Canebrakes are Forlorn Landscapes

200 years ago, landscapes in southeastern North America looked nothing like they do now.  When William Bartram traveled through the piedmont region of the south (circa 1775), the path he followed mostly stayed on the high ground because impenetrable thickets of bamboo cane (Arundinerea gigantea) grew alongside creeks and river bottoms.  His party was always in sight of canebrakes as they traveled through the open woodlands on the high ground.  Canebrakes covered tracts that were hundreds of square miles in extent.  Today, canebrakes are nearly an extinct type of environment.

I looked for this photo on google images and couldn’t find it.  I did find it within a pdf document but I couldn’t link the photo directly. So I scanned it from the book Forgotten Grasslands of the South by Reed Noss.  Click to enlarge.  It’s of a man on a horseback dwarfed by a stand of 40 foot tall cane in 1906.  This was probably one of the last stands of a primeval canebrake.

I found this stand of bamboo cane growing behind a Burger King in Madison, Georgia.  Cane is planted as an ornamental.  It’s probably not even American bamboo, but rather Asian bamboo.

Canebrakes are an ancient environment, dating back to at least the Miocene (25 million-5 million years BP).  It’s a species of grass.  Grasses began to become abundant during the Oligocene (33 million-25 million years BP).  Scientists unearthed ~5 million year old fossil bamboo from the Gray Fossil Site in Tennessee along with the bones of an extinct species of red panda (Pristinailurus bristoli) that fed upon it.  American bamboo likely shares an ancestry with Asian bamboo back when both continents were composed of a continous mosaic of tropical environments.  ( https://markgelbart.wordpress.com/2012/12/05/the-gray-fossil-site-in-washington-county-tennessee/)  Scientists disagree over whether giant gane (Arundinerea gigantea) is the same species as switch cane  (A. tecta).  Some botanists argue a structure inside switch cane makes it a different species, but others don’t think the difference is significant enough.  In any case cane grew in dense stands on rich soils, either by itself in pure stands or with an occasional tree in a savannah-like landscape.  Cane is shade intolerant and today seems to be restricted to wooded swamp edges.

Canebrakes require a complicated combination of forcing events to exist.  Formerly, floods, flocks of passenger pigeons, windstorms, or ice storms destroyed great tracts of forest.  Passenger pigeons (Ectopistes migratorius) used to roost in flocks estimated to be in the billions.  Witnesses described their roosting areas as resembling tornado damage.  Great limbs and even whole trees broke in half under the weight of the birds, and the pigeon dung killed the trees via overfertilization.  (See also https://markgelbart.wordpress.com/2010/08/27/pleistocene-passenger-pigeon-populations/) The New Madrid earthquakes in 1811 also caused the creation of large tracts of canebrakes.  Following these natural disturbances of the forest, a great amount of flammable dead wood covered the forest floor.  Lightning or human set fires burned through the woody refuse, creating vast sunny areas that allowed shade-intolerant bamboo cane to colonize large tracts of land.  Cane growing in small sunny patches within the forest could take advantage of these disturbances by spreading clonally from root rhizomes into the newly suitable habitat.  As long as fire occurred at least once a decade, canebrakes could be maintained indefinitely.  Dr. Noss suggests canebrakes were an alternate climax stage with bottomland forests near rivers and streams.  Without disturbances these areas succeeded to bottomland forests, but disturbances were so common that canebrakes may have covered an equal amount of territory.

Modern studies show that fire and windstorm double the growth of cane which can grow as fast as 20 feet annually.  Cane formerly reached heights of 40 feet, perhaps because they were enriched with pigeon dung.  Today, the tallest cane known grows in Louisiana and reaches just 30 feet in height.  It depends mostly on clonal growth and only flowers and produces seed once every 40-50 years.  It prefers rich river bottomland soils where it can become dominant.  Surprisingly, rich soils have less species diversity than poor soils.  On poor soils no one species can become dominant due to more difficult growing conditions.

Canebrakes were undoubtedly a widespread environment during the Pleistocene before man colonized North America.  There are many endemic species of animals that depend exclusively upon canebrake habitats, and it’s unlikely they evolved that dependence within the last 15,000 years.  However, canebrakes likely enjoyed a heyday during the 18th century when Native American populations collapsed.  Indians preferred to grow their crops on rich river bottomland soils and when they abandoned their fields cane rapidly colonized the land.

Modern anthropogenic changes in land use have nearly eliminated canebrakes.  Humans built levees and dams to prevent flooding.  People suppress fires.  People exterminated passenger pigeons.  These activities ended ancient patterns of disturbances that bamboo cane requires to form vast monotypical stands.  Moreover, cane grew on rich soils that farmers coveted for field crops, and the farmers let their livestock overgraze cane growing on any land left unplanted.  Today, river bottomlands left undeveloped are dominated by trees that shade out cane.  Canebrakes are a forlorn landscape and will be difficult to re-establish.

Canebrakes were a rich habitat utilized by many species of animals.  Cane is a high quality forage that formerly provided food for grazers such as mammoths, horses, and bison.  Bears and big cats liked to den inside the thickets where they could hide their cubs.  Swamp rabbits (Sylvilagus aquaticus) are also known as canecutters because they feed upon cane by gnawing through the stem to fell the tall grass so they can get at the leaves.  If it’s not extinct, Bachman’s warbler (Vermivora bachmanii) and Swainson’s warbler (Limnothlypis swainsonii) depend upon canebrake habitat.  Eastern diamondback rattlesnakes (Crotalus adamteus), also known as canebrake rattlesnakes, hunt swamp rabbits in the thickets.  6 species of butterfly depend entirely upon bamboo cane as part of their life history.

Swamp rabbits are also called canecutters.  They’re much larger than cottontails.

Bachman’s warbler.  This bird is probably extinct.  They formerly summered in canebrakes.  They built their nests in the cane thickets and foraged for insects on the ground in the fallen cane leaves.  They wintered in Cuba.  They became extinct (probably) because canebrakes are gone.  None have been seen since 1988.

A man holding an eastern diamondback rattlesnake.  They are big serpents growing to 8 feet long and weighing 35 pounds.

Southern pearly eye (Enodia portlandia).  5 other species of butterfly depend upon canebrakes for at least part of their life cycle including Creole pearly eye (E. creota), southern swamp skipper (Poanes yehl), cobweb little skipper (Amblyscertes aesolypia), cane little skipper (A.reversa), and yellow little skipper (A. carolina).  These endemic species are evidence canebrakes predate anthropogenic influences on the environment.

Native Americans also used to rely on bamboo cane.  They used to mix mud with strips of cane to build houses, and they covered the floors inside with mats made of cane.  They made baskets and fish traps and coffins from cane.  Weapons fashioned out of bamboo cane included spears, knives, body armor, and blowguns.  Indians incorporated cane into the structures of their famous mounds.  Cane even provided food.  Bamboo shoots are a tasty vegetable, and the seeds could be ground into a flour that was reputed to be almost as good as wheat flour.

References:

Ellsworth, J.W.; and B.C. McComb

“Potential Effects of Passenger Pigeon Flocks on the Structure and Composition of Presettlement Forests of Eastern North America”

Conservation Biology 17: 1548-1558 2003

Gagnon, P.R.; and W.J Platt

“Multiple disturbances accelerate clonal growth in potentially monodominant bamboo”

Ecology 89: 612-618 2008

Platt, W.J.; and C.J. Brantley

“Canebrakes: An Ecological and Historical Perspective”

Castanea 62: 8-21 1997

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Tags: Arundinerea gigantea, Arundinerea tecta, bamboo cane, bison, diamond back rattlesnake, Gray Fossil Site Swainson's warbler, horse, mammoths, southern pearly eye butterfly, swamp rabbit