Mountain wetland restoration: The role of hydrologic regime and plant introductions after 15 years in the Colorado Rocky Mountains, U.S.A.

•Restoring sites with hydrologic regimes similar to suitable reference sites was critical in our wetland restoration program.•Suitable water table depths were established soon after the fill material and drains were removed.•Development of stable shoot density differed between sedges (5 years) and willows (greater than 15 years).•Restoration monitoring requires multiple time lines that may extend out for more than one decade.•Exotic plant invasion is a problem in restored wetlands, with higher invasion in riparian areas than fens or wet meadows.

Twelve wetland complexes were buried and/or drained by golf course and ski area development in the Colorado Rocky Mountains in the 1980s and early 1990s. We restored all or portions of each wetland, including fens, wet meadows and riparian areas, during 1997-2002. Intensive pre- and post-construction monitoring was used to develop restoration plans and evaluate their success. We revisited the sites to analyze long-term restoration processes in 2013-2016. Prior to construction the depth to the water table was measured weekly in monitoring wells installed through the fill, and into the wetland surfaces during and following restoration. Reference sites for each wetland type were used to characterize water table depth and vegetation for each wetland type. Restoration included removal of fill material and drains to create land surfaces with water table depth and dynamics similar to the reference areas for each wetland type. We planted each site with nursery grown sedges, willows and herbaceous dicots. Post restoration monitoring of water table depth, vegetation composition, sedge shoot density and willow growth was analyzed.The water table depth and dynamics of each restored wetland was similar to suitable reference sites on short and long time scales, indicating a stable hydrologic regime. Carex utriculata reached its maximum shoot density 4-5 years after planting indicating rapid growth and high production. Willow stems were still increasing in height 15 years after planting and basal stem density was also increasing. Most planted herbaceous dicots disappeared, indicating the difficulty of establishing them from plantings. Exotic (non-native) plants have invaded all three wetland types, with their highest cover in riparian areas. Critical factors that led to success were careful hydrological analysis of reference and restoration sites prior to earthwork, creating appropriate land/ground water interactions, and establishing clonal rhizomatous sedges and native willows.