Christopher S. Lowry, University of Wisconsin-Madison
Title: Delineation of peat using ground penetrating radar, Vilas County, Wisconsin
Co-Authors:
Mary P. Anderson, University of Wisconsin-Madison
Randy Hunt, U. S. Geological Survey, Middleton Office
Abstract:
Hydrology and specifically groundwater-surface water interaction are critical components of wetland function that need to be understood in order to protect and restore wetlands. Describing the subsurface environment is the first step in understanding how groundwater and surface water interactions maintain wetland environments; this has important implication for fens, which are groundwater dominated. In this study, ground penetrating radar (GPR) was used to determine the thickness and extent of peat in a fen in Vilas County Wisconsin. GPR is a nondestructive geophysical tool that measures the changes in electromagnetic wave velocities as they propagate through the subsurface. GPR is less time intensive and physically demanding than other methods of peat characterization such as, peat coring. Results from the GPR survey show a clear delineation between the upper peat and lower sand units in the wetland. Variations within the peat record in the GPR record are attributed to variations in organic matter, specifically wood content. These results will be used to define layer thicknesses in a groundwater flow and heat transport model of the wetland/groundwater system.

Monika J. Freyman, Loyola University Chicago
Title: The effect of litter accumulation of the invasive cattail Typha x glauca on a Great Lakes coastal marsh
Co-Authors:
Kathi Jo Jankowski
Nancy C. Tuchman
Abstract:
The aggressive invasive cattail Typha x glauca has replaced much of the native plant community in Cheboygan Marsh on Lake Huron. A striking feature of the invasion is the accumulation of above ground biomass which is 2.2 times greater in the Typha zone than the native wetland plant community. Using wetland mesocosms we mimicked an invasion of T. x glauca with and without its litter to determine the role both live and dead Typha plays in its invasive success. In litter treatments below-ground temperature was 2°C cooler and light levels were reduced to less than half. Soil ammonium levels were 2 times higher in treatments containing T. x glauca and litter. Interestingly the combined treatment of T. x glauca with its own litter had a far greater impact on densities of native plants, reducing them to half their densities in the litter-only treatment. In Cheboygan marsh the rate of litter decomposition, and litter-associated microbial activities across different plant species and different zones (invaded and non-invaded) is also being studied. We have found fungal colonization of T. x glauca litter to be over two times greater than that of any other native plant in the marsh, suggesting different decomposition mechanisms between Typha and the native plant species. A better understanding of this invasive’s litter dynamics will give wetland managers more options in slowing Typha’s expansion and therefore preserve the biodiversity of the remaining wetlands in Wisconsin and the Great Lakes region.

Rachel Hart, Nelson Institute for Environmental Studies, University of Wisconsin
Title: Analysis of Wisconsin Department of Transportation wetland impacts and mitigation policy
Abstract:
Despite their ecological importance, wetlands continue to be drained and filled in the state of Wisconsin. The state Department of Transportation (DOT) destroys significant wetland acreage every year with a mitigation policy designed to offset these impacts. This study investigated the trends in numbers of wetland acres impacted by the DOT across the state of Wisconsin. Since 1991, the DOT has performed 1,902 projects that impacted a total of 2,565 acres. Wet meadow, shrub scrub, and wooded swamp were the wetland types most affected. The study also analyzed the DOT’s wetland mitigation policy. DOT records show 3,504 acres of unknown wetland type have been restored. However, monitoring periods of five years for on-site mitigation sites and no monitoring requirements for bank sites after all acres have been allocated suggest the need for further investigation into the efficacy of the DOT mitigation program.

Natalie White, University of Minnesota Duluth
Title: Flowering effort and seed production in native and alien subspecies of Phragmites australis in Northwest Wisconsin and Northeast Minnesota
Abstract:
Phragmites australis (giant reed) is a wetland species of management concern. It grows quickly, and sites dominated by P. australis have lower species diversity. Recently, it was discovered that introduced European lineages exist in North America. North American and European P. australis are now recognized as distinct subspecies, both of which are present in Wisconsin. Management of P. australis may be more effective if the mechanisms of spread in the two subspecies are better understood. The objective of this work was to quantify differences in sexual reproductive effort between native North American and introduced alien P. australis. Alien and native stands were identified using morphological characters. Aliens were identified in the field by internode color and leaf sheath adherence. Ligule length was used to more confidently differentiate the subspecies. Percentage of flowering stems and stem density were estimated using quadrats. To assess seed production, whole panicles were collected in fall of 2005 and dissected to remove mature seed. Stem density was higher in alien Phragmites australis, as was percentage of flowering stems, excepting one alien stand that showed other anomalous morphological characters. Seed production per panicle was greater in the aliens as well. There was greater sexual reproductive effort in the alien subspecies versus the native P. australis. Therefore, alien and native P. australis may require different management strategies where they threaten Wisconsin wetlands.