Why is the Oaks Bottom Reservoir So Dead and Brown? A Success Story of Purple Loosestrife Control
Start Date
3-11-2024 9:50 AM
End Date
3-11-2024 9:59 AM
Abstract
Ever since the early 1990’s, when a water control structure was used to flood the 60acre ponded wetland at Oaks Bottom to increase waterfowl overwintering habitat, Purple Loosestrife (Lythrum salicaria) has thrived. Starting in 2008, Portland Parks and Recreation (PPR) and the Bureau of Environmental Services (BES) partnered with the Oregon Department of Agriculture (ODA) to annually release thousands of three different species of biocontrol beetles throughout the wetland. However, the unnatural flooding regime due to the water control structure and a greatly undersized culvert connecting the refuge to the Willamette River, resulted in annual reproductive and overwintering failure for the beetles. It wasn’t until 2018 when the Army Corps of Engineers, BES and PPR partnered to restore the natural hydrology of the refuge, that the biocontrol was able to take a foothold. Regular monitoring of 5x 1-meter plots along each of 5 transects throughout the wetland show that in just the 5 years since that tidal restoration project concluded, nearly 100% of the L. salicaria has been eradicated. Additionally, the biocontrol beetles can successfully overwinter in the wetland, making future beetle releases unnecessary. While complete eradication of the L. salicaria is NOT the ultimate goal for this site, the next 5 years will be a time of great replanting of native trees, shrubs, and emergents to restore this 60acre wildlife refuge to its former health and floral diversity. To better understand the history of Oaks Bottom, please watch the 30min documentary “Riverine” at https://www.youtube.com/watch?v=gQgrq9qf3Ck.
Subjects
Conservation biology, Habitat restoration
Persistent Identifier
https://archives.pdx.edu/ds/psu/41407
Creative Commons License
This work is licensed under a Creative Commons Attribution-Share Alike 4.0 License.
Why is the Oaks Bottom Reservoir So Dead and Brown? A Success Story of Purple Loosestrife Control
Ever since the early 1990’s, when a water control structure was used to flood the 60acre ponded wetland at Oaks Bottom to increase waterfowl overwintering habitat, Purple Loosestrife (Lythrum salicaria) has thrived. Starting in 2008, Portland Parks and Recreation (PPR) and the Bureau of Environmental Services (BES) partnered with the Oregon Department of Agriculture (ODA) to annually release thousands of three different species of biocontrol beetles throughout the wetland. However, the unnatural flooding regime due to the water control structure and a greatly undersized culvert connecting the refuge to the Willamette River, resulted in annual reproductive and overwintering failure for the beetles. It wasn’t until 2018 when the Army Corps of Engineers, BES and PPR partnered to restore the natural hydrology of the refuge, that the biocontrol was able to take a foothold. Regular monitoring of 5x 1-meter plots along each of 5 transects throughout the wetland show that in just the 5 years since that tidal restoration project concluded, nearly 100% of the L. salicaria has been eradicated. Additionally, the biocontrol beetles can successfully overwinter in the wetland, making future beetle releases unnecessary. While complete eradication of the L. salicaria is NOT the ultimate goal for this site, the next 5 years will be a time of great replanting of native trees, shrubs, and emergents to restore this 60acre wildlife refuge to its former health and floral diversity. To better understand the history of Oaks Bottom, please watch the 30min documentary “Riverine” at https://www.youtube.com/watch?v=gQgrq9qf3Ck.