Dennis A. Albert

Hydrogeomorphic Classification for Great Lakes Coastal Wetlands

Abstract A hydrogeomorphic classification scheme for Great Lakes coastal wetlands is presented. The classification is hierarchical and first divides the wetlands into three broad hydrogeomorphic systems, lacustrine, riverine, and barrier-protected, each with unique hydrologic flow characteristics and residence time. These systems are further subdivided into finer geomorphic types based on physical features and shoreline processes. Each hydrogeomorphic wetland type has associated plant and animal communities and specific physical attributes related to sediment type, wave energy, water quality, and hydrology.

Rapid Plant Community Response to a Water Level Peak in Northern Lake Huron Coastal Wetlands

Abstract Aquatic plants were sampled in five coastal wetlands of northern Lake Huron during July 1996, 1997, and 1998. Mean annual water levels of Lake Huron changed during this period from 176.37 m (below the long-term average) in January 1996 to above average water levels of 176.83 m in July 1996 to 177.19 m in July 1997 and then declined to 176.88 m by July 1998. Boundaries of plant zones as indicated by distribution of the 1–3 dominant species along permanently established transect points across the wetland did not shift spatially over this 3-year period. Instead, relative abundance (percent of total stems per three 0.25 m 2 quadrats per plot) and presence/absence of plant species responded individually to water level changes within major zones. In 1996, the first season sampled, the wet meadow had recently been inundated by rising water level. In 1997, after more than a year of above average and rising water levels, emergent stem densities were reduced in the Carex/Calamagrostis (sedge/blue-joint) dominated wet meadow and mixed transition sedge, narrow-leafed cattail, and hardstem bulrush ( Carex, Typha angustifolia , and Schoenoplectus acutus ) dominated zones compared to stem densities in 1996. Stem densities remained low in 1998, even though water levels dropped 31 cm from 1997 levels. The relative dominance (% of stems/3 quadrats/plot) and presence/absence of some plant species changed rapidly in the wet meadow zone in response to increases in water levels in 1997 and to decreases in water levels in 1998. In contrast, changes in emergent species were minimal in the deeper emergent zone dominated by hardstem bulrush. We conclude that temporary flooding and drying in response to water level changes are critical to maintaining a diverse arrray of plant species in the wet meadow zones of these marshes. Furthermore, short-term water level changes do not affect the relative spatial position of major plant zones within the marsh nor the relative abundance of emergent species in the deepest zone.

Characterization of Schoenoplectus pungens in a Great Lakes Coastal Wetland and a Pacific Northwestern Estuary

This study seeks to identify key components of structure and growth habit of Schoenoplectus pungens (bulrush) that allow it to thrive in severe environments. Schoenoplectus pungens, an emergent herbaceous plant growing in shallow, high energy freshwater and brackish coastal wetlands, occurs throughout North America and several continents. We observe the plant in ecologically distinctive Laurentian Great Lakes and Pacific Northwestern estuaries. Plant populations were characterized in terms of above-ground and below-ground biomass, stem density, diameter, height, and flexibility. Plants grown in flooded planters for research were compared with populations in their natural environments. The modulus of elasticity was found to be similar for planter- and wild-grown plants from fresh and brackish waters. Aerenchyma tissue, important for conducting oxygen to roots, increased with flooding and possibly reduced stem flexibility. Stem diameter and height increased as water depths or flooding increased, while below-ground biomass decreased. Soils ranging from coarse gravels to clays supported S. pungens. Most regeneration occurs as sprouts from rhizomes, not seedlings. Below-ground biomass accounted for a greater proportion of total biomass than above-ground biomass in most zones. This study collected large below-ground biomass samples that allowed for more effective evaluation of root and rhizome structure than traditional small samples.

Mechanical Harvesting Effectively Controls Young Typha spp. Invasion and Unmanned Aerial Vehicle Data Enhances Post-treatment Monitoring

The ecological impacts of invasive plants increase dramatically with time since invasion. Targeting young populations for treatment is therefore an economically and ecologically effective management approach, especially when linked to post-treatment monitoring to evaluate the efficacy of management. However, collecting detailed field-based post-treatment data is prohibitively expensive, typically resulting in inadequate documentation of the ecological effects of invasive plant management. Alternative approaches, such as remote detection with unmanned aerial vehicles (UAV), provide an opportunity to advance the science and practice of restoration ecology. In this study, we sought to determine the plant community response to different mechanical removal treatments to a dominant invasive wetland macrophyte (Typha spp.) along an age-gradient within a Great Lakes coastal wetland. We assessed the post-treatment responses with both intensive field vegetation and UAV data. Prior to treatment, the oldest Typha stands had the lowest plant diversity, lowest native sedge (Carex spp.) cover, and the greatest Typha cover. Following treatment, plots that were mechanically harvested below the surface of the water differed from unharvested control and above-water harvested plots for several plant community measures, including lower Typha dominance, lower native plant cover, and greater floating and submerged aquatic species cover. Repeated-measures analysis revealed that above-water cutting increased plant diversity and aquatic species cover across all ages, and maintained native Carex spp. cover in the youngest portions of Typha stands. UAV data revealed significant post-treatment differences in normalized difference vegetation index (NDVI) scores, blue band reflectance, and vegetation height, and these remotely collected measures corresponded to field observations. Our findings suggest that both mechanically harvesting the above-water biomass of young Typha stands and harvesting older stands below-water will promote overall native community resilience, and increase the abundance of the floating and submerged aquatic plant guilds, which are the most vulnerable to invasions by large macrophytes. UAVs provided fast and spatially expansive data compared to field monitoring, and effectively measured plant community structural responses to different treatments. Study results suggest pairing UAV flights with targeted field data collection to maximize the quality of post-restoration vegetation monitoring.