Plant Community Composition and Waterfowl Food Production on Wetland Reserve Program Easements Compared to Those on Managed Public Lands in Western Oregon and Washington

Abstract

The Wetland Reserve Program (WRP) is one conservation tool used to mitigate national wetland loss, but few studies have evaluated the WRP for wildlife. During falls 2008 and 2009, we evaluated wetland plant communities and seed densities on 23 WRP wetlands in relation to 23 reference wetlands on managed public lands in the Willamette Valley and Lower Columbia River Valley (LCRV) of western Oregon and southwest Washington. Plant community on WRP easements differed by management intensity (A = 0.111, p = 0.002) with perennial and introduced species indicative of unmanaged easements and annuals indicative of actively managed wetlands, but plant community composition did not differ between WRP and reference wetlands (A = 0.003, p = 0.21). Overall, seed biomass was similar between WRP and reference wetlands (F1, 41 = 2.44, p = 0.12), but this relationship varied by study region (F1, 41 = 12.6, p = 0.001) related to management intensity. Seed biomass was greater on actively (765 ± 105 kg/ha) vs. passively (349 ± 105 kg/ha) managed sites (F3, 34 = 9.90, p = 0.003). Seasonal wetlands on WRP easements can achieve a structure and function similar to reference sites. However, we suspect that in the absence of active management the value of WRP sites will decline as the plant community shifts to being dominated by introduced perennial species like reed-canary grass that will reduce the diversity of native wetland plants and lower seed abundance for waterbirds.