Geology topics

D.A. Wilcox

Publications and source records attributed to D.A. Wilcox.

8 recordsLinked to original sources

USGS2011

Mid Holocene lake level and shoreline behavior during the Nipissing phase of the upper Great Lakes at Alpena, Michigan, USA

The Nipissing phase was the last pre-modern high-water stage of the upper Great Lakes. Represented as either a one- or two-peak highstand, the Nipissing occurred following a long-term lake-level rise. This transgression was primarily an erosional event with only the final stage of the transgression preserved as barriers, spits, and strandplains of beach ridges. South of Alpena, Michigan, mid to late Holocene coastal deposits occur as a strandplain between Devils Lake and Lake Huron. The landward part of this strandplain is a higher elevation platform that formed during the final stage of lake-level rise to the Nipissing peak. The pre-Nipissing shoreline transgressed over Devils Lake lagoonal deposits from 6.4 to 6.1 ka. The first beach ridge formed ~ 6 ka, and then the shoreline advanced toward Lake Huron, producing beach ridges about every 70 years. This depositional regression produced a slightly thickening wedge of sediment during a lake-level rise that formed 20 beach ridges. The rise ended at 4.5 ka at the Nipissing peak. This peak was short-lived, as lake level fell > 4 m during the following 500 years. During this lake-level rise and subsequent fall, the shoreline underwent several forms of shoreline behavior, including erosional transgression, aggradation, depositional transgression, depositional regression, and forced regression. Other upper Great Lakes Nipissing platforms indicate that the lake-level change observed at Alpena of a rapid pre-Nipissing lake-level rise followed by a slower rise to the Nipissing peak, and a post-Nipissing rapid lake-level fall is representative of mid Holocene lake level in the upper Great Lakes.

Michigan↗

USGS2009

Promoting species establishment in a phragmites-dominated great lakes coastal wetland

This study examined efforts to promote species establishment and maintain diversity in a Phragmites-dominated wetland where primary control measures were underway. A treatment experiment was performed at Crane Creek, a drowned-river-mouth wetland in Ottawa National Wildlife Refuge along the shore of western Lake Erie. Following initial aerial spraying of Phragmites with glyphosate, this study tested combinations of cutting, raking, and additional hand spraying of Phragmites with glyphosate as methods to promote growth of other wetland species and increase plant diversity. Percent-cover vegetation data were collected in permanent plots before and after treatments, and follow-up sampling was performed the following year. Increased species richness, species emergence, and relative dominance of non-Phragmites taxa were used as measures of treatment success. We also examined treatment effects on Phragmites cover. Dimensionality of seedbank and soil properties was reduced using principal component analysis. With the exception of nitrogen, soil nutrients affected species establishment, non-Phragmites taxa dominance, and Phragmites cover. A more viable seedbank led to greater species emergence. Treatments had differential effects on diversity depending on elevation and resulting degree of hydrologic inundation. Whereas raking to remove dead Phragmites biomass was central to promoting species establishment in dry areas, spraying had a greater impact in continually inundated areas. For treatment success across elevations into the year following treatments, spraying in combination with cutting and raking had the greatest effect. The results of this study suggest that secondary treatments can produce a short-term benefit to the plant community in areas treated for Phragmites.

Natural Areas Journal↗

USGS2008

Education and training of future wetland scientists and managers

Wetland science emerged as a distinct discipline in the 1980s. In response, courses addressing various aspects of wetland science and management were developed by universities, government agencies, and private firms. Professional certification of wetland scientists began in the mid-1990s to provide confirmation of the quality of education and experience of persons involved in regulatory, management, restoration/construction, and research involving wetland resources. The education requirements for certification and the need for persons with specific wetland training to fill an increasing number of wetland-related positions identified a critical need to develop curriculum guidelines for an undergraduate wetland science and management major for potential accreditation by the Society of Wetland Scientists. That proposed major contains options directed toward either wetland science or management. Both options include required basic courses to meet the general education requirements of many universities, required upper-level specialized courses that address critical aspects of physical and biological sciences applicable to wetlands, and a minimum of four additional upper-level specialized courses that can be used to tailor a degree to students' interests. The program would be administered by an independent review board that would develop guidelines and evaluate university applications for accreditation. Students that complete the required coursework will fulfill the education requirements for professional wetland scientist certification and possess qualifications that make them attractive candidates for graduate school or entry-level positions in wetland science or management. Universities that offer this degree program could gain an advantage in recruiting highly qualified students with an interest in natural resources. Alternative means of educating established wetland scientists are likewise important, especially to provide specialized knowledge and experience or updates related to new management discoveries, policies, and regulations. ?? 2008 The Society of Wetland Scientists.

Wetlands↗

USGS2008

The effects of water-level fluctuations on vegetation in a Lake Huron wetland

The diversity and resultant habitat value of wetland plant communities in the Laurentian Great Lake's are dependent on water-level fluctuations of varying frequency and amplitude. Conceptual models have described the response of vegetation to alternating high and low lake levels, but few quantitative studies have documented the changes that occur. In response to recent concerns over shoreline management activities during an ongoing period of low lake levels in lakes Superior, Michigan, and Huron that began in 1999, we analyzed a quantitative data set from Saginaw Bay of Lake Huron collected from 1988 to 1993 during a previous lake-level decline to provide the needed information on vegetation responses. Transects were established that followed topographic contours with water-level histories that differed across a six-year period, ranging from barely flooded to dewatered for varying numbers of years to never dewatered. Percent cover data from randomly placed quadrats along those transects were analyzed to assess floristic changes over time, document development of distinct plant assemblages, and relate the results to lake-level changes. Ordinations showed that plant assemblages sorted out by transects that reflect differing water-level histories. Distinction of assemblages was maintained for at least three years, although the composition and positioning of those assemblages changed as lake levels changed. We present a model that uses orthogonal axes to plot transects by years out of water against distance above water and sorted those transects in a manner that matched ordination results. The model suggests that vegetation response following dewatering is dependent on both position along the water level/soil moisture gradient and length of time since dewatering. This study provided quantitative evidence that lake-level fluctuations drive vegetative change in Great Lakes wetlands, and it may assist in making decisions regarding shoreline management in areas that historically supported wetlands. ?? 2008, The Society of Wetland Scientists.

Wetlands↗

USGS2008

Cattail invasion of sedge/grass meadows in Lake Ontario: Photointerpretation analysis of sixteen wetlands over five decades

Photointerpretation studies were conducted to evaluate vegetation changes in wetlands of Lake Ontario and the upper St. Lawrence River associated with regulation of water levels since about 1960. The studies used photographs from 16 sites (four each from drowned river mouth, barrier beach, open embayment, and protected embayment wetlands) and spanned a period from the 1950s to 2001 at roughly decadal intervals. Meadow marsh was the most prominent vegetation type in most wetlands in the late 1950s when water levels had declined following high lake levels in the early 1950s. Meadow marsh increased at some sites in the mid-1960s in response to low lake levels and decreased at all sites in the late 1970s following a period of high lake levels. Typha increased at nearly all sites, except wave-exposed open embayments, in the 1970s. Meadow marsh continued to decrease and Typha to increase at most sites during sustained higher lake levels through the 1980s, 1990s, and into 2001. Most vegetation changes could be correlated with lake-level changes and with life-history strategies and physiological tolerances to water depth of prominent taxa. Analyses of GIS coverages demonstrated that much of the Typha invasion was landward into meadow marsh, largely by Typha x glauca. Lesser expansion toward open water included both T. x glauca and T. angustifolia. Although many models focus on the seed bank as a key component of vegetative change in wetlands, our results suggest that canopy-dominating, moisture-requiring Typha was able to invade meadow marsh at higher elevations because sustained higher lake levels allowed it to survive and overtake sedges and grasses that can tolerate periods of drier soil conditions.

Journal of Great Lakes Research↗

USGS2008

Predicted effects of proposed new regulation plans on sedge/grass meadows of Lake Ontario

Previously described models for predicting the percent of Lake Ontario wetlands that would be occupied by sedge/grass-dominated meadow marsh were used to test four proposed new plans for regulation of lake levels and to make comparisons with the current plan and unregulated conditions. The models for drowned river mouth, barrier beach, open embayment, and protected embayment wetlands assessed responses to lake levels that would be generated by each plan under net total supplies modified from those that occurred from1900 to 2000. In years when reduced supplies would allow meadow marsh regeneration, simulated unregulated lake levels produced the most meadow marsh in all wetland geomorphic types; current Plan 1958DD produced the least. Overall predicted percent meadow marsh under the test plans decreased in the order B+, 2007, D+, and A+, and the latter three plans produced rather similar results in many cases. Lower percentages of meadow marsh under some plans were due to insufficient low lake levels that could allow soils to dry and restrict invasion by cattails, as well as lack of periodic high lake levels that could kill invading upland plants. An assessment of seasonal lake-level characteristics demonstrated that Plan 2007 would reduce mean winter lake levels by 13 cm or more than Plan B+ and springtime lake levels by more than 10 cm. These seasonal differences could result in less winter habitat for muskrats and reduced access to spring spawning habitats for fish such as northern pike. Our model results provide important information for use in the process of selecting a new regulation plan for Lake Ontario.

Journal of Great Lakes Research↗

USGS2006

Research opportunities in interdisciplinary ground-water science in the U.S. Geological Survey

This report is written for the scientifically literate reader but is not limited to those who are involved in ground-water science. The report is intended to encourage U.S. Geological Survey scientists to develop a sense of excitement about ground-water science in the agency, to inform scientists about existing and potential ground-water science opportunities, and to engage scientists and managers in interdisciplinary discussions and collaboration. The report is intended for use by U.S. Geological Survey and Department of the Interior management to formulate long-term ground-water science programs and to continue sustained support of ground-water monitoring and research, some of which may not have an immediate impact. Finally, the report can be used to communicate the U.S. Geological Survey's vision of ground-water science to Congress, partners, other agencies, and the research community at large with the goals of enhancing collaborative opportunities, sharing information, and maintaining dialogue regarding the directions of U.S. Geological Survey ground-water science.

Circular↗

USGS1999

Hydrogeomorphic factors and ecosystem responses in coastal wetlands of the Great Lakes

Gauging the impact of manipulative activities, such as rehabilitation or management, on wetlands requires having a notion of the unmanipulated condition as a reference. And understanding of the reference condition requires knowledge of dominant factors influencing ecosystem processes and biological communities. In this paper, we focus on natural physical factors (conditions and processes) that drive coastal wetland ecosystems of the Laurentian Great Lakes. Great Lakes coastal wetlands develop under conditions of large-lake hydrology and disturbance imposed at a hiearchy of spatial and temporal scales and contain biotic communities adapted to unstable and unpredictable conditions. Coastal wetlands are configured along a continuum of hydrogeomorphic types: open coastal wetlands, drowned river mouth and flooded delta wetlands, and protected wetlands, each developing distinct ecosystem propertics and biotic communities. Hydrogeomorphic factors associated with the lake and watershed operate at a hierarchy of scales: a) local and short-term (seiches and ice action), b) watershed / lakewide / annual (seasonal water-level change), and c) larger or year-to-year and longer (regional and/or greater than one-year). Other physical factors include the unique water quality features of each lake. The aim of this paper is to provide scientists and managers with a framework for considering regional and site-specific geomorphometry and a hierarchy of physical processes in planning management and conservation projects.

Great Lakes↗