PARENT SESSION
Contributed Oral Session 96: Restoration and Adaptive Management: Fresh and Salt Water Wetlands; Deer
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 516 D, Level 5, Palais des congrès de Montréal

Functional restoration and trajectories of constructed freshwater marshes: A need for adaptive management in wetland mitigation?

Gutrich, John^{*,1, 2, 5}, Fennessy, Siobhan³, Taylor, Kevin ^{4, 5}, Moriarty, Colleen¹, ¹ Hawaii Pacific University, Honolulu, HI² Dartmouth College, Hanover, NH⁵ Rocky Mountain Biological Lab, Gothic, CO³ Kenyon College, Gambier, OH⁴ Teton Science School, Jackson Hole, Wyoming

ABSTRACT- Numerous studies have attempted to assess the ability of constructed wetlands to replace the functions of natural wetlands over short time periods (< 5 years). Constructed wetlands of varying age have also been studied to estimate paths of functional equivalency of sites at similar elevations. However, few studies have returned to the field to monitor sites multiple times over longer time frames or compare constructed sites across elevations. Here, we return to the field to assess the functional restoration of constructed inland freshwater marshes at low and high elevations. Sixteen constructed marshes were monitored over multiple years and range in age from 5 to 19 years. Findings suggest that constructed marshes at low elevations in Ohio failed to achieve natural equivalency for percent native plant species and percent hydrophytes given at least 5 years of development. However, constructed marshes achieved equivalency for plant species richness, floristic quality and percent plant cover in 5 years. Years required to achieve full functional equivalency for both floristic and soil indicators for the Ohio sites under logarithmic growth ranged from 8 to 50 years with a median of 33 years. At high elevations, constructed marshes failed to achieve plant species richness after 14 and 19 years respectively. Soil chemistry data suggest that equivalency for characteristics such as percent organic matter at low and high elevations will require long time periods (> 14 years). Data suggest that constructed marshes that seem to be approaching equivalency may level off or dramatically decline over longer time periods (10 to 20 years) for certain floristic functional indicators. Adaptive management can be critical in redirecting functional trajectories toward standards of natural equivalency.

Key words: wetlands, restoration, mitigation, functional trajectory