Progress 09/01/09 to 08/31/14
Outputs
Target Audience: Target audiences include the research communities in aerobiology and biosafety; policymakers who need findings to inform regulatory aspects of gene flow; producers with responsibilities for maintaining genetic purity; and those concerned with regulatory aspects of genetically-modified plants. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? The grant has provide training for one postdoctoral associate (Landon Bunderson) who has completed field studies and will assist with integration of switchgrass into the dispersion model. The investigators are furthering Dr. Bunderson's professional development through mentoring as well as giving him opportunities for manuscript reviews, project design, and other activities expected of a mature scientist. The project also has provided research experience for one undergraduate student (Cody Simons) who has assisted with field measurements. Mr. Simons has expressed interest in summarizing his work for the project in a conference presentation. How have the results been disseminated to communities of interest? A presentation was made at the Agronomy Society of America, Crop Science Society of America, Soil Science Society of America joint annual meeting in Long Beach, CA in 2014. The presentation was titled, "Simulated Pollen Dispersion in an Island Environment." What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
We have successfully coupled our pollen dispersion model with a nationally-adopted atmospheric wind model (Weather Regional Forcast) and tested its utility over highly variable terrain. We also have generalized the model hybrid so it can be used for a wide range of wind-pollinated crops. Our simulations of pollen dispersal over the very complex terrain of the Hawaiian island of Kauai, for example, indicate the local terrain and coastlines have a profound influence on predicted pollen dispersion, which may be different from expected patterns used for spatial isolation. Dispersion of smaller pollen grains can be greatly extended inland by channeling within valleys, or extended offshore by local sea breeze circulations. Small pollen grains typical of grass pollen had the potential for transport as far as the island of Ni'ihau, about 30 km (18 miles) to the west. More than 99% of larger pollen grains typical of maize, however, were predicted to land within 10 meters (30 ft) of the source. The capacity to predict such effects of fine-scale circulations on pollen dispersion could support commercial efforts to ensure seed purity where high-value seed production facilities are located. Owing to current USDA interest in biofuels and biomass crops, we are implementing the model for switchgrass. This requires knowledge of aerodynamic properties of the pollen grain and timing of pollen shed, which presently are not well quantified for this important biofuel crop.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Viner, B.J., M.E. Westgate, and R. Arritt. 2014. Simulated Pollen Dispersion in an Island Environment. ASA, CSSA and SSSA Annual Meeting, Nov. 2-5, Long Beach, CA.
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Progress 09/01/12 to 08/31/13
Outputs
Target Audience: Other scientists. Changes/Problems: As noted in our previous report the project has been delayed for some months because the previous postdoctoral associate (Brian Viner) moved to employment at a Federal laboratory. We advertised internationally and ultimately were successful in hiring an outstanding postdoctoral associate, Dr. Landon Bunderson, whose Ph.D. work dealt specifically with pollen dispersion. Owing to his prior experience Dr. Bunderson has required very little training and the project now is proceeding. What opportunities for training and professional development has the project provided? The grant has provide training for one postdoctoral associate (Landon Bunderson) who is performing field studies and will assist with integration of switchgrass into the dispersion model. The investigators are furthering Dr. Bunderson's professional development through mentoring as well as giving him opportunities for manuscript reviews, project design, and other activities expected of a mature scientist. The project also has provided research experience for one undergraduate student (Cody Simons) who has assisted with field measurements. Mr. Simons has expressed interest in summarizing his work for the project in a conference presentation. How have the results been disseminated to communities of interest? A paper describing our pollen dispersion simulations for the Hawaiian island of Kauai has been submitted to International Journal of Biometeorology and is presently under review. A presentation was made to the European Geosciences Union General Assembly 2013, Vienna, Austria, 7- 12 April 2013. What do you plan to do during the next reporting period to accomplish the goals? We have successfully coupled our dispersion model with the Weather Research and Forecasting (WRF) atmospheric model and have generalized it so that it can be used for other wind-pollinated crops. As stated in the proposal, the model should be implemented for a range of wind-pollinated species in order to assess the model's generality. Owing to current USDA interest in biofuels and biomass crops we will implement the model for switchgrass. This requires knowledge of aerodynamic properties of the pollen grain and timing of pollen shed, which presently are not well quantified for switchgrass. We have begun obtaining measurements of these quantities at a nearby switchgrass research plot. During the next reporting period these measurements will be completed. Spatial and temporal trends of pollen shed will be quantified relative to measured weather conditions. We will supplement the field data with laboratory measurements of switchgrass pollen size spectra and fall speed. Results of both the field and laboratory data will be analyzed and cast into functional relationships that can be implemented in our pollen dispersion model. We then will execute the dispersion model and test the results against observations. Findings will be submitted for publication in the peer-reviewed literature.
Impacts
What was accomplished under these goals?
We continued our analysis of high-resolution simulations over the Hawaiian island of Kauai that were described in our previous annual report. These simulations indicate that modification of local airflow by terrain and coastlines has a profound influence on predicted pollen dispersion. Our simulations indicate that pollen grains typical of the size of grass pollen had the potential to be transported as far as the island of Ni'ihau, about 30 km (18 miles) to the west. We have submitted a paper summarizing these findings to the International Journal of Biometeorology (currently in review). We also have begun measurements of the seasonal and daily pattern of pollen shed from switchgrass as a preparatory step for including switchgrass into our dispersion model. A portable weather station immediately adjacent to the switchgrass plot is providing contemporaneous weather data (temperature, humidity, winds) so that the relationship of pollen shed environmental conditions can be quantified. Preliminary results indicate that pollen shed from switchgrass is at a much lower rate than from maize, and that the pollen shed period is of much longer duration during the season. On the other hand, the daily pattern of pollen shed for switchgrass is similar to that for maize, with a peak in early to mid-morning. Field and laboratory experimentation will continue to quantify this shed pattern in terms of specific biophysical controls.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Arritt, R.W., B.J. Viner and M.E. Westgate, 2013: Influence of boundary-layer dynamics on pollen dispersion and viability. Presented at European Geosciences Union General Assembly 2013, Vienna, Austria, 7- 12 April 2013.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2013
Citation:
Viner, B.J., R.W. Arritt and M.E. Westgate. 2013. Simulated pollen dispersion in an island environment. Submitted to International Journal of Biometeorology.
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Progress 09/01/11 to 08/31/12
Outputs
OUTPUTS: We have accomplished the goal stated in our original proposal of generalizing our pollen dispersion modeling system from its original formulation for maize to include the capability of modeling pollen dispersion from other types of plants and to highly complex terrain. We have then proceeded to apply the model to novel situations. Most recently, a suite of high-resolution simulations over the Hawaiian island of Kauai was completed for representative dates during an El Nino-La Nina-neutral cycle and have been analyzed in detail. These results showed both expected and surprising results, reflecting the influence of terrain and coastlines on local circulations both near the surface and aloft that determine pollen dispersion. PARTICIPANTS: Mark Westgate, Professor (project director; advises on plant physiology and pollen shed and properties of various species). Raymond W. Arritt, Professor (numerical model development; design of numerical simulations). Brian J. Viner, Postdoctoral Associate (performs simulations using the coupled modeling system; compares model results to observed data); now at Savannah River National Laboratory. TARGET AUDIENCES: Target audiences include the research communities in aerobiology and biosafety; policymakers who need findings to inform regulatory aspects of gene flow; producers with responsibilities for maintaining genetic purity; and those concerned with regulatory aspects of genetically-modified plants. PROJECT MODIFICATIONS: No major changes. A delay was experienced when the postdoctoral associate moved to new employment, necessitating a request for a no-cost extension to the project.
Impacts
As expected, predicted pollen transport for representative situations in Kauai is sensitive to the aerodynamic characteristics of the pollen grain. In most cases large pollen grains (such as maize) are not predicted to travel far. There are a few source locations where transport is extended owing to the release site's orientation relative to terrain and coastline, especially when the local terrain is high compared to its immediate surroundings. Such variability in transport points to the need for fine spatial detail when evaluating pollen dispersion in regions of complex terrain. Our findings also indicate that dispersion of smaller pollen grains can be greatly extended inland by channeling within valleys, or extended offshore by local sea breeze circulations. Model results show the potential for pollen grains of diameter 20 microns or less to be transported from Kauai to the island of Ni'ihau about 25 km (16 miles) to the east. These results indicate potential for dispersal of pollen from genetically modified crops to induce gene flow at a locations that might otherwise be presumed to be isolated by distance or water. We have presented our approach and results to an international conference on implications of large-scale production of genetically modified crops, at which policymakers and NGO representatives were in attendance.
Publications
- Viner, B.J. and Arritt, R.W. 2011 Small-scale circulations caused by complex terrain affect pollen deposition. Crop Science 52, 904-913, doi: 10.2135/cropsci2011.07.0354.
- Arritt, R., Viner, B. and Westgate, M. 2012. Predicting GM pollen dispersion at large spatial scales. Abstracts, International Conference on Implications of GM-Crop Cultivation at Large Spatial Scales. Bremen, Germany. 14-15 June 2012. Available at http://www.mapserver.uni-vechta.de/generisk/tagung/text/Programmheft. pdf
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Progress 09/01/10 to 08/31/11
Outputs
OUTPUTS: Our pollen dispersion modeling system, which combines a Lagrangian dispersion model (LDM) with the Weather Research and Forecasting (WRF) model for atmospheric flow, has been generalized from its original formulation for maize. As planned in our proposal it has now been applied to other species (bentgrass and sugarbeet) and to other locations (such as Hawaii). This generalization of the model is accomplished by specifying the aerodynamic characteristics of pollen grains for the species under consideration. We have found that model results agree with previous reports of outcross events from genetically-modified pollen at a site in highly complex terrain in Oregon. A journal paper on these results has been accepted subject to revision. Simulations over Hawaii have been completed and are being prepared for dissemination. PARTICIPANTS: Mark Westgate, Professor (project director; advises on plant physiology and pollen shed and properties of various species). Raymond W. Arritt, Professor. (model development; design of numerical simulations). Brian J. Viner, Postdoctoral Associate (performs simulations using the coupled modeling system; compares model results to observed data). TARGET AUDIENCES: The main target audiences are the research community in aerobiology; policymakers who need information on unintended gene flow; and those concerned with regulatory aspects of genetically-modified plants. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
As stated earlier our combined modeling system has been found to be consistent with observations of gene flow in a site of highly complex terrain in central Oregon (reported by Watrud and colleagues). We successfully predicted that pollen would be deposited at locations where outcross events were found. We also compared results for different days to infer the specific circumstances leading to outcross; these results broadly agree with suggestions from a simpler pollen transport model. We have found interesting and unexpected absence of pollen deposition on the windward side of mountains, which we attribute to flow convergence and terrain-relative ascent of the flow. In another application we have simulated dispersion of pollen around the island of Kauai, where there is intensive commercial seed production activity. We find that large pollen grains (such as maize) usually do not travel more than a kilometer from their origin. In contrast smaller pollen grains are predicted to travel 10 kilometers or more and their dispersion can be strongly affected by slope flows induced by the island's mountainous terrain and in sea breeze circulations, leading to highly complex patterns of dispersion and deposition. These effects of fine-scale circulations on pollen dispersion suggest that seed purity could differ significantly depending on the specific site where seed production facilities are located. Therefore, meteorological monitoring and modeling should be conducted when siting such operations in order to evaluate the occurrence of complex atmospheric circulations that could lead to long-distance pollen transport and thus increased potential for unintended outcrossing. In order to fully evaluate the potential for outcrossing further research is needed to assess whether pollen will be viable after traveling long distances. At present it is not possible to predict changes in pollen variability during travel for most species because supporting measurements are unavailable. Measurement programs to support modeling of pollen viability will be a topic of our future research.
Publications
- No publications reported this period
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Progress 09/01/09 to 08/31/10
Outputs
OUTPUTS: We have generalized and extended our pollen dispersion modeling system which combines a Lagrangian dispersion model (LDM) with the Weather Research and Forecasting (WRF) model for atmospheric flow. The WRF model predicts fields of the atmospheric variables that drive dispersion (three-dimensional winds and turbulence) while the Lagrangian dispersion model uses these predicted fields from WRF to determine potential flight paths of tracer particles. The tracer particles are prescribed the characteristics of simulated pollen grains based on model input including the type of particle, the terminal fall speed, and prescribed changes in pollen viability. The model was originally developed for maize and we have recently extended it to bentgrass. This year we also extended the model to sugar beet. For bentgrass, model results agree with previous reports of outcross events from genetically-modified pollen at a site in Oregon. Results have also been presented at the 19th Symposium on Boundary Layers and Turbulence and the 29th Conference on Agricultural and Forest Meteorology. PARTICIPANTS: Mark Westgate, Professor. Project director and guidance for modeling plant and pollen charactistics. Raymond W. Arritt, Professor. Guidance for model development. Brian J. Viner, Postdoctoral Research Associate. Performs simulations of the WRF/LDM/Outcross model, analyzes model results and compares to collected and published data. TARGET AUDIENCES: Our target audience is primarily researchers focusing on issues in aerobiology and those with an interest in policy decisions related to the isolation genetically-modified plants. Our results have also been presented at the 19th Symposium on Boundary Layers and Turbulence and the 29th Conference on Agricultural and Forest Meteorology. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The combined WRF/LDM model was found to be consistent with observed data for bentgrass dispersion. Our simulation of bentgrass pollen dispersion predicted the presence of adventitious pollen at all of the locations with observed outcross. Our results also agree with earlier results using a simpler model, in that the observed outcross was attributable to dispersion on a specific date rather than general pollen flow during the period of pollen release. Another aspect of pollen dispersion that has been seen in our results is gaps in pollen deposition over valleys or on the upwind slopes of mountains in regions of complex terrain. Though we are still seeking the underlying causes for these gaps in deposition, their presence could be important when planning where to plant crops that need to be shielded from adventitious genetically-modified pollen. We note that characteristics of pollen shed and viability in other plants, such as bentgrass, have not been examined to as great an extent as in maize. As a result, predictions of outcross in plants other than maize will be subject to limited data. Exposing this lack of data in plants with genetically-modified relatives should encourage further research into the mechanisms of pollen dispersion and potential outcross.
Publications
- Viner, B.J. and R.W. Arritt (2010). Increased pollen viability resulting from transport to the upper boundary layer. Field Crops Research 119, 195-200.
- Viner, B.J., M.E. Westgate and R.W. Arritt (2010). A model to predict diurnal pollen shed in maize. Crop Science 50, 235-245.
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