Tuesday, August 4, 2009 - 9:00 AM

OOS 10-4: Experimental manipulation of habitat to increase sexual reproduction of the federally endangered michaux's sumac (Rhus michauxii) at Fort Pickett, Virginia

Verl R. Emrick, Virginia Tech and Amy O. Haynes, Fort Pickett.


Michaux’s sumac (Rhus michauxii Sargent) is a federally endangered species native to the lower piedmont and upper coastal plain of the Southeastern United States. Michaux’s sumac is a rhizomatous shrub in the Anacardiaceae family and is a disturbance dependent species. Fort Pickett, Virginia has the largest known population in the world and is unique because the majority of the colonies are located in habitats maintained by frequent fire caused by military training. Previous work showed a significant negative relationship between woody competition in the 2-5m strata and Michaux’s sumac density. The objectives of this project were to experimentally manipulate above ground and below ground resources through removal of woody competition and fertilization and measure the change in numbers of Michaux’s sumac non-flowering, male, female and total stems. We randomly selected 14 of the larger colonies at Fort Pickett for the experiment. Within each colony we located four circular 5m2 subplots. Prior to applying treatments the number of Michaux’s sumac occurring within each subplot and the gender of flowers was determined.  We randomly applied four treatments to the subplots within each colony 1) Removal of all woody species less than 10 cm dbh, 2) application of 100g of slow release fertilizer, 3) Removal of all woody species less than 10 cm dbh and application of 100g of slow release fertilizer and 4) control. In July 2008 the number of Michaux’s sumac occurring within each subplot was determined.


Pre and post treatment Michaux’s sumac numbers were compared using a paired t-test. In the woody removal and fertilization treatments all stem types decreased between years, though none of the changes were significant. In the woody removal/fertilizer treatment non-flowering, female, and total stems decreased between years. However the number of male flowering stems increased between years. The increase in male flowering Michaux’s sumac stems is an indicator that woody removal/fertilizer treatment may have a positive effect. However, because of drought and the short experimental time the impact of the treatments have yet to be reflected in stem number. After collecting response variables we applied the same treatments for a second year. If normal rainfall occurs during the 2009 growing season, it may be possible to draw more definitive conclusions regarding the effectiveness of the habitat manipulation treatments in increasing the flowering of Michaux’s sumac.