X. Ben Wu - Academia.edu (original) (raw)
Papers by X. Ben Wu
Circulation, 2008
Background— Torcetrapib, an inhibitor of cholesteryl ester transfer protein, has been shown to in... more Background— Torcetrapib, an inhibitor of cholesteryl ester transfer protein, has been shown to increase the cardiovascular event rate despite conferring a significant high-density lipoprotein cholesterol increase. Using data from the Rating Atherosclerotic Disease Change by Imaging with a New CETP Inhibitor (RADIANCE) trials, which assessed the impact of torcetrapib on carotid intima-media thickness (cIMT), we sought to explore potential mechanisms underlying this adverse outcome. Methods and Results— Data from the RADIANCE 1 and 2 studies, which examined cIMT in 904 subjects with familial hypercholesterolemia and in 752 subjects with mixed dyslipidemia, were pooled. Subjects were randomized to either atorvastatin or torcetrapib combined with atorvastatin. Mean common cIMT progression was increased in subjects receiving torcetrapib plus atorvastatin compared with subjects receiving atorvastatin alone (0.0076±0.0011 versus 0.0025±0.0011 mm/y; P =0.0014). Subjects treated with torcetr...
National Quail Symposium Proceedings, 2017
Although biologists have studied northern bobwhite (Colinus virginianus) genetic diversity and po... more Although biologists have studied northern bobwhite (Colinus virginianus) genetic diversity and population structure, there is little known about the genetic diversity, structure, and relatedness of their winter coveys. Both flexible mating strategies and the fall shuffle may have implications for inbreeding and genetic diversity in northern bobwhite populations. Our goal was to determine genetic diversity and relatedness for coveys on a private ranch in Jim Hogg County in South Texas. During the 2010-2011 and 2011-2012 hunting seasons, 96 northern bobwhites were sampled from 29 coveys. We analyzed 11 northern bobwhite microsatellite DNA loci, measured genetic structure with an Analysis of Molecular Variance and F ST , and determined an inbreeding coefficient (F i). We determined Queller and Goodnight's coefficients of relatedness (R) and then used a maximum-likelihood algorithm in COLONY to assign relationships (parent-offspring, full siblings, and half siblings). Most genetic variation (92%) was within coveys. The overall F ST was 0.073, indicating moderate genetic structure among coveys. Relationship coefficients ranged from À0.82 to 1.00 but most of the bird pairs were unrelated (R ¼À0.004 6 0.002 SE). In 2010-2011, COLONY assigned 130-149 half sibling, 1-4 full sibling, and 0-3 parent-offspring pairs (n ¼ 2,887, 5 trials, probability .0.99). Thirteen coveys (56%) had related individuals (n ¼ 20 pairs). In 2011-2012, COLONY assigned 5-10 half sibling and 1 full sibling pairs (n ¼ 161). Two coveys (33%) had related individuals (2 pairs). The occurrence of relatives in different coveys suggests that the fall shuffle is effective at mixing families and the high half sibling count among coveys may suggest polygamy. These strategies may help northern bobwhite populations maintain moderate genetic diversity.
Redberry juniper (Juniperus pinchotii) is a major prob- lem on Texas rangelands, yet little is kn... more Redberry juniper (Juniperus pinchotii) is a major prob- lem on Texas rangelands, yet little is known about the rate it is increasing. This study estimated long-term rates of change of redberry juniper canopy cover on undisturbed sites and adjacent sites that were either chained or grubbed at five locations in western Texas. Juniper cover was estimated from positive transparencies of aerial photographs by the line intercept method using a 10-X monocular lense with a vernier. Juniper cover increased at an average rate of 0.37 percentage unit year -1 (range 0.12 to 0.59) on undisturbed sites from the mid 1950s or early 1960s to the late 1990s (34 to 41 years). Following chaining or grubbing treatments during 1970 to 1978, juniper cover increased at an average rate of 1.00 percentage unit year -1 , which was significantly faster than the average rate of 0.5 percentage unit year -1 on untreated rangeland for the same time interval. Juniper cover returned to pre-treatment levels in an ave...
Presentation made as part of the "Bringing Research Data to the Ecology Classroom: Opportuni... more Presentation made as part of the "Bringing Research Data to the Ecology Classroom: Opportunities, Barriers, and Next Steps” Session at the Ecological Society of American annual meeting, August 8th, 2017 Portland Oregon
International Journal of STEM Education, 2021
BackgroundContinuous calls for reform in science education emphasize the need to provide science ... more BackgroundContinuous calls for reform in science education emphasize the need to provide science experiences in lower-division courses to improve the retention of STEM majors and to develop science literacy and STEM skills for all students. Open or authentic inquiry and undergraduate research are effective science experiences leading to multiple gains in student learning and development. Most inquiry-based learning activities, however, are implemented in laboratory classes and the majority of them are guided inquiries. Although course-based undergraduate research experiences have significantly expanded the reach of the traditional apprentice approach, it is still challenging to provide research experiences to nonmajors and in large introductory courses. We examined student learning through a web-based authentic inquiry project implemented in a high-enrollment introductory ecology course for over a decade.ResultsResults from 10 years of student self-assessment of learning showed that...
Landscape Ecology, 2017
Context In the Rio Grande Plains of southern Texas, subtropical savanna vegetation is characteriz... more Context In the Rio Grande Plains of southern Texas, subtropical savanna vegetation is characterized by a two-phase pattern consisting of discrete woody patches embedded within a C 4 grassland matrix. Prior trench transect studies have suggested that, on upland portions of the landscape, large woody patches (groves) occur on non-argillic inclusions, while small woody patches (clusters) are dispersed among herbaceous vegetation where the argillic horizon is present. Objective To test whether spatial heterogeneity of subsurface soil texture drives the landscape-scale pattern of woody patches in this subtropical savanna. Methods Landscape-scale spatial patterns of soil texture were quantified by taking spatially-specific soil samples to a depth of 1.2 m in a 160 m 9 100 m plot. Kriged maps of soil texture were developed, and the locations of non-argillic inclusions were mapped. Results Visual comparison of kriged maps of soil texture to a high resolution aerial photograph of the study area revealed that groves were present exclusively where the non-argillic inclusions were present. This clear visual relationship was further supported by positive correlations between soil sand concentration in the lower soil layers and total fine root biomass which mapped the locations of groves. Conclusions Subsurface non-argillic inclusions may favor the establishment and persistence of groves by enabling root penetration deeper into the profile, providing greater access to water and nutrients that are less accessible on those portions of the landscape where the argillic horizon is present, thereby regulating the distribution of grove vegetation and structuring the evolution of this landscape.
CourseSource, 2016
Learning through authentic scientific inquiries is essential for understanding the nature and pro... more Learning through authentic scientific inquiries is essential for understanding the nature and process of science and for developing critical thinking and communication skills. It is logistically challenging, however, to offer experiences of authentic scientific inquiries in large-enrollment introductory science courses. We developed a web-based ecological inquiry project using archived BearCam photos to provide an authentic scientific inquiry experience for students in a large introductory ecology course. Students conduct web-based individual research projects outside of class over a five-week period with ongoing peer feedback through online group discussions as well as instructor-facilitated discussions in class. They conduct a background study of grizzly bear biology and behavior; observe BearCam photos and generate testable hypotheses; design sampling and collect and analyze data; interpret results and develop inquiry reports guided by a rubric; conduct Calibrated Peer Review; and revise their reports based on peer feedback and self-assessment. Formative and summative assessments are used to facilitate and assess student learning, using direct and indirect measures. A rubric for the inquiry report communicates expectations, facilitates peer feedback and self-assessment, and forms the basis for evaluating student products and learning. Students have consistently reported significant learning gains in interest in ecology, ability to formulate testable hypotheses, understanding of how ecologists conduct research, and ability to evaluate quality of scientific reports.
List of Tables 3.1 Average annual increment of radial growth (mm) of noncanopy trees during the l... more List of Tables 3.1 Average annual increment of radial growth (mm) of noncanopy trees during the last 3 and 5 years. .. .. 6 4.1 Composition and structure of stand I. 4.2 Composition and structure of stand II 11 4.3 Growth of red spruce populations. . .
ABSTRACT Background/Question/Methods Knowledge of scale-dependent factors that affect the distrib... more ABSTRACT Background/Question/Methods Knowledge of scale-dependent factors that affect the distribution of ungulate herds, such as cattle, is essential for the development of more accurate predictive models of animal movement and the management of sustainable agriculture. Our objectives were to (1) evaluate the seasonal and diurnal patterns of herd spread and (2) evaluate the influence of shade, water and supplemental feed areas on cattle distribution. Positional information of eleven free-ranging Bonsmara, Bos taurus, cows were obtained at five minute intervals using Global Positioning System collars. We conducted a total of 8 trials each of three weeks from September 2007 to August 2008 in a 457ha shrub-dominated savanna in South Texas. Spread was obtained by calculating the average Euclidean distance of individuals to the center of the herd. Number of GPS fixes was used as an indicator of animal use of shade patches and water and supplemental feeding areas. Results/Conclusions In this semi-arid environment, herd spread was greatest during summer when forage biomass was high. Herd spread was the least and shade patches were used more during winter when forage biomass was low. This is in contrast to patterns seen in more northerly rangelands. Throughout the year spread was smallest and use of shade patches highest during the midday period compared to other periods of the day. There was no significant overall pattern of seasonal changes in cattle use of water and supplemental feeding areas. Forage availability and shade patches seem to have a greater influence on herd dispersion patterns than the influence of water and supplemental feed areas. Herd distribution is likely related to changes in seasonal forage biomass and diurnal temperature fluctuations which drive compensatory night-time feeding and thermoregulatory actions. Accurate ethological studies of herds depend on our ability to understand herd dynamics at multiple scales that affect and are relevant to animal’s response to the landscape.
Soil Biology and Biochemistry, 2012
Spatial patterns of soil d 13 C were quantified in a subtropical C 3 woodland in the Rio Grande P... more Spatial patterns of soil d 13 C were quantified in a subtropical C 3 woodland in the Rio Grande Plains of southern Texas, USA that developed during the past 100 yrs on a lowland site that was once C 4 grassland. A 50 Â 30 m plot and two transects were established, and soil cores (0e15 cm, n ¼ 207) were collected, spatially referenced, and analyzed for d 13 C, soil organic carbon (SOC), and soil particle size distribution. Cross-variogram analysis indicated that SOC remaining from the past C 4 grassland community co-varied with soil texture over a distance of 23.7 m. In contrast, newer SOC derived from C 3 woody plants was spatially correlated with root biomass within a range of 7.1 m. Although mesquite trees initiate grassland-to-woodland succession and create well-defined islands of soil modification in adjoining upland areas at this site, direct gradient and proximity analyses accounting for the number, size, and distance of mesquite plants in the vicinity of soil sample points failed to reveal any relationship between mesquite tree abundance and soil properties. Variogram analysis further indicated soil d 13 C, texture and organic carbon content were spatially autocorrelated over distances (ranges ¼ 15.6, 16.2 and 18.7 m, respectively) far greater than that of individual tree canopy diameters in these lowland communities. Cross-variogram analysis also revealed that d 13 C e SOC and d 13 C-texture relationships were spatially structured at distances much greater than that of mesquite canopies (range ¼ 17.6 and 16.5 m, respectively). These results suggest fundamental differences in the functional nature and consequences of shrub encroachment between upland and lowland landscapes and challenge us to identify the earth system processes and ecosystem structures that are driving carbon cycling at these contrasting scales. Improvements in our understanding how controls over soil carbon cycling change with spatial scale will enhance our ability to design vegetation and soil sampling schemes; and to more effectively use soil d 13 C as a tool to infer vegetation and soil organic carbon dynamics in ecosystems where C 3 eC 4 transitions and changes in structure and function are occurring.
Organic Geochemistry, 2012
Many grasslands and savannas around the world have experienced woody plant encroachment in recent... more Many grasslands and savannas around the world have experienced woody plant encroachment in recent history. In the Rio Grande Plains of southern Texas, subtropical woodlands dominated by C 3 trees and shrubs have become significant components of landscapes once dominated almost exclusively by C 4 grasslands. In this study, spatial variation of soil d 13 C to was used to investigate patterns of transformation. Previous research has shown that grassland-to-shrubland transitions are initiated when discrete, multi-species shrub clusters organized around a honey mesquite (Prosopis glandulosa) tree nucleus established in grassland. It is inferred from space-for-time substitution and modeling studies that as new shrub clusters are initiated and existing clusters enlarge, coalescence will occur, leading to the formation of groves; and that groves will eventually merge to form woodlands. The hypothesis that present-day mesquite groves represent areas where individual discrete shrub clusters have proliferated and coalesced was evaluated by comparing patterns of soil d 13 C within isolated shrub clusters (n = 6) to those in nearby groves (n = 3). Mean soil d 13 C within discrete clusters was lowest in the center (À23.3‰), increased exponentially toward the dripline (À20.1‰), and stabilized at a relatively high value approximately 15 cm beyond the dripline (À18.9‰). The spatial structure of soil d 13 C in groves was consistent with that which would be expected to occur if present-day grove communities were a collection of what once were individual discrete clusters that had fused. As such, it provides direct evidence in support of conceptual and mathematical models derived from indirect assessments. However, spatial patterns of soil d 13 C suggest that groves are not simply a collection of clusters with respect to primary production and SOC turnover. This study illustrates how soil d 13 C values can be used to reconstruct successional processes accompanying vegetation compositional change, and its consequences for ecosystem function.
CBE—Life Sciences Education, 2008
Combining field experience with use of information technology has the potential to create a probl... more Combining field experience with use of information technology has the potential to create a problem-based learning environment that engages learners in authentic scientific inquiry. This study, conducted over a 2-yr period, determined differences in attitudes and conceptual knowledge between students in a field lab and students with combined field and geographic information systems (GIS) experience. All students used radio-telemetry equipment to locate fox squirrels, while one group of students was provided an additional data set in a GIS to visualize and quantify squirrel locations. Pre/postsurveys and tests revealed that attitudes improved in year 1 for both groups of students, but differences were minimal between groups. Attitudes generally declined in year 2 due to a change in the authenticity of the field experience; however, attitudes for students that used GIS declined less than those with field experience only. Conceptual knowledge also increased for both groups in both year...
Ecosphere, 2021
Selective grazing of livestock creates lightly and heavily grazed vegetation patches, which toget... more Selective grazing of livestock creates lightly and heavily grazed vegetation patches, which together contribute to the whole community in grazed grasslands. The intermediate disturbance hypothesis (IDH) predicts moderate grazing intensity can increase species diversity. However, grazing patchiness complicates predicted responses to grazing intensity from ecological theory and may influence how various management regimes affect biodiversity at the whole community scale. We examined effects of management regime and grazing intensity on plant species diversity, community composition, aboveground net primary production (ANPP), and soil compaction. Two management regimes (season‐long continuous grazing and grazing and mowing alternated annually) and seven levels of grazing intensity were applied over the past 10 yr. We assessed how α diversity within patches and β diversity across patches contributed to the diversity of the whole plot and how these relationships responded to both grazing...
Water, 2021
Following successful abatement of external nutrient sources, one must shift the focus to the role... more Following successful abatement of external nutrient sources, one must shift the focus to the role of phosphorus (P) release from sediment. This enables us to better assess the causes for sustained eutrophication in freshwater ecosystem and how to deal with this challenge. In this study, five sediment cores from the shallow YuQiao Reservoir in northern China were investigated. The reservoir serves as the main raw water source for tap water services of Tianjin megacity, with a population of 15.6 million. Sediment characteristics and P fractions were determined in order to assess the role of the sediments as the P source to the water body. The total P content (TP) in sediments was similar to what was found in catchment soils, although the P sorption capacity of sediments was 7–10 times greater than for the catchment soils. Isotherm adsorption experiments documented that when P concentration in overlying water drops below 0.032–0.070 mg L−1, depending on the site, the sediment contribut...
Environmental Management, 2007
Journal of Range Management, 2001
Woody cover, when expressed at the scale of the 207 km 2 Cusenbary Draw basin, remained unchanged... more Woody cover, when expressed at the scale of the 207 km 2 Cusenbary Draw basin, remained unchanged (~23%) from 1955 to 1990. When expressed at the scale of range sites, woody cover declined on sites with relatively high production potential and increased on sites with relatively low production potential. Change in woody cover distribution at sub-range site scales, increased low and high woody covers and decreased intermediate woody cover, would be expected to lead to increased water yield at the basin scale because there was an apparent threshold woody cover (~20%) above which simulated evapotranspiration (ET) changed little with increasing woody cover. This potential increase, however, was more than offset by the decreased water yield due to increased ET loss associated with compositional changes of woody vegetation from oak to juniper. A set of woody cover-ET regression curves was developed for different range sites based on simulation studies using the SPUR-91 hydrologic model. Based on these woody cover-ET regression curves and GIS analysis, no brush management would result in a 35% decrease in water yield, while a hypothetical brush management cost-share program would increase water yield by 43% over the 1990 level. Benefits in water yield and forage production from brush management differ in different range sites. A brush management cost-share program that preferentially allocated brush management to sites with deep soil and the highest forage production potential increased water yield by 50%, compared to a 100% increase if brush management were preferentially allocated on sites with shallow soil and highest water yield potential. These model results illustrate that the spatial scale of assessment and spatial distribution of brush management among range sites should be important concerns associated with developing and evaluating brush management policies.
Journal of Range Management, 2001
It is necessary to quantify rates of woody plant encroachment on southwestern USA rangelands to d... more It is necessary to quantify rates of woody plant encroachment on southwestern USA rangelands to determine the economic feasibility of treatments designed to manage these plants. This study observed changes in honey mesquite (Prosopis glandulosa Torr.) canopy cover over a 20-year period (1976-1995) in 2 treatments: an untreated area that initially had a moderately dense mesquite stand (14.6% cover), and an area cleared of mesquite with rootplowing in 1974. Canopy cover of mesquite was estimated from scanned color-infrared aerial photograph images by manually delineating mesquite canopies with a computer using ArcView software. During the 20 years, mesquite cover in the untreated area increased (P ≤ 0.05) from 14.6 to 58.7%, averaging 2.2 percentage units per year. Cover in the root-plow treatment also significantly increased during the same period from 0 to 21.9% (1.1 percentage units per year), but the rate of increase was significantly lower than in the untreated area because mesquite growth was from new seedlings instead of established plants and/or new seedlings as occurred in the untreated area. Rate of increase was significantly lower from 1976 to 1990 (1.6 and 0.2 percentage units per year) than from 1990 to 1995 (4.1 and 3.7 percentage units per year) in the untreated and root-plow treatment, respectively. These differences were attributed to precipitation which was near normal from 1976 to 1990 but 25% above normal from 1991 to 1995.
Journal of Range Management, 2003
Several studies have examined the impact of woody plant (i.e., brush) management efforts on mesqu... more Several studies have examined the impact of woody plant (i.e., brush) management efforts on mesquite (Prosopis glandulosa Torr.) cover and associated ecological impacts, but little research has been done on spatial attributes of vegetation following mesquite management treatments. This study examined the effects of above-ground mortality (triclopyr or 2,4,5-T) and whole-plant mortality (clopyralid or triclopyr+clopyralid) mesquite herbicide treatments on the canopy cover and spatial pattern of vegetation in a mesquite savanna and the associated ecological and management implications. A GIS and landscape analysis based on classified color-infrared aerial photos were used to quantify the spatial patterns of woody and non-woody vegetation. The results indicate long-term (> 20 year) persistence of disturbance effects on the amount and spatial pattern of woody vegetation. Significant differences in spatial pattern were found between the herbicide treatments and the non-treated plots, as well as between the above-ground mortality (AGM) and whole-plant mortality (WPM) herbicide treatments. The differential changes in the amount and spatial distribution of woody cover under different treatments resulted in substantially different spatial distributions of non-woody vegetation with respect to distance to nearest woody vegetation. These spatial variations may influence production and zonation of herbaceous vegetation due to modified shading and root competition from mesquite. Our results support observations of differential rates of mesquite seedling recruitment and establishment between treatment types. We conclude that consideration of spatial pattern should be an important component of future brush management plans.
Journal of Hydrology, 2006
Genetic Algorithm (GA) is globally oriented in searching and thus useful in optimizing multiobjec... more Genetic Algorithm (GA) is globally oriented in searching and thus useful in optimizing multiobjective problems, especially where the objective functions are ill-defined. Conceptual rainfall-runoff models that aim at predicting streamflow from the knowledge of precipitation over a catchment have become a basic tool for flood forecasting. The parameter calibration of a conceptual model usually involves the multiple criteria for judging the performances of observed data. However, it is often difficult to derive all objective functions for the parameter calibration problem of a conceptual model. Thus, a new framework to the multiple criteria parameter calibration problem, which combines GA with TOPSIS (technique for order performance by similarity to ideal solution) for Xinanjiang model, is presented. The current method integrates the two parts of Xinanjiang rainfall-runoff model calibration together, simplifying the procedures of model calibration and validation and easily demonstrating the intrinsic phenomenon of observed data in integrity. Comparing results with two-step procedure show that the current methodology is also feasible and robust, but simpler and easier to be applied in practice.
Circulation, 2008
Background— Torcetrapib, an inhibitor of cholesteryl ester transfer protein, has been shown to in... more Background— Torcetrapib, an inhibitor of cholesteryl ester transfer protein, has been shown to increase the cardiovascular event rate despite conferring a significant high-density lipoprotein cholesterol increase. Using data from the Rating Atherosclerotic Disease Change by Imaging with a New CETP Inhibitor (RADIANCE) trials, which assessed the impact of torcetrapib on carotid intima-media thickness (cIMT), we sought to explore potential mechanisms underlying this adverse outcome. Methods and Results— Data from the RADIANCE 1 and 2 studies, which examined cIMT in 904 subjects with familial hypercholesterolemia and in 752 subjects with mixed dyslipidemia, were pooled. Subjects were randomized to either atorvastatin or torcetrapib combined with atorvastatin. Mean common cIMT progression was increased in subjects receiving torcetrapib plus atorvastatin compared with subjects receiving atorvastatin alone (0.0076±0.0011 versus 0.0025±0.0011 mm/y; P =0.0014). Subjects treated with torcetr...
National Quail Symposium Proceedings, 2017
Although biologists have studied northern bobwhite (Colinus virginianus) genetic diversity and po... more Although biologists have studied northern bobwhite (Colinus virginianus) genetic diversity and population structure, there is little known about the genetic diversity, structure, and relatedness of their winter coveys. Both flexible mating strategies and the fall shuffle may have implications for inbreeding and genetic diversity in northern bobwhite populations. Our goal was to determine genetic diversity and relatedness for coveys on a private ranch in Jim Hogg County in South Texas. During the 2010-2011 and 2011-2012 hunting seasons, 96 northern bobwhites were sampled from 29 coveys. We analyzed 11 northern bobwhite microsatellite DNA loci, measured genetic structure with an Analysis of Molecular Variance and F ST , and determined an inbreeding coefficient (F i). We determined Queller and Goodnight's coefficients of relatedness (R) and then used a maximum-likelihood algorithm in COLONY to assign relationships (parent-offspring, full siblings, and half siblings). Most genetic variation (92%) was within coveys. The overall F ST was 0.073, indicating moderate genetic structure among coveys. Relationship coefficients ranged from À0.82 to 1.00 but most of the bird pairs were unrelated (R ¼À0.004 6 0.002 SE). In 2010-2011, COLONY assigned 130-149 half sibling, 1-4 full sibling, and 0-3 parent-offspring pairs (n ¼ 2,887, 5 trials, probability .0.99). Thirteen coveys (56%) had related individuals (n ¼ 20 pairs). In 2011-2012, COLONY assigned 5-10 half sibling and 1 full sibling pairs (n ¼ 161). Two coveys (33%) had related individuals (2 pairs). The occurrence of relatives in different coveys suggests that the fall shuffle is effective at mixing families and the high half sibling count among coveys may suggest polygamy. These strategies may help northern bobwhite populations maintain moderate genetic diversity.
Redberry juniper (Juniperus pinchotii) is a major prob- lem on Texas rangelands, yet little is kn... more Redberry juniper (Juniperus pinchotii) is a major prob- lem on Texas rangelands, yet little is known about the rate it is increasing. This study estimated long-term rates of change of redberry juniper canopy cover on undisturbed sites and adjacent sites that were either chained or grubbed at five locations in western Texas. Juniper cover was estimated from positive transparencies of aerial photographs by the line intercept method using a 10-X monocular lense with a vernier. Juniper cover increased at an average rate of 0.37 percentage unit year -1 (range 0.12 to 0.59) on undisturbed sites from the mid 1950s or early 1960s to the late 1990s (34 to 41 years). Following chaining or grubbing treatments during 1970 to 1978, juniper cover increased at an average rate of 1.00 percentage unit year -1 , which was significantly faster than the average rate of 0.5 percentage unit year -1 on untreated rangeland for the same time interval. Juniper cover returned to pre-treatment levels in an ave...
Presentation made as part of the "Bringing Research Data to the Ecology Classroom: Opportuni... more Presentation made as part of the "Bringing Research Data to the Ecology Classroom: Opportunities, Barriers, and Next Steps” Session at the Ecological Society of American annual meeting, August 8th, 2017 Portland Oregon
International Journal of STEM Education, 2021
BackgroundContinuous calls for reform in science education emphasize the need to provide science ... more BackgroundContinuous calls for reform in science education emphasize the need to provide science experiences in lower-division courses to improve the retention of STEM majors and to develop science literacy and STEM skills for all students. Open or authentic inquiry and undergraduate research are effective science experiences leading to multiple gains in student learning and development. Most inquiry-based learning activities, however, are implemented in laboratory classes and the majority of them are guided inquiries. Although course-based undergraduate research experiences have significantly expanded the reach of the traditional apprentice approach, it is still challenging to provide research experiences to nonmajors and in large introductory courses. We examined student learning through a web-based authentic inquiry project implemented in a high-enrollment introductory ecology course for over a decade.ResultsResults from 10 years of student self-assessment of learning showed that...
Landscape Ecology, 2017
Context In the Rio Grande Plains of southern Texas, subtropical savanna vegetation is characteriz... more Context In the Rio Grande Plains of southern Texas, subtropical savanna vegetation is characterized by a two-phase pattern consisting of discrete woody patches embedded within a C 4 grassland matrix. Prior trench transect studies have suggested that, on upland portions of the landscape, large woody patches (groves) occur on non-argillic inclusions, while small woody patches (clusters) are dispersed among herbaceous vegetation where the argillic horizon is present. Objective To test whether spatial heterogeneity of subsurface soil texture drives the landscape-scale pattern of woody patches in this subtropical savanna. Methods Landscape-scale spatial patterns of soil texture were quantified by taking spatially-specific soil samples to a depth of 1.2 m in a 160 m 9 100 m plot. Kriged maps of soil texture were developed, and the locations of non-argillic inclusions were mapped. Results Visual comparison of kriged maps of soil texture to a high resolution aerial photograph of the study area revealed that groves were present exclusively where the non-argillic inclusions were present. This clear visual relationship was further supported by positive correlations between soil sand concentration in the lower soil layers and total fine root biomass which mapped the locations of groves. Conclusions Subsurface non-argillic inclusions may favor the establishment and persistence of groves by enabling root penetration deeper into the profile, providing greater access to water and nutrients that are less accessible on those portions of the landscape where the argillic horizon is present, thereby regulating the distribution of grove vegetation and structuring the evolution of this landscape.
CourseSource, 2016
Learning through authentic scientific inquiries is essential for understanding the nature and pro... more Learning through authentic scientific inquiries is essential for understanding the nature and process of science and for developing critical thinking and communication skills. It is logistically challenging, however, to offer experiences of authentic scientific inquiries in large-enrollment introductory science courses. We developed a web-based ecological inquiry project using archived BearCam photos to provide an authentic scientific inquiry experience for students in a large introductory ecology course. Students conduct web-based individual research projects outside of class over a five-week period with ongoing peer feedback through online group discussions as well as instructor-facilitated discussions in class. They conduct a background study of grizzly bear biology and behavior; observe BearCam photos and generate testable hypotheses; design sampling and collect and analyze data; interpret results and develop inquiry reports guided by a rubric; conduct Calibrated Peer Review; and revise their reports based on peer feedback and self-assessment. Formative and summative assessments are used to facilitate and assess student learning, using direct and indirect measures. A rubric for the inquiry report communicates expectations, facilitates peer feedback and self-assessment, and forms the basis for evaluating student products and learning. Students have consistently reported significant learning gains in interest in ecology, ability to formulate testable hypotheses, understanding of how ecologists conduct research, and ability to evaluate quality of scientific reports.
List of Tables 3.1 Average annual increment of radial growth (mm) of noncanopy trees during the l... more List of Tables 3.1 Average annual increment of radial growth (mm) of noncanopy trees during the last 3 and 5 years. .. .. 6 4.1 Composition and structure of stand I. 4.2 Composition and structure of stand II 11 4.3 Growth of red spruce populations. . .
ABSTRACT Background/Question/Methods Knowledge of scale-dependent factors that affect the distrib... more ABSTRACT Background/Question/Methods Knowledge of scale-dependent factors that affect the distribution of ungulate herds, such as cattle, is essential for the development of more accurate predictive models of animal movement and the management of sustainable agriculture. Our objectives were to (1) evaluate the seasonal and diurnal patterns of herd spread and (2) evaluate the influence of shade, water and supplemental feed areas on cattle distribution. Positional information of eleven free-ranging Bonsmara, Bos taurus, cows were obtained at five minute intervals using Global Positioning System collars. We conducted a total of 8 trials each of three weeks from September 2007 to August 2008 in a 457ha shrub-dominated savanna in South Texas. Spread was obtained by calculating the average Euclidean distance of individuals to the center of the herd. Number of GPS fixes was used as an indicator of animal use of shade patches and water and supplemental feeding areas. Results/Conclusions In this semi-arid environment, herd spread was greatest during summer when forage biomass was high. Herd spread was the least and shade patches were used more during winter when forage biomass was low. This is in contrast to patterns seen in more northerly rangelands. Throughout the year spread was smallest and use of shade patches highest during the midday period compared to other periods of the day. There was no significant overall pattern of seasonal changes in cattle use of water and supplemental feeding areas. Forage availability and shade patches seem to have a greater influence on herd dispersion patterns than the influence of water and supplemental feed areas. Herd distribution is likely related to changes in seasonal forage biomass and diurnal temperature fluctuations which drive compensatory night-time feeding and thermoregulatory actions. Accurate ethological studies of herds depend on our ability to understand herd dynamics at multiple scales that affect and are relevant to animal’s response to the landscape.
Soil Biology and Biochemistry, 2012
Spatial patterns of soil d 13 C were quantified in a subtropical C 3 woodland in the Rio Grande P... more Spatial patterns of soil d 13 C were quantified in a subtropical C 3 woodland in the Rio Grande Plains of southern Texas, USA that developed during the past 100 yrs on a lowland site that was once C 4 grassland. A 50 Â 30 m plot and two transects were established, and soil cores (0e15 cm, n ¼ 207) were collected, spatially referenced, and analyzed for d 13 C, soil organic carbon (SOC), and soil particle size distribution. Cross-variogram analysis indicated that SOC remaining from the past C 4 grassland community co-varied with soil texture over a distance of 23.7 m. In contrast, newer SOC derived from C 3 woody plants was spatially correlated with root biomass within a range of 7.1 m. Although mesquite trees initiate grassland-to-woodland succession and create well-defined islands of soil modification in adjoining upland areas at this site, direct gradient and proximity analyses accounting for the number, size, and distance of mesquite plants in the vicinity of soil sample points failed to reveal any relationship between mesquite tree abundance and soil properties. Variogram analysis further indicated soil d 13 C, texture and organic carbon content were spatially autocorrelated over distances (ranges ¼ 15.6, 16.2 and 18.7 m, respectively) far greater than that of individual tree canopy diameters in these lowland communities. Cross-variogram analysis also revealed that d 13 C e SOC and d 13 C-texture relationships were spatially structured at distances much greater than that of mesquite canopies (range ¼ 17.6 and 16.5 m, respectively). These results suggest fundamental differences in the functional nature and consequences of shrub encroachment between upland and lowland landscapes and challenge us to identify the earth system processes and ecosystem structures that are driving carbon cycling at these contrasting scales. Improvements in our understanding how controls over soil carbon cycling change with spatial scale will enhance our ability to design vegetation and soil sampling schemes; and to more effectively use soil d 13 C as a tool to infer vegetation and soil organic carbon dynamics in ecosystems where C 3 eC 4 transitions and changes in structure and function are occurring.
Organic Geochemistry, 2012
Many grasslands and savannas around the world have experienced woody plant encroachment in recent... more Many grasslands and savannas around the world have experienced woody plant encroachment in recent history. In the Rio Grande Plains of southern Texas, subtropical woodlands dominated by C 3 trees and shrubs have become significant components of landscapes once dominated almost exclusively by C 4 grasslands. In this study, spatial variation of soil d 13 C to was used to investigate patterns of transformation. Previous research has shown that grassland-to-shrubland transitions are initiated when discrete, multi-species shrub clusters organized around a honey mesquite (Prosopis glandulosa) tree nucleus established in grassland. It is inferred from space-for-time substitution and modeling studies that as new shrub clusters are initiated and existing clusters enlarge, coalescence will occur, leading to the formation of groves; and that groves will eventually merge to form woodlands. The hypothesis that present-day mesquite groves represent areas where individual discrete shrub clusters have proliferated and coalesced was evaluated by comparing patterns of soil d 13 C within isolated shrub clusters (n = 6) to those in nearby groves (n = 3). Mean soil d 13 C within discrete clusters was lowest in the center (À23.3‰), increased exponentially toward the dripline (À20.1‰), and stabilized at a relatively high value approximately 15 cm beyond the dripline (À18.9‰). The spatial structure of soil d 13 C in groves was consistent with that which would be expected to occur if present-day grove communities were a collection of what once were individual discrete clusters that had fused. As such, it provides direct evidence in support of conceptual and mathematical models derived from indirect assessments. However, spatial patterns of soil d 13 C suggest that groves are not simply a collection of clusters with respect to primary production and SOC turnover. This study illustrates how soil d 13 C values can be used to reconstruct successional processes accompanying vegetation compositional change, and its consequences for ecosystem function.
CBE—Life Sciences Education, 2008
Combining field experience with use of information technology has the potential to create a probl... more Combining field experience with use of information technology has the potential to create a problem-based learning environment that engages learners in authentic scientific inquiry. This study, conducted over a 2-yr period, determined differences in attitudes and conceptual knowledge between students in a field lab and students with combined field and geographic information systems (GIS) experience. All students used radio-telemetry equipment to locate fox squirrels, while one group of students was provided an additional data set in a GIS to visualize and quantify squirrel locations. Pre/postsurveys and tests revealed that attitudes improved in year 1 for both groups of students, but differences were minimal between groups. Attitudes generally declined in year 2 due to a change in the authenticity of the field experience; however, attitudes for students that used GIS declined less than those with field experience only. Conceptual knowledge also increased for both groups in both year...
Ecosphere, 2021
Selective grazing of livestock creates lightly and heavily grazed vegetation patches, which toget... more Selective grazing of livestock creates lightly and heavily grazed vegetation patches, which together contribute to the whole community in grazed grasslands. The intermediate disturbance hypothesis (IDH) predicts moderate grazing intensity can increase species diversity. However, grazing patchiness complicates predicted responses to grazing intensity from ecological theory and may influence how various management regimes affect biodiversity at the whole community scale. We examined effects of management regime and grazing intensity on plant species diversity, community composition, aboveground net primary production (ANPP), and soil compaction. Two management regimes (season‐long continuous grazing and grazing and mowing alternated annually) and seven levels of grazing intensity were applied over the past 10 yr. We assessed how α diversity within patches and β diversity across patches contributed to the diversity of the whole plot and how these relationships responded to both grazing...
Water, 2021
Following successful abatement of external nutrient sources, one must shift the focus to the role... more Following successful abatement of external nutrient sources, one must shift the focus to the role of phosphorus (P) release from sediment. This enables us to better assess the causes for sustained eutrophication in freshwater ecosystem and how to deal with this challenge. In this study, five sediment cores from the shallow YuQiao Reservoir in northern China were investigated. The reservoir serves as the main raw water source for tap water services of Tianjin megacity, with a population of 15.6 million. Sediment characteristics and P fractions were determined in order to assess the role of the sediments as the P source to the water body. The total P content (TP) in sediments was similar to what was found in catchment soils, although the P sorption capacity of sediments was 7–10 times greater than for the catchment soils. Isotherm adsorption experiments documented that when P concentration in overlying water drops below 0.032–0.070 mg L−1, depending on the site, the sediment contribut...
Environmental Management, 2007
Journal of Range Management, 2001
Woody cover, when expressed at the scale of the 207 km 2 Cusenbary Draw basin, remained unchanged... more Woody cover, when expressed at the scale of the 207 km 2 Cusenbary Draw basin, remained unchanged (~23%) from 1955 to 1990. When expressed at the scale of range sites, woody cover declined on sites with relatively high production potential and increased on sites with relatively low production potential. Change in woody cover distribution at sub-range site scales, increased low and high woody covers and decreased intermediate woody cover, would be expected to lead to increased water yield at the basin scale because there was an apparent threshold woody cover (~20%) above which simulated evapotranspiration (ET) changed little with increasing woody cover. This potential increase, however, was more than offset by the decreased water yield due to increased ET loss associated with compositional changes of woody vegetation from oak to juniper. A set of woody cover-ET regression curves was developed for different range sites based on simulation studies using the SPUR-91 hydrologic model. Based on these woody cover-ET regression curves and GIS analysis, no brush management would result in a 35% decrease in water yield, while a hypothetical brush management cost-share program would increase water yield by 43% over the 1990 level. Benefits in water yield and forage production from brush management differ in different range sites. A brush management cost-share program that preferentially allocated brush management to sites with deep soil and the highest forage production potential increased water yield by 50%, compared to a 100% increase if brush management were preferentially allocated on sites with shallow soil and highest water yield potential. These model results illustrate that the spatial scale of assessment and spatial distribution of brush management among range sites should be important concerns associated with developing and evaluating brush management policies.
Journal of Range Management, 2001
It is necessary to quantify rates of woody plant encroachment on southwestern USA rangelands to d... more It is necessary to quantify rates of woody plant encroachment on southwestern USA rangelands to determine the economic feasibility of treatments designed to manage these plants. This study observed changes in honey mesquite (Prosopis glandulosa Torr.) canopy cover over a 20-year period (1976-1995) in 2 treatments: an untreated area that initially had a moderately dense mesquite stand (14.6% cover), and an area cleared of mesquite with rootplowing in 1974. Canopy cover of mesquite was estimated from scanned color-infrared aerial photograph images by manually delineating mesquite canopies with a computer using ArcView software. During the 20 years, mesquite cover in the untreated area increased (P ≤ 0.05) from 14.6 to 58.7%, averaging 2.2 percentage units per year. Cover in the root-plow treatment also significantly increased during the same period from 0 to 21.9% (1.1 percentage units per year), but the rate of increase was significantly lower than in the untreated area because mesquite growth was from new seedlings instead of established plants and/or new seedlings as occurred in the untreated area. Rate of increase was significantly lower from 1976 to 1990 (1.6 and 0.2 percentage units per year) than from 1990 to 1995 (4.1 and 3.7 percentage units per year) in the untreated and root-plow treatment, respectively. These differences were attributed to precipitation which was near normal from 1976 to 1990 but 25% above normal from 1991 to 1995.
Journal of Range Management, 2003
Several studies have examined the impact of woody plant (i.e., brush) management efforts on mesqu... more Several studies have examined the impact of woody plant (i.e., brush) management efforts on mesquite (Prosopis glandulosa Torr.) cover and associated ecological impacts, but little research has been done on spatial attributes of vegetation following mesquite management treatments. This study examined the effects of above-ground mortality (triclopyr or 2,4,5-T) and whole-plant mortality (clopyralid or triclopyr+clopyralid) mesquite herbicide treatments on the canopy cover and spatial pattern of vegetation in a mesquite savanna and the associated ecological and management implications. A GIS and landscape analysis based on classified color-infrared aerial photos were used to quantify the spatial patterns of woody and non-woody vegetation. The results indicate long-term (> 20 year) persistence of disturbance effects on the amount and spatial pattern of woody vegetation. Significant differences in spatial pattern were found between the herbicide treatments and the non-treated plots, as well as between the above-ground mortality (AGM) and whole-plant mortality (WPM) herbicide treatments. The differential changes in the amount and spatial distribution of woody cover under different treatments resulted in substantially different spatial distributions of non-woody vegetation with respect to distance to nearest woody vegetation. These spatial variations may influence production and zonation of herbaceous vegetation due to modified shading and root competition from mesquite. Our results support observations of differential rates of mesquite seedling recruitment and establishment between treatment types. We conclude that consideration of spatial pattern should be an important component of future brush management plans.
Journal of Hydrology, 2006
Genetic Algorithm (GA) is globally oriented in searching and thus useful in optimizing multiobjec... more Genetic Algorithm (GA) is globally oriented in searching and thus useful in optimizing multiobjective problems, especially where the objective functions are ill-defined. Conceptual rainfall-runoff models that aim at predicting streamflow from the knowledge of precipitation over a catchment have become a basic tool for flood forecasting. The parameter calibration of a conceptual model usually involves the multiple criteria for judging the performances of observed data. However, it is often difficult to derive all objective functions for the parameter calibration problem of a conceptual model. Thus, a new framework to the multiple criteria parameter calibration problem, which combines GA with TOPSIS (technique for order performance by similarity to ideal solution) for Xinanjiang model, is presented. The current method integrates the two parts of Xinanjiang rainfall-runoff model calibration together, simplifying the procedures of model calibration and validation and easily demonstrating the intrinsic phenomenon of observed data in integrity. Comparing results with two-step procedure show that the current methodology is also feasible and robust, but simpler and easier to be applied in practice.