Browsing by Subject "Playas"
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Item A Sampling Study of the Macroinvertebrate Ecology of a Desert Playa Lake in Southwestern New Mexico(Texas Tech University, 1971-12) Richardson, Louis GeneNot Available.Item Artificial recharge of playa water through filter drains(Texas Tech University, 1988-05) Wong, Twee ChingNOT AVAILABLEItem Benefits and costs of playa lake modification in the Texas High Plains(Texas Tech University, 1967-05) Parks, Don L.Not availableItem Benefits and costs of playa lake modification in the Texas High Plains(Texas Tech University, 1967-08) Parks, Don L.The landscape of the Texas High Plains region presently is "dotted" with numerous shallow depressions (playas) which collect runoff water and form shallow, wet-weather lakes during periods of precipitation. These lakes result in increased incidences of "sleeping sickness"(Encephalitis) and are impediments to agricultural production through temporary flooding of the lake beds. The lake water has historically been allowed to either percolate into the lake bed or evaporate into the atmosphere. The High Plains area has thus been suffering economic losses through direct health costs, direct crop losses due to flooding, and indirect agricultural losses from failure to use the accumulated water for irrigation purposes.Item Breeding ecology of shorebirds in the play lakes region of Texas(Texas Tech University, 2001-12) Conway, Warren C.The Playa Lakes Region of Texas (PLR) is characterized by playas, the dominant hydrologic characteristic and the main reftigia of biodiversity in an otherwise agriculturally dominated landscape. Other wetland types occur in the region, including saline lakes, manmade lakes, and riparian wetlands on the eastern portion. These wetlands provide habitat for wintering waterfowl and sandhill cranes (Grus canadensis) as well as migrant shorebirds. The PLR of Texas is recognized for its continental importance for migrant shorebirds, but no studies have examined wetland habitat use, nest site selection, or general breeding ecology of nesting shorebirds in the PLR. During 1998 and 1999,1 found American avocets (Recurvirostra americana), black-necked stilts {Himantopus mexicanus), killdeer {Charadrius vociferus), and snowy plovers {Charadrius alexandrinus) nesting in study site wetlands in the PLR. 1 examined general breeding biology for each of the focal species by estimating clutch size, documenting phenology of nest and clutch initiation, quantifying apparent and adjusted nesting success, identifying causes of nest failure, and estimating egg success as an estimate of armual adult productivity. I also examined wetland scale and nest site selection patterns of the four nesting shorebird species in playa, riparian, manmade, and saline lakes.Item Classification of playa lakes based on origin, morphology, and water quality parameters(Texas Tech University, 1995-05) Casula, KavithaPrevious playa lake studies on the Southern High Plains (SHP) were conducted to undCTstand the origin, development, hydrology, and habitat value of playa lakes, with limited work done on the water quality aspects. The few water quality studies were in the form of analyses of samples from a few playa lakes. Results of sample analyses from a few lakes in a particular region were used to geneialize the water quality of nearly 30,000 lakes on the SHP. However, such generalization is not an adequate measure of the water quality variations of lakes OVCT the wide expanse of the SHP (80,000 km^). Hence, models are needed which can predict water quality based on lake specific parameters (such as morphological variables) without performing extensive analyses of field samples. The first objective of this study, therefore, is to initiate development of such mathematical models for wata* quality variables of playa lakes. During the process of model development, water quality variables from 62 lakes distributed over eleven counties were used. The second objective of this study is to use the values of morphological variables (given by Reeves) in the water quality models developed in the first phase. Consequently, a possible range for the water quality variables of the three types of lakes (characterized by Reeves) can be proposed. With respect to the first objective, strong water quality models could not be developed with the set of lake specific parameters used. Since, strong models could not be developed and validated a possible range for the water quality variables could not be proposed.Item Ecological changes in modified playa lakes: with special emphasis on mosquito production(Texas Tech University, 1964-08) Ward, Charles RNot availableItem Evaluation of anuran persistence in an urbanized drought-affected setting in the Southern High Plains(2012-12) Ramesh, Rasika; Griffis-Kyle, Kerry; Perry, Gad; Farmer, Michael; SanFrancisco, MichaelUrbanization, due to associated habitat degradation and fragmentation, is threatening amphibian survival worldwide. Mitigating urban amphibian declines is critical for amphibian conservation and requires understanding of amphibian life-histories and their use of urban landscapes. Since amphibian monitoring is non-existent in urban centers of the Southern High Plains, I conducted amphibian surveys in 2011 and 2012 in the city of Lubbock, west Texas, to establish fundamental baseline data regarding amphibian species occurring within the city, and evaluated site-suitability at site-specific and landscape scales at 23 urban lakes. While droughts are a recurring phenomenon here, the year 2011 broke past records for drought intensity and severity. I observed greater species richness and incidence of amphibian occurrence in 2012 which was relatively wetter; Bufonids (Anaxyrus speciosus and A. cognatus) were the most widespread. Using data from the drought, I attempted to establish a simple method to base management recommendations in the event of data scarcities associated with natural climatic extremes. This was used to create a preliminary grouping of lakes in order of amphibian management priority and level of management effort, thus emphasizing the importance of data gathered under drought conditions towards amphibian management efforts in the region.Item Field verification of a dual-porosity flow model to estimate aquifer recharge rates through playa lakes(Texas Tech University, 1996-05) Huda, Akm NazmulThe Southern High Plains of Texas overiies an extensive aquifer known as the Ogallala formation. This aquifer is the prime source of groundwater resources for this region. This aquifer has been experiencing severe depletion of its groundwater reserve due to the intensive use of water for irrigation. The natural recharge of this aquifer primarily depends on the surface mnoff water that is collected by a large number of playa lakes present in this region. The surface mnoff water retained by the playa lakes infiltrates through the playa beds and contributes to the groundwater recharge. However, the actual amount of recharge that takes place through playa beds is difficuh to quantify. Traditionally, recharge through playa lakes was estimated based only on micropore conductivity ofthe soil. However after long dry periods, playa beds tend to develop shrinkage cracks that increases the overall conductivity of soil significantly. Unfortunately, modeling the flow through a macropore system mathematicaUy is very difficult because ofthe complexities in the geometry and the spatial distribution of macropores. In a recent study, a numerical model, FTSCracks, was developed to incorporate the influence of shrinkage cracks on the overall flow rates through unsaturated soils. In FTSCracks, the systems of macropores were defined with some empirical parameters that were difficult to determine through lab tests. In this study, a series of lab and field experiments were performed to verify the FTSCracks model with field and lab data. This study was conducted also to demonstrate the ability of this model in estimation of aquifer recharge.Item GIS-based classification and comparison of playa lakes as wetlands on the southern high plains(Texas Tech University, 1996-05) Goss, Douglas J.Analysis of the level of agreement between methods of delineation will test the null hypothesis Ho = that there is no difference between the use of USGS 7.5 minute topographic sheets, wetlands inventory maps, and SCS soil surveys for mapping playas on the Southem High Plains. Acceptance of Ho indicates that agreement probably exists between the three criteria used to identify wetlands on the southem high plains. Rejection of Ho indicates the validity or acceptance of the altemative hypothesis HA = some degree of difference exist between criteria used to identify wetlands on the SHP.Item Hydrology of urban playa lakes in Lubbock, Texas(Texas Tech University, 1998-08) West, Eric LaneThe Southern High Plains region of Texas and New Mexico contains more than 20,000 small, circular depressions called playa lakes or playas. These playas create a unique physiographic phenomenon where many watersheds in the region are small closed basins in which no outlet from the watershed is present (Gustavson et al., 1994). The presence of playa lakes implies that runoff from the contributing watershed is focused into the playa lake, including chemical constituents associated with the runoff. Also, the fate of the runoff has only two possibilities, evaporation or infiltration. The chemical constituents are therefore treated naturally in playa waters, bound to playa sediments, or transported to the groundwater flow system. At one time, researchers believed that evaporation, rather than infiltration, controlled the fate of water entering playas in the High Plains. This includes work done by C V. Theis (1937) and the Texas Water Development Board (1965). However, more recent investigations are revealing that not only is infiltration significant in playa lakes, it is the primary source of recharge to the groundwater (Wood and Osterkamp, 1984b; Wood and Sanford, 1994; Wood, Rainwater, and Thompson, 1997). In an urban environment, such as the city of Lubbock, the existence of playa lakes is essential to storm drainage as well as recreation (Hertel and Smith, 1994). Little information has been collected concerning the hydrology of these urban playas, some of which have altered bed sediments due to development. In addition, rising groundwater levels and runoff quality concerns are major considerations for city engineers and administrators as well as researchers. Detailed investigations of urban playas will be a valuable tool for determining the interaction of stormwater runoff and groundwater flow systems.Item Invertebrate communities in vegetated playa wetlands(Texas Tech University, 1997-08) Anderson, James T.Playa wetlands on the Southern High Plains (SHP) of Texas provide important and essential habitat to the native flora and fauna in the region. Wetland invertebrates are important to the biodiversity in the SHP, serve as food sources for waterfowl and other wildlife, and contribute to nutrient cycling in playas. Little is known about macroinvertebrate communities in playa wetlands of the SHP or in any seasonally flooded wetlands managed for moist-soil plants (Le., moist-soil management). Moist-soil management produces abundant seeds, that are consumed by dabbling ducks and other wildlife. An examination of macroinvertebrate communities in moistsoil managed playa wetlands is needed to determine the potential for management to increase invertebrate production, assess the importance of invertebrates in the diets of dabbling ducks, and determine their influence in attracting waterbirds to playas. In addition, by altering hydroperiods and management regimes, hypotheses concerning factors that are most influential in determining invertebrate abundance (density and biomass), community development, and competition can be tested. The objectives of this study were to (1) compare waterbird use during diurnal and nocturnal periods and potential waterbird use-days, based on seed and invertebrate abundance, among water legunes (September and November flooding) and management scenarios (moist-soil managed and unmanaged) in playa wetlands; (2) determine the importance of invertebrates in the diet of wintering and migrating green-winged teal (Anas crecca) as it relates to feather moh intensity; (3) compare macroinvertebrate biomass, density, community structure, and diversity among playas subjected to different water regimes (September and November flooding) and management scenarios (moist-soil managed and unmanaged); (4) determine if colonization from other areas or persistence in playas is more prevalent for invertebrates inhabiting playa wetlands; (5) compare production of protein and energy between invertebrates and seeds, water regimes (September and November flooding), and management scenarios (moist-soil managed and unmanaged) in playa wetlands; (6) determine the effects of physicochemical (e.g., plant species, water depth, water temperature, pH, dissolved oxygen, electrical conductivity) characteristics on playa wetland invertebrate abundance and presence; and (7) determine if patterns of niche partitioning occur among coexisting snails within microhabitats of playas. I chose snails as my test subjects for objective (7), because there were only 3 species that are abundant and wide-spread in my study playas.Item Local and landscape factor influences on avian community composition in playas of the Southern High Plains(Texas Tech University, 2007-12) Tsai, Jo-Szu; Smith, Loren M.; Haukos, David A.; Martin, Clyde F.; McIntyre, Nancy E.; McMurry, Scott T.The more than 25,000 playas on the Southern High Plains (SHP) are essential to the maintenance of regional biodiversity. The SHP landscape has been highly fragmented by intensive cultivation since the 1930s. Cultivation has degraded the condition of playas through sedimentation, resulting in a loss of playa volume in cropland watersheds and shortened hydroperiod. These effects should influence the avian communities that depend on playas for breeding, overwintering, or migratory stopover sites. However, information about the influence of land-use change and other factors on avian community composition in SHP playas is limited. Previous studies have focused on the relationship between game species and local variables during winter; however, systematic documentation of playa variables that are important to birds throughout the year is lacking. To fully understand the importance of playas to different avian communities, information on avian use during the wet and dry phases of playas throughout the year is needed. Therefore, I examined influences of local and landscape factors on avian species richness, diversity, and density in playas and determined how avian community composition was influenced by water-level fluctuation as a disturbance. My objectives were to 1) determine how local variables within a playa (e.g., vegetation cover and playa area) influence richness, density, and diversity of avian communities; 2) evaluate the effect of landscape variables in the wetland complex (i.e., playas and the adjoining habitat patches in 3 defined diameters) on richness, density, and diversity of avian communities; 3) examine the effect of water-level fluctuations as a disturbance on avian community composition; and 4) examine relationships between local variables and percent composition of different avian groups and dominant species during summer. After significant precipitation events in June 2003 and 2004, I selected 80 playas (40 playas each year) across the SHP containing water with watersheds ranging from 100% native grassland to 100% cropland. Wet playas were surveyed biweekly by counting all birds present within the playa boundary for as long as playas retained water, from June 2003 to May 2004 and June 2004 to May 2005. When playas dried, I conducted surveys monthly using distance sampling techniques. Water depth was measured concurrently with each bird survey and percent vegetation cover, vegetation structure, and plant species richness were measured 3 times during each summer. Eight landscape variables (i.e., number of playas, percent cover of playas, interspersion and juxtaposition index, landscape shape index, Shannon evenness index, diversity index of land use, edge density, and mean edge density) were obtained using ESRI® ArcGIS and FRAGSTATS*ARC® for each study playa at 3 distance scales (i.e., 1, 5, and 10 km radii from the study playas, representing a gradient of local to landscape-level influences). I recorded 127 bird species during 1487 surveys over 2 years. Seventy-seven were wetland-dependent species and 50 were non-wetland species. In wet playas, area was a positive predictor for total species richness and diversity in all seasons. Water depth was a consistent predictor across different seasons for total species richness, and species richness was greatest at an intermediate level of water depth (ranging from 40 to 100 cm). Tilled index ([tilled landscape ¡V untilled landscape]/[tilled landscape + untilled landscape]) positively influenced total species richness and native species richness, but I also found a positive relationship between percentage of exotic bird species in the avian community and tilled index, indicating that more exotic bird species (fewer native species) were found in playas surrounded by a greater percentage of cultivated land. Models predicting avian species richness were variable among seasons, and diversity of land use within 1 km had a positive influence on total species composition. In general, variables in the best-fit models for wetland-dependent species richness, diversity, and density were similar to models predicting total species. Models predicting species richness, diversity, and bird density for wetland-dependent species explained more variation than predictive models for total species richness. This is likely because wetland-dependent species outnumbered non-wetland species and were important in driving avian community composition in wet playas. Playa area had a positive influence on waterfowl species richness and density, whereas water depth had a polynomial relationship with waterfowl species richness and density, showing a positive linear and a negative quadratic term. Waterfowl species richness and density peaked when water depth ranged from 40-100 cm. Percent vegetation cover had a polynomial relationship with waterfowl species richness, indicating that waterfowl most frequently occupied wetlands with intermediate levels of vegetation. Landscape variables were important in predicting waterfowl species richness and density, but the appearance of landscape variables in best-fit models varied among seasons, which suggests different habitat requirements for waterfowl in different portions of the annual cycle. Playa area was positively correlated with shorebird species richness but there was a negative relationship between shorebird density and playa area. There was a polynomial relationship, showing a positive linear and a negative quadratic term between water depth and shorebird species richness and density, which indicates that shorebirds tended to occupy wetlands with intermediate levels of water depth (30-80 cm). Percent vegetation cover was negatively correlated with shorebird density. Playa area was a consistent positive variable for predicting wading bird species richness and density. Because of high evaporation rates in summer and unpredictable precipitation, playa hydroperiods are unpredictable and the number of playas that contain water varies among seasons and years. Therefore, the natural wet-dry cycle is ideal for studying the influences of disturbance on wetland biota. The intermediate disturbance hypothesis (IDH) states that the highest levels of species diversity will occur at intermediate levels of disturbance, whereas diversity will be lower at higher and lower levels of disturbance, owing to effects of abiotic limitations and competitive exclusion, respectively. I tested the predictions of the IDH by comparing species richness and similarity index (changes of avian composition; Sorenson¡¦s similarity coefficient) among 3 disturbance regimes (considered different combinations of disturbance intensity and frequency and starting moisture condition). Results did not support the IDH, however, as the highest species richness did not occur at intermediate levels of disturbance. These results suggest that moisture condition itself may be more important in influencing species richness than a change in moisture condition (i.e., disturbance). Because wet playas have more species than dry playas in this semi arid landscape, playas associated with flooded conditions may have higher species richness regardless of the degree of disturbance. Playas with a higher degree of disturbance were associated with higher tilled indices in summer. The increased degree of disturbance due to sedimentation and lack of protection from the cultivated watershed had a negative impact on avian community composition. I used canonical correspondence analysis to examine the influence of local environmental variables (i.e., playa area, tilled index, water depth, percent vegetation cover, vegetation structure, vegetation height) on percent composition of the avian assemblage. Waterfowl, shorebirds, and wading bird were analyzed as groups, along with individual analyses on blue-winged teal (Anas discors), mallard (Anas platyrhynchos), American avocet (Recurvirostra americana), killdeer (Charadrius vociferus), long-billed curlew (Numenius americana), upland sandpiper (Bartramia longicauda), mourning dove (Zenaida macroura), and red-winged blackbird (Agelaius phoeniceus). Water depth, vegetation structure, and percent vegetation cover were consistently the top 3 variables influencing percent composition of birds throughout the summer. In general, percent composition of waterfowl as a group peaked when water depth ranged from 40-70 cm. Percent composition of shorebirds as a group was negatively correlated to water depth and vegetation-related variables, indicating that shorebirds occupied playas with shallower water and sparse vegetation. Percent composition of long-billed curlew was negatively correlated with tilled index, suggesting that playas within grassland watersheds are important for this species. In contrast, percent composition of mourning dove and red-winged blackbirds were positively associated with vegetation structure and percent vegetation cover. Watershed management surrounding playas should be given a high priority depending on the goals in the conservation plans, as increasing cultivation in playa watersheds increases total species richness but also favors exotic avian species and increases the degree of disturbance (i.e., water level fluctuation). With shortened hydroperiod of sedimented playas, the value of playas for avian species is decreased. Larger playas should also receive higher emphasis when other conditions (e.g., land use, vegetation, and landscape variables) are the same, since conserving larger playas is likely to maximize species richness. At a local scale, maintaining an intermediate level of water depth (40-100 cm) and 26-50% of vegetation is likely to meet the needs for the highest number of species and for most of the bird groups. Variables at a landscape level should be considered in conservation plans, as landscape-level variables appeared in many of the top models. Considering a group of playas as a complex instead of dealing with individual playas should provide diverse habitat for different groups of birds.Item Local and landscape level variables influencing migratory bird abundance, diversity, behavior, and community structure in Rainwater Basin wetlands(2006-08) Brennan, Elisabeth K.; Smith, Loren M.; Wilde, Gene R.; McIntyre, Nancy E.; Strauss, Richard E.; Vrtiska, MarkThe Rainwater Basin (RWB) region in south-central Nebraska, which currently contains approximately 400 wetlands, is one of the most threatened and least studied wetland complexes in the Great Plains. Early soil surveys indicate the RWB originally included more than 4,000 natural wetland basins, totaling approximately 38,000 ha; however, conversion of wetlands to agricultural fields has resulted in the destruction of over 90% of the wetlands and 88% of the original wetland area. Even in their reduced, degraded condition, RWB wetlands provide essential stopover and staging areas to migratory wetland birds in the Central Flyway. Consequently, the RWB region has been identified as containing waterfowl habitat of major concern by the North American Waterfowl Management Plan. Five to 7 million waterfowl pass through the RWB region every spring, including virtually all of the 600,000 mid-continental white-fronted geese (Anser albifrons), 500,000 Canada geese (Branta canadensis), 50% of the mid-continental mallard (Anas platyrhynchos) population, and 30% of the continental northern pintail (Anas acuta) population. Staging areas and migratory stopovers often function as geographic bottlenecks; entire populations within a flyway can be affected by the quality and quantity of available wetland habitat at stopover sites. This common dependence among migratory birds on staging sites has major implications for wetland conservation and restoration. In an effort to guide wetland stopover site restoration and conservation efforts, there has been an increased effort to determine what factors influence wetland habitat quality for migrating shorebirds and waterfowl. Although previous studies have shown that local and landscape-level factors influence abundance, diversity, and behavior of breeding birds on wetlands, few studies have assessed the impact of these factors on wetland birds during migration. Moreover, examination of wetland bird habitat use, behavior, and community structure provides the opportunity to test hypotheses about the mechanisms that allow wetland birds to coexist while migrating through a region with unpredictable resources. My objectives were to 1) examine local (within wetland and immediate watershed) factors influencing abundance, species richness, and diversity of waterfowl, shorebirds, and wading birds; 2) evaluate landscape-level factors influencing abundance, species richness, and diversity of waterfowl, shorebirds, and wading birds at various spatial scales; 3) determine the effects of hunting disturbance, time period, and migration chronology on bird behavior; and 4) examine community patterns and species associations to assess the importance of assembly rules in structuring wetland bird distribution and communities during migration. I conducted biweekly avian surveys in 36-40 wetlands from mid-February through mid-May, 2002-2004. Concurrently, I recorded behaviors of wetland birds during 1 of 6 time periods, using a flock scan technique. I measured 16 local wetland habitat variables in mid-May of each year, including percent emergent vegetation, water depth and organic matter depth. Using ArcView and various spatial datasets, I calculated landscape variables for each study wetland within 5 and 10 km. Landscape variables included area, number of patches, and mean patch size of agricultural land, grassland, wetlands, riparian area, and land with high sedimentation potential. Using multiple linear regression, I tested hypotheses about how local and landscape variables influenced species richness, diversity, and abundance of geese, dabbling ducks, diving ducks, shorebirds, and wading birds. The best models containing local and landscape variables for each dependent variable were selected using Akaike’s Information Criterion. I observed an estimated 945,333 individual migratory wetland birds representing 61 species during 2002 surveys (n = 637), 517,650 birds representing 62 species during 2003 surveys (n = 873), and 1,097,950 birds representing 64 species during 2004 surveys (n = 955). Wetland area had a positive influence on goose abundance in all years, whereas percent emergent vegetation and hunting pressure had negative influences. Models predicting dabbling duck abundance were variable among years; however, number of wetlands within 5 km was the best predictor of dabbling duck abundance. Area of agriculture within 10 km of a wetland had a positive influence on dabbling duck abundance in years with low precipitation (2002 and 2003), whereas wetland vegetation was important for dabbling ducks in the wetter year (2004). Wetland area and percent of vegetation composed of inner marsh (drawdown and aquatic bed species) were the best and most consistent predictors of diving duck abundance. Shorebird abundance was best predicted by wetland area and area of agricultural land within 10 km. Wetland area was the only consistent predictor of wading bird abundance. Models predicting species richness contained wetland area as a positive predictor and water depth as a negative predictor. In addition, percent emergent vegetation was a positive predictor of species richness, indicating that species richness was greatest in wetlands with intermediate levels of vegetation. To determine for what purpose birds are using wetlands during migration, I examined the effects of time period, hunting pressure, and year on behavior. I used a multivariate analysis of variance to test for differences in behavior among time periods, hunting categories (hunted within season, hunted out of season, and closed to hunting), and years for geese, dabbling ducks, diving ducks, and shorebirds. I also compared behaviors of early (before March 17) and late (after March 17) migrating dabbling ducks to determine whether a greater proportion of early migrants were observed feeding in wetlands than later migrants. Goose behavior did not differ among time periods; however, a smaller proportion of geese was observed feeding on hunted wetlands than unhunted wetlands in 2004. A smaller proportion of dabbling ducks was observed feeding on hunted wetlands compared to unhunted wetlands and in 2004 compared to other years. Diving duck behavior did not differ among time periods, years, or hunting categories. Shorebirds spent most of the time feeding; however, proportion of birds feeding was lower in 2004 than other years. Early migrating dabbling ducks fed less and rested more than did later migrants. I used null model analysis to examine spatial and temporal co-occurrence patterns of geese, dabbling ducks, diving ducks, and shorebirds. I also calculated species association values to determine if dabbling ducks were avoiding wetlands occupied by snow geese (Chen caerluscens). Goose species co-occurred less often than expected in all years of the study, whereas co-occurrence patterns of dabbling ducks were not different than expected by chance in all years. However, when evaluated at a weekly scale, dabbling ducks co-occurred less often than expected during weeks of peak migration (high abundance). Diving ducks co-occurred less often than expected in 2002 and 2004 but not in 2003, whereas shorebirds co-occurred less often than expected in all years. The majority of association values among snow geese and dabbling species were positive, indicating that dabbling ducks are not avoiding wetlands with snow geese. However, negative associations among snow geese and dabbling ducks species might be observed in high precipitation years, when greater wetland availability would permit segregation and increase the chances of detecting co-occurrence patterns. Wetland conservation in the RWB should focus on providing wetland complexes for migratory birds, particularly dabbling ducks. In addition, allowing wetlands to go through their natural hydrologic cycle should promote intermediate levels of emergent vegetation, which will increase use by dabbling ducks, shorebirds, and wading birds, while discouraging goose use of these wetlands. Spring hunting, especially in low precipitation years, causes a re-distribution of geese and dabbling ducks as well as decreasing dabbling duck feeding opportunities. During dry years, flooding temporary and seasonal wetlands and closing them to hunting will help offset the effects of hunting on non-target species by providing more protected feeding areas. In addition, a clearly defined, comprehensive plan for measuring the success of these objectives, as well as standardized monitoring protocols, are necessary for incorporating adaptive management into the conservation goals of the RWBJV. In particular, the ability to quickly and accurately assess wetland availability in the RWB will be crucial to making the best possible management decisions on where and when to distribute water on the landscape.Item Mineralogical and chemical relationships of a playa and associated upland soil from the High Plains coarse-textured soil zone(Texas Tech University, 1971-05) Miller, Glen BurrowNot availableItem Mineralogy of a playa soil and underlying sediments from the High Plains medium-textured soil zone(Texas Tech University, 1970-12) Davis, Kenneth RayThe primary objectives of this study were (a) to determine the mineralogy of a selected playa soil and its underlying sediments and (b) to determine the relationship of the sediments to the associated upland soils. The mineralogical and chemical data obtained may prove valuable in determining the use of playa lakes for aquifer recharge purposes, water storage basins, and as catchment basins for various effluents.Item Pathogenic bacteria of urban playa lakes(Texas Tech University, 1996-12) Westerfield, Max MurrayControl of urban surface water quality has been an important goal for federal and state regulators since the passage of the Clean Water Act (CWA) in 1972. Since then, taxpayers and the private sector have spent more than $541 billion on water pollution control in the USA (Carlin, 1990). The reduction of urban water pollution by "end-of-pipe" controls on industrial and municipal point sources has been the primary mechanism to meet CWA guidelines. Less emphasis has been placed on nonpoint source pollution (NPS), i.e., those pollutants mobilized by storm events and transported by runoff across the land surface (Niedzialkowski and Athayde, 1985). NPS pollution, by its very nature, is much more difficult to identify, measure, and control than point source pollution. Conflicts between some federal agency policies and state water quality goals, insufficient data to define NPS impacts and control effectiveness, and politics of local land-use control are also major barriers to controlling NPS pollution (USGAO, 1990). In a 1984 report to Congress, the US Environmental Protection Agency (USEPA) concluded that NPS was the principle cause of the nation's remaining water quality problems. However, only in recent years have studies begun to tackle the problem of NPS pollution. NPS pollution results from diffuse land-use activities that diminish the quality of groundwater and surface water (Spooner et al., 1991). Episodic inputs of stormwater runoff deliver a variety of nutrients and allochthonous materials that drive rapid fluctuations in the quality of receiving waters. Studies have shown that a large proportion of metals, organics, toxics, nutrients, and dissolved solids are attributable to NPS pollution and stormwater runoff (Gianessi and Peskin, 1981; Livingston and Cox, 1989). Impervious, man-made surfaces in urban settings increase the amount of runoff from roofs, lawns, parking lots, streets, gutters, city parks and playgrounds. Rainwater flows down the path of least resistance, acquiring a wide array of contaminants en route to the urban impoundment. The urban impoundment's proximity to humans increases the likelihood of contamination, human to water and water to human.Item Permian salt dissolution related to alkaline lake basins, southern High Plains, Texas(Texas Tech University, 1986-05) Temple, James MNot availableItem Species diversity of aquatic macroinvertebrates in playa lakes: island biogeographic and landscape influences(Texas Tech University, 1997-12) Hall, Dianne L.Patterns of species diversity have long intrigued ecologists. This fascination has resulted in numerous theories explaining differences among sites in species diversity. Two such theories are those pertaining to island biogeography and landscape ecology. They differ in the import placed on patch versus matrix characteristics. Island biogeographic theory suggests that patch characteristics are the foremost influences on diversity. Conversely, landscape ecology proposes that attributes of the surrounding matrix are of primary significance. Playas of the Southern High Plains are an excellent environment in which to study the relative influence of patch versus matrix characteristics. They are numerous and surrounded by a mosaic of landuse practices. These ephemeral lakes differ greatly in size and contain an abundance of aquatic macroinvertebrates. Macroinvertebrates were sampled three times over a two month period and were categorized as resident or transient species based on life history characteristics. Species richness and diversity were analyzed for the effects of landuse practices, basin size, and surface area via analysis of covariance. In addition, G-tests of independence were used to analyze the influence of landuse practices and surface area on species composition. Surrounding landuse practices were found to influence resident species richness and species composition; total species richness was sensitive to basin size. Surface area affected total, resident, and transient species richness, resident species diversity, and species composition. However, all relationships were contingent on sampling period. Regression analyses revealed that resident species richness and diversity were influenced more by island biogeographic characteristics than by landscape attributes. However, the converse was true for transient species richness and diversity. Neither resident nor transient species richness and diversity were related strongly to differences in water quality. Both island biogeographic and landscape characteristics affect the diversity of macroinvertebrates in playa lakes. However, the extent of the influence of these two factors is dependent on life history strategy of the biota and time since inundation. The idiosyncratic pattern of species diversity is a reflection of the stochastic nature of playa inundation overlain by the effects of island biogeographic and landscape processes.Item Species diversity of aquatic macroinvertebrates in playa lakes: island biogeographic and landscape influences(Texas Tech University, 1997-12) Hall, Dianne L.Patterns of species diversity have long intrigued ecologists. This fascination has resulted in numerous theories explaining differences among sites in species diversity. Two such theories are those pertaining to island biogeography and landscape ecology. They differ in the import placed on patch versus matrix characteristics. Island biogeographic theory suggests that patch characteristics are the foremost influences on diversity. Conversely, landscape ecology proposes that attributes of the surrounding matrix are of primary significance. Playas of the Southern High Plains are an excellent environment in which to study the relative influence of patch versus matrix characteristics. They are numerous and surrounded by a mosaic of landuse practices. These ephemeral lakes differ greatly in size and contain an abundance of aquatic macroinvertebrates.