Location: Range and Livestock Research2010 Annual Report
1a. Objectives (from AD-416)
Objective 1: Develop strategies and decision tools to proactively manage livestock grazing, fire, and drought impacts on Great Plains community structure and function. Sub-objective 1.A. Determine plant community and livestock response to post-fire grazing deferment. Sub-objective 1.B. Determine plant community response to fire return interval and seasonality. Sub-objective 1.C. Determine patch burning effects on plant community dynamics, animal performance, grazing distribution, and foraging efficiency. Sub-objective 1.D. Characterize grazing history effects on rangeland integrity and stability. Objective 2: Improve animal productivity and product quality based on predicted nutrient intake, forage dynamics, and diet selection processes in the northern Great Plains. Sub-objective 2.A. Determine effects of forage quality on autumn forage intake as it interacts with cow lactation and gestation status. Sub-objective 2.B. Determine rumen microbial response to noxious weed consumption by sheep and cattle. Objective 3: Develop management strategies to restore rangelands degraded by weeds and prevent weed invasions in the northern Great Plains. Sub-objective 3.A. Determine interacting effects of fire and grazing on annual brome dynamics. Sub-objective 3.B. Provide weed management protocols adjusting for inter-annual variation. Sub-objective 3.C. Develop an internet-available system to quantify site-specific invasive weed impacts. Sub-objective 3.D. Develop grazing strategies to reduce invasive weed population growth rates.
1b. Approach (from AD-416)
The planned research is designed to improve sustainability of rangeland production by addressing the interacting effects of disturbances on stability and integrity of rangelands and efficiency of livestock nutrient conversion. Objectives are to: 1) Develop strategies and decision tools to proactively manage livestock grazing, fire, and drought impacts on Great Plains community structure and function; 2) Improve animal productivity and product quality based on predicted nutrient intake, forage dynamics, and diet selection processes in the northern Great Plains; and 3) Develop management strategies to restore rangelands degraded by weeds and prevent weed invasions in the northern Great Plains. Experiments are integrated across objectives and will determine the interacting effects of grazing, fire, drought, and invasive plants on plant communities (production, species composition, diversity, heterogeneity, propagation, and survival) and the effects of changes in vegetation and animal physiology on livestock (weight gain, distribution, diet quality, diet selection, diet diversity, foraging efficiency, forage intake, and rumen microbial diversity). Two experiments are replicated across three locations (Miles City, MT, Nunn, CO and Woodward, OK) to determine ecological ramifications of fire seasonality, return interval, and grazing interactions in semiarid rangelands on a north-south gradient across the western Great Plains. Understanding the mechanisms that control disturbance effects on rangelands and animal responses to alterations in the plant community will promote development of proactive management strategies for improved stability in rangelands and rangeland livestock production systems.
3. Progress Report
This report documents research conducted under the in-house associated project 5434-21630-002-00D, Proactive Management for Sustainable Rangeland Production. All milestones were primarily limited to treatment application and data collection during this reporting period. This project addresses goals outlined in the NP 215 Rangeland, Pasture and Forages Action Plan under Component I (Rangeland Management Systems to Enhance the Environment and Economic Viability) and supports ARS strategic plan Objective 5.1 (Provide Science-Based Knowledge and Education To Improve the Management of Forest, Rangelands, and Pastures). For Objective A.2 of the NP 215 Action Plan, sheep performance and diet selection under post-fire deferment options revealed deferment until late summer will reduce animal performance compared to deferment until early or late spring. Plant community response data are being analyzed. Final data have been collected observing fire effects on livestock distribution. Addressing Objective B.1, a weed impact model has been made available on the internet and presented to extension and producer groups so with minor data input customers can estimate the impact of spotted knapweed or leafy spurge on their location’s forage availability. Final data were collected examining fire and grazing interactions on annual brome population dynamics and field and laboratory experiments revealed that growth regulating herbicides effectively reduce seed production of Japanese brome, in support of Objective C.1. Portions of this project are related to or coordinated with research in NP 304 Crop Protection and Quarantine (weed biology and ecology; plant, pest and natural enemy interactions and ecology).
1. Growth regulator herbicides are commonly used to control broadleaf weeds in rangelands, cereal crops and noncroplands. The herbicides often reduce cereal seed production if applied to cereals while the grasses are developing reproductive parts. ARS scientists at Miles City, MT, tested whether 2,4-D, dicamba, and picloram at typical field use rates would reduce Japanese brome seed production. They discovered that picloram reduced seed production nearly 100% when applied at the internode elongation, boot, or heading stages of growth, whereas dicamba appeared to be slightly less effective and 2,4-D was much less effective. Results were corroborated in the field where typical use rates of aminopyralid and picloram reduced Japanese brome seed production by more than 95% when applied at three different plant growth stages. Our results indicate it may be possible to control Japanese brome by using growth regulator herbicides to reduce its seed production, thereby depleting its short-lived seed bank.
2. Invasive plants are thought to perform better in their non-native than native ranges due to the lack of natural enemies typical of populations in their native ranges. However, this has rarely been empirically validated especially for soil-borne pathogens. Soil samples from numerous populations of P. serotina in its native and non-native ranges were collected and used to develop a bank of soil-borne pathogen (Pythium spp.) isolates. Comparative pathogenicity experiments revealed the presence of highly virulent taxa among P. serotina populations in its native range but the apparent lack of similar taxa in association with populations in its non-native range. This study suggests that the increased dominance by P. serotina in its non-native range is due in part to the absence of effects by virulent pathogens compared to populations in its native range. This study provides some of the first empirical evidence suggesting that biogeographical variation in plant performance is explained at least in part by the non-native populations having escaped from the effects of virulent soil-borne pathogens.
Rinella, M.J., Haferkamp, M.R., Masters, R.A., Muscha, J.M., Bellows, S.E., Vermeire, L.T. 2010. Growth Regulator Herbicides Prevent Invasive Annual Grass Seed Production. Journal of Invasive Plant Science and Management. 3:12-16.