Valerie J. Brady

Peatlands are globally important ecosystems because their vegetation drives key ecosystem services such as peat formation and hydrologic regulation. As drained peatlands have lost these functions, restoration is critical but there is limited understanding on how floristic composition, a primary indicator of peatland ecosystem health, can quickly return to a reference point when a targeted restoration technique is applied. We evaluated the outcomes of vegetation restoration at two formerly drained acidic peatland sites (North Field and South Field) in northern Minnesota where the moss layer transfer Technique (MLTT) was applied to accelerate the reestablishment of peatland species and the return of peatland functions. Following drain blocking to raise water tables, site leveling, and the MLTT, plant communities at both the North and South Field sites shifted rapidly within five years from upland-dominated to wetland-dominated plant assemblages. Non-metric multidimensional scaling and PERMANOVA showed significant temporal shifts, with plant community similarity to 43 regional reference wetlands rising from <5% initially to 9 to 15% by the end of monitoring in 2022. Mean Coefficient of Conservatism values (C-values) increased from 2.0 to 4.3 at the North Field and from 3.5 to 5.5 at the South Field, indicating replacement of generalist upland plant species by higher-fidelity peatland taxa. Non-native plant cover peaked early, then declined after approximately five years, but showed minor increases after herbicide treatments ceased. These results show that rewetting coupled with the MLTT can enhance floristic quality, but compositional convergence with reference peatlands remains slow and spatially variable within each site.

Large sand bed loads in trout stream headwaters can limit salmonid spawning habitat and reproductive success. This phenomenon has been observed in many northern Wisconsin watersheds, where historic logging practices are the likely source of the sediment loading. Presently, sediment transport is limited by abundant woody debris, causing channels to aggrade and bury gravels. We evaluated the impacts of a wood debris and beaver dam removal remediation strategy on fine sediment transport and exposure of the underlying gravel and cobble substrates in a second-order Lake Superior tributary. A 300-m treatment reach received selective wood removals and was compared with both an upstream 300-m reference reach receiving no alteration and a downstream reach to monitor the effects of transferred fine sediment. Physical channel measurements were taken before the wood removal process, with repeat sampling at 10 and 12 months posttreatment. The wood removal treatment resulted in a significant 25% narrowing of mean stream widths, a 32% increase in mean flow velocities, a 58% reduction in the sand bed load, and a 400% increase in the available coarse substrate across the channel. Grain size distributions coarsened noticeably from pre- to posttreatment. Water depth and temperature were not altered by the treatment, and the reference station physical measures were relatively unchanged over the 12-month study period. Immediately after the wood removal there was an observable pulse of sediment traveling through the downstream reach that increased the sand bed load, increased stream widths, and filled pools. However, these impacts diminished with time, and near-preremoval conditions had returned after 12 months. The wood removal treatment caused a significant reduction in sand content and enhanced the availability of salmonid spawning substrates.