Cultural Methods for the Control of the Invasive Japanese Stiltgrass (Microstegium vimineum) in Stream Restoration
Robert Sullivan
TNT Environmental
Leesburg, VA
Authors: Robert Sullivan, Dr. Doug DeBerry
This research focused on addressing the invasion of Microstegium vimineum (Japanese stiltgrass) in restored streams and floodplains. One of the most common solutions practitioners use to combat M. vimineum is non-selective herbicides, which can harm ecosystems and even lead to reinvasion.
The study aimed to find which cultural treatment (a method derived from agriculture, horticulture, and other industries and common practices), or combination of treatments, is most successful at reducing the dominance of M. vimineum in a restored stream site compared to the standard glyphosate treatment. The treatments tested in this study included canopy shade (light limitation), sawdust soil amendments (short-term nitrogen limitation), wood mulch soil amendments (longer-term nitrogen limitation), double seeding rates (native species competition), and a combination of these treatments, as well as glyphosate (positive control) and no treatments (negative control). The canopy shade treatment used areas with canopies that had ≥ 50% shade, and the sawdust and wood mulch treatments tilled into the top 10 cm of soil using a 2:1 volumetric ratio of soil to processed wood. The treatments were applied to plots within 14 separate blocks (7 shade and 7 open canopy) within previously restored stream branches (Snakeden and The Glade, Reston, VA) invaded by M. vimineum. Each plot was then mowed then tilled to simulate the disturbance of stream restoration. A ratio of the importance value (IV; the sum of each species’ cover and density) of M. vimineum to native species was used to calculate the dominance of M. vimineum versus native plants.
At the end of year two the shade, sawdust, and double seeding combination had the lowest ratio of M. vimineum to native species, almost half that of the herbicide and shade combination. In the open canopy plots the sawdust had the lowest ratio and the herbicide had the highest ratio. This presentation will talk about how using a combination of sawdust and large canopy trees in stream restoration can help reduce the invasion of M. vimineum in restored floodplains and connected wetlands and how this can be practicable done in the stream restoration industry.
About Robert Sullivan
Robert Sullivan is a plant and wetland biologist who conducted his graduate research on preventing the invasion of Japanese stilt grass in restored riparian areas. He graduated from William and Mary for both his undergraduate and graduate degrees and worked with Dr. Doug DeBerry on his research. Robert is currently an Environmental Scientist at TNT Environmental, Inc. and is also the Education Committee Chair on the board of the Virginia Wetland Professional Association (VAWP).