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Vegetation dynamics of restored and remnant Willamette Valley, OR wet prairie wetlands
Highland, S., M. Santelmann, AND R. Schwindt. Vegetation dynamics of restored and remnant Willamette Valley, OR wet prairie wetlands. Ecological Restoration. Society for Ecological Restoration, 33(2):156-170, (2015).
Wetlands are important habitats in that they provide water filtration services and are home to a wide variety of species of plants and animals. In the Willamette Valley, wet prairie wetlands are one type of wetland that was very widely distributed 150 years ago but now occupies less than two percent of its prior extent. This habitat is important for water filtration and for the preservation of many rare plants and animals. As so little of this habitat remains, restoration of former wet prairie wetlands is one method for expanding the range of this habitat. This study compares the changes in plant communities from four remnant and four restoration wet prairie wetlands from 2000-2011. We found that the differences between remnant and restoration wet prairies is largely due to differences in the native species found in each, as the community of introduced species is similar. We also found that, over time, the restorations are becoming more like the remnants. This study shows that restoration of rare habitats is a viable way of expanding the range and services provided by those habitats. This study illustrates the importance and success of restorations, while also showing that no one restoration technique will provide the desired structure.
Wet prairie wetlands are now one of the rarest habitat types in the Willamette Valley of Oregon, USA. Less than two percent of their historic extent remains, with most having been converted into agricultural fields (Christy and Alverson 2011, ONHP 1983). This habitat is the obligate or preferred habitat for multiple threatened or endangered species of plants (Lomatium bradshawii, Sidalcea nelsoniana, Erigeron decumbens var. decumbens). Identification of remnant patches and restoration of prior patches is an ongoing effort. Although a number of studies have explored the effects of management practices (especially burning) on wet prairie vegetation, most of these have focused on responses to management at one or two sites; the work presented here is the first to report data on long-term changes in restored or remnant patches or effects of different management practices at multiple sites for over a decade. Eight wet prairies in the southern Willamette Valley, including four remnants and four restorations, were sampled in 2000, 2005, and 2011 using 100 m2 Relevé plots to examine plant species richness and percent cover. Non-metric multidimensional scaling (NMDS) and multi-response permutation procedure (MRPP) were used to identify patterns and trends in species assemblages at each site and trajectories of change among all sites, in order to assess the effects of time and management practices. Sites located in the southern portion of the study area tend to have the highest species richness, with one remnant and one restoration in the southern study area exhibiting the highest species richness. The four sites in the northern portion of the study area are becoming more similar over time, as are the four sites in the southern portion of the study area. Additionally, while geographic location is a statistically significant and biologically relevant grouping variable according to MRPP, the distinction between remnant and restored prairie is not. In the decade that has passed since restoration, the vegetation of the restorations has become similar to that of the remnants of their region. The implications of different management practices including mowing, controlled burning, use of herbicides, and hydrological alterations are currently being investigated and may help explain some of these trends.