Trends indicate that wildfires have become larger and more intense over the past few decades. Experts suggest this is due to multiple factors including long-term shifts in land use that disrupt the balance of fuels and fire regimes. Research predicts that climate change will exacerbate this trend but will do so in spatially variable ways across the globe, causing increases in fire activity for some regions and decreases for others. In the United States, increased wildfire activity combined with the rapid expansion of residential development in fire-prone land necessitate billions of dollars in suppression efforts every year to protect human lives and property. The confluence of these issues has catalyzed momentum for communities to actively participate in mitigation at the local level. Yet, the precursor to developing effective solutions is to understand the unique environmental and social components of wildfire hazards at local and regional scales and how these components influence the deleterious impact of fire. This thesis takes a case study approach to understanding and communicating wildfire hazard potential in the Edwards Plateau ecoregion of central Texas. Wildfire simulations were conducted at the regional scale to quantify the magnitude of predicted fire behaviors under various spatial and temporal conditions. Simulations were also conducted within two focal communities to illuminate how patterns of wildfire susceptibility overlap with residential development. Finally, an investigation was made into the emergency response infrastructure and mitigation strategies adopted by each of the focal communities. As a result of simulations under drought conditions, forty-four percent of the study area exhibited flame lengths over eleven feet and ninety-six percent of the tree canopy exhibited crown fire activity. Simulations also revealed an increased potential for crown fire activity and extreme flame lengths along the heavily-populated Balcones Escarpment. Third, physical forms of communities appeared to influence the spatial distribution of burn susceptibility. Finally, the infrastructure and practices of the surrounding region impacted community resilience to wildfire hazards. While these findings are specific to the eastern Edwards Plateau, they showcase how mixed methods can be used to build a comprehensive wildfire hazard assessment for a community. / text

The life history and case-making behaviors of Phylloicus ornatus from two springfed first order streams in the Edwards Plateau Bioregion of Texas were studied from January 1998 to November 1999. Field larval, pupal and adult samples and laboratory rearings indicated a multivoltine cycle. First instars differ from late instars in number of labral setae and in having a unique spur-like claw on each lateral hump. Larval development was asynchronous with second through fifth instars and pupae present most months. First instars were present April through July, October and November. Case making of first instar and case reconstruction of later instars extracted from their cases was documented by videophotography.

The failure of regeneration of oak (Quercus spp.) and other hardwood species has been noted throughout eastern North America as well as on the eastern Edwards Plateau of central Texas. Previous research has suggested that two factors—prolonged periods of fire suppression and high densities of white-tailed deer—may be particularly influential in preventing seedlings of certain species from reaching the adult size class. It is also possible that these two factors interact, and the success of reintroducing fire to promote hardwood regeneration may depend on local deer density. This study, composed of observational and experimental components, first compared browsing frequency on woody plants in burned and unburned plots at six sites in central Texas. We found that although fire history did not affect browsing frequency, browsing frequency varied significantly among sites (likely due to differences in local deer densities) and among species. In our experimental study, we used cages to protect woody plants from deer herbivory in burned and unburned areas and compared growth after one year to plants of similar size and species that were exposed to herbivory. Plants in burned areas were significantly more likely to increase in height than plants in unburned areas. Similarly, plants protected from herbivory were more likely to increase in height after one year than plants that were browsed. There were no significant differences in the amount of growth woody plants in burned and unburned areas or plants that were caged or uncaged put on during one year. This is likely due to the extreme hot and dry weather that occurred across central Texas during the course of this study. These results support previous research showing that deer are currently limiting hardwood growth of multiple species on the eastern Edwards Plateau. Further, although it appears that fire can be used to stimulate hardwood growth (particularly during a non-drought year) successful hardwood regeneration is unlikely at current deer densities. / text

Thesis (M.S.)--Texas State University-San Marcos, 2008. / Vita. Appendices: leaves 34-54. Includes bibliographical references (leaves 31-33). Also available on microfilm.

Genetic variation was analyzed for populations of seven taxa comprising four cytotypes of the Geomys bursarius chromosome complex, including G. b. major, G. b. knoxjonesi, and the Edwards Plateau taxa, G. b. llanensis and G. b. texensis. Genetic relationships of the Edwards Plateau gophers with other taxa and between themselves were examined. Genetic similarity, number of fixed allelic differences, and ectoparasite distribution indicate the Edwards Plateau gophers are a distinct gene pool. Isolation of the Edwards Plateau taxa precludes contact zone analysis. However, genetic differentiation is typical of that between other species of Geomys, and the Edwards Plateau taxa should be recognized as G. texensis. Distributions of allelic frequencies indicate little justification in retaining the subspecific status of the Edwards Plateau forms.

Wooded plant encroachment has dramatically changed the composition of rangelands in the arid and semiarid rangelands of the southwestern United States and may have significantly affected hydrologic and biogeochemical process in these environments. In particular, suspicions that encroaching species waste an undue amount of water through evapotranspiration (ET) has prompted much discussion concerning the possibility of using brush control to enhance water supplies in Texas. This study focuses on two broad goals for evaluating the effects of wooded growth in rangelands. The first of these is the assessment of wooded cover with the use of remotely sensed imagery. A methodology for delineating differing land cover classes, including different levels of brush cover, is described, applied, and validated for the Upper Guadalupe River watershed, Texas. This portion of the research resulted in an 81.81% success rate for correctly matching land cover varieties and showed that 88.8% of the watershed was covered with various amounts of woody plant growth. The second portion of this study incorporated the previously developed land cover product along with a number of other highly detailed data sources to model the North Fork of the Upper Guadalupe River watershed using the Soil and Water Assessment Tool (SWAT). The role of topography, brush cover, and soil slope, which are hypothesized to contribute to successful implementation of brush removal for water yield, were tested in a scientifically conscious and practical experiment to determine their influence upon water availability at a watershed scale. The effects of brush removal were found to be comparable to the quantities documented in field experiments, but less than the levels presented in previous modeling studies. Brush density was found to be the most important factor in determining locations for successful brush removal in regards to reducing ET. Slope was also found to have significant effect in increasing lateral flow while shallow soil had lesser effects on hydrology than other criteria. Large quantities of deep recharge simulated by the model raise questions concerning measurement of ET in the Edwards Plateau region and the extent of deep water recharge to the Trinity Aquifer.

Wooded plant encroachment has dramatically changed the composition of rangelands in the arid and semiarid rangelands of the southwestern United States and may have significantly affected hydrologic and biogeochemical process in these environments. In particular, suspicions that encroaching species waste an undue amount of water through evapotranspiration (ET) has prompted much discussion concerning the possibility of using brush control to enhance water supplies in Texas. This study focuses on two broad goals for evaluating the effects of wooded growth in rangelands. The first of these is the assessment of wooded cover with the use of remotely sensed imagery. A methodology for delineating differing land cover classes, including different levels of brush cover, is described, applied, and validated for the Upper Guadalupe River watershed, Texas. This portion of the research resulted in an 81.81% success rate for correctly matching land cover varieties and showed that 88.8% of the watershed was covered with various amounts of woody plant growth. The second portion of this study incorporated the previously developed land cover product along with a number of other highly detailed data sources to model the North Fork of the Upper Guadalupe River watershed using the Soil and Water Assessment Tool (SWAT). The role of topography, brush cover, and soil slope, which are hypothesized to contribute to successful implementation of brush removal for water yield, were tested in a scientifically conscious and practical experiment to determine their influence upon water availability at a watershed scale. The effects of brush removal were found to be comparable to the quantities documented in field experiments, but less than the levels presented in previous modeling studies. Brush density was found to be the most important factor in determining locations for successful brush removal in regards to reducing ET. Slope was also found to have significant effect in increasing lateral flow while shallow soil had lesser effects on hydrology than other criteria. Large quantities of deep recharge simulated by the model raise questions concerning measurement of ET in the Edwards Plateau region and the extent of deep water recharge to the Trinity Aquifer.

Since 1970, Rio Grande wild turkey (Meleagris gallapavo intermedia) numbers in the southern region of the Edwards Plateau of Texas have been declining. Nest-site characteristics and invertebrate abundance were hypothesized as limiting wild turkey numbers in declining regions. Wild turkeys were trapped and fitted with mortality-sensitive radio transmitters on 4 study areas; 2 within a region of stable (northern Edwards Plateau) populations, and 2 within a region of declining populations. Monitoring occurred from February 2001 to August 2003. Nest-site locations were determined via homing during the breeding season. Following nesting attempts/completions, nest fate, vegetation height, visual obstruction, litter depth, percent cover, and cover scores of forbs, grass, litter, and bare ground at each nest site and surrounding area were sampled. This was done to determine if wild turkey hens selected nest sites with vegetative characteristics differing from surrounding habitat. Brood survival was calculated as >1 poult surviving to 2-weeks. Broods were followed for 6-weeks post-hatch or to brood failure. Invertebrates were collected, via sweep-net and D-vac, at each visually confirmed brood location and a paired random site to determine if wild turkey hens selected brood habitat based on invertebrate abundance. Analyses were performed to determine if invertebrate abundance differed between study regions. Turkey hens selected nest sites with greater visual obstruction and more litter depth on both regions of stable and declining turkey abundance. No vegetative differences were detected between stable and declining region nest sites. Frequency of Orthoptera was 3–5 times greater at nest sites on stable regions than declining regions in all 3 years. Orthoptera is a noted food source for young galliformes and comprised the majority of dry mass in invertebrate samples, nest sites and brood locations, on both the stable and declining regions. No differences in total invertebrate dry mass were detected between regional brood locations. Nest-site vegetative characteristics did not alter nest success between regions. The 2 overall objectives of this study were to determine if nest-site vegetation characteristics and invertebrate abundance affected wild turkey numbers in the Edwards Plateau. Regional differences in vegetative characteristics were not detected, thus not likely to be causing differences in turkey numbers between regions. Nest-site invertebrates were found to be 3–5 times greater at stable region nest sites, possibly giving wild turkey poults from stable regions greater initial chances of survival.

In dryland regions, where water is a limited resource, land use/land cover has undergone and continues to undergo significant change mainly due to human activities. The nature of runoff from dryland regions and the influence of land use/land cover change are largely not quantified. The objective of this study is to examine runoff dynamics and the influence of land cover in drylands of western Texas across multiple spatial and temporal scales. The study consists of four major components: (1) an experimental study at Honey Creek upland catchment (19 ha) to assess vegetation treatment effects on runoff by hydrometric and isotopic methods; (2) a hydrochemical evaluation of hydrologic linkage between the upland and bottomland at the second-order Honey Creek watershed; (3) a detailed precipitation-streamflow analysis at North Concho River basin to assess long-term and large-scale precipitation-streamflowvegetation dynamics; and (4) a comparison of streamflow in North, Middle, and South Concho River basins and a regional streamflow trend analysis for the entire western Texas. The study indicates runoff production in the drylands of western Texas is dominated by a few large runoff-producing events. The small catchment experiment indicated that runoff increased about 40 mm per year when 60% of woody plants were removed. This effect may relate to the presence of a baseflow component, but was not verified in regional trend analysis for the Edwards Plateau region where most rivers are spring-fed. The decrease in streamflow in North Concho River basin after the 1950's is in large part related to the enhanced infiltration capacity from reduced grazing pressure and improved vegetation cover. Regional streamflow trend analysis suggests some headwater areas outside the Edwards Plateau region experienced patterns of streamflow change similar to those in North Concho River basin, although artificial impoundments complicated the analysis. The study has broader application in ecohydrological research beyond specific geographic areas and specific vegetation types when evaluating the impact of ecosystem structure change on hydrology and water resources.

Since 1970, Rio Grande wild turkey (Meleagris gallapavo intermedia) numbers in the southern region of the Edwards Plateau of Texas have been declining. Nest-site characteristics and invertebrate abundance were hypothesized as limiting wild turkey numbers in declining regions. Wild turkeys were trapped and fitted with mortality-sensitive radio transmitters on 4 study areas; 2 within a region of stable (northern Edwards Plateau) populations, and 2 within a region of declining populations. Monitoring occurred from February 2001 to August 2003. Nest-site locations were determined via homing during the breeding season. Following nesting attempts/completions, nest fate, vegetation height, visual obstruction, litter depth, percent cover, and cover scores of forbs, grass, litter, and bare ground at each nest site and surrounding area were sampled. This was done to determine if wild turkey hens selected nest sites with vegetative characteristics differing from surrounding habitat. Brood survival was calculated as >1 poult surviving to 2-weeks. Broods were followed for 6-weeks post-hatch or to brood failure. Invertebrates were collected, via sweep-net and D-vac, at each visually confirmed brood location and a paired random site to determine if wild turkey hens selected brood habitat based on invertebrate abundance. Analyses were performed to determine if invertebrate abundance differed between study regions. Turkey hens selected nest sites with greater visual obstruction and more litter depth on both regions of stable and declining turkey abundance. No vegetative differences were detected between stable and declining region nest sites. Frequency of Orthoptera was 3–5 times greater at nest sites on stable regions than declining regions in all 3 years. Orthoptera is a noted food source for young galliformes and comprised the majority of dry mass in invertebrate samples, nest sites and brood locations, on both the stable and declining regions. No differences in total invertebrate dry mass were detected between regional brood locations. Nest-site vegetative characteristics did not alter nest success between regions. The 2 overall objectives of this study were to determine if nest-site vegetation characteristics and invertebrate abundance affected wild turkey numbers in the Edwards Plateau. Regional differences in vegetative characteristics were not detected, thus not likely to be causing differences in turkey numbers between regions. Nest-site invertebrates were found to be 3–5 times greater at stable region nest sites, possibly giving wild turkey poults from stable regions greater initial chances of survival.