This study conducts watershed analysis using biological and geo-spatial techniques. Incorporating landscape features with biological attributes has been shown to be an effective method of monitoring environmental quality within watersheds. In situ biomonitoring using the Asiatic Clam, Corbicula fluminea, habitat suitability, and water quality data were evaluated for their potential to describe ecological conditions in agricultural and urban areas within the Upper Trinity River watershed. These data were analyzed with GIS to identify effects of land use on ecological conditions. C. fluminea downstream of point source effluents was effective detecting in-stream toxicity. Ambient toxicity appears to have improved in the Trinity, although urban influences limit aspects of aquatic life. No association between habitat quality and land use was identified.

The south-central United States serves as an important biogeographical link and dispersal corridor between Nearctic and Neotropical elements of western hemisphere odonate faunas. Its species are reasonably well known because of substantial collections, but there has been no concerted effort to document the extent of biodiversity and possible geographic affinities of dragonflies and damselflies of this region. The recent discoveries of Argia leonorae Garrison, Gomphus gonzalezi Dunkle and Erpetogomphus heterodon Garrison from southern and western Texas and northern Mexico suggest that Odonata species remain to be discovered in this area, particularly from far south Texas and northern Mexico. I have documented a total of 12,515 records of Odonata found in 408 counties within the south-central U.S. A total of 73 species of damselflies and 160 species of dragonflies was revealed in the region. The 233 (197 in Texas) Odonata species are distributed among 10 families and 66 genera. Illustrated family, generic, and species-level keys are provided. Since the beginning of this work in the Fall of 1993, one species has been added each to the Louisiana and Oklahoma faunas, and 12 species have been added, previously unreported from Texas, including four new to the U.S. The area of highest Odonata …

Hygrophila polysperma is a plant native to Asia that has been introduced into the Comal River, TX and is thriving while Ludwigia repens, a species native to the river appears to be declining. Both plants have similar morphologies and occupy similar habitats in the river. Two plant competition experiments were conducted to examine the competitive interactions between the two species. First, an experimental design was developed in which established Ludwigia plants were 'invaded' by sprigs of Hygrophila to determine if established Ludwigia populations would be negatively impacted by invasion. The second experiment focused on establishment and growth of sprigs of each species under three competition scenarios. Results show that the continued growth of well-established Ludwigia plants was significantly depressed by the invasion of Hygrophila in comparison with those that had not been invaded. Furthermore, the growth of Hygrophila sprigs was uninhibited by the presence of Ludwigia, but the presence of Hygrophila negatively impacted the growth of Ludwigia sprigs. There was no difference in the growth of Hygrophila sprigs whether planted alone, with Ludwigia sprigs or even if planted into stands of established Ludwigia.

An examination of the effectiveness of seeding, burning, and mowing in the reestablishment of tallgrass prairie species on overgrazed and abandoned pastureland. The study site is a 20 acre tract on U.S. Corps of Engineers land below Lake Lewisville in Denton County, Texas. The site was partitioned into thirty-nine 40 by 40 meter plots with seeding (carried out in 1996) and management treatment (burning, mowing, and no maintenance carried out in 1998) randomly applied following a two level design. For each plot, nine stratified-random 0.1 m2 subplots were examined and shoot counts for each species recorded. The effects of the treatments on individual species and species richness were analyzed with a two-way ANOVA followed by a SNK multiple range test, both on ranked data. Community level analysis was conducted with both a MANOVA on ranked data and a Canonical Correspondence Analysis on raw data. Results indicate that seeding positively affected species richness, particularly when combined with either burning or mowing in the early spring. Mowing also significantly increased species richness in areas that were not seeded, while burning negatively affected species richness on unseeded plots. Treatments significantly affected community composition with treatments having the most clear effect on spring and …