Browsing by Author "Wang, Xianzhong"
Now showing 1 - 10 of 13
Results Per Page
Sort Options
Item Biological potential and diffusion limitation of methane oxidation in no-till soils(2014-05-21) Prajapati, Prajaya; Wang, Xianzhong; Martin, Pamela; Jacinthe, Pierre-AndréLong term no-till (NT) farming can improve the CH4 oxidation capacity of agricultural lands through creation of a favorable soil environment for methanotrophs and diffusive gas transport. However, limited data is available to evaluate the merit of that contention. Although the potential for biological CH4 oxidation may exist in NT soils, restricted diffusion could limit expression of that potential in fine-textured soils. A study was conducted to assess the CH4 oxidation potential and gaseous diffusivity of soils under plow till (PT) and NT for > 50 years. Intact cores and composite soils samples (0-10 and 10-20 cm) were collected from NT and PT plots located at a well-drained site (Wooster silt loam) and at a poorly-drained (Crosby silt loam) site in Ohio. Adjacent deciduous forest soils were also sampled to determine maximum rate expected in undisturbed soils in the region. Regardless of study sites and soil depth, CH4 oxidation rate (measured at near ambient CH4) and oxidation potential (Vmax, measured at elevated CH4) were 3-4 and 1.5 times higher in NT than in PT soils, respectively. Activity in the NT soils approached (66-80 %) that in the forest soils. Half saturation constants (Km) and threshold for CH4 oxidation (Th) were lower in NT (Km: 100.5 µL CH4 L-1; Th: 0.5 µL CH4 L-1) than in PT soils (Km: 134 µL CH4 L-1; Th: 2.8 µL CH4 L-1) suggesting a greater affinity of long-term NT soils for CH4, and a possible shift in methanotrophic community composition. CH4 oxidation rates were lower in intact soil cores compared to sieved soils, suggesting that CH4 oxidation was limited by diffusion, a factor that could lead to lower field-measured CH4 uptake than suggested by biological oxidation capacity measured in the laboratory. Regardless of soil drainage characteristic, long-term NT resulted in significantly higher (2-3 times) CH4 diffusivity (mean: 2.5 x 10-3 cm2 s-1) than PT (1.5 x 10-3 cm2 s-1), probably due to improved soil aggregation and greater macro-pores volume in NT soils. Overall, these results confirm the positive impact of NT on the restoration of the biological (Vmax, Km and Th) and physical (diffusivity) soil attributes essential for CH4 uptake in croplands. Long-term implementation of NT farming can therefore contribute to the mitigation of CH4 emission from agriculture.Item Effects of carbon nanotubes on airway epithelial cells and model lipid bilayers : proteomic and biophysical studies(2014) Li, Pin; Blazer-Yost, Bonnie; Witzmann, F. A. (Frank A.); Randall, Stephen Karl, 1953-; Petrache, Horia; Wang, XianzhongCarbon nanomaterials are widely produced and used in industry, medicine and scientific research. To examine the impact of exposure to nanoparticles on human health, the human airway epithelial cell line, Calu-3, was used to evaluate changes in the cellular proteome that could account for alterations in cellular function of airway epithelia after 24 h exposure to 10 μg/mL and 100 ng/mL of two common carbon nanoparticles, singleand multi-wall carbon nanotubes (SWCNT, MWCNT). After exposure to the nanoparticles, label-free quantitative mass spectrometry (LFQMS) was used to study differential protein expression. Ingenuity Pathway Analysis (IPA) was used to conduct a bioinformatics analysis of proteins identified by LFQMS. Interestingly, after exposure to a high concentration (10 μg/mL; 0.4 μg/cm2) of MWCNT or SWCNT, only 8 and 13 proteins, respectively, exhibited changes in abundance. In contrast, the abundance of hundreds of proteins was altered in response to a low concentration (100 ng/mL; 4 ng/cm2) of either CNT. Of the 281 and 282 proteins that were significantly altered in response to MWCNT or SWCNT, respectively, 231 proteins were the same. Bioinformatic analyses found that the proteins common to both kinds of nanotubes are associated with the cellular functions of cell death and survival, cell-to-cell signaling and interaction, cellular assembly and organization, cellular growth and proliferation, infectious disease, molecular transport and protein synthesis. The decrease in expression of the majority proteins suggests a general stress response to protect cells. The STRING database was used to analyze the various functional protein networks. Interestingly, some proteins like cadherin 1 (CDH1), signal transducer and activator of transcription 1 (STAT1), junction plakoglobin (JUP), and apoptosis-associated speck-like protein containing a CARD (PYCARD), appear in several functional categories and tend to be in the center of the networks. This central positioning suggests they may play important roles in multiple cellular functions and activities that are altered in response to carbon nanotube exposure. To examine the effect of nanotubes on the plasma membrane, we investigated the interaction of short purified MWCNT with model lipid membranes using a planar bilayer workstation. Bilayer lipid membranes were synthesized using neutral 1, 2-diphytanoylsn-glycero-3-phosphocholine (DPhPC) in 1 M KCl. The ion channel model protein, Gramicidin A (gA), was incorporated into the bilayers and used to measure the effect of MWCNT on ion transport. The opening and closing of ion channels, amplitude of current, and open probability and lifetime of ion channels were measured and analyzed by Clampfit. The presence of an intermediate concentration of MWCNT (2 μg/ml) could be related to a statistically significant decrease of the open probability and lifetime of gA channels. The proteomic studies revealed changes in response to CNT exposure. An analysis of the changes using multiple databases revealed alterations in pathways, which were consistent with the physiological changes that were observed in cultured cells exposed to very low concentrations of CNT. The physiological changes included the break down of the barrier function and the inhibition of the mucocillary clearance, both of which could increase the risk of CNT’s toxicity to human health. The biophysical studies indicate MWCNTs have an effect on single channel kinetics of Gramicidin A model cation channel. These changes are consistent with the inhibitory effect of nanoparticles on hormone stimulated transepithelial ion flux, but additional experiments will be necessary to substantiate this correlation.Item A field experimental study on the impact of Acer platanoides, an urban tree invader, on forest ecosystem processes in North America(Springer, 2020-03) Fang, Wei; Wang, Xianzhong; Biology, School of ScienceBackground Invasive species affect community dynamics and ecosystem functions, but the mechanisms of their impacts are poorly understood. Hypotheses on invasion impact range from Superior Competitor to Novel Function, from Enemy Escape to Microbial Mediation. In this study, we examined the effects of an urban tree invader, Acer platanoides (Norway maple, NM), on a mesic deciduous forest in contrast to its native congener Acer rubrum (red maple, RM) with a split-plot design experiment. A total of 720 maple seedlings were transplanted to 72 plots under 24 trees of three canopy types. The three experimental treatments were removal of resource competition at above- and belowground and removal of leaf-litter effect. Soil moisture and nitrogen-related microbial activities were followed for each plot. Results We found that partial canopy removal increased canopy openness and light transmission to the forest floor, but to a greater extent under NM than under RM trees. NM seedlings were more shade tolerant than RM seedlings in height growth. During the reciprocal transplantation in the mixed forest, biomass accumulation of NM seedlings under RM trees were twice as much as under NM, while that of RM seedlings under NM trees was 23.5% less than under RM. Soil net nitrification and relative nitrification were significantly higher, but mineralization rate was much lower under NM than under RM trees, which would lead to faster N leaching and lower N availability in the soil. Plots with litter removal had significantly higher seedling mortality due to herbivory by the end of 2 years, especially for NM seedlings under NM trees. Trenching enhanced soil water availability but there was no difference among canopy types. Conclusions Our results demonstrated that invasion of NM not only altered forest canopy structure but also changed herbivory rate for seedlings and N dynamics in the soils. NM seedlings were more shade tolerant under NM canopies than RM seedlings and were more protected by NM litter under NM canopies than under RM canopies. These altered biotic and abiotic environments will likely facilitate further invasion of NM in the forests, hence positive feedbacks, and make it an increasingly serious tree invader in North America.Item The impact of glaciation and climate change on biogeochemical cycling and landscape development(2012-03-19) Mabry, James Brice; Filippelli, Gabriel M.; Licht, Kathy J.; Wang, XianzhongLake cores from Dry Lake, California and Crystal Lake, Illinois were analyzed to identify climate variability and characterize landscape response to glacial/deglacial climate transitions. Geochemical analysis of the Dry Lake sediment prior to the 8.2 kyr event revealed average values for percent total organic carbon to be 4% with a range of 0.2% to 15.2%. The average decreased to approximately 2.1% with a range of 0.4% to 5.3% during and after the event. Occluded phosphorus averaged 488 µg/g before the 8.2 kyr event and 547 µg/g after but was much lower during the event at 287 µg/g. These results were interpreted as an environment which began as warm, wet, and productive then quickly turned colder and drier during the 8.2 kyr event which resulted in a resetting of soil development. The higher temperatures returned after the 8.2 kyr event which allowed for continued soil development despite its drier climate. Previous research corroborated these conclusions. The Crystal Lake geochemical record was very different from Dry Lake. Percent total organic carbon averaged 6.7% with a range of 3.9% to 8.5% during the Younger Dryas but recorded a lower average before and after at 4.9% and 4.6% respectively. Occluded phosphorus acted similarly with a higher average during the cooling event, 2626 µg/g, and lower averages before and after, 1404 µg/g and 1461 µg/g, respectively. This was interpreted as continued productivity and soil development through the cold period which was attributed to a change in biomass.Item The impact of global environmental changes on an exotic invasive species, Alliaria petiolata (garlic mustard)(2016) Collins, Scott J.; Wang, Xianzhong; Clark, Patricia Bohnke; Watson, John C.; Randall, Stephen K.Invasive exotic species have caused severe ecological and economic damages to many communities in the United States and elsewhere. It is therefore important to improve our understanding of how global environmental changes will affect the invasiveness and severity of these invasive species. Over the last century, anthropogenic activities have caused multiple environmental changes. Previous studies have generally focused on the impact of the increasing atmospheric CO2 level on the physiology and growth of invasive species. With atmospheric nitrogen (N) deposition on the rise over the past decades, it is essential to recognize how an increase in soil N will affect the invasiveness of some exotic species. To determine the impact of increased atmospheric N deposition and drought stress on invasive species, I studied the impact of different levels of N on Alliaria petiolata (garlic mustard), an exotic invasive species. In addition, I examined the interactive effects of N deposition and drought stress on garlic mustard. Multiple morphological measurements were used to analyze the growth rate at varying levels of N and soil moisture. The study on N deposition on plant growth will improve our understanding of the invasiveness of garlic mustard. The changes in precipitation patterns must also be examined to foresee if plants in increased atmospheric N conditions can overcome drought stress conditions. I found an increase in plant growth and photosynthetic rate at higher levels of N. Plants with adequate water displayed a continued increase from the lowest level to the highest level of N. Increases in drought stressed plants plateaued at an intermediate N level of 20 kg ha-1. My results demonstrated that during drought stress garlic mustard does not benefit from an increase in N above a certain level. These results are important to take into consideration when we analyze the spreading of invasive weeds due to global environmental changes, including increased atmospheric N deposition and regional drought, in order to apply the optimal management strategies for controlling invasive species.Item INTERACTIVE EFFECTS OF ELEVATED CO2 AND SALINITY ON THREE(Office of the Vice Chancellor for Research, 2012-04-13) Moxley, Donovan; Wang, XianzhongAtmospheric carbon dioxide (CO2) has increased steadily since Pre-Industrial times. The need for a better understanding of the effects of ele-vated CO2 on plant physiology is clear, particularly in the context of other changes and stresses. Previous studies have focused on how plants are af-fected by either elevated CO2 or salinity, one of many plant stresses. How-ever, little is known about the interaction of these two factors on plant growth. In my project, plants were exposed to both elevated CO2 and salini-ty, so that the effects of either factor and the interaction of the two on common grass species could be examined. Three grass species were sub-jects for my experiment. Kentucky bluegrass (Poa pratensis L.) and red fes-cue (Festuca rubra L.), both C3 cool season grasses, as well as buffalo grass(Buchloe dactyloides (Nutt.)Engelm.), a C4 warm season grass, were studied. The CO2 levels were set to 400 μmol mol-1, close to the current concentration, or 760 μmol mol-1, projected to be reached by the end of this century. The salt concentrations were 0, 25, 50, 75, and 100 mM NaCl with CaCl2 added at lower rates (1% of each respective molarity for NaCl). Five replicates per treatment (a total of 150 pots) were grown for 100 days. My results demonstrated stimulated growth at elevated CO2 and inhibited growth with increasing salinity. Collection and statistical analysis of data for variance is being performed to determine which, if any, of the fixed factors had significant effects on the given parameters. My results will improve the understanding of plant responses to multiple environmental changes in the future.Item Interactive Effects of Elevated CO2 and Salinity on Three Common Grass Species(2013-08-14) Moxley, Donovan J.; Wang, Xianzhong; Clark, Patricia; Vaughan, Martin; Atkinson, SimonCarbon dioxide (CO2) level in the atmosphere has increased steadily since Pre-Industrial times. The need for a better understanding of the effects of elevated CO2 on plant physiology and growth is clear. Previous studies have focused on how plants are affected by either elevated CO2 or salinity, one of many environmental stresses for plants. However, little research has been focused on the interaction of these two factors. In my project, three common grass species were exposed to both elevated CO2 and salinity, so that the effects of either of these factors and the interaction of the two on these species could be examined. The CO2 levels were set to 400 µmol mol-1, close to the current concentration, or 760 µmol mol-1, projected to be reached by the end of this century. Salt solutions of 0, 25, 50, 75, and 100 mM NaCl with CaCl2 at lower rates (1% of each respective molarity for NaCl) were used to water the grasses, which are unlikely to experience prolonged exposure to salt conditions beyond this range in their natural habitats. The three common grass species studied in my experiment were Kentucky bluegrass (Poa pratensis L.) and red fescue (Festuca rubra L.), both C3 cool season grasses, as well as buffalo grass (Buchloe dactyloides (Nutt.) Engelm.), a C4 warm season grass. Each treatment had five replicates, bringing the total number of experimental pots to 150. Various growth parameters were monitored, and all data was statistically analyzed for statistical significance. My results showed that elevated CO2 had a stimulating effect on most growth parameters, particularly when plants were given more time to grow. In a 100-day growth experiment, CO2 affected the number and dry biomass of plants of all species, regardless of their C3 or C¬4 photosynthetic pathways. Salinity consistently inhibited germination and growth at all stages, from germination through plant emergences, numbers of established plants, and dry biomasses at harvest. Interactive effects of CO2 and salinity did occur, though often in seemingly specific instances rather than forming clear and consistent trends. My findings suggested that growth of common grasses would be enhanced by the rising level of CO2 in the atmosphere, but the effect would be modified by environmental stresses, such as salinity.Item Investigating the Effects of Synoptic-Scale Climatic Processes on Local-Scale Hydrology by Combining Multi-Proxy Analyses of Lacustrine Sediments and Instrumental Records(2022-09) Gibson, Derek Keith; Bird, Broxton; Gilhooly, William, III; Jacinthe, Pierre-André; Licht, Kathy; Wang, XianzhongPaleoclimate records from North and South America were used to develop a holistic understanding of global paleo-hydroclimatic drivers across a range of boundary conditions. Here, geophysical analysis of lacustrine sediment stratigraphy at Lago de Tota, Boyaca, Colombia provided evidence for significant lake-level fluctuations through the late Quaternary and produced a record that potentially spans the last 60 ka. Seismic data revealed a series of off-lap and on-lap sequences in the upper ~20 m of sediments that indicated large amplitude changes in lake-level, driven by variability in the mean latitude of the Intertropical Convergence Zone as controlled by insolation- and ocean circulation-driven hemispheric temperature gradients during glacial/stadial and interglacial/interstadial events. In North America, late Holocene flood recurrence in the Midwest and Holocene changes in the mean latitude of the polar front jet stream were investigated through multi-proxy examinations of sediment cores collected from swale lakes in northern Kentucky and southern Indiana, and a glacially formed kettle lake in northern Indiana. These results showed that the midlatitude jet stream was displaced to the south during the late Holocene, which increased the amount of Midwestern precipitation sourced from the northern Pacific and Arctic, especially during prolonged cool conditions. During these cool periods, when atmospheric flow was meridional and a greater amount of precipitation was delivered from the northerly sources, Ohio River flooding increased. During warm conditions, when clockwise mean-state atmospheric circulation advected southerly moisture from the Gulf of Mexico into the Midwest, flooding on the Ohio River decreased. At present, streamflow in the Midwest is demonstrated here to be generally increasing, despite atmospheric conditions typically associated with reduced streamflow in the paleo-record, due in part to increasing precipitation and modern land-use dynamics. Together, these studies demonstrate the sensitivity and vulnerability of local-scale hydrological processes to synoptic climate change.Item Mechanistic examination of causes for narrow distribution in an endangered shrub: a comparison of its responses to drought stress with a widespread congeneric species(Springer, 2016-12) Cui, Hongxia; Cong, Shuhua; Wang, Xianzhong; Hao, Haiping; Shi, Lei; Zhang, Huijin; Li, Zhigang; Hu, Tianhua; Qin, Yongsheng; Department of Biology, School of ScienceAlthough deep rooting is usually considered a drought-tolerant trait, we found that Syringapinnatifolia, a deep rooting and hydrotropic shrub, has a limited distribution in arid areas. To elucidate the mechanisms for its narrow distribution, we conducted two experiments to examine the physiological and morphological responses to water availability and heterogeneity in S. pinnatifolia and a widespread congeneric species, S. oblata. We measured gas exchange, water use efficiency, and plasticity index in plants of these two species grown at different levels of soil water regimes and in containers with patched water distribution. Our results showed that high photosynthetic capacity in the narrowly distributed S. pinnatifolia was an important factor enabling its survival in the harsh sub-alpine environment. High photosynthetic capacity in S. pinnatifolia, however, was obtained at the expense of high transpiratory water loss, resulting in lower integrative water use efficiency. Biomass allocation to roots in S. pinnatifolia increased by 73 % when soil water increased from 75 to 95 % field capacity, suggesting that S. pinnatifolia could be less competitive for above-ground resources under favorable water regimes. The horizontal root hydrotropism and vertical root hydrotropism of S. pinnatifolia in soil with patched water patterns were likely related to compensation for leaf water loss at low soil water level, indicating a limited capacity for homeostasis within the plant for water conservation and lower level of inherent drought-tolerance. In summary, greater degree of morphological plasticity but lower degree of physiological adjustment may be the main causes for the hydrotropism and narrow distribution of S. pinnatifolia in the sub-alpine habitats.Item Mediators of Fine-Scale Population Genetic Structure in the Black Blow Fly, Phormia regina (Meigen) (Diptera: Calliphoridae)(2019-08) Owings, Charity Grace; Picard, Christine J.; Walsh, Susan; Wang, Xianzhong; Holland, Jeffery D.; Gilhooly, William, IIIPopulation genetic structure is difficult to assess in blow flies (Diptera: Calliphoridae) due to high connectivity and genetic diversity of subpopulations. Previous studies revealed high relatedness among individuals within wild samples of blow fly populations, however broad geographic structure was absent. The aim of this research was to determine if blow fly genetic structure exists at a fine spatiotemporal resolution and, if so, to elucidate the influence of environmental factors and resource availability on fly genetics. Specifically, blow fly population genetic patterns were tested against a null hypothesis that flies adhere to a patchy population model with high genetic diversity (i.e. no structure) and high resource availability. Samples of the black blow fly, Phormia regina Meigen (Diptera: Calliphoridae), were collected at six urban parks in Indiana, USA (=urban) in 2016 and 2017 (N = 14 and 16 timepoints, respectively). Additional sampling in different ecoregions was performed to determine if trends observed at a high-resolution scale were also present at a broad geographic scale. Therefore, P. regina were also collected at four sites within two national parks (the Great Smoky Mountains and Yellowstone National Parks) over a three-day period. Randomly selected females (N = 10) from each sample underwent the following analyses: 1) gut DNA extraction, 2) molecular analysis at 6 microsatellite loci, 3) vertebrate-specific 12S and 16S rRNA sequencing, and, 4) vertebrate fecal metabolite screening. Flies from the national parks and a comparable subset of urban data also underwent stable isotope analysis (SIA) to determine larval food source. Overall, strong seasonal population genetic structure was observed over both years in the urban environment (2016 F’ST = 0.47, 2017 F’ST 0.34), however spatial structure was lacking, as seen in previous studies (2016 F’ST = 0.04, 2017 F’ST 0.03). Weather conditions prior to and on the day of blow fly collections, interspecific competition, and resource availability greatly impacted the genetic diversity and kinship of P. regina. A total of 17 and 19 vertebrate species were detected by flies in 2016 and 2017, respectively, and many flies tested positive for vertebrate feces, suggesting that many varied resources are important for maintaining high gene flow among geographic locations. Genetic diversity was non-existent in flies collected from the Smokies (F’ST = 0.00), while very slight spatial structure existed in the Yellowstone populations (F’ST = 0.07). Environmental factors such as temperature, humidity, and wind speed were all statistically relevant in maximizing fly collections with vertebrate resources. In 720 min of total sampling time in the national parks and a subset of urban data, 28 vertebrate species were identified, and fecal resources appeared to be the most abundant in Yellowstone. Stable isotope analysis revealed a majority of larval resources in the national parks were herbivores, with a more even distribution of carnivore and herbivore carcasses present in the urban environment, which likely explains the high genetic diversity of adult flies in these regions. Overall, the null hypothesis that P. regina adheres to a patchy population model could not be rejected for the Smokies populations. However, the urban and Yellowstone populations appear to adhere to a Levins metapopulation model in which variable availability in resources leads to random bottleneck events in the local populations. Overall, environmental conditions, competition, and resource availability are all important factors influencing P. regina population genetic structure in different environments.