95th ESA Annual Meeting (August 1 -- 6, 2010)

PS 70-40 - Microstegium vimineum experiences negative soil feedback when grown in competition with natives

Thursday, August 5, 2010
Exhibit Hall A, David L Lawrence Convention Center
Sarah M. Shannon, Department of Biology, Indiana University, Bloomington, IN, Luke Flory, Agronomy Department, University of Florida, Gainesville, FL and Heather L. Reynolds, Biology, Indiana University, Bloomington, IN

Microstegium vimineum (Japanese stilt-grass) is an invasive grass introduced to the U.S. in the early 20th century, which has since spread to 23 states.  It rapidly colonizes and dominates forests after a disturbance such as a timber harvest, road cut, or scouring flood.  Once M. vimineum has colonized a site, it forms a dense, monospecific stand, reducing plant diversity and inhibiting forest regeneration. Positive soil feedback has been suggested as a mechanism behind the dominance of invasive plants such as M. vimineum.  Previous studies have determined that M. vimineum alters the structure and function of the soil community; specifically, this species alters the soil pH, bacterial community structure, and enzyme activity.  However, no research had yet determined whether M. vimineum participates in a positive soil feedback, promoting a soil microbial community that facilitates greater relative growth or flowering in M. vimineum compared to the native plant community.  To investigate this mechanism, we conducted a full factorial experiment with three plant treatments (M. vimineum alone, M. vimineum with a native community, and the native community alone) and three soil inocula (live inoculum from an invaded site, live inoculum from a control site, and a sterile mixed inoculum).  The three inoculum treatments were added as liquids to a sterile sand/soil mixture in the greenhouse to control for soil nutrients, texture, and seed bank.  

Our results show a negative soil feedback occurring under interspecific competition, with the native plants having a higher relative biomass in the invaded inoculum.  These results suggest that M. vimineum promotes a soil microbial community more beneficial to native plants than to itself, which has two implications: 1) M. vimineum’s ability to outcompete natives is not due to a positive soil feedback; and 2) the native community can be re-established on a restoration site without the use of soil inoculum.