| Title |
Investigators | Department | Objectives | Approach Keywords | Progress Reports | Impact Statements | Publications | |
Project * COL00735 | |
| Title | Vegetation Change and Risk in Management of Rangeland Plants |
| Investigator(s) | Child, RD; Knight, AP; Ralphs, MH; |
| Department | Forest, Rangeland, & Watershed Sciences |
| Objectives | The three main objectives of this project are: 1) Determining the relationship of the endophytic fungi Alternaria sp. with swainsonine concentrations in Oxytropis sericea; 2) Determining the interaction of soil moisture and soil nitrogen levels with the relationship of the endophytic fungi Alternaria sp. with swainsonine concentrations in Oxytropis sericea; and 3) Identifying management strategies that can be used by Colorado rangeland users to minimize livestock losses to locoweed poisoning. |
| Approach | Native vegetation is an expression of soil, climate, and past use. The interactions of plants and animals with soil micro fauna are often poorly understood on rangelands. Organisms, like fungi, often form a mutualistic relationship with plants providing the plant with a chemical protection from herbivory while gaining essential nutrients for fungal growth and maintenance. Locoweed toxicity is an example of this relationship. A combination of greenhouse and field experiments will be conducted to quantify the amount of swainsonine in locoweed as correlated with varying levels of the endophytic fungi Alternaria sp., soil water, and soil nitrogen levels. Analysis of the data will include the use of multivariate statistical and mathematical procedures to identify important relationships which determine toxicity levels in locoweeds. |
| Keywords | Locoweed, Livestock poisoning, swainsonine, Oxytropis sericea, endophytic fungi, Alternaria sp., plant ecology, rangelands, range management, forage plants, risk assessment, ecosystem management, plant communities, revegetation, weeds, native plants, invasive plants, poisonous plants |
| Progress Reports | |
| 1998 | **Seed mix formulation based on patterns found in native environments enhance rangeland restoration** Studies of species-environmental combinations on Colorado rangelands are important because successful return of disturbed ranges to native vegetation-environmental systems are dependent upon patterns found in native environments. Future species patterns depend upon topographic features and long-term survival of certain species used in seed mixes will be placed at risk while others will be favored by chance placement in favorable sites. Little attention has been given to the fact that not all species are equal competitors on all sites when seed mixes are formulated. Thus, interpretation of patterns of species-environmental systems found in native sites will provide information for development of more appropriate mixes of species to minimize risks to desired species needed in restoration efforts. Methods: Relations among plant species and topographic features were examined to define patterns of rangeland plants with respect to topographic features. Native and "go-back" pastures of the Central Plains Experimental Range of north central Colorado were studied for species patterns that had developed over time. Percent plant cover of plant species with respect to slope, aspect, and topographic position was obtained in 98 stands on each pasture. Correlation analyses were conducted on the data set. Results: Data were collected for one growing season and results show that patterns in some plant species from both pasture conditions were related to slope, topographic position on the slope, and to aspect. Individual species differed in response to topographic features revealing that species are selective in forming patterns with other species depending upon life forms present on various topographic features. Pairwise combinations of species showed positive or negative relationships with respect to a given topographic feature. Buffalo grass and sun sedge cover decreased as slope increased while cover of western wheat grass increased. Then the former two species will not be at risk when planted together on slight slopes or on level areas. On the other hand, the addition of the latter species to a seed mix probably will not be at risk on slopes of the area. Blue grama cover was greatest at the top of slopes and on flat areas; its cover was reduced by the presence of buffalo grass, broom snakeweed, and needle-and-thread grass. The latter species will be at risk in establishment if mixed with blue grama and used to restore level areas. Efforts to restore disturbed rangelands will benefit by knowledge gained from this study because seed mixes can be constructed to restore areas specific to aspect, slope, and topographic combinations. One seed mixture for one area, ignoring these features, will place various plant species at risk in the germination and establishment phase of plant community development. Further observations and analyses will provide methods for selecting combinations of native plant species to use in restoration efforts and in turn, minimize risks to establishing species that meet long-term management objectives. |
| 1999 | A key component of research project is a study of white-point locoweed (Oxytropis sericea Nutt). Information is needed on ecology of species to develop management strategies that include risks to species as well as to forage species. This species is poisonous to livestock and occurs in Larimer County, Colorado. Data on distribution and abundance of locoweed, associated plants species, and habitat characteristics are needed to develop strategies to reduce risk of livestock poisoning and to reduce risk to forage species that react negatively to the presence of locoweed. Therefore, a non-exhaustive survey was made of the County to locate locoweed populations and record UTM coordinates (GPS), elevation, slope, and aspect. Two hundred and thirty four populations were found and of these 65 were inventoried for all plant species cover, locoweed density, and soil and topographic features. These data were also obtained from 24 of the 65 populations and paired with 24 adjacent areas. Another subset of 16 populations was chosen to study effects of slope and aspect on locoweed plant height, basal area, number of seed stalks per plant, and number of plants per square meter. Results from the 65 populations showed that 23 grass species, 47 forb species, and 3 shrub species occurred with locoweed. In the 24 populations paired to adjacent areas without locoweed, 16 species with greater than 1% cover occurred in the populations while 15 species were found in adjacent areas without locoweed. A total of 13 species with cover exceeding 1% was common to both populations and their adjacent areas. Nine grass species occurred in the 24 populations, 7 of which were also common to the 24 adjacent areas. Blue grama, needle and thread grass, and club moss were dominant in locoweed populations while blue grama and club moss also were dominant in adjacent areas. However, both club moss and lichen had twice the amount of cover in the latter areas compared to populated areas. Soil pH was the same whether locoweed was present (6 .2) or not (6.3) while nitrate N and P were significantly lower in populations of locoweed (respectively, 5.9 ppm and 19.2 mg/L) compared to adjacent areas (14.2 ppm and 38.5 mg/L) ; K was significantly higher in populations compared to adjacent areas (respectively, 159.5 and 133.2 mg/L). This species may not have nitrogen- forming nodules and N is taken directly from the soil, lowering N in populated areas. North aspects had the fewest number of seed stalks per plant. Plants on east-facing aspects were larger than those on other aspects, while the number of plants per square meter was greater on west- facing aspects. Effects of slope on plant height and number of seed stalks per plant were not significant. However, basal area of plants was significantly reduced, but number of plants per square meter increased two-fold as slope increased. Plants on west-facing slopes were taller, larger, and produced more seed stalks as slope angle decreased; in contrast plant density per square meter decreased on this aspect. On the other hand, plants were shorter as slope decreased on the east-facing aspect while other attributes were not affected by slope. |
| 2000 | Spatial distributions and natural patterns of rangeland plant species and their respective soil properties across landscape units, such as large pastures, have not been widely studied. Yet, this information is needed to formulate seeding combinations so that disturbed rangelands can be re- established to their natural species composition and patterns in much shorter time periods. Then seeded species will be at a lower risk in establishment and reproduction because effects of species competition will be less. The specific objective of this study was to describe spatial patterns of major plant species and soil characteristics found within a native shortgrass steppe pasture. Spatial patterns among rangeland plant species and associated soil features were determined from a native shortgrass pasture (130 ha) at the Central Plains Experimental Range located in north-central Colorado. The pasture was subdivided into a grid of 98 cells of equal size from which an estimate of percent foliage cover for all plant species, percent cover of litter and rock, and percent bare ground were obtained.. Estimates also were made for soil pH, percentages of sand, silt and clay, and percentages of total nitrogen (TN) and total organic carbon (TOC). Moran's I was used to determine spatial autocorrelation for plant species cover and soil variables while Moran's I was decomposed into small areas progressively across the pasture to estimate scales at which species-soil combinations occurred. Spatial patterns existed for 14 species, including 5 perennial grasses and 6 forbs. Consideration of blue grama cover alone, 2 patterns with scales of 25 and 50 meters were found; with topography included, scales of 6 and 125 m were found after which cover amounts were randomly distributed over the site. Buffalo grass cover occurred in patterns with scales sizes of 6, 75, and 125 m and then these 3 patterns were randomly distributed over the area. Other species were also observed in various patterns which corresponded to those of dominant species. A given species scale of pattern successively formed larger scales over the study area. The largest scales were found at approximately 700 m which in turn formed a random pattern over the entire study area. Individual patterns for 10 species were selected for study of seeded combinations in small plots. Each pattern was used to determine areas to be seeded to combinations of plant species in small, experimental plots. |
| 2001 | **Advances made in understanding toxicity and presence of locoweed.** Most native plant species had germinated and established by August, 2001 after being seeded in various patterns during May, 2001. Native plant species were selected from previous studies of species patterns and associations. Pattern scales of blue grama grass, buffalo grass, needle-and-thread grass, and fringed sagewort were among species seeded in varying combinations of scales and mixtures. Monitoring data will be collected in subsequent years to determine effects of intra-and inter-competition resulting in greater risks to lesser desirable forage plants while increasing quality and quantity of forage through restoration of degraded rangelands in eastern Colorado. Soil amounts of pH, No3N, Zn, Fe, Mn, and Cu as a set could predict levels of added fertilizer after application to white-point locoweed areas. In addition, amounts of EC, K, and Total N were also needed for the list to distinquish fertilizer levels in areas of non-occurrence of locoweed. Swainsonine levels in locoweed varied inversely with biomass of individual locoweed plants, forb biomass, and total vegetation biomass over all fertilizer treatments. Swainsonine levels in locoweed was positively correlated to levels of soil Fe and Zn. This study was initiated to determine effects of NPK on biomass levels of associated species and subsequently, on locoweed biomass. Three levels and two replications of fertilizer: 0, 100, and 200lbs/acre were applied within two small, but adjacent sites, one with locoweed and one without the plant. Information is usually for development of a long-term study of increasing risk to locoweed survival while increasing forage quantity. |
| 2002 | ** A potential key was found in the management of locoweed poisoning -- An endophytic fungi was identified in Oxytropis sericea that was significantly correlated to levels of the toxin swainsonine. It was found that nitrogen fertilizer amendments significantly reduced levels of this endophytic fungi. Further research is being designed to clarify this relationship** Locoweed poisoning of livestock is the most widespread poisonous plant problem in the western United States. Locoweed poisoning is due to the presence of the indolizidine alkaloid swainsonine in locoweed plants. Comprised of many species from the genera Oxytropis and Astragalus, locoweeds have established themselves as an important consideration in ecosystem planning and management. This study investigated the effects of soil chemistry and nutrient enrichment in populations of Oxytropis sericea and native rangeland vegetation over time. Replicate plots were treated with three commercial fertilizer treatments, 0 kg N/ha (control), 112 kg N/ha (intermediate), and 224 kg N/ha (elevated). Presence of endophytic fungi in white point loco was also measured in August 2001. Fertilizer amendments significantly increased native species productivity over time both inside and outside white point loco populations. In contrast, total average production of Oxytropis sericea was not significantly different for all three-treatment levels, indicating that the significant increase in total vegetation over time was not due to an increase in total white point loco production. In addition, factors of soil chemistry including soil nitrate, Zn, Mn, organic matter (OM) and Fe were significantly correlated to total average production of individual species groups, total vegetation and Oxytropis sericea. Fertilizer amendments applied to populations of Oxytropis sericea to improve native species production did not significantly affect levels of the toxin swainsonine in white point loco. In addition, soil microelements Fe and Zn were significantly correlated to levels of swainsonine in species of Oxytropis sericea. Significant levels of the endophytic fungi Alternaria sp. nova were present in Oxytropis sericea and infection of Alternaria sp. nova was significantly correlated to levels of the toxin swainsonine in Oxytropis sericea. In addition, fertilizer amendments of 224 kg N/ha significantly reduced levels of endophytic fungi infection in Oxytropis sericea. |
| 2003 | An endophytic fungi has been identified in Oxytropis sericea that is significantly correlated to levels of the toxin swainsonine. It was found that nitrogen fertilizer amendments significantly reduced levels of this endophytic fungi. Further research is being conducted to clarify this relationship. The first step is to determine if Oxytropis sericea produces N2-fixing root nodules when inoculated with Rhizobium spp, Bradyrhizobium spp, and Sinorhizobium spp under low nitrogen conditions. A second study has been established to determine if fungicide applications significantly reduce swainsonine levels in Oxytropis sericea. Both studies are being conducted in a greenhouse under controlled conditions. These studies will begin to identify the effects of soil nitrogen and endophytic fungi in populations of Oxytropis sericea and native rangeland vegetation over time and provide essential information for the next phase of this research. |
| 2004 | Advances made in understanding toxicity and presence of locoweed. An endophytic fungi has previously been identified in Oxytropis sericea that is significantly correlated to levels of the toxin swainsonine and that nitrogen fertilizer amendments significantly reduced levels of this endophytic fungi. During this past year further research was conducted to clarify the role of nitrogen. It was determined that Oxytropis sericea produces N2-fixing root nodules when inoculated with Rhizobium spp, Bradyrhizobium spp, and Sinorhizobium spp under low nitrogen conditions. A second study determined that fungicide applications to seeds significantly reduce levels of this endophytic fungi and swainsonine levels in Oxytropis sericea. Both studies were conducted in a greenhouse under controlled conditions. These studies are beginning to identify the effects of soil nitrogen and endophytic fungi in populations of Oxytropis sericea and native rangeland vegetation over time and provide essential information for the competition phase of this research. Populations of Oxytropis in Inner Mongolia have been found that dont appear to be toxic. Genetic mapping in cooperation with the U.S. Poisonous Plant Laboratory and the Inner Mongolian Agricultural University will be conducted to identify potential management options. |
| 2005 | 2005 Advances made in understanding toxicity and the competitive nature of locoweed. Locoweed poisoning of livestock is the most widespread poisonous plant problem in the western United States. Endophytic fungi and soil nitrogen levels have been identified in Oxytropis sericea as being significantly correlated to levels of the toxin swainsonine. Understanding the relationship between the endophytic fungi and the presence of the toxin swainsonine as related to soil nitrogen of the Oxytropis species may provide a key to the management of locoweed poisoning. This study is the first report of nodulation and dinitrogen fixation in O . sericea. It demonstrates that dinitrogen fixation increases the production of swainsonine in O. sericea and is associated with the presence of the endophyte Embellisia sp. These results suggest a possible link between O. sericea, Rhizobium and Embellisia sp., and a tripartite mutualistic benefit for the three organisms. Interspecific plant competition plays an important role in the vegetation dynamics and community structure of grassland ecosystems in Western North America. Three introduced cool-season grasses (CDII crested wheatgrass, Vavilov Siberian wheatgrass and Bozoisky Russian wildrye) were successfully established in the mixed-grass prairie in Colorado and the short-grass steppe in New Mexico. These cool season grasses increased forage production 2 to 3 fold over the native plant community. Where locoweed reinvasion occurred the seeded treatments greatly reduced the number of new indigenous plants establishing. Our results suggest that these cool season grasses will suppress reestablishment of locoweed, and provide abundant and nutritious green forage in the spring when locoweed is the greatest threat to livestock. |
| 2006 | 2006 **Advances made in understanding white locoweed toxicity as facilitated by a tripartite mutualism involving a fungal endophyte and nitrogen-fixing bacteria**. Mutualistic interactions with fungal endophytes and dinitrogen fixing bacteria are known to exert key biological influences on the host plant. The influence of a fungal endophyte alkaloid over the toxicity of a plant has been documented in Oxytropis sericea. Oxytropis sericea is a perennial legume responsible for livestock poisoning in Western North America, a result of the alkaloid swainsonine. In this study, the ability of Oxytropis sericea to form a dinitrogen fixing symbiosis with Rhizobium, and the effects of this symbiosis on fungal endophyte (Embellisia sp.) production of swainsonine, were evaluated in a greenhouse environment. Seeds of O. sericea were grown in plastic containers. Twenty week old O. sericea seedlings were inoculated with four strains of Rhizobium. Twenty weeks after inoculation, plant growth and root nodulation by Rhizobium were measured. Dinitrogen fixation was confirmed using an acetylene reduction assay (ARA) on excised root nodules. Dry leaves were analyzed for swainsonine content. A second set of plants was treated with fungicide to evaluate the effect of reduced fungal endophyte infection on plant growth and swainsonine production. All inoculated plants produced indeterminate nodules. The ARA indicated that 98% of the excised nodules were fixing dinitrogen. Rhizobium treated plants had greater swainsonine concentrations than the non-inoculated controls. Plants that established from seeds treated with fungicide had lower biomass than non-fungicide treated controls and plants treated with foliar fungicide. Plants treated with foliar fungicide and the controls, had greater swainsonine concentrations than the plants that received seed fungicide. |
| Impact | |
| 1999 | Information on plant species cover and soil nutrients associated with white-point locoweed will enable the prediction of areas that might be invaded by the latter species in Larimer County, Colorado. A prediction model may be constructed that uses cover values for needle and thread grass, club moss, and lichen, and amounts of soil N, P, and K. These factors clearly define differences in very similar plant communities, but with and without locoweed. |
| 2000 | At the present, surface disturbed rangelands are restored by using a seed-mix that remains uniform over the entire area whether a few acres or hundreds of acres in size. Yet, native rangelands have vegetation that is not only a mixture of species, but mixtures of patterns of various combinations of these species. Information on the sizes of patterns exhibited by plant species occurring on native rangelands will enable restoration of these lands, when disturbed, to the original species combinations in natural patterns. This will return restored areas to their approximate pre-disturbed vegetation condition in a shorter length of time. Risk to individual species will be reduced when optimum combinations of species are used instead of all species in a bulk mix. Restored patterns will approach those in native sites sooner as competition is reduced among species within a given pattern. |
| 2001 | Livestock losses from locoweed continue to be a significant economic factor for producers in Colorado and other western states. Information derived from this study could help reduce these losses and result in an increase of forage available to livestock and wildlife. |
| 2002 | Locoweed poisoning of livestock is the most widespread poisonous plant problem in the western United States. An endophytic fungi was identified in Oxytropis sericea that was significantly correlated to levels of the toxin swainsonine. It was found that nitrogen fertilizer amendments significantly reduced levels of this endophytic fungi. Understanding the relationship between the endophytic fungi and the presence of the toxin swainsonine may provide a potential key to the management of locoweed poisoning. This could significantly reduce loss of livestock and reduced productivity to livestock producers. |
| 2003 | Locoweed poisoning of livestock is the most widespread poisonous plant problem in the western United States. Endophytic fungi and soil nitrogen levels have been identified in Oxytropis sericea as being significantly correlated to levels of the toxin swainsonine. Understanding the relationship between the endophytic fungi and the presence of the toxin swainsonine as related to soil nitrogen may provide a key to the management of locoweed poisoning. |
| 2004 | Locoweed poisoning of livestock is the most widespread poisonous plant problem in the western United States. Endophytic fungi and soil nitrogen levels have been identified in Oxytropis sericea as being significantly correlated to levels of the toxin swainsonine. Understanding the relationship between the endophytic fungi and the presence of the toxin swainsonine as related to soil nitrogen and genetic mapping of the Oxytropis species may provide a key to the management of locoweed poisoning. |
| 2005 | Locoweed poisoning of livestock is the most widespread poisonous plant problem in the western United States. Locoweeds contain the toxic alkaloid swainsonine that causes chronic poisoning in livestock or wildlife that graze it. Endophytic fungi and soil nitrogen levels have been identified in Oxytropis sericea as being significantly correlated to levels of the toxin swainsonine. Understanding the tripartite mutualistic relationship between the endophytic fungi, the presence of the toxin swainsonine as they relate to soil nitrogen may provide the key to the management of locoweed poisoning. On short grass plant communities, poisoning occurs in spring when locoweeds are green and growing before warm season grasses begin growth. Presently, there are few cool-season grasses growing in short-grass communities where white locoweed (Oxytropis sericea Nutt. Ex T&G) is abundant. Overgrazing by livestock in the western US during the late 1800s and early 1900s may have reduced or eliminated the cool-season grasses. Reestablishing vigorous cool-season grasses may provide sufficient competition to suppress locoweed, or reduce establishment following its control. In addition, these grasses may provide alternative palatable forage to livestock early in the spring. |
| 2006 | 2006 This greenhouse study is the first report of nodulation and dinitrogen fixation in O. sericea. It also demonstrated that dinitrogen fixation increases the production of swainsonine in O. sericea plants infected with Embellisia sp. Results from this study suggest that dinitrogen fixation affects swainsonine production, and has the potential to support the symbiosis between Embellisia sp. and O. sericea when soil nitrogen is limited. Oxytropis sericea competitiveness appears to be facilitated by an ability to simultaneously associate with Rhizobium and a fungal symbiont. Results from this experiment hi-light the significance of dinitrogen fixation in plant toxicity, giving basic information about possible pathways used by the endophyte to synthesize swainsonine. Results will help Identify management strategies that can be used by Colorado rangeland users to minimize livestock losses to locoweed poisoning |
| Publications | |
| 1998 |
Bousquin, Stephen G. 1998. Association patterns on a gradient of water deficit in Mojave Desert shrub communities. Ph.D. Thesis. Colorado State University Dudley, S.J., Bonham, C.D., Abt, S.R., and Fischenich, J.C. 1998. Modification of the point frame for quantitative hydraulic investigations. Rangelands 20:25-27 |
| 1999 |
Starosta, J. A. 1999. Distribution and attributes of Oxytropsis species in Larimer County, Colorado. M.S. Thesis. Colorado State University. 70 pp Strenge, E. N. 1999. Spatial pattern analyses of vegetation and soil factors within the shortgrass steppe of North-central Colorado. M.S. Thesis. Colorado State University. 134 pp |
| 2002 |
Moberly, C. 2002. Soil Chemistry and Nutrient Enrichment in Populations of Oxytropis sericea and Native Rangeland Vegetation in Larimer County, Colorado. M.S. Thesis. Colorado State University. 74 pp. |
| 2005 |
Valdez, Jose Rudolpho. 2005. Dinitrogen Fixation in White Locoweed (Oxytropis sericea var. sericea) and Swainsonine Production. M.S. Thesis. Dept. of Forest, Rangeland and Watershed Stewardship, Colorado State Univesity. Fort Collins, CO. 96 pages. |