Progress 08/01/05 to 07/31/08
Outputs
OUTPUTS: We studied the biochemical interactions between invasive knapweeds and native rangeland plants. In a laboratory study, we discovered that many native plants from the western US seem to resist the toxin produced by spotted knapweed roots, while others are more susceptible to it (Perry et al., 2005). In a follow-up greenhouse study we found that these tolerant native species were quite good at growing with knapweed while the less tolerant native plants were not. We then conducted similar greenhouse experiments with native species from knapweed-invaded grasslands in Wisconsin and Washington (Alford et al, in press). Based upon the results of these greenhouse studies, we have initiated two field experiments in knapweed infested areas of Montana to study the effects of different seed mixes on resistance to knapweed reinvasion. This study is ongoing, and due to a record heat wave in 2006 we saw little native recruitment in 2006 or 2007, but limited recruitment in 2008. Therefore, a similar study was established on two additional sites in Montana during the fall of 2007. Additional field studies were established in Wisconsin and Washington during 2006. These field studies have been sampled during the summer of 2007 and 2008 and data publication is pending. Results from these field studies should result in recommended seed mixtures for reclaiming knapweed infested rangelands in the western US. In addition to these applied studies we also worked on figuring out the underlying mechanisms responsible for our previous observations. In laboratory studies we discovered that oxalic acid was a contributing factor in the resistance of some native species to knapweed toxins (Weir et al., 2006). We found that oxalic acid is secreted by these native plant species and alleviates the effects of damage to their root tissues caused by knapweeds. We conducted a greenhouse experiment from August 2006 to April 2007 to evaluate whether these resistant plants might be used to ameliorate knapweed soils and facilitate the subsequent establishment of native species that are more susceptible to catechin. Results from this study were detailed in the MS thesis of Matt Schultz and are currently being prepared for publication. PARTICIPANTS: Individuals Mark W. Paschke, PI/PD Jorge M. Vivanco, coPI Ragan M. Callaway, coPI Laura G. Perry, post doctoral research associate Giles C. Thelan, research associate Tiffany L. Weir, PhD student Mathew Schultz, MS student Partner Organizations University of Montana, Division of Biological Sciences Training or professional development The project currently involves the training of one post doc (Laura Perry), one PhD student (Tiffany Weir) and one MS student (Matthew Schultz). TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Previous work by our research team and others has indicated that invasive knapweeds have evolved a strategy in which allelochemicals play a critical role in their invasion success. In this study, we hypothesized that some plants possess effective counter-chemical strategies to resist knapweed, which could be exploited in order to control knapweed invasions. Our work focused on exploring the use of knapweed-resistant native species for the integrated management of spotted knapweed. Along the way, we have further examined the mechanisms underlying the interactions between knapweeds and native species that appear to be successful competitors. Our greenhouse and lab studies have indicated that the nature of below-ground chemical interactions between knapweeds and native plants are complex, conditional, and episodic. Nevertheless, several of our field studies have indicated that planting native species, which have been shown to be resistant to knapweed phytotoxins, can increase the diversity and abundance of native plants within knapweed infestations. We are hopeful that this knowledge could eventually lead to the development of better revegetation regimes utilizing native plants that will tolerate knapweed chemical interference and eventually facilitate the establishment of desirable vegetation. Such knowledge would lessen dependence on herbicides for the control of knapweeds. Results from these studies have the potential to lead to an innovative and novel approach for the management of some of the most problematic and extensive weed infestations in Western North America. As the field studies established under this project mature, we will make recommendations regarding seed mixtures and species that would be useful for revegetating infestations of spotted and Russian knapweeds. This approach might be extended to other known, or yet to be discovered, allelopathic invasive species. Results from these studies could be rapidly assimilated and utilized by land managers because our approach involves existing methodologies (seeding) and does not necessitate additional equipment or expenditures. Rather, implementing results from these studies involves a switch to more effective revegetation species. Such weed-combating seed mixtures would reduce control costs because competitive plant communities should hinder re-invation by weeds and would thus lessen the need for additional management actions while at the same time, restore value to degraded rangelands. Results from this research have been transmitted to the scientific and land management community through, publication in professional peer-reviewed scientific journals and presentations at professional symposia. A list of publications and presentations follows:
Publications
- Broz, A.K. R.M. Callaway, M.W. Paschke, D.K. Manter and J.M. Vivanco. 2008. A molecular approach to understanding plant-plant interactions in the context of invasion biology. Functional Plant Biology 35, 1123-1134.
- Alford, E.R., J.M. Vivanco and M.W. Paschke. 2008. The effects of flavonoid allelochemicals from knapweeds on legume - rhizobia candidates for restoration. Restoration Ecology (DOI: 10.1111/j.1526-100X.2008.00405.x).
- Schultz, M.J. 2008. Soil Ecological interactions of spotted knapweed and native plant species. M.S. Thesis. Colorado State University, Graduate Degree Program in Ecology. 66pp.
- Broeckling, C.D., D.K. Manter, M.W. Paschke and J.M. Vivanco. 2008. General ecology: Rhizosphere. Pages. 3030-3035. In: S.E. Jorgensen and B.D. Fath (Eds.). Encyclopedia of Ecology volume 4, Elsevier, Oxford, UK.
- Perry, L.G, Alford, E.R., Horiuchi, J., Paschke, M.W., and Vivanco, J.M. 2007. Chemical signals in the rhizosphere: root-root and root-microbe communication. In The Rhizosphere (Second Edition). Pinton, R., Varanini, Z. and P. Nannipieri, eds. CRC Press. Boca Raton, FL. pp. 297-330.
- Prithiviraj, B., Paschke, M.W., and Vivanco, J.M. 2007. Root communication: the role of root exudates. Encyclopedia of Plant and Crop Science 1:1, 1-4 DOI: 10.1081/E-EPCS-120042072
- Broz, A. K., Vivanco, J. M., Schultz, M. J., Perry, L. G., and Paschke, M. W. 2006. Secondary Metabolites and Allelopathy in Plant Invasions: A Case Study of Centaurea maculosa. In Plant Physiology, Fourth Edition, L. Taiz and E. Zeiger, eds. On line Essay 13.7. http://4e.plantphys.net/article.php?ch=e&id=377
- Inderjit, Callaway, R.M., and Vivanco, J.M. 2006. Can plant biochemistry contribute to understanding of invasion ecology? Trends in Plant Sciences 11:574-580
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Progress 08/01/06 to 07/31/07
Outputs
OUTPUTS: We are studying the biochemical interactions between invasive knapweeds and native rangeland plants. In a laboratory study, we discovered that many native plants from the western US seem to resist the toxin produced by spotted knapweed roots, while others are more susceptible to it (Perry et al., 2005). In a follow-up greenhouse study we found that these tolerant native species were quite good at growing with knapweed while the less tolerant native plants were not. We then conducted similar greenhouse experiments with native species from knapweed-invaded grasslands in Wisconsin and Washington (Alford et al, in press). Based upon the results of these greenhouse studies, we have initiated two field experiments in knapweed infested areas of Montana to study the effects of different seed mixes on resistance to knapweed reinvasion. This study is ongoing, and due to a record heat wave in 2006 we have seen little native recruitment in 2006 or 2007. Therefore, a similar study is
being established on two additional sites in Montana during the fall of 2007. Additional field studies were established in Wisconsin and Washington during 2006. These field studies have been sampled during the summer of 2007 and data analysis is pending. Results from these field studies should result in recommended seed mixtures for reclaiming knapweed infested rangelands in the western US. In addition to these applied studies we are also working on figuring out the underlying mechanisms responsible for our previous observations. In laboratory studies we discovered that oxalic acid was a contributing factor in the resistance of some native species to knapweed toxins (Weir et al., 2006). We found that oxalic acid is secreted by these native plant species and alleviates the effects of damage to their root tissues caused by knapweeds. We conducted a greenhouse experiment from August 2006 to April 2007 to evaluate whether these resistant plants might be used to ameliorate knapweed soils
and facilitate the subsequent establishment of native species that are more susceptible to catechin. Results from this study are being analyzed and will be prepared for publication as part of the MS thesis of Matt Schultz.
PARTICIPANTS: Individuals: Mark W. Paschke, PI/PD Jorge M. Vivanco, coPI Ragan M. Callaway, coPI Laura G. Perry, post doctoral research associate Giles C. Thelan, research associate Tiffany L. Weir, PhD student Mathew Schultz, MS student Partner Organizations: University of Montana, Division of Biological Sciences Training or professional development: The project currently involves the training of one post doc (Laura Perry), one PhD student (Tiffany Weir) and one MS student (Matthew Schultz).
TARGET AUDIENCES: The target audience for this work is land managers and scientists working in rangelands in the western United States.
Impacts
Our studies of native rangeland plants that are superior competitors with spotted knapweed resulted in recommended seed mixtures for reclaiming knapweed infested rangelands in the western US. Our laboratory studies on the mechanisms used by native plants to deal with knapweeds will allow us to develop a more complete understanding of the belowground biochemical interactions that occur between invasive and native plants. We hope that this knowledge will lead to innovative new methods for managing weed infestations.
Publications
- No publications reported this period
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Progress 08/01/05 to 07/31/06
Outputs
We are studying the biochemical interactions between invasive knapweeds and native rangeland plants. In a laboratory study, we discovered that many native plants from the western US seem to resist the toxin produced by spotted knapweed roots, while others are more susceptible to it (Perry et al., 2005). In a follow-up greenhouse study, we found that these tolerant native species were quite good at growing with knapweed while the less tolerant native plants were not. We are currently conducting a similar greenhouse experiment with native species from knapweed-invaded grasslands in Wisconsin, where spotted knapweed has recently invaded. Based upon the results of our greenhouse studies, we have initiated two field experiments in knapweed infested areas of Montana to study the effects of different seed mixes on resistance to knapweed reinvasion. In addition to these applied studies we are also working on figuring out the underlying mechanisms responsible for our previous
observations. In laboratory studies, we discovered that oxalic acid was a contributing factor in the resistance of some native species to knapweed toxins (Weir et al., 2006). We found that oxalic acid is secreted by these native plant species and alleviates the effects of damage to their root tissues caused by knapweeds. We are currently examining the root exudates of numerous plant species for the presence of oxalic acid. We want to determine if this is a widespread mechanism that conveys tolerance to plant species that have not coevolved with knapweeds and therefore have not developed more specific defenses. In another series of experiments, we are developing new methods for studying interactions between the roots of invasive knapweeds and native resistant species.
Impacts
Our greenhouse and field studies of native rangeland plants that are superior competitors with spotted knapweed should result in recommended seed mixtures for reclaiming knapweed infested rangelands in the western U.S. Our laboratory studies on the mechanisms used by native plants to deal with knapweeds will allow us to develop a more complete understanding of the belowground biochemical interactions that occur between invasive and native plants. We hope that this knowledge will lead to innovative new methods for managing weed infestations.
Publications
- Perry, L.G., Johnson, C., Alford, E.R., Vivanco, J.M., and Paschke, M.W. 2005. Screening of grassland plants for restoration after spotted knapweed invasion. Restoration Ecology 13:725-735.
- Weir, T.L., Bais, H.P., Stull, V.J., Callaway, R.M., Thelen, G.C., Ridenour, W.M., Bhamidi, S., Stermitz, F.R., and Vivanco, J.M. 2006. Oxalate contributes to the resistance of Gaillardia grandiflora and Lupinus sericeus to a phytotoxin produced by Centaurea maculosa. Planta 223:785-795.
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