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United States Department of Agriculture

Agricultural Research Service

2009 Annual Report

1a.Objectives (from AD-416)
Improve our ability to prevent invasion of rangeland by medusahead, determine the most ecologically sound and cost-effective methods for managing medusahead using herbicides, and develop landscape-scale restoration strategies for medusahead-infested rangeland using successional management.

1b.Approach (from AD-416)
This research will build upon existing efforts to develop ecologically-based invasive weed management strategies. This research will test ecological theories that have potential to become principles that guide invasive plant management and develop those principles into methods for managing weeds. Part of this effort will focus on understanding the key species and grazing strategies that minimize medusahead invasion. Since herbicides are one of the few effective tools for medusahead, this research will attempt to define ecological and economic thresholds for applying them. Finally, the studies will test two novel approaches to restoring medusahead infested rangeland using current ecological theory to guide the implementation. Decision-support tools will be researched and developed to assist land managers in applying existing and new knowledge associated with medusahead in the Great Basin and Columbia Plateau. Replacing 5360-22000-002-00D (5/05)

3.Progress Report
In 2009 we continued progressing toward achieving the objectives outlined above and the stated milestones describe the specific progress for the past year. In response to NP 304 Action Plan component V, we increased efforts on annual grass dominated rangeland by testing various short-term watering systems to aid the survival of newly emerging seedling of desired species during drought. We also developed and designed a decision-making process that links assessment, successional dynamics, management strategies, and adaptive management into logical thought pattern. Complimentary to Components VI and VII, we continue collecting data and information from ongoing studies to determine the economically and ecologically sound methods for managing medusahead infested rangeland. In support of Component X, maintenance and evaluation of studies aimed at restoring medusahead infested rangeland were continued.

1. Control effort exacerbates invasive-species problem. Ecosystem managers face a difficult decision when managing invasive species. Invasion often lowers native species abundances to rare so avoiding practices that might further rarify them is prudent ecosystem management. ARS scientists at the Range and Meadow Forage Management Unit in Burns, OR and Fort Keogh in Miles City, MT, in cooperation with scientists and Montana State University, Bozeman, MT tested the long-term (16 years) ramifications of a one-time spraying of leafy spurge with and without subsequent grazing. We found that leafy spurge was likely more productive after herbicide application and many native species were increasingly rare. A few native species became locally extinct, but less if grazing was applied after application. Results of this study can be used to consider approaches for invasive-species management to prevent damage to native species.

2. Applying ecologically-based invasive plant management. The need for unified ecological theories, principles, frameworks and models that improves our ability to predict vegetation change and guides the implementation of restoration is substantial and unmet. ARS scientists in the Range and Meadow Forage Management Research Unit in Burns, OR developed our ecologically-based framework into a holistic decision-making process to include a linkage between ecological processes and management with ecological principles. Ecologically-based invasive plant management is aimed at designing management that addresses the causes of invasions by altering the key processes in a particular ecosystem to direct succession on a desired trajectory. Previously, three causes of succession have been identified, which are site availability, relative species availability, and relative species performance. In this improved framework, we provide principles synthesized from existing scientific literature and improved over time to provide direction for how managers can influence these ecological processes to promote desired plant communities. Expanding the decision-making portion of the model and incorporating ecological principles into our ecologically-based invasive plant management will improve decision-making and provide a framework on which managers develop management programs that address the underlying ecological causes for invasion.

3. Principles for ecologically based invasive plant management. A holistic, ecologically-based invasive plant management (EBIPM) framework that integrates ecosystem health assessment, knowledge of ecological processes, and adaptive management into a successional management model has recently been developed. However, well-defined principles that link tools and strategies managers typically use to ecological processes that needed to be repaired have been slow to emerge, thus greatly limiting the ability of managers to easily apply EBIPM across a range of restoration scenarios. ARS scientists in the Range and Meadow Forage Management Research Unit in Burns, OR have synthesized current knowledge of the mechanisms and processes that drive plant community succession into ecological principles for EBIPM. Using the core concepts of successional management that identify site availability, species availability, and species performance as the three general causes of plant community change, we detail key principles that can provide guidance for imposing tools and strategies in EBIPM based upon ecological processes predicted to influence the three general causes of succession. Managers now have basic ecological principles that they can use to design and implement effective invasive plant strategies that address the cause of invasion, rather than continue to treat symptoms.

4. Managing litter to manage invasive weeds. Manipulating litter in an attempt to direct successional trajectories is rarely considered as a management strategy, but plant litter is related to almost every ecological driver of vegetation change. ARS scientists in the Range and Meadow Forage Management Research Unit in Burns, OR, have determined the influence of litter collected from an intact native plant community on a community dominated by an invasive species with the same habitat type and vice versa. We discovered that managers may be able to direct vegetation dynamics in a favorable direction by using strategies that maintain low amounts of native plant litter, especially if it is finely fragmented. Litter influences multiple mechanisms and processes that direct successional trajectories, and thus may be a characteristic of vegetation that can be managed to shift plant communities toward those that are desired.

5. Promoting native vegetation and diversity in exotic annual grass infestations. Exotic annual grass invasions are especially problematic because reestablishment of perennial vegetation is rarely successful. However, the effects of annual grass control treatments are rarely evaluated in infestations that still have some remaining native vegetation and thus, may not require revegetation efforts. We evaluated the effects of different combinations of prescribed burning and pre-emergence herbicide application to control medusahead, an exotic annual grass, and promote remaining native vegetation. Our results demonstrated that fall or spring prescribed burning followed by a fall pre-emergence herbicide application were the most successful treatments at controlling medusahead and promoting native perennial vegetation. These results compared to previous reseach suggest that restoration of plant communities invaded by exotic annual grasses may be more successful if efforts focus on infestations with some residual native perennial vegetation compared to near monocultures of invasive annual grasses.

5.Significant Activities that Support Special Target Populations
These studies may all potentially benefit small farms (including ranching families and holders of grazing allotments on public land) by maintaining the quality and quantity of the forage base, and by increasing the profitability of pasture and hay production.

Review Publications
Roche, C.T., Sheley, R.L., Korfhage, R.C. 2008. Native species replace introduced grass cultivars seeded following wildfire. Ecological Restoration. 26(4)321-330.

Davies, K.W., Johnson, D. 2008. Managing Medusahead in the Intermountain West is at a Critical Threshold. Rangelands. 30:13-15.

Davies, K.W., Svejcar, A.J. 2008. Comparison of medusahead invaded and non-invaded wyoming big sagebrush steppe in southeastern oregon. Rangeland Ecol Manage 61:623-629

Rinella, M.J., Maxwell, B.D., Fay, P.K., Weaver, T., Sheley, R.L. 2009. Control Effort Exacerbates Invasive Species Problem. Ecological Applications 19(1):155-162.

Last Modified: 7/4/2015
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