Microstegium vimineum Spread Rate in Relation to Two Different Leaf Litter Disturbances and an Evaluation of Aboveground Biomass Accumulation and Photosynthetic Efficiency in Response to Four Light Treatments

Microstegium vimineum is a non-native invasive plant species classified as an annual, shade-tolerant C4 grass. There is limited research regarding variables affecting the spread of M. vimineum. Two studies were conducted to investigate the spread of M. vimineum. A field study was undertaken in 2009 to determine how M. vimineum spreads in relation to litter disturbance. In 2010, a greenhouse study was conducted to determine the impact light has on M. vimineum aboveground biomass, height growth, and photosynthetic efficiency.

The field study consisted of three treatments, Undisturbed (Control), Stirring, and Removal of leaf litter, employed along the boundary of existing M. vimineum populations in ½-meter by 2-meter plots. Distance of spread from the existing population and percent cover were documented for one growing season. Plants were counted at the end of the study. Neither stirring nor removal of leaf litter had a significant impact on spread rate, percent cover, or the number of plants in a given treatment suggesting pre-growing season leaf litter disturbance does not influence M. vimineum spread, percent cover, or number of plants.

The greenhouse study consisted of growing M. vimineum under four light treatments: 100, 70, 45, and 20 percent of full light. Heights were measured weekly while minimum, maximum, and variable fluorescence emission, non-photochemical and photochemical quenching, and maximum quantum yield of Photosystem II photochemistry (QYmax) were measured every 10 days. Aboveground biomass accumulation was calculated at the end of the study. Results indicate that M. viminuem aboveground biomass accumulation is highest in 70 percent to 100 percent light while photosynthetic efficiency is highest between 45 percent and 70 percent light.

This research indicates that M. vimineum does not spread appreciably at low light levels (closed canopies) in areas with litter disturbances that do not change the light regime. M. vimineum has greater aboveground biomass and photosynthetic efficiencies at higher levels of light. Thus, forest disturbances that result in more light reaching the ground may influence the spread of M. vimineum by creating a more favorable environment.