Rhus michauxii – If You Burn It, They May Come

The beneficial effects of controlled burns have been discussed in a previous article:

https://bwwellsassociation.wordpress.com/2013/09/20/prescribed-burns-aid-the-hoary-puccoon-lithospermum-canescens/

In that article, well planned, prescribed burns led to a large increase in numbers and a significant range extension for a population of Hoary Puccoon (Lithospermum canescens).  Rarely, prescribed burns can even lead to the appearance of fire-tolerant species that were previously unknown to the area and location.  So it was that Rhus michauxii (Michaux’s Sumac) appeared in a preserve managed by the state Plant Conservation Program.  A previously undisturbed area of the preserve had been cleared and burned, and a few months later, a population of Rhus michauxii was discovered.  The discovery was unanticipated and extremely fortunate, for Rhus michauxii is one of the rarest shrubs in the Southeast, and is a State and Federally listed Endangered Species.

Rhus michauxii is a short, densely pubescent shrub in the Sumac family (Anacardiaceae). It requires the light of open spaces, and prefers basic soils.  The long divided leaves are distinctly serrated at the margins.

Rhus michauxii Michaux's Sumac

Rhus michauxii
Michaux’s Sumac

The dense hairs can even be seen in the central leaflet veins.  The dense hairs and short stature help to separate Michaux’s Sumac from the more common sumacs in the state.

Rhus michauxii Michaux's Sumac Dense Hairs on Stem and Leaves

Rhus michauxii
Michaux’s Sumac
Dense Hairs on Stem and Leaves

There are a complex number of factors that explain the endangered status of Rhus michauxii.  Certainly fire suppression and habitat destruction have a huge impact on the plant’s populations.  The thick coated seeds have been described as “super tough” and are nearly impossible to germinate in the laboratory, except by manual scarification.  Conventional thinking has been that seeds in native habitats germinate following the intense heat of natural fires.  So far, however,  attempts to simulate natural fires by exposing seeds in the laboratory to various levels of heat over different time intervals have failed to cause germination.

Poor reproductive capacity is another very important factor.  Most known populations are either all male or all female.  So far, all the flowering plants in the newly discovered  population have been male.    The following three photos show the progression of early budding into flowering.

Rhus michauxii Michaux's Sumac Early Budding

Rhus michauxii
Michaux’s Sumac
Early Budding

Rhus michauxii Michaux's Sumac Early Budding

Rhus michauxii
Michaux’s Sumac
Early Budding

Rhus michauxii Michaux's Sumac Flowers

Rhus michauxii
Michaux’s Sumac
Flowers

MALE  FLOWERS

The stamens can be seen best in a closer view.  There are five stamens in each male flower.

Rhus michauxii Michaux's Sumac Male Flower

Rhus michauxii
Michaux’s Sumac
Male Flower

The largest known population of Rhus michauxii is found at the Virginia Army National Guard, Maneuver Training Center, Fort Pickett, Virginia.  Live-fire training with small arms, tanks and artillery have been  ongoing at this facility for the past 50+ years.  Most of the R. michauxii colonies are found in a buffer zone for the live-fire ranges.  The rounds fired on the ranges result in wildfires that burn the buffer zone once or twice a year.  Ironically, the plants there lie in an ecological “sweet spot” where they are not injured by the live-fire action, but benefit from the wildfires generated around them.

Herb Amyx

 

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