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United States Department of Agriculture

Agricultural Research Service

2010 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/or a rhizobacteria, 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)

FY 10 Program Increase.

3.Progress Report
Throughout the life of this project we have made substantial progress in three primary areas of the ecology and management of medusahead infested rangeland, including prevention, control, and restoration. With respect to prevention, we have provided a new ecologically-based framework for designing and implementing prevention programs, identified plant functional groups conveying invasion resistance, developed new medusahead prevention strategies, and provided guidelines for grazing management to minimize invasion by medusahead. We have developed a biomass optimization model using herbicides and grazing for controlling medusahead. Lastly, we have developed ecologically-based restoration strategies for medusahead infested rangeland. Will be replaced by Project #5360-22000-004-00D

1. Grazing medusahead. Grazing invasive weeds can provide a cost-effective method for their control. Medusahead has been considered unpalatable and useless as forage. ARS scientists in the Range and Meadow Forage Management Research Unit in Burns, OR determined that cattle readily consume medusahead during its growing period, prior to the production of awns. Once awns are produced, cattle will reluctantly eat the annual grass. Medusahead infested rangeland produced from 1/8 to 1/16 of an Animal Unit Month per acre and cows maintained or improved body condition and weight. Results of this study suggest grazing medusahead infested rangeland may be feasible using cattle.

2. Best management practices using Plateau. Plateau is the herbicide most commonly used to control annual grasses, such as medusahead. In many cases, the application of this herbicide does not lead to desired vegetation and medusahead rapidly reinvades the site. It is critical to identify the conditions under which Plateau has a desired and long lasting effect on vegetation during medusahead control. ARS scientists in the Range and Meadow Forage Management Research Unit in Burns, OR determined that prediction of the vegetation response to Plateau in not possible using pre-application vegetation information. We found that there was no relationship between the density, biomass, and cover of desired species or medusahead on post treatment species composition. It is likely that spraying Plateau to control medusahead will produce variable responses in vegetation, thus the decision to use this herbicide is somewhat arbitrary.

3. Resistance of native plant functional groups. Understanding the relative importance of various plant groups in minimizing invasion by medusahead is central to increasing the resistance of native plant communities. ARS scientists in the Range and Meadow Forage Management Research Unit in Burns, OR determined the functional groups of native plants that provided the most invasion resistance to medusahead. We found that perennial grasses play a relatively more significant role than other species in minimizing invasion by medusahead. We suggest that the most effective basis for establishing medusahead-resistant plant communities is to establish two or three highly productive grasses that occupy different resource pools.

4. Using rangeland health assessment to inform successional management. Overcoming barriers to adoption of ecologically-based invasive plant management (EBIPM) will require developing a useful format for land managers to easily link ecological processes that need to be repaired to allow vegetation to change in a favorable direction. The Rangeland Health Assessment procedures are currently being adopted by land managers across the western U. S. ARS scientists in the Range and Meadow Forage Management Research Unit in Burns, OR developed a method to integrate the Rangeland Health Assessment with the step by step EBIPM framework. This now allows managers to quantify a point-in-time indication of rangeland health and additionally use this information to determine ecological processes that need to be repaired. Integrating EBIPM with the Rangeland Health Assessment is advantageous for land managers in avoiding unnecessary inputs and minimizing unintended negative impacts on ecological processes. This development has the potential to substantially advance how invasive plants are managed throughout the west.

5. Traits contributing to invasive annual grass success in low nutrient environments. Plant invasion is classically assumed to be positively related to resource availability. However, we also know invaders can be successful in nutrient-poor systems. In practical terms this is problematic because nutrient poor systems also are difficult to restore. ARS scientists in the Range and Meadow Forage Management Research Unit in Burns, OR evaluated a suite of germination, root growth, shoot growth and nitrogen use efficiency traits for native and invasive species. From this research, it was determined that early germination, root growth at low temperature and a high specific leaf area were important traits influencing variation in fitness across accessions. There was substantial variability among accessions within a species and in some cases native plant populations had trait values similar to the invader. The impact of this finding for rangeland restoration is that in some situations native grass accessions could be strategically paired to maximize annual grass interference in low nitrogen soils.

6. Bottlenecks to restoring degraded rangeland. Recruitment often is a central limitation to plant community restoration. Seeding native species is a critical tool that allows managers to overcome these limitations and positively influence plant community assembly. However, seeding is a high-risk and expensive practice in arid systems where year-to-year variation in environmental conditions can lead to large year-to-year variation in recruitment success. In this multiyear experiment, ARS scientists in the Range and Meadow Forage Management Research Unit in Burns, OR examined the demography of seeded grass species to determine what critical life stages may be central drivers of seeding failures and to identify management opportunities to improve establishment. Across years, the largest bottleneck for native species was the transition between germination and emergence but this was not necessarily true for the introduced crested wheatgrass. The results of this research indicate an ability to identify and modify the ecological processes influencing rangeland restoration outcomes, which can substantially advance the percentage of successful restorations on degraded rangeland.

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
Sheley, R.L., Vasquez, E.A. 2009. Functional Group Responses to Reciprocal Plant Litter Exchanges between Native and Invasive Plant Dominated Grasslands. Journal of Invasive Plant Science and Management. 2:158-165.

Last Modified: 6/30/2015
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