Date of Award
Master of Science
Natural Resource Ecology and Management
Dr. Jannette R. Thompson
Abstract. Historic losses of wetlands from land use conversion led to federal regulations requiring mitigation for impacts to them. Recent regulatory changes stipulate area mitigation at ratios of at least 2:1 for forested wetlands and certain densities of live trees on project sites after a 10-year monitoring period. Road development projects are among activities that impact wetlands, and responsible agencies have expended considerable resources to meet these requirements, but with variable success. We conducted this study to evaluate site characteristics and tree seedling performance for 14 forested wetland restoration projects in Iowa where bare-root (BR) or Root Production Method™ (RPM) stock were planted with or without tree shelters. We assessed 2,533 seedlings of 22 species, including 1,994 BR and 539 RPM trees. Among these, BR trees had higher mean survival (91%) than RPM stock (74%). Tree shelters were negatively associated with survival (p = 0.071), as was soil percent clay (p = 0.018) at the planting site. More detailed assessment of 1,050 seedlings of seven species common to both stock types indicated variation in performance across species, and that average height (p = 0.011), crown depth (p = 0.010), and root collar diameter (p = 0.021) were greater for BR than RPM seedlings. Among these seedlings, tree shelters also had a negative association with survival (p = 0.035). Overall, we observed greater survival and growth for BR seedlings and recommend their use, without tree shelters, but with careful attention to species selection, seedling placement, and post-planting maintenance to enhance project success.
William Gerald Heber
Heber, William Gerald, "Assessing the effects of stock type and tree shelters on forested wetland restoration in Iowa" (2017). Graduate Theses and Dissertations. 16144.