Roadside habitat through major urban areas may offer remnant examples of natural grasslands.These habitats may be subjected to frequent as mowing and exposure to automobile emissions and runoff.This study was conducte...Roadside habitat through major urban areas may offer remnant examples of natural grasslands.These habitats may be subjected to frequent as mowing and exposure to automobile emissions and runoff.This study was conducted on interstate highway right-of-ways in San Antonio,Texas,U.S.A.We compared the vegetation species and diversity,and the organic carbon of leaf litter,plants,and soils.Two non-native grasses accounted for 50.9% cover,while all native forbs and grasses accounted for only 9.8% cover.The mean biomass of nonnative grasseswas 4.5 times greater than that of all native species.Organic carbon content of leaf litter,plants,and soils was variable among the study sites,possibly due to management practices and a drought that occurred during the study.Themean organic carbon content in the upper 20 cm soil was 5.0 kg C/m^(2) and organic carbon content was greater in the upper 10 cm than organic carbon in the 10.1 to 20 cm portion.Cynodon dactylon and Bouteloua curtipendula exhibited the greatest photosynthesis efficiency indicating these grasses are more adaptable to hot summer temperatures found in Central Texas.The organic carbon content along a major interstate was 13,793 kg·C/ha for leaf litter,vegetation,and the upper 20 cm of the soil.We conclude that interstate highways provide habitat for some native species,but the vegetation along right-of-ways is dominated by two non-native grasses.It appears unlikely that roadside habitat can be restored to resemble native grasslands without large scale and costly restoration efforts.展开更多
Texas experienced the worst drought in its 100-year history in 2011,resulting in the death of approximately 300 million trees.The high number of sudden deaths had a significant impact on forest ecosystems.This study a...Texas experienced the worst drought in its 100-year history in 2011,resulting in the death of approximately 300 million trees.The high number of sudden deaths had a significant impact on forest ecosystems.This study aimed to gain insight into the long-term and combined impacts of drought-induced forest tree deaths and their effects on biomass.This study used data obtained from 1797 National Forest Inventory(NFI)plots to analyze trends and major causes of changes in tree biomass at the sample plot level in East Texas forests over the past 20 years(2000-2019).In this study,forest trees in East Texas were divided into diameter at breast height(dbh),height,stand types,latitude,elevation,ecological zones,and FIA Unit.Principal component analysis(PCA)was also performed using drought intensity,drought duration,the four competing factor indicators,and the biomass loss rate of forest trees to better understand r drought impacts on forest trees.The results showed the lowest biomass loss rate of Pine species.Similarly,trees with shorter height and smaller dbh experienced a higher biomass loss rate.A higher biomass loss rate was observed in natural forests,West Gulf Coastal Plain and Plain and Southern East Texas ecoregion experienced higher biomass loss.Principal component analyses of drought intensity,drought duration,and the four competing metrics revealed that overall drought was the main contributor to biomass loss rates,and that drought intensity and drought duration had comparable effects on biomass loss rates.展开更多
This research directly supported the author’s thesis work in partial fulfilment of Master of Science in biology from the University of North Texas(United States)from August 1996 to September 1997.Two sites at Lake Ra...This research directly supported the author’s thesis work in partial fulfilment of Master of Science in biology from the University of North Texas(United States)from August 1996 to September 1997.Two sites at Lake Ray Roberts,Denton County,Texas(United States)were examined and contrasted for productivity.The site located in the pelagic zone exhibited a slight,thermal gradient with no stratification,and a slightly stratified clinograde oxygen profile which is typical for summer-stratified eutrophic lakes.The site located in the shallow,littoral zone exhibited high,increasing turbidity with depth,marked by shallow light attenuation through the water column.Temperature was constant at every depth in the littoral site,with a slight,clinograde oxygen profile,typical for shallow,littoral areas subject to wind-induced mixing.Volume estimations of chlorophyll-α shows a strong presence in the euphotic zone,indicating photosynthesis occurs until approximately 2.2 m below the surface.The shallow,littoral site showed the basic signs of higher productivity than the open,pelagic site.展开更多
This study evaluates the dynamics of trace metals impacts on the ecosystems of the Bartlett Pond, a small shallow wetland pond located in Laredo, Texas by analyzing sediment samples taken from four quadrants of the po...This study evaluates the dynamics of trace metals impacts on the ecosystems of the Bartlett Pond, a small shallow wetland pond located in Laredo, Texas by analyzing sediment samples taken from four quadrants of the pond. The concentrations of trace elements in sediment samples are highest for iron (Fe), followed by chromium (Cr), then lead (Pb), with lower concentration of antimony (Sb), cobalt (Co), arsenic (As), cadmium (Cd), and the lowest concentration being thallium (Tl) within Bartlett Pond. The sediment quality of the pond is acceptable for organisms and the environment as trace element concentrations (e.g. As, Cd, Cr, and Pb) are within the probable effect concentration (PEC) of National Ocean and Atmospheric Administration (NOAA) guidelines although the PEC values for Co, Fe, Sb and Tl are not given. Bivariate and multivariate correlation analysis shows that most trace elements exhibit a strong positive correlation among them indicating the same anthropogenic sources and biogeochemical processes control these trace elements concentrations within the pond. We provided a comprehensive snapshot of trace element concentrations in sediments through descriptive analysis, laying the foundation for future environmental risk assessments. Correlation analysis of eight trace elements helped identify relationships, offering insights into pollution sources and potential health impacts. Additionally, univariate and multivariate predictive analyses generated numerous models, extending beyond the interpretation of partial and full regression coefficients. We also included graphical analyses of trace element variations, which are critical for understanding environmental processes and geochemical patterns. These findings advance our understanding about trace metals dynamics in sediments and may be a valuable reference for ecosystems and environmental management of different landscapes.展开更多
Changes in tree mortality due to severe drought can alter forest structure,composition,dynamics,ecosystem services,carbon fl uxes,and energy interactions between the atmosphere and land surfaces.We utilized long-term(...Changes in tree mortality due to severe drought can alter forest structure,composition,dynamics,ecosystem services,carbon fl uxes,and energy interactions between the atmosphere and land surfaces.We utilized long-term(2000‒2017,3 full inventory cycles)Forest Inventory and Analysis(FIA)data to examine tree mortality and biomass loss in drought-aff ected forests for East Texas,USA.Plots that experienced six or more years of droughts during those censuses were selected based on 12-month moderate drought severity[Standardized Precipitation Evaporation Index(SPEI)-1.0].Plots that experienced other disturbances and inconsistent records were excluded from the analysis.In total,222 plots were retained from nearly 4000 plots.Generalized nonlinear mixed models(GNMMs)were used to examine the changes in tree mortality and recruitment rates for selected plots.The results showed that tree mortality rates and biomass loss to mortality increased overall,and across tree sizes,dominant genera,height classes,and ecoregions.An average mortality rate of 5.89%year−1 during the study period could be incited by water stress created by the regional prolonged and episodic drought events.The overall plot and species-group level recruitment rates decreased during the study period.Forest mortality showed mixed results regarding basal area and forest density using all plots together and when analyzed the plots by stand origin and ecoregion.Higher mortality rates of smaller trees were detected and were likely compounded by densitydependent factors.Comparative analysis of drought-induced tree mortality using hydro-meteorological data along with drought severity and length gradient is suggested to better understand the eff ects of drought on tree mortality and biomass loss around and beyond East Texas in the southeastern United States.展开更多
Understanding physiological responses and drought adaptation strategies of woody plant leaf traits in sub-humid to semi-arid regions is of vital importance to understand the interplay between ecological processes and ...Understanding physiological responses and drought adaptation strategies of woody plant leaf traits in sub-humid to semi-arid regions is of vital importance to understand the interplay between ecological processes and plant resource-allocation strategies of different tree species.Seasonal variations of leaf morphological traits,stoichiometric traits and their relationships of two drought tolerant woody species,live oak(Quercus virginiana)and honey mesquite(Prosopis glandulosa)and two less drought tolerant species,sugarberry(Celtis laevigata)and white ash(Fraxinus americana)were analyzed in a sub-humid to semi-arid area of south Texas,USA.Our findings demonstrate that for the two drought tolerant species,the leguminous P.glandulosa had the highest specific leaf area,leaf N,P,and lowest leaf area and dry mass,indicating that P.glandulosa adapts to an arid habitat by decreasing leaf area,thus reducing water loss,reflecting a resource acquisition strategy.While the evergreen species Q.virginiana exhibited higher leaf dry mass,leaf dry matter content,C content,C:N,C:P and N:P ratios,adapts to an arid habitat through increased leaf thickness and thus reduced water loss,reflecting a resource conservation strategy in south Texas.For the two less drought tolerant deciduous species,the variations of leaf traits in C.laevigata and F.americana varied between Q.virginiana and P.glandulosa,reflecting a trade-off between rapid plant growth and nutrient maintenance in a semi-arid environment.展开更多
This study addresses sustainable transportation in the Texas Urban Triangle at the regional scale. Its aim is to determine the most suitable corridor for new transport infrastructure by employing a spatial decision su...This study addresses sustainable transportation in the Texas Urban Triangle at the regional scale. Its aim is to determine the most suitable corridor for new transport infrastructure by employing a spatial decision support system proposed in this project. The system is being tested through its application to a prototype corridor parallel to Interstate 35 between San Antonio and Austin. The basic research questions asked are spatial in nature, so accordingly the geographic information system is the primary method of data analysis. The overall modeling approach is devoted to answering the following questions: What are the considerations to support sustainable growth? What scale or type of infrastructure is necessary? And how to adequately model the transportation corridors to meet the demands and to sustain the living environment at the same time?展开更多
The continued decline in the availability of water from the Ogallala Aquifer in the Texas Panhandle has led to an increased interest in conservation policies designed to extend the life of the aquifer and sustain rura...The continued decline in the availability of water from the Ogallala Aquifer in the Texas Panhandle has led to an increased interest in conservation policies designed to extend the life of the aquifer and sustain rural economies. Four counties were chosen for evaluation. This study evaluates the effectiveness of five policies in terms of changes in the saturated thickness, crop mix, water use per acre, and the net present value of farm profits over a 60-year planning horizon. The dynamic optimization models were developed using GAMS for the baseline as well as one for all five of the policy alternatives for each county. Results indicate that the policy scenarios of biotechnology adoption and a water use restriction will conserve the most water among the policies analyzed. In terms of economic returns, the biotechnology adoption policy by far provides the greatest benefit to producers due to yield increases that are estimated with current annual growth rates in new seed varieties. The water use restriction policy, on the other hand, has the lowest net present value of returns, indicating that conservation is accompanied with significant costs to producers. The irrigation adoption technology scenario is the next best policy in terms of net present value of returns (following biotechnology);however, it ranks last in terms of reducing aquifer depletion. It is important to note that while the models do not perfectly predict the factors being evaluated, it is the basis for comparison between the policy scenarios which are important. These comparisons will aid policy makers in determining the most effective strategy to conserve water while simultaneously considering the economic costs to producers. In addition, the results of this study can be applied to other areas facing similar conditions, either currently or in the future, throughout the Texas Panhandle.展开更多
As a hazard, flood is an extremely important indicator of how a city is resilient to waterborne diseases and epidemics. Over many decades, flood as a hazard has been a major factor in inducing displacement of marginal...As a hazard, flood is an extremely important indicator of how a city is resilient to waterborne diseases and epidemics. Over many decades, flood as a hazard has been a major factor in inducing displacement of marginalized section of the people. Austin city within Central Texas has been identified as one of the major hotspots for flooding in recent decades. Thus, the objectives of the paper are two folded: 1) Empirically, we analyzed and mapped out the susceptibility levels from the factors of physical environments to assess the risk of urban flooding (rainfall data, surface water bodies and topography);in Austin, Texas and 2) Methodologically, we created a re-useable ArcGIS scripting tool that can be used by researchers to automate the process of flood risk modelling with certain criteria. The paper showcases a novel time sensitive building of a tool which will enable better visibility of flood within the city of Austin.展开更多
With the increased attention on community sustainability and resilience, different poles have developed voicing similarities and/or differences of the two concepts. This study quantifies adaptive capacity of Jefferson...With the increased attention on community sustainability and resilience, different poles have developed voicing similarities and/or differences of the two concepts. This study quantifies adaptive capacity of Jefferson County, Texas, one of the coastal communities at the Gulf of Mexico having some of the worse adverse effects. Review of existing methods is presented. Analyses were conducted for the last ten years: from 2005 to 2014. Interestingly, statistical analyses showed that the County’s socio-economic profile or indicators have not changed throughout the ten years, but the environmental, institutional, and infrastructure indicators have. Focusing on one location magnifies the adaptive capacity of Jefferson County, the temporal aspect of both perspectives, and the relevance of existing methods to this community with its peculiarities. Future assessments need to be based on primary data collected through participatory engagement of all stakeholders. This calls for attempts to quantify adaptive capacity using the comparatively more challenging deductive reasoning, which would allow for incorporation of more risks and thus higher readiness.展开更多
This research evaluates the responses of hydrology and geomorphology regarding climate change and illustrates the change in regional streamflow during the period 1955-2001. The Neches River Basin, Texas, is an importa...This research evaluates the responses of hydrology and geomorphology regarding climate change and illustrates the change in regional streamflow during the period 1955-2001. The Neches River Basin, Texas, is an important source of water for fanning, cities, and electrical power production. A 15.9% increase in precipitation and a 20.4% increase in streamflow discharge were observed. The areas of river-flow boundaries also increased. The hydrologic changes appear to be associated with the geomorphic adjustments. To accomplish this research, the Neches River Basin is evaluated using hydro-climate data, historical aerial photography, and GIS in a multiscale approach by using linked geomorphic systems. Changes in the streamflow discharge are main factors that must be considered in undertaking a hydrological impact assessment of climate change.展开更多
Chronic obstructive pulmonary disease (COPD) is one of the major causes of morbidity and mortality in the United State. The investigation of the continuing increase in its prevalence and mortality has increased attemp...Chronic obstructive pulmonary disease (COPD) is one of the major causes of morbidity and mortality in the United State. The investigation of the continuing increase in its prevalence and mortality has increased attempts to further understand its causes and how to manage it. Understanding the spatial and temporal distribution of COPD emergency room (ER) visits in Harris County (Houston) can guide these efforts in a uniform yet diverse setting like this one. The objectives of this study were to identify the temporal and spatial variations of COPD emergency room visits adjusted by age, gender, ethnicity, day of the week, month, and year, and to estimate the odds ratio of COPD emergency room visits adjusted by the six risk factors. The dataset used were extracted from two resources: ER Utilization Study and Harris County centroid coordinates. Exploratory statistical analyses were conducted to study the spatiotemporal disparities and investigate associations. Logistic regression was performed to estimate the odds ratio of COPD primary diagnosis adjusted for age, race, gender, day of the week, month, and year. The number of COPD ER visits kept increasing from 2004 throughout 2009 but there was a significant increase after the year 2005. Spring and summer had lower visits compared to winter and autumn. Lowest visits were during June and July and higher during December and January. Tuesdays had the highest number of visits compared to the remaining days of the week with Saturdays having had the lowest number of visits. Temporal analyses show the continuous increase in COPD ER visits in Houston as well as the consistent spatial disparities between zip regions. After adjustment for age, race, gender, day of the week, month, and year, there were statistically significant associations between emergency room chronic obstructive pulmonary disease diagnoses in Houston, Texas, with these six predictors.展开更多
Although many studies have explored the quality of Texas groundwater, very few have investigated the concurrent distributions of more than one pollutant, which provides insight on the temporal and spatial behavior of ...Although many studies have explored the quality of Texas groundwater, very few have investigated the concurrent distributions of more than one pollutant, which provides insight on the temporal and spatial behavior of constituents within and between aquifers. The purpose of this research is to study the multivariate spatial patterns of seven health-related Texas groundwater constituents, which are calcium (Ca), chloride (Cl), nitrate (NO3), sodium (Na), magnesium (Mg), sulfate (SO4), and potassium (K). Data is extracted from Texas Water Development Board’s database including nine years: 2000 through 2008. A multivariate geostatistical model was developed to examine the interactions between the constituents. The model had seven dependent variables—one for each of the constituents, and five independent variables: altitude, latitude, longitude, major aquifer and water level. Exploratory analyses show that the data has no temporal patterns, but hold spatial patterns as well as intrinsic correlation. The intrinsic correlation allowed for the use of a Kronecker form for the covariance matrix. The model was validated with a split-sample. Estimates of iteratively re-weighted generalized least squares converged after four iterations. Matern covariance function estimates are zero nugget, practical range is 44 miles, 0.8340 variance and kappa was fixed at 2. To show that our assumptions are reasonable and the choice of the model is appropriate, we perform residual validation and universal kriging. Moreover, prediction maps for the seven constituents are estimated from new locations data. The results point to an alarmingly increasing levels of these constituents’ concentrations, which calls for more intensive monitoring and groundwater management.展开更多
The Texas High Plains faces projections of increasing temperature and declining precipitation in the future on account of its semi-arid climate. This research evaluated the impact of climatic variability on agricultur...The Texas High Plains faces projections of increasing temperature and declining precipitation in the future on account of its semi-arid climate. This research evaluated the impact of climatic variability on agricultural land prices under different land uses in the Texas High Plains, employing the Ricardian approach of land climate pricing over a study period of 1991-2011. The results indicate that climatic variability had a greater impact on irrigated land prices as compared to dryland and ranchland. This study could be instrumental in predictive market analyses of rural land values in semi-arid economies which are vulnerable to future climate change.展开更多
Integrating alleles from Gossypium species into G.hirsutum is important for the enhancement of genetic variability and for creating polymorphism useful in molecular mapping studies.Through collaborative efforts,severa...Integrating alleles from Gossypium species into G.hirsutum is important for the enhancement of genetic variability and for creating polymorphism useful in molecular mapping studies.Through collaborative efforts,several species including G.barbadense,G.tomentosum,and G.mustelinum展开更多
The trace elements chemistry of Bartlett Pond, a small shallow wetland pond in Laredo, Southern Texas, was sampled to evaluate the dynamics of trace elements impacts on water quality and ecosystems ecology of the pond...The trace elements chemistry of Bartlett Pond, a small shallow wetland pond in Laredo, Southern Texas, was sampled to evaluate the dynamics of trace elements impacts on water quality and ecosystems ecology of the pond. Two types of fish (bass and tilapia) were also sampled to see the trace element accumulation in different parts of their body. The concentrations of trace elements in water samples were found in the following order: Fe ≫Sb > Pb > As ≫Co > Tl > Cr > Cd within Bartlett Pond. Overall, the water quality of the pond is unacceptable for drinking and any other purposes as trace element concentrations (e.g. As, Cd, Co, Cr, Pb, Fe, Sb and Tl) are exceedingly higher (several fold) than the WHO and US EPA guidelines. Predictive and correlation analysis shows that most trace elements exhibit a strong positive correlation among them indicating the same anthropogenic sources and biogeochemical processes regulate these trace elements within the pond. Distributions of the trace elements in water exhibit different shapes mostly as positively skewed distribution for As, Cd, Co, Cr, and Tl, symmetrical distribution for Fe and almost symmetrical distribution for Pb and Sb. Concentrations of As, Co and Tl accumulated much higher in different parts of the Bass than Tilapia fish. The concentrations of As, Tl, Co, and Sb appeared significantly higher in different parts of the body of both Bass and Tilapia than the maximum SRM certified values. Accumulation of these contaminants in fish tissues pose increased health risks to humans who consume these contaminated fish although fishing is prohibited. Anthropogenic activities in the region primarily degrade the whole pond ecosystem ecology of the Bartlett Pond and waters of this pond to be not recommended for any use. These findings may be useful for the scientific community and concerned authorities to improve understanding about these precious natural resources and conservation of the ecosystem ecology.展开更多
Spatial and temporal heterogeneity in pollutant concentrations exists at the intra-urban level. In this research work, the concentrations of various pollutants and meteorological parameters are characterized between v...Spatial and temporal heterogeneity in pollutant concentrations exists at the intra-urban level. In this research work, the concentrations of various pollutants and meteorological parameters are characterized between various central ambient monitoring sites at Houston, TX, and the Rio Grande Valley Regions of South Texas. Meteorological (temperature, relative humidity, wind speed and direction) and pollutant (O<sub>3</sub>, SO<sub>2</sub>, CO, NO<sub>2</sub>, and various PM species) concentrations were downloaded from the appropriate Texas Commission on Environmental Quality (TCEQ) Central Ambient Monitoring Station (CAMS) sites for the year 2016. Correlation Analyses and Coefficient of Divergence (COD) analyses suggest that statistically significant differences occur between the various TCEQ CAMS sites in the Houston Region. Findings from this study will help the various stakeholders involved in assessing the overall air pollutants exposure burden for the local populations.展开更多
This article returns to the topic of sustainability. West Texas, mainly known for its cotton and cattle production, is facing problems related to the dispensation of agricultural waste produced by these operations. Th...This article returns to the topic of sustainability. West Texas, mainly known for its cotton and cattle production, is facing problems related to the dispensation of agricultural waste produced by these operations. The article looks at the ways of handling agricultural waste and the opportunities of dispensing it in West Texas. Since between 30 - 40 percent of food produced in the US is not consumed, reduction of food waste is another sustainability problem that, when solved, would lead to the reduction of agricultural production and, in turn, the reduction of agricultural waste. Waste reduction management practices of large food chain stores in West Texas are discussed, with a final goal of bringing waste to a zero level. Public sources of sustainable agricultural and non-agricultural waste handling are also mentioned. This research adds to the previous knowledge on sustainability by discussing agricultural waste practices of a specific local area, i.e. West Texas.展开更多
The purpose of this study was to assess the feasibility of growing olives along coastal Texas where the winter temperatures are relatively mild compared to most olive growing regions. For this purpose five sites along...The purpose of this study was to assess the feasibility of growing olives along coastal Texas where the winter temperatures are relatively mild compared to most olive growing regions. For this purpose five sites along the Texas coastline （Seadrift, Galveston, Brazoria, Santa Fe, and Orange） were evaluated for feasibility of growing olives. In addition, two non-coastal sites （Carrizo Springs and Weslaco） were also included in the study for comparative purposes. Flowering and fruiting data were collected during four seasons starting from the 2005-2006 until the 2008-2009 season. In addition to the flowering and fruiting data, half-hourly temperature data were also collected at each site during each season. The results indicate that while olives can grow on all of the sites tested, there is a greater probability of success for commercial growing of olive between and along coastal sites where large scale experiment are highly recommended for rigorous evaluation of potential for commercial production of olives in these areas. In conclusion, there is a good probability that olives could be grown along the northeast coastline of Texas.展开更多
Round Top Mountain in Hudspeth County, west Texas, USA is a surface-exposed rhyolite intrusion enriched in Y and heavy rare earth elements （HREEs）, as well as Nb, Ta, Be, Li, F, Sn, Rb, Th, and U. The massive tonnag...Round Top Mountain in Hudspeth County, west Texas, USA is a surface-exposed rhyolite intrusion enriched in Y and heavy rare earth elements （HREEs）, as well as Nb, Ta, Be, Li, F, Sn, Rb, Th, and U. The massive tonnage, estimated at well over 1 billion tons, of the deposit makes it a target for recovery of valuable yttrium and HREEs （YHREEs）, and possibly other scarce ele-ments. Because of the extremely fine grain size of the mineralized rhyolite matrix, it has not been clear which minerals host the YHREEs and in what proportions. REE-bearing minerals reported in the deposit included bastn？site-Ce, Y-bearing fluorite, xeno-time-Y, zircon, aeschynite-Ce, a Ca-Th-Pb fluoride, and possibly ancylite-La and cerianite-Ce. Extended X-ray absorption fine struc-ture （EXAFS） indicated that virtually all of the yttrium, a proxy for the HREEs, resided in a coordination in the fluorite-type crystal structure, rather than those in the structures of bastn？site-Ce and xenotime-Y. The YREE grade of the Round Top deposit was just over 0.05%, with 72%of this consisting of YHREEs. This grade was in the range of the South China ionic clay deposits that supply essentially all of the world’s YHREEs. Because the host Y-bearing fluorite is soluble in dilute sulfuric acid at room temperature, a heap leaching of the deposit appeared feasible, aided by the fact that 90%-95%of the rock consists of unreactive and insoluble feld-spars and quartz. The absence of overburden, remarkable consistency of mineralization grade throughout the massive rhyolite, prox-imity （a few km） to a US interstate highway, major rail systems and gas and electricity, temperate climate, and stable political location in the world’s largest economy all enhanced the potential economic appeal of Round Top.展开更多
基金supported by the Transportation Consortium of South-Central States (No.18HSTSA01)support was provided by the University of San Antonio, Department of Integrated Biology from the principal investigator’s startup funds to support student research assistants.
文摘Roadside habitat through major urban areas may offer remnant examples of natural grasslands.These habitats may be subjected to frequent as mowing and exposure to automobile emissions and runoff.This study was conducted on interstate highway right-of-ways in San Antonio,Texas,U.S.A.We compared the vegetation species and diversity,and the organic carbon of leaf litter,plants,and soils.Two non-native grasses accounted for 50.9% cover,while all native forbs and grasses accounted for only 9.8% cover.The mean biomass of nonnative grasseswas 4.5 times greater than that of all native species.Organic carbon content of leaf litter,plants,and soils was variable among the study sites,possibly due to management practices and a drought that occurred during the study.Themean organic carbon content in the upper 20 cm soil was 5.0 kg C/m^(2) and organic carbon content was greater in the upper 10 cm than organic carbon in the 10.1 to 20 cm portion.Cynodon dactylon and Bouteloua curtipendula exhibited the greatest photosynthesis efficiency indicating these grasses are more adaptable to hot summer temperatures found in Central Texas.The organic carbon content along a major interstate was 13,793 kg·C/ha for leaf litter,vegetation,and the upper 20 cm of the soil.We conclude that interstate highways provide habitat for some native species,but the vegetation along right-of-ways is dominated by two non-native grasses.It appears unlikely that roadside habitat can be restored to resemble native grasslands without large scale and costly restoration efforts.
基金supported by a Forest Health Monitoring(FHM)award from the USDA Forest Service(Grant No.:19-DG-11083150-030)to Dr.Weimin Xi。
文摘Texas experienced the worst drought in its 100-year history in 2011,resulting in the death of approximately 300 million trees.The high number of sudden deaths had a significant impact on forest ecosystems.This study aimed to gain insight into the long-term and combined impacts of drought-induced forest tree deaths and their effects on biomass.This study used data obtained from 1797 National Forest Inventory(NFI)plots to analyze trends and major causes of changes in tree biomass at the sample plot level in East Texas forests over the past 20 years(2000-2019).In this study,forest trees in East Texas were divided into diameter at breast height(dbh),height,stand types,latitude,elevation,ecological zones,and FIA Unit.Principal component analysis(PCA)was also performed using drought intensity,drought duration,the four competing factor indicators,and the biomass loss rate of forest trees to better understand r drought impacts on forest trees.The results showed the lowest biomass loss rate of Pine species.Similarly,trees with shorter height and smaller dbh experienced a higher biomass loss rate.A higher biomass loss rate was observed in natural forests,West Gulf Coastal Plain and Plain and Southern East Texas ecoregion experienced higher biomass loss.Principal component analyses of drought intensity,drought duration,and the four competing metrics revealed that overall drought was the main contributor to biomass loss rates,and that drought intensity and drought duration had comparable effects on biomass loss rates.
文摘This research directly supported the author’s thesis work in partial fulfilment of Master of Science in biology from the University of North Texas(United States)from August 1996 to September 1997.Two sites at Lake Ray Roberts,Denton County,Texas(United States)were examined and contrasted for productivity.The site located in the pelagic zone exhibited a slight,thermal gradient with no stratification,and a slightly stratified clinograde oxygen profile which is typical for summer-stratified eutrophic lakes.The site located in the shallow,littoral zone exhibited high,increasing turbidity with depth,marked by shallow light attenuation through the water column.Temperature was constant at every depth in the littoral site,with a slight,clinograde oxygen profile,typical for shallow,littoral areas subject to wind-induced mixing.Volume estimations of chlorophyll-α shows a strong presence in the euphotic zone,indicating photosynthesis occurs until approximately 2.2 m below the surface.The shallow,littoral site showed the basic signs of higher productivity than the open,pelagic site.
文摘This study evaluates the dynamics of trace metals impacts on the ecosystems of the Bartlett Pond, a small shallow wetland pond located in Laredo, Texas by analyzing sediment samples taken from four quadrants of the pond. The concentrations of trace elements in sediment samples are highest for iron (Fe), followed by chromium (Cr), then lead (Pb), with lower concentration of antimony (Sb), cobalt (Co), arsenic (As), cadmium (Cd), and the lowest concentration being thallium (Tl) within Bartlett Pond. The sediment quality of the pond is acceptable for organisms and the environment as trace element concentrations (e.g. As, Cd, Cr, and Pb) are within the probable effect concentration (PEC) of National Ocean and Atmospheric Administration (NOAA) guidelines although the PEC values for Co, Fe, Sb and Tl are not given. Bivariate and multivariate correlation analysis shows that most trace elements exhibit a strong positive correlation among them indicating the same anthropogenic sources and biogeochemical processes control these trace elements concentrations within the pond. We provided a comprehensive snapshot of trace element concentrations in sediments through descriptive analysis, laying the foundation for future environmental risk assessments. Correlation analysis of eight trace elements helped identify relationships, offering insights into pollution sources and potential health impacts. Additionally, univariate and multivariate predictive analyses generated numerous models, extending beyond the interpretation of partial and full regression coefficients. We also included graphical analyses of trace element variations, which are critical for understanding environmental processes and geochemical patterns. These findings advance our understanding about trace metals dynamics in sediments and may be a valuable reference for ecosystems and environmental management of different landscapes.
文摘Changes in tree mortality due to severe drought can alter forest structure,composition,dynamics,ecosystem services,carbon fl uxes,and energy interactions between the atmosphere and land surfaces.We utilized long-term(2000‒2017,3 full inventory cycles)Forest Inventory and Analysis(FIA)data to examine tree mortality and biomass loss in drought-aff ected forests for East Texas,USA.Plots that experienced six or more years of droughts during those censuses were selected based on 12-month moderate drought severity[Standardized Precipitation Evaporation Index(SPEI)-1.0].Plots that experienced other disturbances and inconsistent records were excluded from the analysis.In total,222 plots were retained from nearly 4000 plots.Generalized nonlinear mixed models(GNMMs)were used to examine the changes in tree mortality and recruitment rates for selected plots.The results showed that tree mortality rates and biomass loss to mortality increased overall,and across tree sizes,dominant genera,height classes,and ecoregions.An average mortality rate of 5.89%year−1 during the study period could be incited by water stress created by the regional prolonged and episodic drought events.The overall plot and species-group level recruitment rates decreased during the study period.Forest mortality showed mixed results regarding basal area and forest density using all plots together and when analyzed the plots by stand origin and ecoregion.Higher mortality rates of smaller trees were detected and were likely compounded by densitydependent factors.Comparative analysis of drought-induced tree mortality using hydro-meteorological data along with drought severity and length gradient is suggested to better understand the eff ects of drought on tree mortality and biomass loss around and beyond East Texas in the southeastern United States.
基金funded by the China Scholarship Council(CSC)a research award from Texas A&M University-Kingsville+1 种基金the Natural Science Foundation of Anhui Province(Grant Number 1408085QC57)Youth Science Fund of Anhui Agricultural University(Grant Number 2012zd015)
文摘Understanding physiological responses and drought adaptation strategies of woody plant leaf traits in sub-humid to semi-arid regions is of vital importance to understand the interplay between ecological processes and plant resource-allocation strategies of different tree species.Seasonal variations of leaf morphological traits,stoichiometric traits and their relationships of two drought tolerant woody species,live oak(Quercus virginiana)and honey mesquite(Prosopis glandulosa)and two less drought tolerant species,sugarberry(Celtis laevigata)and white ash(Fraxinus americana)were analyzed in a sub-humid to semi-arid area of south Texas,USA.Our findings demonstrate that for the two drought tolerant species,the leguminous P.glandulosa had the highest specific leaf area,leaf N,P,and lowest leaf area and dry mass,indicating that P.glandulosa adapts to an arid habitat by decreasing leaf area,thus reducing water loss,reflecting a resource acquisition strategy.While the evergreen species Q.virginiana exhibited higher leaf dry mass,leaf dry matter content,C content,C:N,C:P and N:P ratios,adapts to an arid habitat through increased leaf thickness and thus reduced water loss,reflecting a resource conservation strategy in south Texas.For the two less drought tolerant deciduous species,the variations of leaf traits in C.laevigata and F.americana varied between Q.virginiana and P.glandulosa,reflecting a trade-off between rapid plant growth and nutrient maintenance in a semi-arid environment.
文摘This study addresses sustainable transportation in the Texas Urban Triangle at the regional scale. Its aim is to determine the most suitable corridor for new transport infrastructure by employing a spatial decision support system proposed in this project. The system is being tested through its application to a prototype corridor parallel to Interstate 35 between San Antonio and Austin. The basic research questions asked are spatial in nature, so accordingly the geographic information system is the primary method of data analysis. The overall modeling approach is devoted to answering the following questions: What are the considerations to support sustainable growth? What scale or type of infrastructure is necessary? And how to adequately model the transportation corridors to meet the demands and to sustain the living environment at the same time?
文摘The continued decline in the availability of water from the Ogallala Aquifer in the Texas Panhandle has led to an increased interest in conservation policies designed to extend the life of the aquifer and sustain rural economies. Four counties were chosen for evaluation. This study evaluates the effectiveness of five policies in terms of changes in the saturated thickness, crop mix, water use per acre, and the net present value of farm profits over a 60-year planning horizon. The dynamic optimization models were developed using GAMS for the baseline as well as one for all five of the policy alternatives for each county. Results indicate that the policy scenarios of biotechnology adoption and a water use restriction will conserve the most water among the policies analyzed. In terms of economic returns, the biotechnology adoption policy by far provides the greatest benefit to producers due to yield increases that are estimated with current annual growth rates in new seed varieties. The water use restriction policy, on the other hand, has the lowest net present value of returns, indicating that conservation is accompanied with significant costs to producers. The irrigation adoption technology scenario is the next best policy in terms of net present value of returns (following biotechnology);however, it ranks last in terms of reducing aquifer depletion. It is important to note that while the models do not perfectly predict the factors being evaluated, it is the basis for comparison between the policy scenarios which are important. These comparisons will aid policy makers in determining the most effective strategy to conserve water while simultaneously considering the economic costs to producers. In addition, the results of this study can be applied to other areas facing similar conditions, either currently or in the future, throughout the Texas Panhandle.
文摘As a hazard, flood is an extremely important indicator of how a city is resilient to waterborne diseases and epidemics. Over many decades, flood as a hazard has been a major factor in inducing displacement of marginalized section of the people. Austin city within Central Texas has been identified as one of the major hotspots for flooding in recent decades. Thus, the objectives of the paper are two folded: 1) Empirically, we analyzed and mapped out the susceptibility levels from the factors of physical environments to assess the risk of urban flooding (rainfall data, surface water bodies and topography);in Austin, Texas and 2) Methodologically, we created a re-useable ArcGIS scripting tool that can be used by researchers to automate the process of flood risk modelling with certain criteria. The paper showcases a novel time sensitive building of a tool which will enable better visibility of flood within the city of Austin.
文摘With the increased attention on community sustainability and resilience, different poles have developed voicing similarities and/or differences of the two concepts. This study quantifies adaptive capacity of Jefferson County, Texas, one of the coastal communities at the Gulf of Mexico having some of the worse adverse effects. Review of existing methods is presented. Analyses were conducted for the last ten years: from 2005 to 2014. Interestingly, statistical analyses showed that the County’s socio-economic profile or indicators have not changed throughout the ten years, but the environmental, institutional, and infrastructure indicators have. Focusing on one location magnifies the adaptive capacity of Jefferson County, the temporal aspect of both perspectives, and the relevance of existing methods to this community with its peculiarities. Future assessments need to be based on primary data collected through participatory engagement of all stakeholders. This calls for attempts to quantify adaptive capacity using the comparatively more challenging deductive reasoning, which would allow for incorporation of more risks and thus higher readiness.
文摘This research evaluates the responses of hydrology and geomorphology regarding climate change and illustrates the change in regional streamflow during the period 1955-2001. The Neches River Basin, Texas, is an important source of water for fanning, cities, and electrical power production. A 15.9% increase in precipitation and a 20.4% increase in streamflow discharge were observed. The areas of river-flow boundaries also increased. The hydrologic changes appear to be associated with the geomorphic adjustments. To accomplish this research, the Neches River Basin is evaluated using hydro-climate data, historical aerial photography, and GIS in a multiscale approach by using linked geomorphic systems. Changes in the streamflow discharge are main factors that must be considered in undertaking a hydrological impact assessment of climate change.
文摘Chronic obstructive pulmonary disease (COPD) is one of the major causes of morbidity and mortality in the United State. The investigation of the continuing increase in its prevalence and mortality has increased attempts to further understand its causes and how to manage it. Understanding the spatial and temporal distribution of COPD emergency room (ER) visits in Harris County (Houston) can guide these efforts in a uniform yet diverse setting like this one. The objectives of this study were to identify the temporal and spatial variations of COPD emergency room visits adjusted by age, gender, ethnicity, day of the week, month, and year, and to estimate the odds ratio of COPD emergency room visits adjusted by the six risk factors. The dataset used were extracted from two resources: ER Utilization Study and Harris County centroid coordinates. Exploratory statistical analyses were conducted to study the spatiotemporal disparities and investigate associations. Logistic regression was performed to estimate the odds ratio of COPD primary diagnosis adjusted for age, race, gender, day of the week, month, and year. The number of COPD ER visits kept increasing from 2004 throughout 2009 but there was a significant increase after the year 2005. Spring and summer had lower visits compared to winter and autumn. Lowest visits were during June and July and higher during December and January. Tuesdays had the highest number of visits compared to the remaining days of the week with Saturdays having had the lowest number of visits. Temporal analyses show the continuous increase in COPD ER visits in Houston as well as the consistent spatial disparities between zip regions. After adjustment for age, race, gender, day of the week, month, and year, there were statistically significant associations between emergency room chronic obstructive pulmonary disease diagnoses in Houston, Texas, with these six predictors.
文摘Although many studies have explored the quality of Texas groundwater, very few have investigated the concurrent distributions of more than one pollutant, which provides insight on the temporal and spatial behavior of constituents within and between aquifers. The purpose of this research is to study the multivariate spatial patterns of seven health-related Texas groundwater constituents, which are calcium (Ca), chloride (Cl), nitrate (NO3), sodium (Na), magnesium (Mg), sulfate (SO4), and potassium (K). Data is extracted from Texas Water Development Board’s database including nine years: 2000 through 2008. A multivariate geostatistical model was developed to examine the interactions between the constituents. The model had seven dependent variables—one for each of the constituents, and five independent variables: altitude, latitude, longitude, major aquifer and water level. Exploratory analyses show that the data has no temporal patterns, but hold spatial patterns as well as intrinsic correlation. The intrinsic correlation allowed for the use of a Kronecker form for the covariance matrix. The model was validated with a split-sample. Estimates of iteratively re-weighted generalized least squares converged after four iterations. Matern covariance function estimates are zero nugget, practical range is 44 miles, 0.8340 variance and kappa was fixed at 2. To show that our assumptions are reasonable and the choice of the model is appropriate, we perform residual validation and universal kriging. Moreover, prediction maps for the seven constituents are estimated from new locations data. The results point to an alarmingly increasing levels of these constituents’ concentrations, which calls for more intensive monitoring and groundwater management.
文摘The Texas High Plains faces projections of increasing temperature and declining precipitation in the future on account of its semi-arid climate. This research evaluated the impact of climatic variability on agricultural land prices under different land uses in the Texas High Plains, employing the Ricardian approach of land climate pricing over a study period of 1991-2011. The results indicate that climatic variability had a greater impact on irrigated land prices as compared to dryland and ranchland. This study could be instrumental in predictive market analyses of rural land values in semi-arid economies which are vulnerable to future climate change.
文摘Integrating alleles from Gossypium species into G.hirsutum is important for the enhancement of genetic variability and for creating polymorphism useful in molecular mapping studies.Through collaborative efforts,several species including G.barbadense,G.tomentosum,and G.mustelinum
文摘The trace elements chemistry of Bartlett Pond, a small shallow wetland pond in Laredo, Southern Texas, was sampled to evaluate the dynamics of trace elements impacts on water quality and ecosystems ecology of the pond. Two types of fish (bass and tilapia) were also sampled to see the trace element accumulation in different parts of their body. The concentrations of trace elements in water samples were found in the following order: Fe ≫Sb > Pb > As ≫Co > Tl > Cr > Cd within Bartlett Pond. Overall, the water quality of the pond is unacceptable for drinking and any other purposes as trace element concentrations (e.g. As, Cd, Co, Cr, Pb, Fe, Sb and Tl) are exceedingly higher (several fold) than the WHO and US EPA guidelines. Predictive and correlation analysis shows that most trace elements exhibit a strong positive correlation among them indicating the same anthropogenic sources and biogeochemical processes regulate these trace elements within the pond. Distributions of the trace elements in water exhibit different shapes mostly as positively skewed distribution for As, Cd, Co, Cr, and Tl, symmetrical distribution for Fe and almost symmetrical distribution for Pb and Sb. Concentrations of As, Co and Tl accumulated much higher in different parts of the Bass than Tilapia fish. The concentrations of As, Tl, Co, and Sb appeared significantly higher in different parts of the body of both Bass and Tilapia than the maximum SRM certified values. Accumulation of these contaminants in fish tissues pose increased health risks to humans who consume these contaminated fish although fishing is prohibited. Anthropogenic activities in the region primarily degrade the whole pond ecosystem ecology of the Bartlett Pond and waters of this pond to be not recommended for any use. These findings may be useful for the scientific community and concerned authorities to improve understanding about these precious natural resources and conservation of the ecosystem ecology.
文摘Spatial and temporal heterogeneity in pollutant concentrations exists at the intra-urban level. In this research work, the concentrations of various pollutants and meteorological parameters are characterized between various central ambient monitoring sites at Houston, TX, and the Rio Grande Valley Regions of South Texas. Meteorological (temperature, relative humidity, wind speed and direction) and pollutant (O<sub>3</sub>, SO<sub>2</sub>, CO, NO<sub>2</sub>, and various PM species) concentrations were downloaded from the appropriate Texas Commission on Environmental Quality (TCEQ) Central Ambient Monitoring Station (CAMS) sites for the year 2016. Correlation Analyses and Coefficient of Divergence (COD) analyses suggest that statistically significant differences occur between the various TCEQ CAMS sites in the Houston Region. Findings from this study will help the various stakeholders involved in assessing the overall air pollutants exposure burden for the local populations.
文摘This article returns to the topic of sustainability. West Texas, mainly known for its cotton and cattle production, is facing problems related to the dispensation of agricultural waste produced by these operations. The article looks at the ways of handling agricultural waste and the opportunities of dispensing it in West Texas. Since between 30 - 40 percent of food produced in the US is not consumed, reduction of food waste is another sustainability problem that, when solved, would lead to the reduction of agricultural production and, in turn, the reduction of agricultural waste. Waste reduction management practices of large food chain stores in West Texas are discussed, with a final goal of bringing waste to a zero level. Public sources of sustainable agricultural and non-agricultural waste handling are also mentioned. This research adds to the previous knowledge on sustainability by discussing agricultural waste practices of a specific local area, i.e. West Texas.
文摘The purpose of this study was to assess the feasibility of growing olives along coastal Texas where the winter temperatures are relatively mild compared to most olive growing regions. For this purpose five sites along the Texas coastline （Seadrift, Galveston, Brazoria, Santa Fe, and Orange） were evaluated for feasibility of growing olives. In addition, two non-coastal sites （Carrizo Springs and Weslaco） were also included in the study for comparative purposes. Flowering and fruiting data were collected during four seasons starting from the 2005-2006 until the 2008-2009 season. In addition to the flowering and fruiting data, half-hourly temperature data were also collected at each site during each season. The results indicate that while olives can grow on all of the sites tested, there is a greater probability of success for commercial growing of olive between and along coastal sites where large scale experiment are highly recommended for rigorous evaluation of potential for commercial production of olives in these areas. In conclusion, there is a good probability that olives could be grown along the northeast coastline of Texas.
基金Project supported by Research Contracts 26-8211-12 and 26-8211-16 between Texas Rare Earth Resources,Inc.and the University of Texas at El Paso
文摘Round Top Mountain in Hudspeth County, west Texas, USA is a surface-exposed rhyolite intrusion enriched in Y and heavy rare earth elements （HREEs）, as well as Nb, Ta, Be, Li, F, Sn, Rb, Th, and U. The massive tonnage, estimated at well over 1 billion tons, of the deposit makes it a target for recovery of valuable yttrium and HREEs （YHREEs）, and possibly other scarce ele-ments. Because of the extremely fine grain size of the mineralized rhyolite matrix, it has not been clear which minerals host the YHREEs and in what proportions. REE-bearing minerals reported in the deposit included bastn？site-Ce, Y-bearing fluorite, xeno-time-Y, zircon, aeschynite-Ce, a Ca-Th-Pb fluoride, and possibly ancylite-La and cerianite-Ce. Extended X-ray absorption fine struc-ture （EXAFS） indicated that virtually all of the yttrium, a proxy for the HREEs, resided in a coordination in the fluorite-type crystal structure, rather than those in the structures of bastn？site-Ce and xenotime-Y. The YREE grade of the Round Top deposit was just over 0.05%, with 72%of this consisting of YHREEs. This grade was in the range of the South China ionic clay deposits that supply essentially all of the world’s YHREEs. Because the host Y-bearing fluorite is soluble in dilute sulfuric acid at room temperature, a heap leaching of the deposit appeared feasible, aided by the fact that 90%-95%of the rock consists of unreactive and insoluble feld-spars and quartz. The absence of overburden, remarkable consistency of mineralization grade throughout the massive rhyolite, prox-imity （a few km） to a US interstate highway, major rail systems and gas and electricity, temperate climate, and stable political location in the world’s largest economy all enhanced the potential economic appeal of Round Top.
