” in Ireland) and then air-dried. Working together, an average family could cut enough peat in one week to heat a cottage all winter (Rotherham, 1999).  Cutting and lifting the heavy wet sod was work grown-ups; children usually saw to drying the blocks—carefully turning and restacking them several times over four to six weeks to expose fresh surfaces to the sun and wind.  The blocks are highly friable and break apart easily with rough handling. Drying had to be finished by winter—ice crystals destroy the structure, and frozen wet blocks collapse upon thawing.  An average household needed 5-8,000 turves per year—a stack that could be as large as the house itself (ibid.). 

Preparing peat for fuel was a demanding process–one traditional peoples in Europe had managed for at least two thousand years (Rotherham, 2009), but in the U.S., where labor costs were high, exploiting peat for a mass market faced some daunting challenges.   Nonetheless, a far-thinking group of Quakers came here to Marion, Iowa in 1866 to tackle the challenge, and put the State, and perhaps the Nation, on the path to energy independence.  Next time: The Marion peat enterprise. . . . Dave

References

Cedar Falls Gazette, February 8, 1867.

Davis, C. A. 1907. Peat: essays on its origin, uses and distribution in Michigan. State Board of Geological Survey.  Lansing, MI.

Hawes, J. W. 1912. An Historical Address:  Celebration of the 200^th anniversary of the incorporation of Chatham, Mass. C. W. Swift, Publ.  Where?

Huels, F. W. 1915.  The peat resources of Wisconsin.  Wisconsin Geological and Natural History Survey.

International Peat Society

McDonald, H. G. 1998.  The sloth, the president, and the airport.  Washington Geology 26: 40-42.

Middleton, B. 2002. Nonequilibrium dynamics of sedge meadows grazed by cattle in southern Wisconsin.  Plant Ecology 161  89-110.

Pammel,  L. H.  1909.  Flora of northern Iowa peat bogs. Iowa Geological Survey 19: 739-784.Rettie, W. J. and Messier F. 2000. Hierarchical habitat selection by woodland caribou: its relationship to limiting factors. Ecography 23:466–478.

Rotherham, I. D. 1999.  Peat cutters and their landscapes:  fundamental change in a fragile environment.  Landscape Archaeology and Ecology 4: 28-51

Rotherham, I. D. 2009.  Peat and Peat Cutting.  Shire Publications, Oxford, England

Savage, T. E. 1905. 2  A Preliminary Report of the Peat Resources of Iowa.  Iowa Geological Survey Bulletin No 2. Des Moines, IA

Toennies, J. L. 2003.  Dows Holocene fossil bison assemblage, Franklin County, Iowa:  Its application to conservation, interpretation, and outreach.  University of Iowa, Department of Geoscience, M. Science thesis.

Turetsky, M. and St. Louis, V. L. 2006. Disturbance in boreal peatlands.  In Ecological Studies, Vol. 188,  Boreal Peatland Ecosystems.  R. K. Wieder and D. H. Vitt (Eds.), Springer-Verlag, Heidelberg.

White, C. A.  1867. Marion Register, December 11, 1867.

White, C. A.  1868.  First and Second Annual Report of the State Geologist.  F. W. Palmer, State Printer.  Des Moines, Iowa.

Ground sloths may be extinct but they aren’t dead. The footsteps of these recently departed elephant-sized Ice Age giants continue to echo through Iowa’s woodlands with important implications for today and the future. David Brenzel, former curator at the University of Iowa Museum of Natural History and co-principle investigator on the Tarkio Valley Sloth Project will discuss the excavation to recover the only Jefferson’s sloth family ever discovered, including the most complete adult and second-most complete juvenile of the species ever found, and research to-date. MEMBER:$3-NONMEMBER:$4 FOR MORE INFORMATION CALL 362-0664 .

Driving Directions

I’ve been ruminating again about how our sloths might have died.  Looking for fresh inspiration, I hiked down the Grant Wood trail here on the edge of Marion, IA to the Hughes peat bed, a site not unlike the ancient Tarkio Valley, where I recently learned a pair of bison–adult and juvenile– met their untimely ends 5,000 years ago.

The Grant Wood Trail starts on Hwy 13, just north of Squaw Creek Park and the Hwy. 100 intersection.  It was created in 1999 by members of the Linn County Trails Association, (http://www.linncountytrails.org/) and donated to the county in 2005.   The trail follows a route carved out by the defunct Chicago, Milwaukee, St. Paul and Pacific Railroad Company in 1872 on its way to Denver and places west.   It was Marion’s lifeline and road to prosperity for 100 years. The company abandoned the line in 1980, but telegraph poles and remnants of old sidings still peek out from the overgrowth.

The rolling hills that border the trail reminded residents of the paintings of a locally-born artist and time when more Iowans came from farms, but they speak to a geologist of a period more than 500,000 years ago when glaciers last visited these parts.  Erosion and the intense cold of the last ice advance softened the contours of the landscape (Prior, 1991) but left loess-covered hills that still compel nearly every first-time visitor to remark, “I thought Iowa was flatter.”

The railroad company planned to stay a while–sections of the old roadbed are paved with sparkling pink Sioux quartzite.  The rock is indestructible and has resisted erosion for 1.6 billion years where it is exposed in the NW corner of the state (Anderson, 1998). More diligent early road builders–train and auto—decided it was well worth the extra expense of hauling the crushed rock across the state for the maintenance costs it saved forever after.   Dorothy’s highway to Oz would have glistening pink if she had grown up a few hundred miles East.

Mammoth boulders line the fringes of the trail. Early observers called them “erratics,” recognizing their unusual character.  Iowa’s long stay at the bottom of the sea left it with a surfeit of sedimentary deposits, but these rocks are igneous and metamorphic—granite mostly—and don’t belong.   They were carried here from Canada by one of the early glacial advances and dumped.  They are the oldest rocks exposed in Iowa, aside from the meteorites that drop in from time to time.  Hikers walk passed them nowadays with hardly a glance, oblivious to their age and the unimaginable forces that brought them here.  Early settlers noticed–identifying Iowa’s geological resources was a priority.  Farming was too though, so they hitched up their teams and moved the smaller boulders into the farthest corners of these fields.  The biggest ones show signs that maybe dynamite helped with the moving.

Half way down the trail the land rises up on both sides as it cuts through a glacial paha—a Dakota Sioux word for hill (Anderson, 1998).  Hurricane-force winds sweeping off the last glacier blew sand and silt into massive dunes like this hill, mostly trending NW to SE.  Many an E. Iowa church, college or TV tower claims their peaks today, but the destiny of this paha lay in the calculations of a slick  RR accountant.  I wonder sometimes about railroad economics and why a company selects one path over another. . .  and their capacity–financial and technological–literally to move mountains.  The natural way forward for railroads is straight ahead, and in this instance they figured the fill they needed to bury the peat bog in their way lay just 1/4 mile further west . . . so onward!  Who needs a glacier when you have a railroad?  Did mining the peat before they buried it fit into their calculations?  Probably.

Scattered along both sides of the trail are traces of another ancient relic—remnants of Iowa’s tall-grass prairie.   Protection from rampaging plows and an occasional fire  sparked by a passing train were the only breaks these plants asked for to survive.  The tallest grass here is Spartina pectinata–prairie cord grass, or “ripgut” to those who know it especially well.  (Run your hand along the leaf-edge carefully.) Cord grass loves deep poorly-drained soil, and its appearance here tells me, as it told early settlers arriving by wagon, that soggy ground lies ahead and it would be wise to steer for high ground. The grass spreads  by extending its rhizomes and forms a thick gnarly mat which made the best sod houses (Madson, 1985).   Each clump is a clone–one individual self-renewing plant.  Spreading underground is common on the prairie–it’s difficult for seeds to get a toe-hold in the sod.  How long a clone can live is anyone’s guess–possibly hundreds of years. . . thousands isn’t out of the question (Steinger et al., 1996).    Sequoia trees tend to swagger, but this is Iowa, and our way is quiet dignity.

A sign overlooking the peat bed commemorates the discovery of a 5,000 year-old bison in 1969.  The skeleton was complete and articulated.  The animal may have been wandering through in the winter and broken through the ice.  Unable to extricate itself from the muck, it looked like it just hunkered down to die (Semken, pers. com.). The spring that keeps water flowing freely through the peat bed even in drought years when the nearby creek dries up (Hall, 1971) probably keeps areas of the ice thin–a death trap for large animals that misstep.  In 1988 the Cedar Valley Rocks and Minerals Society recovered a heifer and calf here lying side by side (Sonnleitner,  pers. com.) which apparently died the same way.  Could our sloths died like this?  Not mired down certainly–our bones aren’t articulated. . . but we’ve had other indications that winter may figure in the puzzle (also see Micozzi, 1986).

The Hughes peat bed is a bona fide ice age relic.  Hall (1971) dated the bottom layer to 11,880 years-old.  Snails and pollen suggest the area was a boreal spruce forest which gave way to oaks and elms by 9,300 years ago.  Ecologists would define this wetland as a spring fen—one of the rarest ecosystems in Iowa.  Pearson and Leoschke (1992) cataloged over 200 unique native plant species living in fens–10% of our native flora on less than 0.01% of the land. Fens truly are our emerald cities, and the Hughes peat bed is still a gem despite 150 years of peat extraction (White, 1868). More about the importance of peat lands in the past and in our future next time. . . . Dave

References

Anderson, W.I. 1998.  Iowa’s Geological Past:  three billion years of change.  University of Iowa Press, Iowa City, IA

Hall, S. A. 1971. Paleoecological interpretation of bison, mollusks and pollen from the Hughes peat bed, Linn County, Iowa.   Masters Thesis, Department of Geology, University of Iowa.

Madson, J.  1985.  Where the Sky Began.  Houghton Mifflin Company,  Boston MA

Pearson, J. A. and Leoschke, M. J. 1992.  Floristic composition and conservation status of fens in Iowa.  Journal of the Iowa Academy of Science 99: 41-52.

Prior, J. C. 1991. v Landforms of Iowa.  University of Iowa Press.  Iowa City, IA.

Steinger, T., Körner, C. and Schmid, B. 1996.  Long-term persistence in a changing climate:  DNA analysis suggests very old ages of clones of Alpine Carex curvula.  Oecologia 105: 94-99.

White, C. A.  1868.  First and Second Annual Report on the Geological Survey of the State of Iowa. Des Moines, IA.

Megalonyx upper caniniforms(L); molariforms (R)

Despite all evidence of their enduring success, the traditional view of sloths has long been that their simple ever-growing pegs of soft dentine imposed a serious constraint on their evolution. Even the scientists who acknowledge ground sloth achievements in South America discount the significance by pointing to their long isolation on the continent, supposedly inferior competition, and extinction after the Great American Biotic Interchange. They disregard sloths like Megalonyx and Paramylodon which successfully invaded the homeland of the allegedly superior mammals, dispersed widely, and competed successfully for millions of years, showing considerable adaptability in a wide range of habitats–faulty teeth and all (McDonald, 2005). Now Vizcaíno (2009) says scientists have overlooked some significant advantages of dentine teeth, and enamel isn’t something sloths lost but dumped to escape its limitations–opening the door for them to exploit niches unavailable to regular herbivores.

Abandoning enamel, Vizcaino says, and evolving ever-growing dentine teeth 60+ million years ago was the key innovation that allowed Xenarthrans to become abundant and widespread. The simple peg-like teeth that their earliest sloth ancestors evolved proved to be a remarkably flexible innovation. The enamel teeth of other herbivores wear out with age. Older animals have to adapt to the decline in their oral processing ability by altering what they eat and the way they eat it–selecting less fibrous leaves, chewing faster, spending more time chewing and eating greater quantities. They get less nutrition from their food because less of the interior of the cells is exposed to digestion by intestinal microbes and enzymes. The animals aren’t as well nourished so they suffer more stress due to disease, parasites and plant toxins. They spend more time in habitats providing less concealment and are more exposed to predators. Some herbivores simply starve to death because their teeth wear out, but most die for other reasons. Predation, parasites or disease may be the proximal cause of death, but theyare all the inevitable outcome of being born with enamel. Ever-renewing, self-sharpening teeth made of dentine, like sloths’, stay in optimal condition for life. [more about sloth teeth]

Were dentine teeth and their concomitant breeding advantages the evolutionary tools ground sloths used to conquer North America? An aging female Megalonyx with two healthy juveniles in tow, such as we may have in the Tarkio Valley would be compelling support for Vizcaíno’s theory. First, we need to prove our adult sloth was female, and then that the indications of arthritis we see come from old age and not an injury or a different disorder. . . ever-growing teeth aren’t much help when paleontologists need to determine a sloth’s age. If our adult was truly elderly you would expect more signs of the arthritis (McDonald, pers. com.). . . on the other hand, we shouldn’t expect zoo animal-age arthritis symptoms. . . life is hard, and relatively short, even in the Tarkio Valley. In any case, Vizcaíno presents an exciting new perspective. Maybe Buffon was right after all and sloths are a test. . . for us, to learn more about the wonders of life. . . . Dave

References:

Martin, P. S., Sabels, B. E. and Shutler, D. 1961. Rampart Cave coprolite and ecology of the Shasta ground sloth. American Journal of Science 259: 102-127.

McDonald, H. G. 2005. Paleoecology of extinxt xenarthrans and the great American Biotic Interchange. Bulletin of the Florida Museum of Natural History 45: 313-333.

Meritt, D. A. 2008. Xenarthrans of the Paraguayan Chaco. In The biology of the Xenarthra, S. F. Vizcaino and W. J. Loughry (eds.). University Press of Florida. pp. 294-299.

Nowak, R. M. 1991. Walker’s mammals of the world. Vol.1. John Hopkins University Press, Baltimore

Vizcaíno, S. F. 2009 The teeth of “toothless”: novelties and key innovations in the evolution of xenarthrans (mammalia, Xenarthra). Paleobiology 35: 343-366.

Dress up as your favorite Ice Age ghost or orphan. 

Thanks to Jan Ailes and the Cedar Rapids Indian Creek Nature Center for  sponsoring the Things that go Bump in the Night program again this year and the opportunity to tell guests more about ground sloths and their food.    

Much fun had by one and all.

 Watch the ICNC schedule for a  program about the Sloth Project this winter. 

More  about Honeylocusts and other Ice age orphans. . . . Dave

More photos in Flickr. . . . Dave

Holmes,

I got a mitochondrial amp from one of the extracts, but I haven’t cloned it yet to check for contamination.  I wasn’t able to get nuclear amplifications using our current stock of primers.  It wouldn’t surprise me if we get endogenous DNA from this thing, but it may not be in high enough copy numbers to do much more than generate a few scraps.  If we can determine that there is endogenous DNA via old school PCR and cloning(what I’m trying to do now), then the next step might be large scale extracts.  We’d then use the concentrate to build libraries to go on GS (Genome Sequencer) FLX plates and try to shotgun generate at least a significant portion of the mitochondrial genome.

Beth Shapiro at Penn State has her sample. . . hope to hear from her soon.

(GS-FLX) is actually the way to go. . . . Old school targeted PCR characterization is plagued by a lot of issues, including low endogenous copy number, PCR inhibitors in the extract, contamination (from a bunch of possible sources)  and primer specificity. . . .

We would initially generate say ~100,000 reads of ~100bp apiece and then sort through those to determine which represent environmental contamination (bacteria, fungus, etc), human contamination and actual endogenous sloth DNA (if any). . . .  When you do it on that scale you can get a much better idea of what’s going on in the specimen/extract. You can then use that info to design species specific primers of appropriate base composition and target length.

Best

AC

Andy’s results aren’t unexpected. Finding ancient DNA is like winning the lottery–its almost always highly degraded and finding a specific segment still intact with the PCR process that he’s using is a long shot. That’s especially true for nuclear DNA (nDNA). A cell has only one nucleus, and one set of nDNA, but it has 1,000 or more mitochondria and thus 1,000X as many copies of the mDNA genes. We’ll keep our fingers crossed about the mDNA signal, but as we learned before, chances are good it’s contamination. Winning this lottery is hard even when you are holding 1,000 extra tickets. No one has ever succeeded in the Megalonyx DNA sequencing game.

Even if you are lucky enough to have your ancient DNA (aDNA) survive 12,000 years of oxidation, heat and humidity, the fundamental limitation of the traditional Polymerase Chain Reaction (PCR) process is the focus on specific genes.  Old school (i.e. targeted) PCR is like going fishing—there may be a lot of DNA swimming around but you’ll never know it if you are using the wrong “bait,” or primer.   Primers are synthesized strings of nucleotides–just 15-25 base pairs usually–designed to complement a specific DNA segment (the target).  Drop the primer in the test tube and if a DNA fragment with the complementary sequence is in there, chances are  they’ll link up  and you can reel them in–hopefully with a long piece of the ancient  genome  attached.  Andy’s primers are derived from tree sloths and have proven successful with other ground sloths, but millions of years of separate evolution increases the likelihood that a mutation will inhibit primer binding. 

Andy’s recommendation takes advantage of new technology that avoids many of the problems that come from working in a heterogeous soup of contaminants, inhibitors and aDNA fragments.  The rapid genome sequencer GS-FLX from Roche moves each DNA fragment in the extraction to an individual microscopic compartment before  PCR amplification, and then  sequences everything.   It’s a formidable task made easier by a fast computer and massively parallel lab-on-a-chip technology.  DNA scientists have assembled a huge database  of known DNA sequences from every kind of life-form; workers worldwide add new species to the GenBank library every day. Basic Local Alignment Search Tool (BLAST) software provides a quick means of searching the database and identifying unknown sequences.   The vast majority of the DNA Andy finds will be contamination, of course—from the vast array of life that moves in after death, browsing on the different organic molecules that remain, and each other.  Many of the sequences aren’t identifiable yet, but the success rate improves daily.

Holmes gave Andy the go-ahead. We have a great-looking bone and no one wants to give up yet.  It would have been nice if it had been buried in permafrost or protected inside a dry cave, but the thick clay blanket that we found it sealed in gives us as much hope as anyone has ever had with this species.  Stay tuned. . . . Dave

Sarah Horgen and I will be at the Story County Conservation Center at McFarland Park near Ames on Tuesday October 6 to repeat the program for their Older, Wiser, Livelier Seniors (OWLS)  series.  The program begins at 11:00 AM.   For registration and information about the O.W.L.S. program, contact the Story County Conservation Center at 515-232-2516 (8:30 a.m.-4:30 p.m., Monday-Friday).