scholarly journals Assesment of the Littoral Macrophyte Community in Jackson Lake, Grand Teton National Park, Wyoming Following Reconstruction of the Jackson Lake Dam

Author(s):  
Carol Brewer

Beginning in 1978, the water level of Jackson Lake, Grand Teton National Park, Wyoming, was lowered first from 2064.5m (normal pool) to between 2060.3m-2061.8m, and then in 1985 to 2057.2m. The purpose of these drawdowns was to facilitate repair and modification of the Jackson Lake dam. In 1989, repair was completed and the reservoir was allowed to fill back to the normal pool elevation of 2064.5m Because of impacts to the littoral habitat in Jackson Lake caused by restoration of the dam at the Snake River outlet, the status of the aquatic plant community was assessed in August, 1989, to follow up to investigations conducted in 1983 (prior to reconstruction) and 1985 (immediately following drawdown to 2055.4m) by Brewer (1986). This report summarizes findings from the 1989 study on impacts to the littoral macrophyte community caused by the repair-related drawdowns. A detailed report assessing current physical and biological conditions in Jackson Lake was submitted to the U.S. Fish and Wildlife Service in October (Brewer, 1989).

Author(s):  
Carol Brewer

Beginning in 1978, the water level of Jackson Lake, Grand Teton National Park, Wyoming, was lowered first from 2064.5 m (normal pool) to somewhere between 2060-2061 m, and then in 1985 to 2057 m. The purpose of these drawdowns was to facilitate repair and modification of the Jackson Lake dam. In 1989, repair was completed and the reservoir was allowed to fill back to the normal pool elevation of 2065 m. Because of impacts to the littoral habitat in Jackson Lake caused by restoration of the dam at the Snake River outlet, the status of the aquatic plant community was assessed in August, 1989 and 1990. Previous investigations conducted in 1983 (prior to reconstruction) and 1985 (immediately following drawdown to 2055 m) served as a baseline for comparisons. this report summarizes findings from the 1989 and 1990 studies on impacts to the littoral macrophyte community caused by the repair-related drawdowns. To evaluate the current status of the plant community in Jackson Lake, the following objectives were addressed during August, 1990: 1. Re-examine sites sampled in 1989; 2. Examine sites planted during the summers of 1989 and 1990 by the Bureau of Reclamation.


Author(s):  
Carol Brewer

Since the construction of the first dam at the Snake River outlet at Jackson Lake in the early 1900's, the littoral habitat has been subjected to numerous perturbations of varying intensities. Changing water levels, a consequence of reservoir drawdown schedules, alter plant community species composition and distribution over time. From the perspective of a plant, water level changes present a challenge to growth and community persistence. A plant which begins the growing season 2 m deep may be under 4 m of water after spring runoff fills the reservoir. Later in the summer, the same plant may be left at a depth of only 1 m as water is removed from the reservoir during summer drawdown. The magnitude and timing of water level fluctuations may be one of the most important factors regulating macrophyte community processes upslope on the vertical gradient in Jackson Lake (Brewer and Parker 1990). Under normal regulation, annual changes of 3-4 m are sufficient to select for a plant community with a typically weedy phenology (e.g., Elodea canadensis). In natural lakes with substantially lower annual changes in water levels, species that produce seeds annually are favored (e.g., Potamogeton species). Moreover, drawdowns greater than several meters substantially reduce the lake bed area suitable for the development of extensive shallow water plant beds. The most recent perturbations to the littoral habitat in Jackson Lake began in 1978, when the water level was lowered first from 2065 m (normal pool) to somewhere between 2060 - 2062 m. Then in 1985, the surface elevation of Jackson Lake was further lowered to 2057 m to facilitate repair and modification of the Jackson Lake dam. The entire lake bed was seriously impacted during the four years that the dam was being restored. While the lake bed in the borrow zone and the area adjacent to the dam were obviously impacted by repair activities, the entire shallow littoral zone was severely perturbed when previously inundated sediments were exposed for four years. In 1989, repair was completed and the reservoir was allowed to fill back to the normal pool elevation of 2065 m. Because of severe impacts to the littoral habitat and significant reduction of the submergent plant community caused by restoration of the dam, the status of the aquatic plant community was monitored during the summers of 1989-1991. This report summarizes the status of the aquatic plant community three years after repair of the dam was completed.


Author(s):  
Carol Brewer ◽  
Melissa Brown

The submersed plant community in Jackson Lake is an important resource in Grand Teton National Park for both terrestrial and aquatic organisms. Since the early 1900's, Jackson Lake has been influenced by a series of drawdowns of varying magnitude that influenced the composition and extent of the macrophyte community in the littoral zone. While many physical conditions have been linked to macrophyte growth and distribution in lakes (e.g., light, sediments, nutrients, slope) recent work suggests that the magnitude and timing of water level fluctuations may be the most important factor regulating macrophyte community processes at shallower depths in regulated reservoirs (Brewer and Parker 1990; Gasith and Gafny 1990; Rerslett 1984, 1987). Because of the importance of the aquatic plant community in Jackson Lake as a food source and shelter for wildlife (waterfowl, fish,invertebrates, mammals), the factors affecting growth and recovery after disturbance have received periodic attention since the late 1960's (Hayden 1969; Brewer 1986; Brewer and Rerslett 1987; Brewer and Parker 1990; Brewer and Thompson 1994). Initial work on plant community dynamics in Jackson Lake has shown that the aquatic plant community in Jackson Lake has been exposed to a varied disturbance regime that has impacted recolonization, species diversity and peak biomass development. Because the extent of littoral habitat suitable for macrophyte growth in regulated lakes depends on the timing and magnitude of seasonal and long-term drawdowns, drawdown schedules and resulting fluctuating water levels may be selecting for a plant community characterized by low diversity and patchy distribution. Peak production under such conditions in Jackson Lake tends to be shifted into deeper waters (Brewer and Parker 1990; Brewer and Thompson 1994). Furthermore, clonal, weedy species with reduced value for wildlife (e.g., Elodea canadensis, Myriophyllum sibericum) have enhanced opportunities for dispersal under such a disturbance regime and are favored when maximum drawdown occurs during the period of peak standing crop. While historical records describing changing patterns of macrophyte distribution are available for Jackson Lake, few data are available to evaluate the influence of fluctuating water levels on the seed bed, and the potential for recruitment after disturbance from this source. The objective for our work was to establish protocols and collect preliminary data on the potential for recruiting macrophytes from the littoral seed bank by measuring germination of seeds from lake sediments.


Author(s):  
C. Brewer ◽  
M. Parker

The research described here is part of a 2-year study to characterize the structure and function of the littoral macrophyte community in Jackson Lake, Grand Teton National Park. The objectives for the 1st year were: 1) to identify the plant species occuring in the lake; 2) to quantify their relative abundances; 3) to characterize the littoral habitat, and; 4) to construct a detailed map of macrophyte distribution. Data collected during the first field season will be used to help evaluate results of experiments conducted during year two on mechanisms affecting macrophyte segregation.


Author(s):  
Michael Smith ◽  
Jerrold Dodd ◽  
Paul Meiman

The Snake River plains and foothill areas of Jackson Hole have been grazed by domestic livestock since settlement of the area. Wildlife populations, including elk, mule deer, and antelope have historically used and continue to use the area. Moose are currently relatively abundant and a small herd of bison have been introduced. Currently, livestock use part of the area contained in Grand Teton National Park either as a concession or due to authorization by Park enabling legislation. Park managers need information concerning the effects of grazing by large ungulates on vegetation resources to assist in effectively managing grazing to service forage needs and achieve desired plant community goals.


Author(s):  
Lusha Tronstad ◽  
Gary Beauvais ◽  
Jeanne Serb ◽  
Kevin Roe

Invertebrates are receiving an increasing amount of conservation attention across North America. Currently, about 40% of the animals listed under the U.S. Endangered Species Act (ESA) are invertebrates (www.NatureServe.org). The National Park Service and other agencies require better information on invertebrate faunas in order to effectively conserve this important group of animals. One way to prioritize invertebrate groups for study is to assess the number of rare taxa within a given genus. In this context, Oreohelix (mountainsnails) are a top priority because the genus is assumed to support a very high percentage of rare and endemic taxa. Additionally, Oreohelix species in Wyoming and surrounding states have been petitioned for ESA listing in the recent past. The diversity of Oreohelix forms in Wyoming is not well-understood, and the current taxonomy may not reflect the true pattern of diversity within the state. Therefore, we are studying both the morphology and genetic structure of Oreohelix in Grand Teton National Park to begin to understand the diversity of mountainsnails in the state. We collected Oreohelix from 4 locations in Grand Teton National Park. Based on shell and internal characteristics, all individuals were identified as O. subrudis. We are currently preparing specimens for DNA sequencing.


Author(s):  
Michael Parker ◽  
Carol Brewer ◽  
Thomas Thompson

The research described here is part of a two year study to characterize the structure and function of the littoral macrophyte community in Jackson Lake, Wyoming. The objectives for the second year were to perform experiments to: 1) Index water movement in the littoral zone of the lake; 2) Identify the zones where the greatest plant breakage occured; 3) Determine the mechanisms and the absolute force required to break the main axis of a plant, and; 4) Measure the productivity of several species of macrophytes.


Author(s):  
Michael Smith ◽  
Jerrold Dodd ◽  
Uyapo Omphile ◽  
Paul Meiman

The Snake River plains and foothill areas of Jackson Hole have been grazed by domestic livestock since settlement of the area. Wildlife populations, including elk, mule deer, and antelope have historically used and continue to use the area. Moose are currently relatively abundant and a small herd of bison have been introduced. Currently, livestock continue to use part of the area contained in Grand Teton National Park either as a concession or due to authorization by Park enabling legislation. Park managers need information concerning the effects of grazing by large ungulates on vegetation resources to assist in effectively managing grazing to achieve desired plant community goals.


Author(s):  
Robert Eng ◽  
Kurt Alt

With the accelerated use of our national parks there is growing concern over the impact this increased visitation might have on their flora and fauna. For this reason it is important to gather baseline data on the biota for future management and interpretive programs. Two species of concern in Grand Teton National Park are the bald eagle (Haliaeetus leucocephalus) and osprey (Pandion haliaetus).


Author(s):  
Robert Eng ◽  
Kurt Alt

Yellowstone National Park funded a research study conducted by Jon Swenson from 1972 through 1974 on the ecology of the bald eagle (Haliaeetus leucocephalus) and osprey (Pandion haliaetus). The present study was initiated to further the information on the ecology of the bald eagle and osprey in Grand Teton National Park and to obtain comparative data to that obtained by Swenson from Yellowstone National Park.


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