Habitat Evaluation Procedure data gathered at Ray Roberts Lake in 1989 and 1990 were analysed for temporal variability, observer variability and relationships between Habitat Units (HUs) and species density/diversity. observer variability within a group was analysed by cluster analysis and bootstrapping. Five out of 36 sites showed significant differences in Habitat Suitability Index (HSI) values within the group. A nonparametric Mann-Whitney test was used to analyze temporal variability. One of 6 sites showed a significant difference in HSI values between years. Using Spearman's Rank Correlation Coefficient, a correlation was found between indicator species density and HUs. No significant correlation was indicated between species diversity and HUs.
The purpose of this study is to provide a qualitative, detailed description of individual and social behavior in a free-living population of thirteen-lined ground squirrels. Behavioral differences in relation to various periods of the annual cycle are also evaluated.
Excessive nutrient loading of natural and artificial lakes has led, in some systems, to plethoric algal and aquatic macrophyte growth which can result in aesthetic degradation and undesirable tastes and odors. It would be advantageous to have some indication of the potential trophic status of a reservoir before it is filled. An objective of this study was to assess the water quality and nutrient loading potential of the tributaries entering Ray Roberts Lake, a large reservoir located in north central Texas. Samples from a maximum of thirteen sites were collected on the Elm Fork, Trinity River, Isle duBois Creek, and five additional tributaries. Data were also collected during six storms, from atmospheric deposition collectors, and from soil-water microcosms. The relationship between watershed landuse and mean water nutrient concentrations was evaluated. Significant differences will exist between the two major arms of Ray Roberts Lake: Elm Fork, Trinity River and Isle duBois Creek. While the majority of the annual phosphorus and nitrogen load entering both tributaries is coming from overland flow, the proportion is higher in Isle duBois Creek. Point sources in the Elm Fork contribute a larger percentage of the bioavailable phosphorus, which is significantly greater than in Isle duBois Creek. The water quality of Isle duBois Creek, especially nitrogen, is affected to a greater degree by the landuses in its watershed. Predictive regression models made accurate estimations of stream nutrient concentrations in Isle duBois Creek. The entire reservoir, upon reaching equilibrium conditions, will be classified as a eutrophic lake. The Trinity arm, with a higher phosphorus load, will display a higher trophic status. The Isle duBois arm has a lower phosphorus load which will give it a lower trophic status. The long hydraulic residence time of the two arms of the reservoir will remove nutrients upstream of the main body, …
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