Can restored wetlands resist invasion by weeds?  We're looking for ways to give native plants an advantage while keeping the door closed to invaders.  And we're hoping to find a way to do this that can help restored wetlands anywhere.

Background
The City of Eugene, Lane Council of Governments (LCOG), and the Institute for Applied Ecology (IAE) were awarded an EPA Wetland Program Development Grant that began in early 2010 to study methods of improving wetland prairie restoration through innovations in restoration process and long-term management techniques. Specifically, the study will focus on methods to manage plant communities with a goal of retaining a high level of native diversity while maintaining resistance to weed invasion.   A commonly encountered problem with wetland prairie restoration is the trade-off between maximizing native cover (of a few dominant species, often grasses) and maximizing native diversity. While high cover of native grasses inhibits weed invasion, a diverse native plant community is essential for providing key ecosystem services (pollinators, nutrient cycling) and wildlife habitat. The discussion the Experts Workshop held at LCOG on January 12, 2010 was used as the starting point for development of the research questions, experimental design, and timeline.

Summary of Research
We are testing four management techniques to determine plant community response. The management techniques include:

 - Grazing (sheep)
 - Mowing
 - Haying (mowing + removing thatch)
 - Ecological Burning

Following the implementation of the management treatments, the plots were seeded with three different native seed mixes, plus small areas were seeded with common invasive plants that are the focus of weed control in wetland prairie restorations. The plots will be monitored for native plant community establishment and invisibility through 2013. 

Test Plots : 

 We are utilizing our existing wetland prairie restoration test plots located at Coyote Prairie, just to the west of Eugene. There are a total of 50 12x12 meter test plots that were established in 2005. At the initiation of this project, the plots contained a relatively low diversity, but mostly native, plant community with some variability between plots. Each of the management techniques listed above was applied to 10 randomly placed test plots, with 10 plots reserved for control (no management).

Progress to Date
 - Research Plan completed (May 2010)
 - Quality Assurance Plan completed (June 2010)
 - Baseline vegetation monitoring completed (June/July 2010)
 - Grazing – 20 sheep per plot for a 24 hour period (June 2010)

Seeding strategy
In general, it has been found that plots with high native plant abundance tend to be more resistance to invasion by exotic plants. However, it is not always clear what is responsible for this relationship. Although species diversity has been found to be important for providing invasion resistance, it has also been found that this may be because plots with high species diversity have a higher chance of containing species that are strong competitors. Other studies have found that it isn’t species diversity per se, but rather the diversity of functional groups (annual forbs, perennial grasses, etc.) that provides for invasion resistance. Our study has been designed to tease out the influence of these different factors – the # of species, # of functional groups, and native dominance (# of individuals of each species) in weed invasion.

In mid-October 2010 we added native seed to 3 quarters of all 50 plots, resulting in four seeding treatments per plot (no seed, low, med, and high diversity mixes). Species were included in the seed mix based on availability and suitability. We identified 8 functional groups and had 1, 2, or 3 species randomly chosen from each, with the exception that 2 functional groups only had 2 species. The total # of species in each mix was 8, 16, and 22.

Weed seed was subsequently added to 10cm x 2 m strips in each quarter of each plot. We used 50 live seeds each of Vulpia spp., Festuca arundinacea, Holcus lanatus, Rubus armeniacus, Hypochaeris radicata, Mentha pelugium, Daucus carota, Lythrum hyssopifolia (species that are already common to the area). All seedlings were removed from the plots after monitoring.

Weed monitoring
IAE monitored the seeded weed strips in June and July, 2011. Although the data has yet to be analyzed, we observed that weed abundance tended to be higher in the plots that were treated with prescribed fire and lowest in control and mow plots. However, the plots that had been burned also appeared to have the highest diversity of native plants.

Future activities
This project is currently expected to continue through 2014. Future project activities include:

 - Monitoring community diversity in all plots (2013)
 - Repeating weed seeding and monitoring (2012-2013)
 - ‘Mini-experiment’ to test the effect of seed predation on restoration projects (2011-2013).
 - ‘Mini-experiment’ to test the role of micro-topography in creating diverse native plant communities (2011-2013).
 - Final results from this research should be compiled and available in late 2013.
 - Two wetland prairie restoration "Mobile Workshops" are tentatively planned for May/June 2013 and will include an overview of research results and a step-by-step tutorial on wetland prairie restoration methods.

Your contact information:
If you would like to receive  e-mails directly, and receive  future updates and notified be about the mobile workshops please send an email to Jeff Krueger at jkrueger@lcog.org and we will add you to the distribution list.

Staffing changes
This past summer, Amanda Stanley left IAE to become the Conservation Program Officer at the Wilburforce Foundation. Although we are very sad to see her go, we are happy that she has this new opportunity. Andrea Thorpe, the Conservation Research Program Director at IAE, will be taking over Amanda’s role as lead researcher on this project. Andrea has been involved with this project from the start and has hit the ground running. Feel free to contact Andrea with questions about this ongoing research effort at andrea@appliedeco.org.