Establishment, Growth, Spread, and Ecological Impacts of Microstegium vimineum in Central Hardwood Forests

Microstegium vimineum is an annual exotic grass common through the Southeastern United States. Adding M. vimineum to native plant communities may alter future forest composition through inhibiting the growth and influencing recruitment of seedlings into larger size classes, as well as significantly altering vertical structure and community richness, which may influence the distribution of insects.

The main objectives of these studies were to 1) establish how different mineral soil and litter disturbances, in combination with various forest canopy coverage, influence the establishment, growth, and spread of M. vimineum, 2) quantify effects of competition between M. vimineum and native hardwood seedlings, and 3) identify the influence of M. vimineum on insect community structure and distribution.

As percent canopy cover decreased, M. vimineum mean length and mean number of nodes increased. Also, as soil temperature and soil moisture increased, M. vimineum percent cover increased. Individual seedlings spread further from established populations in both the litter removal and the mineral soil disturbance and litter removal treatments than in the control. The apparent connection between soil disturbance and invasion by M. vimineum provides further impetus for careful planning and use of haul road and skid trails.

There was a reduction in A. rubrum and L. tulipifera leaf area as a result of competition with M. vimineum, which was likely due to competition for moisture. Quercus rubra did not display any differences in leaf characteristics as a result of M. vimineum competition. As a result of reductions in growth for A. rubrum and L. tulipifera, competitive impacts imposed by M. vimineum may alter the rate at which these species are recruited into larger size classes. This may change future forest composition, and have ecological and economic consequences.

In areas with M. vimineum, there were significantly more insects collected than in areas without M. vimineum. These increases in abundance likely resulted from 2.5 times greater plant cover due to the addition of M. vimineum to the plant communities. However, it should be noted that focusing on a single taxonomic group, such as insects, might not provide an adequate measure of exotic species impacts.