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Browsing by Author "Webb, Elisabeth B."

Now showing 1 - 7 of 7
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    Beyond neonicotinoids - Wild pollinators are exposed to a range of pesticides while foraging in agroecosystems
    Main, Anson R.; Hladik, Michelle L.; Webb, Elisabeth B.; Goyne, Keith W.; Mengel, Doreen (2020-11-10)
    Pesticide exposure is a growing global concern for pollinator conservation. While most current pesticide studies have specifically focused on the impacts of neonicotinoid insecticides toward honeybees and some native bee species, wild pollinators may be exposed to a broader range of agrochemicals. In 2016 and 2017 we collected a total of 637 wild bees and butterflies from the margins of cultivated agricultural fields situated on five Conservation Areas in mid-northern Missouri. Pollinators were composited by individual genera (90 samples) and whole tissues were then analyzed for the presence of 168 pesticides and degradation products. At least one pesticide was detected (% frequency) in the following wild bee genera: Bombus (96%), Eucera (75%), Melissodes (73%), Pnlothrix (50%), Xylocopa (50%), and Megachile ( 17%). Similarly, at least one pesticide was detected in the following lepidopteran genera: Hemaris (100%), Hylephila (75%), Danaus (60%), and Colitis (50%). Active ingredients detected in >2% of overall pollinator samples were as follows: metolachlor (24%), tebuconazole (22%), atrazine (18%), iinidadoprid desnitro (13%), bifenthrin (9%), flumetralin (9%), p, p'-DDD (6%), tebupirimfos (4%), Iludioxonil (4%), flutriafol (3%), cyproconazole (2%), and oxacliazon (2%). Concentrations of individual pesticides ranged from 2 to 174 ng/g. Results of this pilot field study indicate that wild pollinators arc exposed to and are potentially bioaccumulating a wide variety of pesticides in addition to neonicotinoids. Here, we provide evidence that wild bee and butterfly genera may face exposure to a wide range of insecticides, fungicides, and herbicides despite being collected from areas managed for conservation. Therefore, even with the presence of extensive habitat, minimal agricultural activity on Conservation Areas may expose pollinators to a range of pesticides. Published by Elsevier B.V.
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    Clothianidin decomposition in Missouri wetland soils
    Beringer, Chelsey J.; Goyne, Keith W.; Lerch, Robert N.; Webb, Elisabeth B.; Mengel, Doreen (2021-01)
    Neonicotinoid pesticides can persist in soils for extended time periods; however, they also have a high potential to contaminate ground and surface waters. Studies have reported negative effects associated with neonicotinoids and nontarget taxa, including aquatic invertebrates, pollinating insect species, and insectivorous birds. This study evaluated factors associated with clothianidin (CTN) degradation and sorption in Missouri wetland soils to assess the potential for wetland soils to mitigate potential environmental risks associated with neonicotinoids. Solid-to-solution partition coefficients (K-d) for CTN sorption to eight wetland soils were determined via single-point sorption experiments, and sorption isotherm experiments were conducted using the two most contrasting soils. Clothianidin degradation was determined under oxic and anoxic conditions over 60 d. Degradation data were fit to zero- and first-order kinetic decay models to determine CTN half-life (t(0.5)). Sorption results indicated CTN sorption to wetland soil was relatively weak (average K-d, 3.58 L kg(-1)); thus, CTN has the potential to be mobile and bioavailable within wetland soils. However, incubation results showed anoxic conditions significantly increased CTN degradation rates in wetland soils (anoxic average t(0.5), 27.2 d; oxic average t(0.5), 149.1 d). A significant negative correlation was observed between anoxic half-life values and soil organic C content (r(2) = .782; p = .046). Greater CTN degradation rates in wetland soils under anoxic conditions suggest that managing wetlands to facilitate anoxic conditions could mitigate CTN presence in the environment and reduce exposure to nontarget organisms.
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    Field-level characteristics influence wild bee functional guilds on public lands managed for conservation
    Main, Anson R.; Webb, Elisabeth B.; Goyne, Keith W.; Mengel, Doreen (2019-01)
    Throughout the Midwestern US, many public lands set aside for conservation engage in management activities (e.g., agriculture) that may act as stressors on wild bee populations. Several studies have investigated how wild bees respond to large-scale agriculture production; however, there has been limited assessment of how wild bees may be impacted by agricultural activity on public lands or how local variables may influence bee communities in these same areas. In this study, we assessed the abundance and richness of wild bee floral and nesting guilds at 30 agricultural field margins located on five Conservation Areas in Missouri. Generally, regardless of guild, bee abundance and richness was greater in field margins with more floral diversity and taller vegetation. Bee guilds responded negatively to agricultural production in Conservation Areas with fewer soil- and cavity-nesting bees collected in margins adjacent to annually cropped fields. Although fewer diet specialists were collected, specialist bee abundance and richness was greater in margins near fields that were uncropped (i.e., vegetated, but not row-cropped) during the previous year. Overall, the percentage of trees and shrubs within 800 m of study fields (i.e., "woodland") was negatively associated with abundance and richness of bees, but specifically, reduced richness of soil-nesters and diet specialists. Our findings indicate agricultural management activities on public lands may lead to decreased abundance and richness of wild bee guilds. If public lands are to be managed for species diversity, including wild bees, maintaining diverse plant communities with taller vegetation (>100 cm) near cultivated fields and/or modifying agricultural production practices on public lands may greatly improve the conservation of local bee communities. (C) 2019 The Authors. Published by Elsevier B.V.
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    Framework for using downscaled climate model projections in ecological experiments to quantify plant and soil responses
    Owen, Rachel K.; Webb, Elisabeth B.; Goyne, Keith W.; Svoma, Bohumil M.; Gautam, Sagar (2019-09)
    Soil and plant responses to climate change can be quantified in controlled settings. However, the complexity of climate projections often leads researchers to evaluate ecosystem response based on general trends, rather than specific climate model outputs. Climate projections capture spatial and temporal climate extremes and variability that are lost when using mean climate trends. In addition, application of climate projections in experimental settings remains limited. Our objective was to develop a framework to incorporate statistically downscaled climate model projections into the design of temperature and precipitation treatments for ecological experiments. To demonstrate the utility of experimental treatments derived from climate projections, we used wetlands in the Great Plains as a model ecosystem for evaluating plant and soil responses. Spatial and temporal projections were selected to capture variability and intensity of projected future conditions for exemplary purposes. To illustrate climate projection application for ecological experiments, we developed temperature and precipitation treatments based on moderate-emissions scenario climate outputs (i.e., RCP4.5-650 ppm CO2 equivalent). Our temperature treatments captured weekly trends that represented cool, average, and warm temperature predictions, and our daily precipitation treatments mimicked various seasonal precipitation trends and extreme events projected for the late 21st century. Treatments were applied to two short-term controlled experiments evaluating (1) plant germination (temperature treatment applied in growth chamber) and (2) soil nitrogen cycling (precipitation treatment applied in greenhouse) responses to projected future conditions in the Great Plains. Our approach provides flexibility for selecting appropriate and precise climate model outputs to design experimental treatments. Using these techniques, ecologists can better incorporate variation in climate model projections for experimentally evaluating ecosystem responses to future climate conditions, reduce uncertainty in predictive ecological models, and apply predicted outcomes when making management and policy decisions.
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    Impacts of neonicotinoid seed treatments on the wild bee community in agricultural field margins
    Main, Anson R.; Webb, Elisabeth B.; Goyne, Keith W.; Abney, Robert; Mengel, Doreen (2021-09-10)
    Wild bees support global agroecosystems via pollination of agricultural crops and maintaining diverse plant communities. However, with an increased reliance on pesticides to enhance crop production, wild bee communities may inadvertently be affected through exposure to chemical residues. Laboratory and semi-field studies have demonstrated lethal and sublethal effects of neonicotinoids on limited genera (e.g., Apis, Bombus, Megachile), yet full field studies evaluating impacts to wild bee communities remain limited. Here, we conducted a two-year field study to assess whether neonicotinoid seed treatment and presence in environmental media (e.g., soil, flowers) influenced bee nest and diet guild abundance and richness. In 2017 and 2018, we planted 23 Missouri agricultural fields to soybeans (Glycine max) using one of three seed treatments: untreated (no insecticide), treated (imidadoprid), or previously-treated (untreated, but neonicotinoid use prior to 2017). During both years, wild bees were collected in study field margins monthly (May to September) in tandem with soil and flowers from fields and field margins that were analyzed for neonicotinoid residues. Insecticide presence in soils and flowers varied over the study with neonicotinoids infrequently detected in both years within margin flowers (0%), soybean flowers (<1%), margin soils (<8%), and field soils (similar to 39%). Wild bee abundance and species richness were not significantly different among field treatments. In contrast, neonicotinoid presence in field soils was associated with significantly lower richness (ground- and aboveground-nesting, diet generalists) of wild bee guilds. Our findings support that soil remains an underexplored route of exposure and long-term persistence of neonicotinoids in field soils may lead to reduced diversity in regional bee communities. Future reduction or elimination of neonicotinoid seed treatment use on areas managed for wildlife may facilitate conservation goals to sustain viable, diverse wild bee populations. Published by Elsevier B.V.
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    Projected climate and land use changes drive plant community composition in agricultural wetlands
    Owen, Rachel K.; Webb, Elisabeth B.; Haukos, David A.; Goyne, Keith W. (2020-07)
    Playa wetlands in the Great Plains, USA support a wide variety of plant species not found elsewhere in this agriculturally-dominated region due to the ephemeral presence of standing water and hydric soils within playas. If longer dry periods occur due to climate change or if changes in surrounding land use alter sediment accumulation rates and water storage capacity in playas, plant communities could experience decreased diversity, with lasting effects on ecosystem services provided by playas in the Great Plains and at a continental-level in North America. We quantified potential changes in playa wetland plant community composition associated with predicted changes in precipitation and land use in the Great Plains through the end of the 21st century. We conducted two six-month greenhouse experiments mimicking field conditions using intact mesocosms collected from playas in Nebraska and Texas. In the precipitation experiment, treatments derived from historical precipitation observations and three future moderate emissions (CMIP5 RCP4.5) downscaled climate projections were applied to mesocosms. For the land use experiment, treatments were simulated by nitrogen (N) applications to soil ranging from 0 to 100 mg-N L-1 with each precipitation event under historical rainfall patterns, representing increasing and decreasing area in agricultural use in playa watersheds. Plant communities tended to shift toward more native species under projected future climate conditions, but as N runoff increased, native species richness decreased. Agricultural land-use surrounding playas may have a greater effect on wetland plant communities than future alterations to hydrology based on climate change in the Great Plains; thus, efforts to reduce nutrient runoff into playas would likely mitigate loss in ecosystem function in the coming decades.
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    Reduced species richness of native bees in field margins associated with neonicotinoid concentrations in non-target soils
    Main, Anson R.; Webb, Elisabeth B.; Goyne, Keith W.; Mengel, Doreen (2020-01-01)
    Native bees are in decline as many species are sensitive to habitat loss, climate change, and non-target exposure to synthetic pesticides. Recent laboratory and semi-field assessments of pesticide impacts on bees have focused on neonicotinoid insecticides. However, field studies evaluating influences of neonicotinoid seed treatments on native bee communities of North America are absent from the literature. On four Conservation Areas of Missouri, we sampled row-cropped (treated, n = 15) and reference (untreated, n = 9) agricultural fields, and their surrounding field margins for neonicotinoids in soil and non-target vegetation (i.e., native wildflowers). Wildflowers were further collected and screened for the presence of fungicides. Concurrently, we sampled native bees over three discrete time points throughout the agricultural growing season to assess potential impacts of seed treatment use on local bee populations over time. Neonicotinoids were detected in 87% to 100% of treated field soils and 22% to 56% of reference field soils. In adjacent field margin soils, quantifiable concentrations were measured near treated (53% to 93% detection) and untreated fields (33% to 56% detection). Fungicides were detected in < 40% of wildflowers, whereas neonicotinoids were rarely detected in field margin vegetation (< 7%). Neonicotinoid concentrations in margin soils were negatively associated with native bee richness (beta = -0.21, P < 0.05). Field margins with a combination of greater neonicotinoid concentrations in soil and fungicides in wildflowers also contained fewer wild bee species (beta = -0.21, P < 0.001). By comparison, bee abundance was positively influenced by the number of wildflower species in bloom with no apparent impact of pesticides. Results of this study indicate that neonicotinoids in soil are a potential route of exposure for pollinator communities, specifically ground-nesting species. Importantly, native bee richness in non-target field margins may be negatively affected by the use of neonicotinoid seed treatments in agroecosystems.