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Item No. 1 of 5ACCESSION NO: 0186176 SUBFILE: CRIS
INVESTIGATOR: Mortensen, D. A.
UNIVERSITY OF NEBRASKA
LINCOLN, NEBRASKA 68583
SPATIAL DISTRIBUTION OF WEED PATCHES: THE INFLUENCE OF HABITAT HETEROGENEITY
OBJECTIVES: 1. Quantify the influence of habitat suitability on velvetleaf (Abutilon theophrasti) and common sunflower (Helianthus annuus) seedbank fate, seedling establishment and reproductive fitness. 2. Determine the extent to which seedbank density of H. annuus and A. theophrasti, as well as the distribution pattern of seeds within the seedbank, can influence the frequency of safe sites by improving the rate of successful germination and seedling establishment. 3. Determine the extent to which distribution of weed patches matches the distribution of areas with a high frequency of safe sites.
APPROACH: Previous results from weed patch characterization studies have shown that weeds tend to form patches that remain relatively stable over time. Our simulation studies indicate that while density dependent mortality plays an important role in this stability it alone can't account for these patterns. Greenhouse and field experiments will be conducted to determine to what extent seedling establishment and reproductive fitness is tied to factors determining habitat suitability. Greenhouse experiments will be conducted using field- collected soil representing the range of soil organic matter and soil texture present at the field study site. Experiments will be conducted in the field and in the greenhouse in which seedbanks will be established in a range of soil conditions. Management practices representative of typical farm fields in the area will be applied to these seedbank populations and the impact of these practices on mortality, seedling and reproductive fitness will be measured. To address the second objective, two contrasting soils with regard to physical properties will be selected from the same study site described in the first objective. A range of seedbank densities will be established in the greenhouse to determine the influence of local seedbank density on survival. A comprehensive spatially explicit weed patch dynamics model will be redesigned than applied to simulate interal patch dynamics as well as explore the factors that limit spread in our study system. Such a model will embody our understanding of the underlying processes. We need to test how closely our model will be able to predict patterns observed in actual fields.
NON-TECHNICAL SUMMARY: Weed patchiness is commonplace in agricultural fields yet little is known about it's causes. This project explores the factors that give rise to weed patchiness through greenhouse and field experiments and through model simulation. From a practical point of view farmers could learn about weak links in management practices or strategies if the mechanisms giving rise to patchiness are understood.
PROGRESS: 2000/08 TO 2001/06
The focus of this project is elucidating the mechanisms giving rise to patchy weed distributions in agricultural fields and assessing their relative importance. Through this work we have demonstrated a strong dependence of weed management outcomes on initial weed infestation level. These results suggest that infestation level varies at the scale of the field and sub-whole field. Therefore, generalizations about the appropriateness of integrated weed management systems necessarily must be aimed at the unique conditions of individual fields. In the past year we used the results of past fieldwork to guide the development of a spatially explicit population dynamics model. The model is designed to assist us in determining the relative importance of a number of life-history traits and population regulation processes on weed population size and distribution. The cellular automata model, written in Visual Basic was completed this Spring and used to run a series of sensitivity analyses. Those analyses indeed underscore the important role that density dependent mortality plays in weed plant survival but the model was also surprisingly sensitive to variation in site suitability. The suitability of a site strongly influenced the shape and extent of weed patches. The results of the model simulations have been used to quide the design of two field experiments initiated this fall to assess the importance of site suitability at several life history stages. Work is underway to identify farmer-cooperators for implementing alternative weed management strategies where intensity of management is varied with weed population density and other factors influencing the success of integrated weed management systems.
IMPACT: 2000/08 TO 2001/06
This is a work in progress. Through the published or presented papers resulting from this project we have been able to assess the relative importance of processes like density dependent mortality occurring during the seed to seedling life history transitions. It's relative importance as a factor regulating population size is far greater than was initially thought and has a more profound impact on weed population size than late season density dependent self thinning. Empirical work continues in which the influence of soil heterogeneity on the seed to seedling transition is being studied and the cellular automata model is being rewritten to be compatible with ARC-VIEW 8.
PUBLICATIONS: 2000/08 TO 2001/06
1. Mortensen, D.A., L. Bastiaans and M. Sattin. 2000. The role of ecology in the development of weed management systems: an outlook. Weed Research 40:49-62.
2. Burton, M.G., D.A. Mortensen, D.B. Marx, and J.L. Lindquist. 2002. Niche effects on wild Helianthus annuus L. in maize (Zea mays L.): Seed germination, emergence and survival. Weed Science, In press.
3. Williams, M.M., R. Gerhards, and D.A. Mortensen. 2002. Two-year weed seedling population responses to a post-emergent method of site-specific weed management. Precision Agriculture, In press.
4. Neeser, C., J.A. Dieleman, and D.A. Mortensen. 2002. The influence of velvetleaf density on the efficacy of bentazon. Weed Science, In review.
5. Burton, M.G., D.A. Mortensen, J.L. Lindquist, and A.R. Martin. 1999. The influence of soil characteristics and location on the fitness and control of common sunflower (Helianthus annuus L). Weed Science Soc. of Amer. 39:67.
6. Dieleman, J.A., D.A. Mortensen, D.D. Buhler, C.A. Cambardella, and T.B. Moorman. 2000. Identifying associations among site properties and weed species abundance. Part I. Multivariate analysis applied to data from a central Iowa corn-soybean field. Weed Science 48: 567-575.
7. Dieleman, J.A., D.A. Mortensen, D.D. Buhler, and R.B. Ferguson. 2000. Identifying associations among site properties and weed species abundance. Part II. Hypothesis generation based on data from two central Nebraska corn fields. Weed Science 48:576-587.
Name: Mortensen, D. A.
Item No. 2 of 5ACCESSION NO: 0187406 SUBFILE: CRIS
INVESTIGATOR: Alfano, J. R.
UNIVERSITY OF NEBRASKA
LINCOLN, NEBRASKA 68583
SECRETION PROPERTIES OF THE TYPE III SECRETION SYSTEM OF PSEUDOMONAS SYRINGAE
OBJECTIVES: In general, the experiments described in this proposal are designed to reveal secretion properties of the type III (Hrp) secretion pathway of Pseudomonas syringae. One major goal is to identify and delimit the secretion signals utilized by one type III-secreted protein, HopPsyA (HrmA). The specific objectives of our work follow: 1. Determination of secretion signals that facilitate the type III secretion of HopPsyA. 2. Identification of additional Hop proteins that travel the P. syringae type III pathway. 3. Establish direct evidence for the translocation of HopPsyA into eucaryotic cells. 4. Identify tomato proteins that interact with HopPtoB using the yeast 2-hybrid system.
APPROACH: Based on preliminary evidence, HopPsyA appears to use a molecular chaperone and we will aoso test whether the hopPsyA mRNA has its own secretion signal. Other experiments will exploit the recent progress that researchers have made in detecting type III-secreted proteins in culture supernatants to isolate additional proteins that travel the Hrp pathway. To properly categorize the type III-secreted proteins, we are developing a series of assays designed to identify effector proteins that are translocated into eucaryotic cells. As an ongoing effort to identify effector targets in the plant, our last objective uses the yeast 2-hybrid system to screen for plant proteins that interact with a protein, HopPtoB, that we have recently identified as a type III-secreted protein.
NON-TECHNICAL SUMMARY: Of plant pathogenic bacteria, the P. syringae type III secretion system is argubly the most developed system and since P. syringae is pathogenic on the genetic amenable model plant, Arabidopsis, it is likely to become a model pathogen to study how type III secretion systems mediate interactions with plants. The research described in this proposal should provide important information about type III secretion systems and be of broad interest to researchers studying bacterial pathogenesis. Increasing our understanding how type III pathways deliver virulence proteins to the interior of host cells may help in the design of pharmaceuticals and/or agricultural pesticidesor herbicides.
PROGRESS: 2000/10 TO 2001/09
The revised objectives of our current USDA/NRI grant (Secretion properties of the type III secretion system of Pseudomonas syringae; proposal Number:2000-05979; $240,000; 12/00-11/03) were to the following: (1) Determination of secretion signals that facilitate the type III secretion of HopPsyA; (2) Identification of additional Hop proteins that travel the P. syringae type III pathway; (3) Identify tomato proteins that interact with HopPtoB using the yeast 2-hybrid system. We have made good progress in the first year of our grant cycle especially when one considers that we moved from the University of Nevada - Las Vegas to the University of Nebraska - Lincoln (UNL) in September 2000. During my first year at UNL, I hired 3 postdoctoral associates, 1 technician, and gained one additional graduate students. Thus, my research group has essentially doubled in size and they are all focused on type III secretion in P. syringae and I expect that year 2 of this project will even produce more progress. Determining whether ShcA binds HopPsyA. For additional evidence that ShcA acts as a chaperone for HopPsyA, we performed protein-protein interaction assays. We originally tried to immunoprecipitate HopPsyA and a FLAG epitope-tagged version of ShcA with anti-HopPsyA antibodies. Briefly, E. coli cells carrying either pFLAG-CTC::shcA or a plasmid that carries hopPsyA were disrupted by sonification and cytoplasmic extracts representing intracellular soluble proteins were isolated. Soluble proteins were mixed with HiTrap Protein G covalently linked to either anti-HopPsyA or anti-FLAG antibodies. Immunoblot analysis was carried out with the antibody not conjugated to the protein G beads. For example, if we mixed the extracts with anti-HopPsyA protein G beads then our experimental immunoblot used anti-FLAG antibodies to determine if SchA-FLAG coprecipitated with HopPsyA. We did produce evidence that ShcA was interaction with HopPsyA using this technique, but the reproducibility of this assay in our hands was not comforting. Thus, we decided to employ another protein-protein assay instead, which avoided immunopreciptiation. In these experiments we had hopPsyA and shcA-flag cloned on the same broad host vector expressed in a P. s. syringae 61 shcA mutant. We then mixed extracts with FLAG affinity gel followed by several wash steps. Using this technique we were successful in clearly demonstrating that ShcA-FLAG binds to HopPsyA. This is essentially the acid test for a type III chaperone. We are now preparing a manuscript to report this finding that also contains the following information: Secretion assays showing that ShcA is required for the type III secretion of HopPsyA based on several independent shcA mutants; and that the translocation of HopPsyA into tobacco cells is severely reduced in the absence of ShcA.
IMPACT: 2000/10 TO 2001/09
This should help in our understanding of the molecular basis of plant pathogenicity by gram-negative plant pathogens.
PUBLICATIONS: 2000/10 TO 2001/09
No publications reported this period
Name: Alfano, J. R.
Item No. 3 of 5ACCESSION NO: 0175617 SUBFILE: CRIS
INVESTIGATOR: Mortensen, D. A.; Dieleman, J. A.
UNIVERSITY OF NEBRASKA
LINCOLN, NEBRASKA 68583
WHY WEED PATCHES PERSIST: DYNAMICS OF EDGES AND DENSITY
OBJECTIVES: 9700606. Determine the influence of weed seedbank and seedling number and density on mortality in a randomly distributed and a spatially aggregated population. Determine the influence of within-patch density variation and mortality on patch edge contraction and expansion. Determine the extent to which dynamics of patch edges and within-patch density can be explained by the mortality responses characterized in I and II.
APPROACH: To address the first objective two sets of conditions will be created: randomly distributed populations of velvetleaf and common sunflower where space is not limiting and spatially aggregated populations where space is limiting. These conditions will be established by seedling 10, 50, 90, 150, 500 and 1000 seeds of a species distributed randomly throughout the plot area or in confined 0.5m x 2m elliptical patches. Three levels of mortality will be applied consisting of high mortality - full label rate of bentazon and row-cultivation; intermediate mortality - half label rate of bentazon and row-cultivation; and low mortality - row-cultivation only. The second objective will be studied by creating patches of weeds in which a range of seedbank densities are established that span the range of low density patch edges to high density patch centers. Mortality events will then be applied to these patches to determine the extent to which within-patch density contributes to the persistence of a population and low density patch edges account for the spatial fluctuations in seedling presence observed in the field.
NON-TECHNICAL SUMMARY: Though intensive weed management is routinely applied to fields, weed infestations persist. Often they persist as spatially aggregated patches with a distinctive internal density gradient. Determine the influence of weed seedbank and seedling number and density on mortality in a randomly distributed and a spatially aggregated population. Determine the influence of within-patch density variation and mortality on patch edge contraction and expansion.
PROGRESS: 1997/07 TO 2000/06
At the start of this project some three years ago we set out to determine the importance of population size as a factor regulating patch persistence. At the time evidence from field studies and in the published literature suggested that density dependent mortality may indeed account for higher proportional survivorship in high-density patch centers. A good deal of progress was made during the life of this proposal. We documented that indeed density dependent mortality does occur at high weed densities; weed densities commonly observed under field conditions. In effect individuals in a population protect neighbors by increasing the frequency of safe-sites in high-density patch centers. Specifically, this safening effect was studied over a range of mortality intensities. Results clearly demonstrated that mortality decreased at high densities. The trend was more pronounced with reduced mortality intensity treatments where percent control declined from 100% at low densities to less than 70% at high densities. In addition to density dependence we studied the dynamics of patch edges and internal density. Patch edge dynamics were studied on selected A. theophrasti patches in two continuous corn fields in central Nebraska. The patches were mapped on the basis of a 1.0 m by 0.75 m grid. The pattern observed in the seedling density distribution maps revealed a relatively high degree of stability with regards to spatial attributes. Patch locations, patch shape and seedling density distribution profiles were easily recognizable over the duration of the study. Seedling density consistently increased towards the patch center when plotted parallel to the directions of the crop rows. Across the crop rows there was a consistant drop in density near the edges, but high-density peaks could be observed toward the patch center. The implications of density dependent mortality with respect to the dynamics of the density profile within patches and patch edge dynamics were then modeled using a spatially explicit cellular automata model developed with support from this project. Results from this work show that density dependent mortality acts as a positive feedback mechanism, which implies that model parameters, such as germination rate and mortality rate, can have critical values at which the population growth rate changes abruptly. This phenomenon was repeatedly observed as parameters in the model were varied systematically. The work conducted through this project identifies mechanisms regulating weed patch population dynamics. It is the first work of it's kind to demonstrate the profound influence population size has on the efficacy of weed management practices. We have demonstrated that pest population size will strongly influence the success of pest management strategies with high pest pressure rendering low input weed management practices ineffective. The model developed under this project is currently being used to guide the development of future experiments to determine the interacting influences of density dependence, site-suitability and weed dispersal curves in shaping future weed populations.
IMPACT: 1997/07 TO 2000/06
Density-dependent mortality plays a major role in weed patch persistence. The model developed under the project has been used by several research groups in hypothesis generation and testing. Understanding the mechanisms underlying stability in weed patches suggests that mapping their occurrence and distribution could be an important piece of information in prescribing site-specific weed management strategies.
PUBLICATIONS: 1997/07 TO 2000/06
1. Dieleman, J.A., Mortensen, D.A., Buhler, D.D., Cambardella, C.A. and Moorman, T.B. 2000. Identifying associations among site properties and weed species abundance. Part I. Multivariate analysis applied to data from a central Iowa corn-soybean field. Weed Sci. 48:(000-000).
2. Dieleman, J.A., Mortensen, D.A., Buhler, D.D. and Ferguson, R.B. 2000. Identifying associations among site properties and weed species abundance. Part II. Hypothesis generation based on data from two central Nebraska corn fields. Weed Sci. 48:(000-000).
3. Mortensen, D.A., Bastiaans, L. and Sattin, M. 2000. The role of ecology in developing weed management systems: an outlook. Weed Res. 40:49-62.
4. Neeser, C. and Mortensen, D.A. 1999. Density dependent velvetleaf (Abutilon theophrasti) seedling survival in response to postermergence herbicide applications. Weed Sci. Soc. Amer. Abst. 39:377.
5. Dieleman, J.A. and Mortensen, D.A. 1999. Characterising the spatial pattern of Abutilon theophrasti seedling patches. Weed Res. 39:455-467.
6. Dieleman, J.A., Mortensen, D.A. and Martin, A.R. 1999. Influence of velvetleaf (Abutilon theophrasti) and common sunflower (Helianthus annuus) density variation on weed management outcomes. Weed Sci. 47:81-89.
7. Gerhards, R., Wyse-Pester, D.Y., Mortensen, D.A. and Johnson, G.A. 1997. Characterizing spatial stability of weed populations using interpolated maps. Weed Sci. 45:108-119.
Name: Mortensen, D. A.
Item No. 4 of 5ACCESSION NO: 0187777 SUBFILE: CRIS
INVESTIGATOR: Louda, S. M.
SCHOOL OF BIOLOGICAL SCIENCES
UNIVERSITY OF NEBRASKA
LINCOLN, NEBRASKA 68583
HERBIVORE-MEDIATED INDIRECT EFFECTS OF AN EXOTIC THISTLE ON NATIVE THISTLES.
OBJECTIVES: The overall objective of this project is evaluate the interaction between an invasive exotic weed and two related native plant species mediated by a shared insect herbivore, a deliberately released biocontrol weevil, Rhinocyllus conicus, in prairie rangelands. The weevil is here and having significant impacts on prairie species. Can this impact be managed and, if so, how? The preliminary data suggested that R. conicus reduced its use and impact on native species in the vicinity of its preferred, exotic host plant, musk thistle (corduus nutans spp.). Thus, the objectives of the research are to: 1) evaluate the generality of this observation in Nebraska grasslands, 2) develop a better mechanistic, experimentally-based understanding of insect-mediated indirect interactions between plant species within this system, and 3) examine the applicability of that new data to managing the impact of R. conicus on sparse or rare native plant species. The study is designed to answer three fundamental questions: 1) how are seed losses of native thistle species related to ecological circumstances, such as proximity to stands of the targeted weed, musk thistle, and surrounding vegetation; 2) are plant co-occurrence and observed levels of impact causally related; and, 3) can the ecological factors be manipulated to minimize negative impacts on rate native species. The aim is to improve our basic understanding of herbivore-mediated indirect interactions between co-occurring plants and apply that understanding to science-based management of non-target effects associated with the biological control of invasive plant species, such as thistles.
APPROACH: The study entails both data collection on the pattern of injury inflicted by Rhinocyllus conicus on native thistles in prairie grasslands and the response of R. conicus to native species in experimentally planted arrays. The hypotheses to be tested are that co-occurrence of the native species with musk thistle: (H1) has no effect on seed loss of the native, or (H2) decreases seed loss by the native (="associational defense"), or (H3) increases seed loss by the native (="associational susceptibility"). The patterns will be documented in relation to proximity to musk thistle (Carduus nutons ssp. leiophyllous) stands as well as variation in weevil densities and identity of the ambient plant community. The experiments will determine directly the degree to which native plant use is influenced by proximity to stands of the targeted, preferred weed species.
NON-TECHNICAL SUMMARY: Exotic invasive plant species, such as thistles, represent a significant threat to sustained productivity and biodiversity in the United States. Such weeds are increasingly targeted for biological control, using imported exotic insects or diseases. However, deliberate importation of exotic species also entails potential environmental risks, such as the impact on non-targeted sparse native plants by the biocontrol weevil Rhinocyllus conicus in national parks and nature preserves. The aim of this research is to better understand when such impacts are likely to occur and to ask whether that understanding can be harnessed to manage such effects if they occur. Preliminary data suggested that R. conicus may reduced its use of the native species when its preferred, exotic host musk thistle, Carduus nutans, was nearby. In this study, we will collect both observational and experimental data to quantify the generality of this observation, assess the direct consequences of association of native thistles with the exotic, targeted thistles on the impact of that the flower head weevil (R. conicus) on them, develop a better understanding of insect-mediated indirect interactions between plants, and study harnessing that knowledge to manage the impact of this insect on rare native plants. The results will contribute to a basic understanding of herbivore-mediated interactions between weeds and native plants and to the application of such understanding in the management of invasive exotic species and the unexpected ecological side effects of biocontrol introductions.
PROGRESS: 2001/10 TO 2002/09
The goal of our research is to determine how ecological factors, specifically local density and proximity of the exotic weed musk thistle (Carduus nutans), affect the amount of damage to a native thistle species, wavyleaf thistle (Cirsium undulatum), by Rhinocyllus conicus, a European weevil introduced to North America for biological control of musk thistle. This project will contribute to the development of management strategies that use manipulation of musk thistle populations to reduce negative, non-target effects of R. conicus on native plants. In 2002 we conducted two experiments to determine whether proximity to musk thistle patches causes high levels of damage to wavyleaf thistles by R. conicus. In the first experiment, we transplanted wavyleaf thistles to create small, sparse and dense wavyleaf patches at 5 m and 50 m from musk patches. In the second experiment, we transplanted wavyleaf thistles 5 m and 15 m from small musk patches and we manipulated the abundance of R. conicus adults in the musk patches to examine whether high ratios of weevils to their preferred resource, musk thistle, causes spillover onto native plants. In the first experiment, we found adult R. conicus on wavyleaf thistles 5 m from musk patches, but not on thistles transplanted 50 m from musk patches. The number of R. conicus egg cases on wavyleaf flower heads, however, did not differ significantly between transplants 5m and transplants 50 m from musk. The second experiment showed a trend toward decreased R. conicus use with increased distance from musk thistles, but the trend did not reach statistical significance. An extreme drought in 2002 significantly shortened the field season by reducing transplant survival rates in both experiments. If drought is less severe in 2003, we expect stronger patterns from both experiments. Also, given the drought in 2002, we should be able to extend the funded research (using the savings to the grant from this summer) to follow-up on these experiments an additional summer (2004) if we are allowed to extend the final date for the proposed work. The opportunity to do this will be especially important if 2003 is also a drought year, as is forecast. In a second component of this project, we quantified number of R. conicus egg cases on naturally-occurring wavyleaf thistles in relation to distance to musk patches and local musk thistle density at 12 sites in southwestern Nebraska. We found significantly less damage to native thistles 80 m from musk thistle patches than within musk patches. Local density of musk thistle did not significantly affect use of wavyleaf thistle by R. conicus. These results are consistent with results from an identical survey we conducted in 2001. Our results to date from the first two years of field work support the hypothesis that musk thistle indirectly, negatively affects wavyleaf thistles by increasing rates of flower and seed herbivory by R. conicus at local spatial scales. Further, our results from 2001 and 2002 suggest that the best management strategy for reducing negative, non-target effects of R. conicus on native thistles is to reduce the area covered by musk thistle.
IMPACT: 2001/10 TO 2002/09
Unintended, negative effects on native species are the primary concern with the safety of introducing exotic, herbivorous insects to limit the spread of weed populations. Our research will contribute to the development of management strategies to reduce detrimental, non-target effects of such an insect, Rhinocyllus conicus, on native thistle species by manipulating populations of musk thistle (Carduus nutans), the exotic, intended target of R. conicus. Specifically, we are evaluating the hypothesis that proximity to musk thistle and local density of musk thistle will affect the amount of damage to native thistles by R. conicus. Management strategies based on our findings could prove critically important in limiting R. conicus impact if R. conicus invades habitats of endangered native Cirsium species, such as C. pitcheri in Michigan lakeshore sand dunes.
PUBLICATIONS: 2001/10 TO 2002/09
Initial results from the first year of this study were included in a manuscript now in press. Also, the survey data for the first two years are now analyzed and a draft manuscript is waiting for the 2003 data prior to submission. Results also have been presented in two oral presentations, including an invited presentation at a meeting of the National Association of County Officials in North Platte NE, and another invited presentation to the Nebraska Department of Agriculture Weeds Supervisory Board.
Name: LOUDA, S. M.
Item No. 5 of 5ACCESSION NO: 0193096 SUBFILE: CRIS
INVESTIGATOR: Dosskey, M. G.; Hoagland, K. D.; Brandle, J. R.
NATIONAL AGROFORESTRY CENTER
NORTH 38TH & EAST CAMPUS LOOP
LINCOLN, NEBRASKA 68583-0822
CHANGE IN FILTER STRIP PERFORMANCE OVER TIME
OBJECTIVES: Determine if, and by how much, the effectiveness of filter strips changes over time since establishment. Determine if temporal change in effectiveness depends on vegetative composition. Partition change among fundamental processes of infiltration, deposition, and dilution.
APPROACH: The same filter strip field plots and experimental protocols used by Schmitt et al. (J. Environ. Qual. 1999, 28:1479-1489) in years 1, 2 and 3 after filter strip establishment will be repeated in years 9 and 10. In general, the methods call for applying identically-prepared solutions that simulate field runoff containing sediment, N and P fertilizer, and bromide tracer to the upper end of filter strip plots, and then measure their load and concentration in outflow. Water and pollutant outflow in years 9 and 10 will be compared to existing data from years 1, 2, and 3 by repeated measures ANOVA. Interaction between vegetation type and time since establishment will be examined by comparing results for two filter strip vegetation types, grasses only and grass plus trees. Individual filter processes for each year and vegetative treatment will be estimated and contrasted using the following relationships: Deposition = % reduction of sediment mass; Dilution = % reduction of bromide concentration; Infiltration = % reduction of bromide mass.
NON-TECHNICAL SUMMARY: Vegetation filter strips are installed at crop field margins for the purpose of removing pollutants from field runoff before they enter streams. This project will determine how much their effectiveness changes over the long term, if that change depends on the kind of plants that are grown in the filter strip, and which soil and vegetation processes account for such change. The information produced will improve our capabilities to predict the level of benefits to expect from filter strip establishment and the potential for success of USDA incentive programs. This information will also improve planning and design of efficient filter strips, in particular improved management schemes that will maintain a high level of benefit to water quality in agricultural watersheds.
Name: DOSSKEY, M. G.