Friday, April 27, 2018

Prairie Goldenrod & Its Unusual Habitats

Prairie Goldenrod (Oligoneuron album) doesn't look like your typical "goldenrod".  But it was once considered a member of the genus Solidago, lending some scientific basis to calling it a goldenrod. To some it is still referred to as Solidago ptarmicoides. This plant has been kicked around taxonomically an almost shocking number of times. But I digress....

Prairie Goldenrod is a legitimate rarity in North Carolina, and is either absent from or rare in most other southeastern states. Why in the world doesn't it occur in Virginia?

The apparent rarity or absence from much of the southeast may not be surprising since it is presumably PRAIRIE Goldenrod and relatively few such habitats occur in the region.  However, one site, perhaps the only extant site in North Carolina, is both botanically rich and very much "prairie-like".

Prairie-like habitat of Oligoneuron album in Granville Co, North Carolina; note faint white specks of Oligoneuron stems in flower., see inset below

Closer view of Oligoneuron album in Prairie-like habitat,in North Carolina; flanked by the basal rosettes of Prairie Dock. (9/18/2013)

The North Carolina site discussed here also includes abundant Prairie Dock (Silphium terebinthinaceum), Stiff Goldenrod (Solidago rigida) and many other species often associated with prairies elsewhere in the country.  This site may be as close to true prairie as it can get in NC and is certainly one of the only known locations resembling a prairie with reasonably intact vegetation on a soil typical of prairie. Broadly, most of the North American Prairie region is closely tied to the occurrence of Mollisols (see map below).

Soil from the North Carolina Oligoneuron "prairie" site,
classified by soil scientists as a Mollisol.
The dark color is one the characteristics of this soil order.

USDA Soil Map, Mollisols

It is hard to overstate how unusual this soil is in Carolina.  As the generalized USDA soil map shows, there are no mapped Mollisols of sufficient extent to appear on the map almost anywhere in the southeastern US outside Florida.  A retired University Soil Scientist once told me it took years for the existence of these soils to be accepted in North Carolina, even having the "dirt in hand", since historical convention suggested such soils couldn't develop in the North Carolina climate.  But again, I digress......

This post was supposed to be about Prairie Goldenrod.

Oligoneuerun album apparently thriving in remnant tallgrass prairies in Paintbrush Prairie, Missouri.(08/17/2015)
Rattlesnake Master (Eryngium yuccifolium) is barely visible as well.

Prairie Goldenrod does actually occur in undeniably classic "tallgrass prairies" in the midwestern US, which some refer to as the Central Tallgrass region.  I have observed it in several tallgrass prairie remnants in Missouri such as that shown above.

Taken together, my admittedly few observations seem to fit into a nice and tidy picture of the habitat for Prairie Goldenrod.

But, then I visited alvars along Lake Huron in Ontario Canada.

I was absolutely shocked to find Prairie Goldenrod on lakeshore pavements (on exposed rock I believe is dolomite), and even in loose sandy soil at the margins of Lake Huron!.  These were NOT PRAIRIES.

Prairie Goldenrod on alvar,lakeshore pavement, Misery Bay

Prairie Goldenrod along Lake Huron, Ontario Canada
I did finally find Prairie Goldenrod in one habitat much more akin to prairie near Lake Huron. Much of the ground surface was littered with small boulders that are likely glacial erratics. The matrix soil was primarily sand that apparently washed in under extreme tides or storm events, covering the underlying dolomite flat rock. Such disturbance events, coupled with the underlying pavement, help keep the habitat from becoming overgrown by shrubs and trees. The most visually dominant herb, other than Prairie Goldenrod was Limestone Calamint (Calamintha arkansana). 

Prairie Goldenrod amidst glacial erratics and loose sand near Lake Huron, 

Interestingly, NatureServe uses Oligoneuron album as a nominal in one of its described alvar natural community types, but rather than it being used to name a "grassland" type it is considered part of a shrubland:


No matter what habitat seems to support Prairie Goldenrod they are all well worth the look!

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