categories

• Managed/Restored High to Moderate Quality Wetland Prairies

  Rare, but increasing in the Willamette Valley, this category includes remnant wetland prairies where significant management actions have been undertaken and in areas where successful wetland prairie restoration projects have been implemented. In both cases, extensive efforts have been undertaken to control invasive species and encroachment by woody vegetation, to reintroduce a high diversity native wetland prairie plant community, and to manage the vegetation in a way that replicates historic disturbances such as fire. These areas will require continued management to maintain this high level of native composition and diversity over time. The Willow Creek Natural Area is an example of a higher quality remnant wetland prairie that has been carefully managed to preserve and improve quality. 

• Low to Moderate Quality Remnant Wetland Prairies

  Rare in the Willamette Valley, these are patches of native wetland prairie that have persisted over time with limited impacts from agriculture uses or hydrologic modification. These areas tend to have a somewhat higher level of native plant cover and diversity, as compared to abandoned agricultural fields, and often include hydrologic complexities in the form of mound-swale topography and/ or pedestals, which are associated with species richness. Non-native plants are typically present in these areas, but not dominant. Invasion by woody vegetation through natural succession will often become an issue in these areas over time in the absence of management.

• Degraded/Old Field Wetland Prairies

  These include remnant wetland prairies that have been heavily impacted by past agricultural practices such as tilling or grazing and sometimes also have modified hydrology, but are not actively being farmed. These areas tend to be dominated by non-native species but often have some native species present in lesser quantities. Woody vegetation will establish in these areas over time.

• Agricultural Wetlands

  These are areas that were native wetland prairie previously, but have been converted to agriculture use and are being actively farmed. Plant composition in these areas is typically limited to a single crop species, often one of several non-native grass species that have been planted for grass seed production. Many of these agricultural areas have been mechanically smoothed during the past several decades as a way of improving agricultural production, but most retain wetland hydrology, or the hydrology could be restored through the removal of ditches or drainage tiles. Agricultural wetlands are the most common condition of former wetland prairies in the valley today and the restoration of these areas is the focus of this guide. There are currently and estimated 180,000 hectares (445,000 acres) of land in grass seed production in the valley (Oregon State University Extension Service 2010), and much of this land possesses wetland hydrology.

• Filled Wetlands

  These are former wetland prairies that have been filled with imported material, often in anticipation of future development or simply because they were a convenient location for disposal of excess soil or debris. These areas have potential to be restored to native wetland prairie, although the cost tends to be very high. With care, the fill material can be removed to the historic grade and native wetland prairie hydrology and vegetation can be restored. It has been observed in several restoration projects in the west Eugene area that the native seed-bank has persisted under fill material for many years and will germinate once the fill is removed. However, non-native invasive species contained in the soil seed-bank at the time the fill occurred may also emerge.