Posts Tagged ‘Red Pine’

The North Charleston Mastodon

October 8, 2017

Construction workers digging a foundation for a building in North Charleston, South Carolina 5 years ago uncovered the remains of a mastodon.  Bones including a partial tusk, femur, vertebrae, jaw, ribs, and feet were excavated.  One scientist also examined the surrounding sediment for pollen and plant remains. Apparently, the site was riverbank, and the mastodon likely was covered in flood-borne sediment.  I hope a paper is published detailing the information yielded by this site.  So far, all the information I can find comes from 2 abstracts that described poster presentations of the find at scientific meetings.  The authors didn’t even put the posters on the internet.

One presentation compared the pollen found here to that from other Pleistocene-aged sites located near the present day coast–St. Catherine’s Island, Reid’s and Bell’s Bluff, and a site along the Georgia-Florida border.  All of these sites were farther inland during Ice Ages.  Like these other sites, the North Charleston locality had a strange admixture of species presently found at higher latitudes with those still found in the region.  Water milfoil, an aquatic plant, occurred here.  This is not surprising because mastodons were semi-aquatic.  Hickory pollen was “unusually” abundant, indicating a moist temperate climate, but the pollen of red pine, a northern species, was found in association with sub-tropical Spanish moss.  Other Pleistocene sites in the region yield hemlock, basswood, and walnut–species no longer found this far south.  However, I’m skeptical about the identification of supposed red pine pollen.  This species currently occurs in New England, a region that was under glacial ice for much of the Ice Age when its range was forced south.  I doubt it occurred as far south as South Carolina though because there are no relic populations in the southeast.  Red pine pollen is distinguished from pollen of southern pines on the basis of size.  Pollen grains under 43 micrometers in size are classified as northern species of pine, while those over 43 micrometers are thought to be from southern pines.  Shortleaf pine is a common southern species of pine whose pollen grains overlap in size with red pine pollen grains.  Moreover, under the atmospheric conditions of low CO2 as occurred during Ice Ages, shortleaf pine pollen grains may have been slightly smaller than those of the present day.  In my opinion they look identical as the below photos show.  I believe pollen classified as red pine in the below reference and several other studies is from shortleaf pine which is still widespread in the region.

Image result for Pinus echinata pollen grain

Shortleaf pine pollen grains average a “maximum” 50-75 micrometers in size.

Image result for comparison of pinus resinosa pollen grains

Photos of northern species of pine pollen grains including red pine (Pinus resinosa), jack pine, and white pine.  Red pine and white pine pollen grains easily overlap in size with shortleaf pine.  Therefore, I’m not convinced of palynologists’ claim that red pine occurred in the southeast during Ice Ages.

Reference:

Rich, Fred

“The North Charleston Mastodon Site–New Insights Drawn from Paleoecological Synthesis”

The Geological Society of America: Southeastern Section–64th annual meeting

 

Pleistocene Soil Cycles

February 24, 2012

In his book The Natural Environments of Georgia Dr. Charles Wharton suggests Ice Age coniferous forests consisting of boreal species built many of the soils in the mountains and piedmont of Georgia.  This is fodder for contemplation of Georgia’s ecology.  Pleistocene soil composition must have gone through cycles that paralleled the climate cycles of stadial to interstadial and glacial to interglacial.  Soils became thin during stadials but were enrichened during interstadials and interglacials.  I am aware of no studies investigating the origins of topsoils in Georgia, and this kind of study is not even possible now because almost all of Georgia’s original topsoil has eroded or blown away, thanks to poor agricultural practices.  Nevertheless, speculation on the ecology of the Pleistocene soil cycle is another fruitful topic for this blog.

Fossil evidence from Bob Black Pond in Bartow County shows that a forest composed of jack pine, red pine, white pine, white spruce, Critchfield’s spruce, and paper birch grew in north Georgia during the Last Glacial Maximum ~21,000 BP.  This probably represents a common dominant forest in north Georgia during climate phases of the Ice Age known as stadials–times of arid cold when the Laurentide Glacier expanded to the north and locked up much of the planet’s atmospheric moisture.  To contemplate a full cycle of Pleistocene soil development, let’s go back farther in time to about 30,000 BP.

30,000 years ago, an interstadial that had lasted for about 4,000 years was coming to an end.  Interstadials were warmer, wetter climate phases within Ice Ages.  Studies of the pollen record show oak pollen always increased during interstadials, while pollen from coniferous trees decreased.  The leaves and debris from oaks and other hardwoods build up a healthy, thick topsoil, usually taking about 100-200 years to do so.  After 4,000 years most of the topsoil in the region must have been particularly rich.

Ice Age climate fluctuated rapidly.  Imagine now, that an ice dam on the St. Lawrence River melted enough during the warming trend of the previous 4,000 years to collapse, sending a torrent of freshwater and ice bergs into the North Atlantic.  This flood of cold freshwater shut down the thermohaline current that had kept the climate warm for millennia.  Climate changed immediately to colder, more arid, and windier conditions.  CO2 levels plummeted as well.  After a few decades many of the oaks and other broadleaf trees that had spread to upland habitats began to die from drought and wind and lower CO2 levels.  Grasses and coniferous trees compete better than hardwoods under these conditions.  Plants need CO2 for respiration.  During stadials CO2 levels fell so low that even some coniferous trees became starved for CO2.  Fossil juniper from the La Brea tarpits, for example, show evidence of CO2 starvation.  Under these conditions broadleaf trees only persist near rivers and streams.  Grasslands and brush thrive in the shade free environment, but the burgeoning bison, horse, and mammoth populations overgrazed the vegetation, leaving bare soil which blows away in the wind and much of the topsoil is thinned or lost.

Jack pine forest in Michigan. The landscape much resembles that of an open pine savannah in the coastal plain of Georgia.  Like an open pine savannah, jack pine forests are fire dependent.  Jack pine grew in the mountains and the piedmont of Georgia during stadials, the coldest stages of the Ice Age, but is completely absent from the state today.  The hilly terrain likely made for a more varied environment though in Georgia than this photo indicates.

Today, Eastern jack pine (Pinus banksiana) grows no farther south than northern Michigan and is a common tree on sandy outwashes in Ontario, Canada.  It’s a pioneer species, able to grow on thin sandy soils.  During the driest coldest phase of stadials, jack pine colonized dry upland sites in Georgia where many oaks could no longer dominate.  Jack pine forests are rich environments.  They grow thinly allowing light to hit the forest floor.  This promotes the growth of grasses and berry bushes.  Kirtland’s warblers, upland sandpipers, bluebirds, cowbirds, deer, bear, snowshoe hare, and rare prairie plants such as Allegheny plum, rough fescue, and Hill’s thistle all thrive in jack pine forests.  In Pleistocene Georgia many of these same species with the addition of extinct grass-eating mammals  were probably also abundant.  The rare Kirtland’s warbler (now summering in only a few counties in Michigan) winters in the Bahamas which were expanded in size due to lowered sea levels during the Ice Age.  (https://markgelbart.wordpress.com/2011/11/11/banana-hole-fossil-sites/) I suspect this bird was more widepread then and may have occurred in Georgia because it is dependent on jack pine forests.  Perhaps not coincidentally, fossils of upland sandpipers have been excavated from Bartow County where the jack pine fossils were found.

Fires were rare during stadials because lightning storms were rare.  Jack pines require fire for regeneration.  Other species of pine less dependent on fire such as red pine (Pinus resinosa) and white pine (Pinus stroba) encroached into jack pine forests in the absence of fire.  Post oaks which are among the most fire resistant and drought resistant oaks also move into these pioneer forests.  Gradually, the needles and debris from Ice Age coniferous forests added humus and thickened he topsoil.  When the next interstadial began (~15,000 BP) the climate warmed, precipitation increased, CO2 levels increased, and oaks and other broadleafed trees expanded from their refuges along waterways and once again colonized their old territory.  Jack pine is the most shade intolerant boreal species and was the first to be completely replaced, retreating to the north where it was able to take advantage of newly deglaciated sandy soils.  Next, red pine retreated, mostly toward New England, though relic populations remain in West Virginia.  Of the boreal species of pine, white pine was the least shade intolerant, so it still persists in north Georgia, though it’s much less common than it was during the Ice Age.

Young mixed boreal and hardwood forest.  At the beginning of interstadials when climate became wetter and warmer, oaks and other hardwoods rapidly displaced boreal conifers in the Georgia mountains and piedmont, shading the pines out.  These climate phases probably fostered the greatest variety of wildlife because northern species of plants and animals would still be present but southern species would begin colonizing the new habitat.

The greatest diversity of wildlife likely occurred during transitions from stadial to interstadial and vice-versa.  Environments in transition harbored a greater variety of habitats that animals and plants of northern and southern affinities would have found favorable.  A study of forest succession in the Georgia piedmont found that bird species abundance peaked at the stage when oaks began replacing pines.

There’s no evidence that northern species of pines ever extended their range into south Georgia.  Central Georgia was probably a transition zone where northern species of pines mixed with southern species of pine in environments that have no modern analog.  Shortleaf pine, the southern pine best adapted to cooler weather, was probably the most common pine species, though some northern pines ranged into the piedmont.  But much of south Georgia became brush, grassy deserts during stadials and much of the topsoil there blew away.  Eolian sand dunes rolled across the landscape, and the wind scooped out depressions and created Carolina Bays–a subject for a future blog entry.

Sagponds Contain a Partial Pollen Record of Ice Age Vegetation in Northwest Georgia

February 2, 2012

In the southern Appalachian mountains when groundwater dissolves underlying limestone the ground slumps to a granite bottom, creating an interesting environment known as a sagpond.  These differ from sagponds located in California which are formed from strike-slip faults.  Georgia sagponds form from the same geological principle that creates limesink lakes in Florida.  Dr. Charles Wharton counted as many as 96 sagponds per square mile in Bartow County.  They range in size from a few feet across to several acres.  Some go seasonally dry; others retain water year round.  Scientists recognize 4 types of sagponds.  Dry sagponds drain within an hour after rain stops.  Young sagponds, where the ground hasn’t finished slumping, hold water during winter and spring.  Mature sagponds are partially filled with colluvial silt and retain water year round.  Extinct sagponds have been completely filled with silt but still might be moist enough to support a marsh.

Topographical map of Green Pond.  Sagponds often form on mountains and provide wetland habitats in otherwise dry upland environments.

These low wet areas dotting the otherwise dry upland ridge and valley region host disjunct populations of at least 49 species of plants that are normally found on the coastal plain, including the evergreen laurel oak, gallberry (a type of holly), fetterbush, rock rose,  joint grass, panic grass, beaked rush, and many others.  Common aquatic plants found in sagponds are tupelo, buttonbush, red maple, and sedges.  Buttonbush and tupelo tend to grow in the middle of a sagpond; grass and sedge grow on the edges; than there is a heath zone ringed by a lowland woods consisting of loblolly pine, laurel oak, and red maple.

Page from the book Natural Environments of Georgia with a photo of a dry sagpond in Bartow County.

Photo by Alan Cressler of a sagpond on Keel Mountain in Madison County, Alabama.  I couldn’t find any photos on the web of sagponds in Georgia, though there are supposed to be a lot of them.

Dr. Wharton reports that Bloody Pond in Chickamauga Battlefield Park has a large stand of willow oaks.  (While researching this topic, I discovered that there are at least 2 other Civil War era battlefields with areas known as “Bloody Pond.”)

Scientists looking for ancient pollen and Pleistocene-aged plant macrofossils have excavated and cored several sagponds–Bob Black Pond, Quicksand Pond, Green Pond, Pigeon Mountain Marsh, and Lookout Mountain Marsh.  The pollen record from all these sites combined cover a timespan of between ~34,000 Bp-~10,000 BP in calender years.  Some of the studies date to before scientists realized carbon-dating gave dates too young when compared to tree rings.  The data I give in this discussion mention dates I’ve adjusted.  They’re just rough estimates based on the inaccurate dates from the early studies.

Pollen from Green Pond, believed to date to the Farmdalian Interstadial, suggests an environment in northwest Georgia consisting of dry oak and hickory woodlands with prairie openings.  Dr. W. A. Watts (of Penn State but now retired) conducted this study in 1973 and gave carbon dates of 29,630 BP- 25,000 BP which should be adjusted to about 34 ka BP-30 ka BP.  Pine pollen was scarce.  ~28,000 years ago pine and spruce pollen began to increase, indicating an abrupt change to a cooler drier climate.  Surprisingly, pond cypress was locally present.  This shows that individual plant species ranges didn’t always change in predictable patterns.  Pond cypress is absent in this region today, despite a warmer climate.  Shortly after this date, the pond filled with sediment and the pollen record ends for this site.  Conveniently, this is when the pollen record from sediment cored from Bob Black Pond, which Dr. Watts also studied in the early 1970’s, begins. 

Dr. Stephen Jackson of Wyoming University also studied Bob Black Pond over 20 years later.  He found boreal forest species dating to about 22,000 BP.  In addition to pollen he found plant macrofossils of white pine, red pine, jack pine, white spruce, Critchfield’s spruce, and paper birch.  Critchfield’s spruce is an extinct species thought to be adapted to temperate climates, and white pine still grows on the mountains of north Georgia, but the other 4 species no longer range much further south than Canada.

Jack pine present day range map.  This species lived as far south as northwest Georgia during the LGM.  Today, it lives no further south than northern Michigan.  Red pine is restricted to New England.  White spruce lives across Canada as does paper birch.

There’s no doubt the climate in north Georgia during the Last Glacial Maximum was cooler than that of today, but it wasn’t necessarily as cool as present day southern Canada, despite the presence of Canadian species of trees.  Scientists may have originally misinterpeted this data when they assumed the climate here was comparable to today’s southern Canada.  Pine and grass grow better in atmospheres with lower CO2 than broad-leafed trees.  So moderately lower temperatures combined with lower CO2 levels allowed northern species of conifers to compete better with oaks, maples, and other broad-leafed trees for space in the southern Appalachians.  It’s a good thing for the boreal species too because their present day range was completely under miles of ice then.

Fossil pollen from Pigeon Marsh in Walker County dates to approximately the LGM.  Jack and red pine pollen ranges from 25%-45%, oak pollen ranges from 30%-40%, and spruce pollen ranges from 1%-2%.  Hickory and chestnut were present but not abundant.   After the LGM, as the climate remained cool but became more moist, beech became the dominant tree here until the modern floral composition took over.

During the Pleistocene sagponds would’ve been prime foraging grounds for herds of hungry mastodons.  Sagponds supported the kinds of aquatic plants (especially buttonbush and pond cypress) that we know mastodons ate from analysis of their coprolites.  And indeed, fossil evidence of mastodons has been found in the ridge and valley region of Georgia and Tennessee.

References:

Watts, W. A.

“The Vegetation Record of a Mid-Wisconsinian Interstadial in Northwest Georgia”

Quaternary Research 3 (2) 1973

Wharton, Charles

The Natural Environments of Georgia

Georgia Department of Natural Resources 1980

If I could live during the Pleistocene (part two)

September 17, 2010

As I noted in last week’s blog entry, I don’t like roughing it.  If I’m going to live 41,000 years BP, I want to live in a nice sturdy house that would keep me safe from hungry bears, big cats, wolves, and rough weather.  I’d build a big adobe brick house with a wall around ten acres behind it where I could have a garden, fruit orchard, grain fields, and room to raise livestock such as milk cows, chickens, ducks and geese.

If I could live 41,000 years BP, I’d reside in an adobe house.  Adobe bricks are simple to make, only requiring mud, grass or sand, and sun.

My adobe house would have double thick walls, and raised windows with bars in front of them to prevent beasts from breaking into my abode and making a meal of me.  (For more about adobe houses see this link–     http://desertphile.org/adobe/adobe.htm)

In front I would have a raised platform or balcony for wildlife viewing, and on occasion to provide a place for hunting when I need meat.  Most of my home would be one story, but I’d have a tower room, built not unlike a lighthouse, which would afford a panoramic view of the surrounding landscape.  To improve the view, I’d clear a circle of land around my dwelling which would also serve as a firebreak.  My water supply would come from a well.  A dry toilet, or clivis multrum, would take care of my waste.  

Woodstoves would keep me warm in the winter, but I don’t think I’d need an air conditioner because this is the Ice Age, and summers are comfortable.  Solar units, and a generator, using wood alcohol that I would manufacture,  provide my electricity.  Of course, I’d have all necessary machines–bulldozers, bushhogs, trucks, boats, etc.  All engines would be modified to run on wood alcohol.

My Pleistocene adobe house is located in what’s now Elbert County on a hill one mile north of the Broad River and two miles west of the Savannah River.  In my opinion the Georgia piedmont (at least in the still rural areas) is the prettiest region of the state.  I even like it better than the north Georgia mountains.  I’d locate my home relatively close to a river for the easy source of protein–fish, turtles, freshwater mussels, and crayfish.  It would be necessary for me to maintain a dirt road between my house and the river.

I can take an educated guess as to what kinds of plants and animals I would encounter around my house.  There are only two Pleistocene-aged fossil sites in central Georgia (Nodoroc and Little Kettle Creek), though there are many more to the north and south.

Nodoroc is a bog that formerly was a mud volcano, last erupting in 1810 with a massive release of carbon dioxide.  These mysterious types of eruptions have also occurred in African lakes within the last few decades.  Nodoroc is a Creek Indian word meaning gateway to hell because the Indians used to execute criminals and toss them in this bog.

Scientists found plant macrofossils and pollen here, dating to 28,000 years BP, during a brief weak interstadial just before the Last Glacial Maximum.  The forest around the site consisted of an interesting mix of northern and southern species of pine as well as oak.  Northern species of pine such as white, red, and jack tend to have smaller grains of pollen, while southern species, such as shortleaf, tend to have larger grains.  Both size variations were found here, though it’s not possible to identify exact species, based on pollen.  But some plant macrofossils, though not in good enough condition for certain identification, compared favorably to red and/or jack pine; others compared favorably to shortleaf pine.  Because both northern and  southern species of pine occurred here then, the climate must have had mild summers and mild winters

Current range map of the red pine (Pinus resinosa).  Most of where it currently ranges was under glacial ice during the Ice Age, so it must have occurred south of this area then.  I propose that northern species of pine such as red and jack (Pinus banksiana) spread throughout the upper south following cold arid climate cycles when river beds dried out and wind blew the sand into large eolian sand dunes.  Scrub oak and grass initially colonized these dunes, but when precipitation increased as an interstadial began, lightning-induced fires burned the scrub oaks forests and grasslands, allowing fire-adapted pines to colonize these areas.  Eventually, as the climate continued to get warmer and wetter, hardwood trees outcompeted and replaced these shade-intolerant species.  Insterstadials never lasted long enough for hardwood forests to completely outcompete northern pines–a return to cold arid conditions would’ve probably killed many deciduous trees, allowing pine to regain territory.  But the current interglacial we live in now has lasted long enough for broad-leafed forests to shade out red and jack pines in the upper south, except for isolated relic populations of the former in small areas of West Virginia.

Hickory, spruce, and fir pollen were also common; chestnut, beech, and maple were present in low numbers.  The understory consisted of alder, blueberry and/or rhodadendron, and hazlenut.  Enough ragweed, grass, and sedge pollen was present to suggest the presence of large meadows or small prairies, making up to 25% of the landscape.

Little Kettle Creek is the only Pleistocene-age animal fossil site in the entire piedmont region of southeastern North America.  Teeth and bones of mammoth, mastodon, bison, white tail deer, (cf) southern bog lemmings, (cf) red backed voles, and catfish were recovered here.  The two rodents no longer range farther south than Kentucky, again indicating cooler summers for central Georgia during the Ice Age.  Mammoth and bison grazed the meadows;  mastodon and deer foraged the forest edge and streamside woodlands.  Growth rings on the catfish bones are evidence of colder winters than those of today because modern day catfish in warm southern states don’t have dormant growth cycles like fish found in northern states.

Fossil sites to the north and south of the piedmont have more species and most of them probably also lived in what’s now central Georgia as well.  Around my Pleistocene house I would also expect to see Jefferson’s ground sloth, elk, horses, tapirs, llamas, peccaries, dire wolves, jaguars, saber-tooths, bears of at least once species, giant beavers, and many smaller species of extant mammals that no longer occur in state but still live to the north and west.  Examples of interesting small species I’d expect to see are the hognosed skunk, red squirrels, and the extinct noble chipmunk.  I’d also expect to see a much greater variety of birds than I’d see today in an unspoiled wilderness devoid of human habitat destruction and pesticide use.  I’d be on the lookout for northern ravens, magpies, prairie chickens, upland sandpipers, terratorns, California Condors, and extinct species of vultures and eagles.  Birds that are rare or extinct today but were common then include bald eagles, ivory-billed woodpeckers, Carolina parakeets, passenger pigeons, swans, and cranes. 

That abundance of wildlife is the reason I really wish I could move into my Pleistocene home.

One final thought for today: This Ice Age ecosystem I describe was the norm.  Today’s interglacial ecosystem is an aberration because Ice Ages last ten times longer than interglacials.